SIRELINE VARIATION IN
NEONATAL LAMB COLD
TOLERANCE
A thesis
submitted in partial fulfilment
of the requirements for the Degree of
Master of Science
At
Lincoln University
by
B.W. Gudex
Lincoln University
2001
Abstract of a thesis submitted in partial fulfilment of the
requirements for the Degree of Master of Science
SIRE-LINE VARIATION IN NEONATAL
LAMB COLD TOLERANCE.
By B.W. Gudex
T h e c o s t o f l a mb m o r t al i t y ca u s e d b y c o l d e x p os u r e h a s be e n
e s t i ma t e d a t a p p r o xi ma t e l y 4 0 mi l l i o n dol l ar s p e r y e a r . T h i s v a l u e i s
probably conservative as it does not include the cost due to the
r e d u c t i o n i n p r o d u c t i v i t y i n h y p o t h er mi c l a mbs t h a t ma n a g e t o
survive or the cost of reduced selec t i o n p o t e n t i a l o f t h i s r e s e a r c h w a s
t o i n v e st i g a t e w h e t h e r s i r e - l i n e v ar i a t i o n e x i s t s i n n e o n a t a l l a mb
c o l d t o l e r a n c e a n d w h e t h e r p o l y mor p h i s m i n t h e  3 a d r e n e r g i c
r e c e pt o r ge n e c a n be u s e d a s a g e n e t i c ma r k e t f o r l a mb c o l d
t o l e r a n c e a n d l e a n m u s c l e g r o w t h . T h e i n f l u e n c e o f t h e c l i ma t e ,
b i r t h w e i g h t , a g e o f d a m a t l am b i n g , g e n d e r a n d b i r t h r a n k o n
n e o n a t a l l a mb c o l d t o l e r a n c e w a s a l s o a n a l y s e d .
N e o n a t a l l a mb mor t a l i t y d u e t o s ol d e x pos u r e w a s a n a l y s e d i n
four field trials that used neon a t a l l a m b mo r a l i t y fr o m c o l d
e x p o s u r e a s a p r e d i c t o r o f n e o n a t a l lamb cold tolerance. Sire-line
v a r i a t i o n i n n e o n a t a l l a mb m o r a li t y w as o b s e r v ed i n a l l t ri a l s ,
though it appeared that this effect was largely mediated through
s i r e - l i n e v a r i a t i o n i n l a mb b i r t h w e i g h t . V a r i a t i o n i n l a mb b i r t h
weight between birth rank clas s e d w a s a l s o f o u n d t o b e
responsible for the influence of birth rank on neonatal lamb
m o r t a l i t y d u e t o c o l d e x p o s u r e . T h e a g e o f d a m a t l a mb i n g a n d t h e
l a mb g e n d e r w a s n o t o b s e r v e d t o i n fl u e nc e n e o n a t a l l a mb m o r t al i t y
due to cold exposure.
T h e s i r e s f r o m t h e c o l d t o l e r an c e s t u d y a n d t h e p r o g e n y o f t h e
l e a n mu s c l e g r o w t h s t u d y w e r e g e n o t y p e d f o r t h e  3 a d r e ne r g i c
r e c e pt o r l o c u s . O t h e r s t u di e s h a v e f o u n d e v i d e nc e t h a t a ma j o r g e n e
e x i s t s i n t h e c a t e c h o l a mi n e s t i mu l a t i o n o f b r o w n a d i p o s e
t h e r mo g e n e s i s a n d e v i d e n c e t h a t t h e  3 - A R g e n e i s a l i k e l y
candidate. However, this hypot h e s i s a n d t h e h y po t h e s i s t h a t
p o l y mo r p h i s m i n t h e  3 - A R g e n e i s a l s o l i n k e d t o l e a n mu s c l e
g r o w t h i n l a mb s w a s n o t c o n f i r me d i n t h i s s t u d y . S o w h i l e i t
a p p e a r s t h a t t h e r e s u l t s w e r e c o n f o u n d e d b y e x p e r i me n t a l d e s i g n ,
t h e r e i s e v i d e n c e t h a t i n f l u e nc e o f p o l y mo r p h i s m i n t h e o v i n e  3 AR
g e n e o n ne o n a t al l am b mor t a l i t y a n d/ o r l e a n mus c l e g r o w t h i s n o t
s u f f i c i e n t t o b e c o ns i d e r e d a ma j o r g e n e e f f e c t .
T h e i mp l i c a t i o n s o f t h i s e x p er i me n t o n t h e s h e e p i n d u s t r y a n d
s h e e p f a r me r s i n g e n e r a l a r e h u g e . W h i l e c o mp l e t e l y e l i mi n a t i n g
l a mb d e a t h s d u e t o i n a d e q u a t e c o l d t ol e r a n c e i s i mp o s s i b l e , t h i s
s t u d y s h o w s t h a t l a r g e g a i n s i n l amb s u r v i v a l c o u l d b e p o s s i b l e
through selective breeding.
Key Words: Sheep (Ovis aries), cold tolerance, lean muscle growth, birthweight,  3
adrenergic receptor
SIRE LINE VARIATION IN NEONATAL LAMB COLD TOLERANCE
Contents
PAGE
A b s t r a ct
ii
Contents
iii
List of Tables
v
List of Figures
vi
Chapter 1
REVIEW OF THE LITERATURE
1
Chapter 2
SIRELINE VARIATION IN NEONAT AL
LAMB COLD MORTALITY
23
2.1
Flocks Investigated & Lambing Locations
24
2.2
Methods
25
2.3
Results
29
2.4
Discussion
35
2.5
Conclusions
43
Chapter 3
THE ROLE OF  3 ADRE NE RGIC
RECEPT OR GE NE POLYM ORPHIS M IN
COLD TOLERANC E AND L EAN
MUSCLE GROWTH
44
3.1
Animals Investigated
46
3.2
Methods
46
3.3
Results
50
3.4
Discussion
55
3.5
Conclusions
59
SIRE LINE VARIATION IN NEONATAL LAMB COLD TOLERANCE
Chapter 4
DISCUS S I ON AND FUTURE DIRECTI ONS
OF RES E ARC H
A c k n o w l e d g e me n t s
References
60
65
67
A p pendices
1
C o s t o f N e o n a t a l L a mb M o r t a l i t y d u e
80
to Cold Exposure
2
H a mp s h i r e A u t o p s y R e p o r t ( 3 / 9 / 1 9 9 9 )
81
3
Manufacturers Instructions for FTA
83
Card Purification.
iv
List of Tables
Table
1.
Page
H eritability estim ate s f or gen e t i c c o mp o n e n t s o f l a mb
c o l d t ol e ra n c e
17
2.
T o t a l l a m b mo r t a l i t y i n e a c h t r i a l
29
3.
T h e l a mb m o r t a l i t y c a u s e d b y c o l d e x pos u r e f o r e a c h
s i r e- l i n e
33
4.
A c c u r a c y o f t h e l o g i s t i c r e g r e s s i o n mo d e l s
34
5.
 3 A R g e n o t y p e o f a l l t h e s i r e s u s e d i n t h e c o l d t o l e r a nc e
study
50
6.
S i r e l i n e Va r i a t i o n i n L e a n M u s c l e G r o w t h
52
7.
V a r i a t i o n b e t w e e n  3 A R g e n o t y p e s i n Le a n M u s c l e
G row th
8.
53
DNA sequ ences of the ovine  3 AR standards and the
t w o mos t c o m m o n a l l el e s p res e n t i n t he L e a n Mus c l e
G r o w t h t ri a l
54
v
List of Figures
F i g ure
1
Pa g e
C a u s e s o f D e a t h i n N e o n a t a l L a mb s U n d e r N e w Z e a l a n d
C o n d i t i o ns
1
2
Starvation - Exposure Interactions
3
3
Thermoregulation in Mamma l s
6
4
S ome factors contr olling non- s h i v e r i n g t h e r mo g e n e s i s
7
5
T h e s t r u c t u r a l c h a n g e s i n w o o l a s w i n d v e l o c i t y i n c r e a se s 1 0
6
Mortality of single and twin Merino lambs relative to
birth w eight
7
12
The response to three years of upward and downward
s e l e c t i o n f o r c o l d r e s i s t a n c e , u s i n g a wa te r ba th te st,
i n n e w b o r n l a mbs o f t h e S c o t t i s h Bl a ck f a c e b r ee d
8
T h e a v e r a g e p r e d i c t e d d a i l y he a t l os s an d t h e c o l d
m o r t a l i t y o n e a c h t r i a l d a y a t t he L i n c oln s i t e i n 20 0 0
9
30
T h e u n c o r r e c t e d a m o u n t o f l am b mo r t a l i t y d u e t o c o l d
e x p o s u r e f o r e a c h  3 AR genotype
13
32
T h e i n f l u e n c e o f b i r t h w e i g h t u p o n l a m b mo r t a l i t y d u e
t o c o l d e xp o s u r e i n e a c h o f t he f o u r t r i a l s a n a l y s e d
12
31
T he influence of bir th r a nk upon l a mb m o r t a l i t y d u e t o
cold exposure
11
30
T h e a v e r a g e p r e d i c t e d d a i l y he a t l os s an d t h e c o l d
m o r t a l i t y o n e a c h t r i a l d a y a t t he L i n c oln s i t e i n 19 9 9
10
15
51
PC R -SS C P gels conta ining the ovine  3 A R a l l e l e
s t a n d a r d s a n d s o me o f t h e p r o g e n y o f 9 8 4 / 9 7
53
vi
Chapter 1: Literature Review. Sire Line Variation in
Neonatal Lamb Cold Tolerance
N e o n a t a l l a mb mo r t a l i t y r e pre s e n t s a la r ge loss to Ne w Ze a la n d
sheep farming. Not only is the industr y affected by the direct loss of
t h e d e a d l a mb s , b u t g e n e t i c p o t entia l ( a nd he nc e f utur e pr oduc tion)
is also reduced through having fe w e r l a mbs a t w e a n i n g a n d f e w e r
rising adults from which flock replacements can be selected (Dalton,
1 9 8 3 ) . T h i s l o s s h a s b e e n v a l u e d i n t h e S h e e p I m p r o v e me n t L i mi t e d
( S . I . L . ) g e n e t i c i m p r o v e me n t s y s t e m a s v a r y i n g b e t w e e n $ 3 4 p e r
l a mb b o r n , f o r d u a l - p u r p o s e b r e e d s t o $ 2 8 f o r t e r mi n a l s i r e b r e e d s
a n d $ 2 3 f o r f i n e w o o l b r e e d s o f s h e e p ( A me r , 2 0 0 0 ) . Wi t h i n N e w
Z e a l a n d i t h a s b e e n e s t i ma t e d t h a t a n a ve r a g e o f f i f t e e n p e r c e n t o f
a l l l a mbs b o r n d i e be f o r e w e a n i n g e a c h y e a r ( Mc C u t c h e o n e t a l .
1981). Of these deaths, an average of 15% is thought to be due to
c o l d e x p o s u r e ( G u m b r e l l & S a v i l le, 1986 - Figure 1), although this
c a n r i s e t o 9 0 % o f n e o n a t a l l a mb d e a t h s u n d e r e x t r e me w e a t h e r
c o nditions (O bst & D ay, 1968) .
T h e ma g n i t u d e o f t h i s l o s s of l a mbs i s i l l u st ra t ed b y t h e fa c t
t h a t , t h e w e i g h t o f me a t a n d w o o l p r o d u c e d e a c h y e a r i s mor e
dependent upon the total number of lambs that survive to weaning,
t h a n upon the individual pe r f orma n c e o f t h e l a mb s ( S i d w e l l e t a l . ,
1 9 6 2 ; L a x & N e w t o n - T u r n e r , 1 9 6 5 ) . T h e r e f o r e a s s u mi n g t h a t i t i s
h e r i t a b l e , i t c o u l d b e c o n c l u d e d t h a t s e l e c t i o n f o r e n h a n c e d l a mb
s u r v i v a l i s e c o n o mi c a l l y mor e i mp o r t a n t t h a n s e l e c t i o n f o r
production traits.
Figure 1: Causes of Death in Neonatal lambs Under New Zealand
Conditions (Data from Gumbrell & Saville, 1986).
1
Chapter 1: Literature Review
1.1 METHODS OF ESTIMATING NEONATAL LAMB COLD
TOLERANCE
T h e r e a r e t w o ma i n t e c h n i q ue s t h a t a r e c o m m o n l y u s e d t o
e s t i ma t e ne o n a t a l c ol d t o l e r a nc e , f i e l d t r i a l s a n d t h e u s e o f a
p r o g r e s s i v e l y c o o l e d w a t e r b a t h s t o me a s u r e t h e l a mb s ’ a b i l i t y t o
ma i n t a i n h o mo t h e r m y . T h e u s e o f f i e l d t r i a l s u s i n g n e o n a t a l c o l d
m o r t a l i t y a l l o w s t he a n a l y si s o f n e o n a t a l c o l d t o l e r a n c e u n d e r
‘ t y p i c a l ’ f a r mi n g c o n d i t i o ns . H o w e v e r , t h i s me t h o d h a s s ome l a r g e
d i s a d v a nta g e s . I t i s v e r y l a b ou r i n t e n s i v e a n d , f o r a c c ur a c y , i t
requires the use of autopsies to diagnose cold exposure deaths
( H aughey, 1993), though the de pr e ssion i n r e c t a l t e mpe r a t u r e 1 5 - 2 5
mi n u t e s a f t e r b i r t h ( S y k e s e t a l . , 1 9 7 6 ) h a s b e e n s u c c e s s f u l l y u s e d i n
a f i e l d t r i a l t o e s t i ma t e n e o n a t a l l amb c o l d t o l e r a n c e . A d i a g n o s i s o f
l a mb d e a t h fr o m i n a d e q u a t e c o l d t ol e ra n c e i n fie l d t r i al s h a s a l s o
b e e n s u c c e s s f u l l y ma d e b a s e d u p o n d i r e c t o b s e r v a t i o n s ma d e b y t h e
shepherd(s) (Purser & Young, 1964).
T h e c l a s sif i c a t i o n of c o l d d e a t h u s i n g a u t o p s i e s i s d i f f i c u l t
o w i n g t o t h e d i f f i c u l t i e s i n s e p a r a t i n g l a mb d e a t h s f r o m e x p o s u r e
from those from simple starvation based on pathological
o b s e r v a t i o n s ( M c Cu t c h e o n e t a l . , 1 9 8 1 ) . T h e r e a s o n f o r t h i s i s t h a t
w h e n a l a m b d i e s f r o m e i t h e r s t a r v a t i o n o r e x p o s u r e t h e p r i ma r y
cause of death is the exhaustion of the body’s energy reserves and
t h e r e i s a l a r g e a mo u n t o f i n t e r a c t i o n b e t w e e n t h e t w o s y n d r o me s
( F igure 2).
2
Chapter 1: Literature Review
Figure 2: Starvation - Exposure interactions (adapted from
McCutcheon et al., 1981).
T h e mo s t c o m m o n l y u s e d a u t o p s y t e c h n i q u e w a s i n i t i a l l y
developed in the Hawkes Bay distri ct o f N e w Z e a l a n d ( M a c F a r l a n e ,
1965) and later refined at the Un i v e r s i t y o f S y d n e y , A u s t r a l i a
( H a u g h e y , 1 9 7 3 ) . H o w e v e r , ma j o r i n a c c uracies have been identified
i n t h i s t e c h n i q u e . Th e p e r i p h e r a l o e d e ma ( s w o l l e n t i s s u e i n t h e
e x t r e mi t i es ( l i mb s , t a i l , ea r s an d muz z l e) d u e t o t h e p r e s e nc e o f
e x c e s s f l u i d ) c o n s i d e r e d i n d i c a t i ve of c old injur y by Ha ughe y ( 197 3 )
i s n o t s e e n i n ma n y l a mb s t h a t d i e s o o n a f t e r b i r t h i n i n c l e me n t
w e a t h e r , e v e n t h o u g h i t i s o f t e n s e e n i n l a mbs d y i n g mor e s l o w l y i n
b a d w e a t h e r a f t e r h a v i n g s u c k l e d ( Ale xa nde r , 1985) . Ha ughe y ( 198 0 )
a l s o f o u n d t h a t s o me l a mb s b o r n b y c a e s a r e a n s e c t i o n ( 7 . 1 % )
e x h i b i t e d a t l e a s t o n e me n i n g e a l l e s ion (injury to one or more of the
t h r e e me m b r a n e s e n v e l o p i n g t h e b r a i n and/or spinal cord) that was
n o r ma l l y c o n s i d e r e d i n d i c a t i v e o f d y s t o c i a ( d i f f i c u l t o r p r o l o n g e d
birth). No explanation was found fo r t h i s a s i t w a s t h o u g h t t h a t
me n i n g e a l l e s i o n s o n l y o c c u r r e d a s a c o n s e q u e n c e o f p h y s i o l o g i c a l
b i r t h t r a u ma a n d h y p o x i a , b o t h c o n d i t i o n s t h a t d o n ’ t o c c u r i n
c a e s a r e a n s e c t i o n l a mb b i r t h s . A s a c o n s e q u e nc e , w h e n u s i n g t hi s
autopsy technique, it appear s t h a t d y s t o c i a i s c o m m o n l y
o v e r e s t i m a t e d ( a s s h o w n f i g u r e 1 , whe r e dystoc ia wa s thought to be
i n v o l v e d i n 7 5 % o f l a mb d e a t h s ) . Another disadvantage of using
f i e l d t r i a l s t o me a s u r e c o l d r e s i s ta n c e i s t h a t t h e w e a t h e r c a n b e a n
3
Chapter 1: Literature Review
u n r e l i a b l e t e s t i n g a g e n t a n d i s v e r y h a r d t o p r e di c t a c c ur a t e l y i n
advance (Slee, 1985).
B e c a u s e of t h e d i f f i c u l t i e s i nv o l v e d w i t h u s i n g a u t o p s i e s t o
d i a g n o s e d e a t h s f r o m i n a d e q u a t e cold tolerance, a laboratory
t e c h n i q ue w a s d e v e l o p e d a t t h e A n i ma l B r e e d i n g R e s e a r c h
O r ganisation (A B R O ), Edinbur gh, Sc otla nd tha t a llowe d the
me a s u r e m e n t o f a l a m b s a b i l i t y t o g e n e r a t e h e a t a n d ma i n t a i n
h o me o t h e r my ( S a ms o n & S l e e , 1 9 8 1 ; S l e e & St o t t , 1 9 8 6 ) . T h i s
t e c h n i q u e i n v o l v e d i m me r s i n g l a mb s i n a p r o g r e s s i v e l y c o o l e d w a t e r
b a t h a n d me a s u r i n g h o w l o n g i t t o o k f o r t h e l a mb ’ s r e c t a l
t e mpe r a t u r e t o f a l l t o a p r e d ete r mi n e d l e v e l . T h i s r e s e a r c h h a s s i n c e
b e e n r e pl i c a t e d b y ot h e r r e s e ar c h e r s i n N e w Z e a l a n d ( Wo l f f e t a l . ,
1 9 8 7 ) u s i n g d i f f e r e n t b r e e d s a n d t h e results have shown, with very
f e w e x c e p t i o n s , t h a t l a mb s f r o m h i g h c o l d r e si s t a n c e l i ne s ( t e st e d i n
w a t e r b at h s ) a l s o t e n d t o s h ow t h e h i ghe s t c ol d r e s i st a n ce i n t h e
fi e l d a n d t h e l o w e st c o l d i n d uc e d mor t a l i t y ( S l e e e t a l . , 1 9 8 0 ; S l e e ,
1985). Unfortunately, the accuracy of this technique is limited
b e c a u s e i t d o e s n o t a c c o u n t for t h e a mo u n t o f t h e r ma l i n s u l a t i o n
p r o v i d e d b y t h e n e w b o r n l a m b ’ s b i r th c o a t a s a c c u r a t e l y a s o t h e r
t e c h n i q u e s ( S l e e e t a l . , 1 9 8 0 ; S a ms o n & S l e e , 1 9 8 1 ) . I t i s f u r t h e r
l i mi t e d b e c a u s e i t f a i l s t o t a k e i n t o a c c o u n t t h e e i t h e r t h e h e a t
p r o d u c e d o r c o n s e r v e d b y b e h a v i o u r a l me c h a n i s ms s u c h a s h u d d l i n g
a n d mo v e me n t .
4
Chapter 1: Literature Review
1.2 HEAT PRODUCTION IN NEW-BORN LAMBS
H e a t p r o d u c t i o n ( t h e r mo g e n e s i s ) in the ne wbor n la mb is
i mp o r t a n t a s i t mo v e s f r o m t h e e n v i r o n me n t i n t h e w o mb ( 3 9 C ) , t o
t h e o u t si de w o r l d w h e r e t he a m b i e n t t e m p e r a t u r e c a n b e b el o w 0C.
T o c o u n t e r t h e l o w e r t e mpe r a t u r e s o f t h e e x t e r n a l e n v i r o n me n t , mo s t
l a mb s a r e a b l e t o g e n e r a t e a p p r o x ima t e l y 6 0 - 7 0 k J o f h e a t p e r k g o f
b o d y f r o m t h e i r r e s e r v e s o f l i v e r a n d m u s c l e g l y c o g e n , a mi n o a c i d s
a n d b r o w n a d i p o s e t i s s u e . T he s e r e se r ve s a r e n or ma l l y s u f f i c i e nt t o
ma i n t a i n a l a mb s b o d y t e mp e r a t u r e f o r b e t w e e n 5 t o 1 2 h o u r s i n c o l d
w e a t h e r a n d u p t o 3 - 4 d a y s i n g o o d w e a t h e r , d e p e n d i n g o n t h e l a mb s
s i z e a n d p r e n a t a l n u t r i t i o n ( Ale xa nde r , 1962; Sle e , 1979) .
Heat production in newborn la mbs o c c ur s b y t wo me c h a n i s ms :
s h i v e r i n g a n d n o n - s h i v e r i n g t h e r mo g en e s i s ( Fi g u r e 3 ) . B o t h o f t h e s e
me c h a n i s ms a r e a c t i v a t e d w i t h i n mi n u t e s o f a l a m b b e i n g b o r n a n d
t h e y h a v e b e e n e s t i ma t e d t o c o n t r i b u t e 4 6 % a n d 3 1 % , r e s p e c t i v e l y ,
o f a n e w b o r n l a mb ’ s s u m mi t me t a b o l i s m ( t h e h i g h e s t a t t a i n a b l e
me t a b o l i c r a t e i n r e s p o n s e t o c ol d e x p os u r e ) ( A l e x a n d e r & Wi l l i a ms ,
1 9 6 8 ) . H o w e v e r , s h i v e r i n g t h e r mo g e n e s i s i s a c o mp a r a t i v e l y
i n e f f i c i e n t me t h o d o f p r o d u c i n g h e a t, a s i t a l s o i n c r e a s e s t h e a mo u n t
o f h e a t l o s t b y t h e l a mb b y d i s r u p t i n g t h e b o u n d a r y l a y e r o f a i r
a r o u n d a l a mb , t h u s r e d u c i n g t h e e xte r na l insula tion ( Cla r ke e t a l . ,
1 9 9 7 ) . T h e mu s c l e m o v e me n t i n v o l v e d i n s h i v e r i n g c a n a l s o
i n t er fe r e w i t h t h e l a mb ’ s a b i l i t y t o find t h e u d de r a n d s u ckl e . It i s a s
a c o n s e q u e n c e t h a t n o n - s h i v e r i n g t hermogenesis is activated before
s h i v e r i n g i n o r d e r t o a v o i d t h e s e dif f ic ultie s ( Ale xa nde r , 1984) .
Brown adipose tissue (BAT) is the pr inc iple site of nons h i v e r i n g t h e r mo g e n e s i s i n t h e n e w b o r n l a mb . B A T a c c o u n t s f o r
a p p r o x i ma t e l y 1 . 5 – 2 . 0 % o f t h e n e w b o r n l a mbs b o d y w e i g h t
( A l e x a n d e r & Wi l l i a ms , 1 9 6 8 ) a n d i s l oc a t e d ma i n l y i n t he p e r i r e n a l a b d o mi n a l , i n g u i n a l a n d p r e s c a p u l a r a r e a s o f t h e l a mb ( A l e x a n d e r ,
1 9 7 8 ) . B A T d i f f e r s f r o m w h i t e a d ip o s e t i s s u e ( W A T ) i n t h a t i t
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Chapter 1: Literature Review
possesses more extensive vascularisation and sympathetic
i n n e r v a t i o n a n d h a s m o r e mi t o c h o n d r ia which are larger and more
c o mplex than those found in W AT ( Hi mms- Ha ge n, 2000) .
Cerebral
Cortex
"Voluntary " responses
Hypothalamic
temperature
Hypothalamus
"Involuntary" responses
Skin
thermoreceptors
Thyroid Releasing Hormone (TRH)
Pituitary
gland
Sympathetic
Nerves
Skin
temperature
Thyroid Stimulating Hormone (TSH)
Thyroid
gland
Thyroxine (T4)
Adrenal
glands
Catecholamines
Sweat
glands
Perspiration
Increased metabolic rate due to Non-shivering thermogenesis
Peripheral
blood
vessels
Skeletal
muscle
Constriction Movement
or dilation
and shivering
(shivering
thermogenesis)
Figure 3: Thermoregulation in mammals. A complex network of
activities involving both the nervous and endocrine systems
(adapted from Curtis & Barnes, 1989).
T h e mi t o c h o n d r i a wi t h i n B A T g i v e i t i t s c o l o u r a n d t h e y
c o n t a i n a 3 2 k D A p r o t e i n o n t h e ir me m b r a n e c a l l e d u n c o u p l i n g
p r o t e i n ( U C P ) . U n t i l r e c e nt l y i t w as t h o u g h t t ha t t h e r e wa s o n l y o ne
type of UCP (UCP- 1). However, i n 1 9 9 7 t w o f u r t h e r s u b t y p e s o f
UCP were identified (UCP-2 and -3), though their function in BAT
h a s not yet been identifie d ( Himms- Ha ge n, 2000) . UCP- 1 is
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Chapter 1: Literature Review
responsible for the uncoupling of oxidative phosphorylation from
mi t o c h o n d r i a l r e s p i r a t i o n ( a d e n o s i ne t r i p h o s p h a t e ( A T P ) s y n t h e s i s ) ,
w hich enables the B A T to ge ne r a te l a r g e a mo u n t s o f h e a t ( C a r s t e n s
e t a l . , 1 9 9 7 ; C l a r k e e t a l . , 1997). This mechanism appears to be
s t i mu l a t e d b y a n u m b e r o f d i f f e r en t e n d o c r i n e fa c t o r s , i n c l u d i n g
t h y r o i d h o r mo n e s a n d c a t e c h o l a mi n e s ( F i g u r e 4 , A l e x a n d e r &
Wi l l i a ms , 1 9 6 8 ; C l a r k e et al., 1 9 9 7 ) .
COLD
Brown Fat Cell
HYPOTHALAMUS
SYMPATHETIC NERVE
3-ADRENERGIC
RECEPTOR
CAPILLARY
MITOCHONDRIA
noradrenaline
C
Gs
uncoupled
oxidation
ADENYLATE
CYCLASE
-
CO2
UCP-1
cAMP
PKA
HSL
HEAT
O2
uptake
FFA
FFA
Transcriptional
regulation of genes required
for lipolysis & thermogenesis NUCLEUS
including the genes for UCP
& LPL
T3 receptors
1 -ADRENERGIC
RECEPTOR
Type II iodo th yrox in e
5’ monod eiod in ase
THYROID
GLAND
T4
T4
T3
T3
F i g u r e 4 : S o me f a c t o r s c o n t r o l l i n g n o n- s h i v e r i n g t h e r mo g e n e s i s
( A d a p t e d f r o m G u n n & G l u c k ma n 1 9 8 9 ) .
T h e s t i mu l a t i o n o f t h e s y mp a t h e t i c n e r v o u s s y s t e m ( F i g u r e 4 )
l e a d s t o t h e r e l e a s e o f n o r a dr e n a l i n e , w h i c h b i n d s t o t h e  3 a d r e n e r g i c r e c e pt o r s ( A R ) . T h e  3 - A R i n t u r n st i m u l a t e s t h e a c t i v i t y
o f a d e n y l a t e c y c l a se , w h i c h r e s u l t s i n i n c r e a se d i n t r a c e l l ul a r
c o n c e n t r a t i o n s o f c y c l i c a d e no s i n e mon o p h o s p h a t e ( c A M P - G u n n &
G l u c k ma n , 1 9 8 9 ) . T h e a mp l i f i e d i ntr a c e llula r c onc e ntr a tions of
c A M P a r e t h e n r es po n s i b l e for s t i mu l a t i n g t h e t ra n s c r i pt i on o f
s e v e r a l g e n e s i mp o r t a n t f o r t h e rmo g e n e s i s i n c l u d i n g t h e g e n e s
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Chapter 1: Literature Review
r e s p o n s i b l e f o r l i p o p r o t e i n l i p a s e ( LPL – r e quir e d f or lipolysis of
t r i g l y c e r i d e s t o f u e l t h e r mo g e n esis) and UCP-1 expression (Gunn &
G l u c k ma n , 1 9 8 9 ; H i m m s - H a g e n , 1 9 9 0 ) . The thyr oid hor mo ne , tr ii o d o t h y r o n i n e ( T 3 ) i s a l s o i n v o l v e d i n r e gulating the expression of
t h e g e n e c o d i n g U C P - 1 ( F i g u r e 4 ) , t h o u g h t h e m a i n e n z y me
r e s p o n s i b l e f o r t h e c o n v er s i o n o f t h y r o x i n e ( T 4 – t h e i n ac t i v e
t h y r o i d h o r mo n e ) t o T 3 in BAT is a lso r e gula te d by nor a dr e na line .
Nor adrenaline stimulates (via  1 -adrenergic receptors) the activity of
type II iodothyroxine 5’ monodeiodinase by up to 10 times within 2
hours of exogenous injection of noradrenaline (Silva & Larsen, 1983).
T h e i n c r e a s e d a d e ny l a t e c y c l a s e a c t i v i t y a l s o pro mo t e s t he
a c tivation of cA MP-depe nde nt pr otein kinase A (PKA) whi c h is
r e s p o n s i b l e f o r t h e a c t i v a t i o n o f h o r mo n e - s e n s i t i v e l i p a s e ( H S L ) .
H S L c a t a l y s e s t h e r a t e l i mi t i n g s t e p in triglyceride breakdown and
l i p o l y s i s , p r o v i d i n g f r e e f a t t y a c i d s ( F FAs ) f o r t h e s t i mu l a t i o n o f
U C P activity resulting in he a t pr oduc tion ( Himms - Ha ge n, 1990) .
B l ood flow to and from BAT is the n e nha nc e d in order to deliver
oxygen and other substrates required for the thermogenic process, and
to remove and distribute the heat produced (Slee et al., 1987; Carstens
et al., 1997). This change in blood flow is regulated by noradrenaline
and can be as much as 5 or 6 times the normal blood flow in lambs
(Gunn & Gluckman, 1989).
Adenosine is also responsible for regulating the metabolism of
BAT and is thought to be responsible for inhibiting BAT activity in the
foetus. A de n o s i n e i nh i b i t s t h e increase of cAMP c a used by  3 a d r e n e r g i c r e c e pt o r s t i mu l a t i o n a n d t he i n c r e a s e i n t y p e I I
i o d o t h y r o x i n e 5 ’ mo n o d e i d i n a s e a c t i v i t y c a u s e d b y  1 a d r e n o r e c e p t o r s t i mu l a t i o n ( Gu n n & G l u c k ma n , 1 9 8 9 ) .
In addition to its body r e s e r ve s , t h e l am b i s a b l e t o u t i l i se 9 0 %
of the energy supplied by ewe colostrum (7.3 MJ/kg) for
t h e r mo g e n e s i s ( V e r m o r e l & V e r n e t , 1 9 8 5 ) . H o w e v e r , h y p o t h e r mi c
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Chapter 1: Literature Review
l a mbs ( w i t h r e c t a l t e mpe r a t u r e s b e l o w 3 7 C ) a p p e a r t o h a v e a
s u p p r e s s e d d e s i r e t o s u c k l e ( A l e x a n d e r & Wi l l i a ms , 1 9 6 6 ) .
E x p e r i me n t s h a v e sh o w n t h a t u s u a l l y 80% o f l a m b s w i l l s uc k l e
w i t h i n 3 0 mi n u t e s o f b i r t h w h e n t he a v e r a g e a mb i e n t t e mpe r a t u r e i s
2 7 C , b u t w h e n t h e t e mpe r a t u r e i s r e d uc e d t o 5 C it takes 100
mi n u t e s f o r t h e s a me p r o p o r t i o n ( 8 0 %) of la mbs to suc kle ( Mc Br ide
e t a l . , 1967). T he suckling inhibition i s p o s s i b l y a r e s p o n s e t o
c o n s e r v e e n e r g y a n d a p p e a r s t o b e me d i a t e d v i a t h e c e n t r a l n e r v o u s
s y s t e m ( A l e x a n d e r & Wi l l i a ms , 1 9 6 6 ) .
O f a l l o f t h e f a c t o r s i n v o l v e d i n r e g ul a t i n g f a t mo b i l i sa t i o n a n d
t h e r mo g e n e s i s i n t h e n e w b o r n l a mb , t h e r o l e p l a y e d b y
c a t e c h ol a mi n e s a n d t h e i r a s soc i a te d r ec e p t o r s ( t h e a d r e n er g i c
r e c e pt o r s) a p p e a r s t o b e t h e m o s t p r o mi n e n t . O t h e r f a c t or s l i ke
t h y r o i d h o r mo n e s , a d e n o s i n e , H S L , P K A a n d U C P a l s o p l a y e s s e n t i a l
r o l e s i n t he r e g u l a t i o n o f f a t m o bi l i s a t i o n a n d t he r mo g e n e s i s , t h o u gh
i t w o u l d a p p e a r t h a t t he i r r o l e s a r e n ot a s p rominent and less diverse
a s t h o s e pl a y e d b y c a t e c h ol a m i n e s a n d t h e i r r e c e pt o r s .
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Chapter 1: Literature Review
1.3 THE THERMAL INSULATION OF NEW-BORN LAMBS.
N e w b o r n l a mbs a r e r e ma r k a b l y c a p a b l e o f r e s i s t i ng c o l d
t e mpe r a t u r e s i n dr y s t i l l ai r co n d i t i o ns . S t u d i e s ha v e s h o w n t h a t
n e w b o r n l a mbs c a n ma i n t a i n h o mot h e rm y a t t e m p e r a t ur e s a s l o w a s 5  C ( A l e x a n d e r , 1 9 6 1 ) . H o w e v e r , t he a mb i e n t t e mp e r a t u r e a t w h i c h
a l a mb c a n ma i n t a i n h o me o t h e r my i s r a i s e d i n t h e p r e s e n c e o r w i n d
a n d / o r r a i n . Wi n d d i s t u r bs t he a mo u n t o f a i r t r a pp e d i n t h e f l e e c e ,
w h i c h i s t h e c h i e f d e t e r mi n a n t o f t h e a m o u n t o f i n s u l a t i o n p r o v i d e d
b y t h e l a m b ’ s b i r t h c o a t ( Fi g u r e 5 ). Thus an increase in wind speed
f r o m 0 . 1 m/ s t o 2 m/ s c a n d e c r e a s e f l e e c e i ns u l a t i o n b y a s muc h a s
3 0 % (Mount & B row n, 1982; Syke s, 1982) . A we t bir thc oa t c a use d
b y r a i n o r t h e a mn i o t i c f l u i d s p r e s e nt a t b i r t h c a n c a u s e a 5 1 %
i n c r e a s e i n a l a mbs me t a b o l i c r a t e a t a n a mb i e n t t e mpe r a t u r e o f 1 5 C
( A n d r e w s & M e r c e r , 1 9 8 5 ) . A s a c o n s e qu e n c e a we t f l e e c e c o mbi n e d
w i t h t h e chi l l i n g e ffe c t s o f w i n d c a n b e d i s a s t r o u s. O b s t a n d E l l i s
( 1 9 77) found that up to 90% of Me r i n o a n d C o r r i e d a l e l a m b s d i e a t
a n a mb i e n t t e mpe r a t u r e o f 8 - 1 2C w h e n w i n d s p e e d s e x c e e d 1 8 k m/ h
a n d mor e t h a n 1 . 5 m m o f r a i n f a l l s d u r i n g t h e f i r s t s i x h o u r s a f t e r
birth.
F i g u r e 5 : T h e s t r u c t u r a l c h a ng e s i n w o o l a s t h e w i n d v e l o c i t y
i n c r e a s e s ( A me s & I n s l e y , 1 9 7 5 ) .
T h e l e n g t h a n d t y p e o f a l a m b ’ s c o a t a t t h e t i me o f b i r t h a l s o
h a s a l a r g e i n f l u e n c e o n t h e n e w b o rn l a m b ’ s a b i l i t y t o w i t h s t a n d
c o l d e x p o s u r e . A l e x a n d e r ( 1 96 1 ) f o u n d t h a t a t a n a mb i e n t
t e mpe r a t u r e o f 0C , l a mb s w i t h f i n e b i r t h c o a t s w e r e r e q u i r e d t o
p r o d u c e 3 0 % mo r e h e a t t o ma i n t a i n h o me o t h e r my t h a n l a m b s w i t h
h a i r y b i r t h c o a t s . He a t c a n a l s o b e conserved in the newborn lamb by
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Chapter 1: Literature Review
t h e p i l o e r e c t i o n o f t h e h a i r s t h a t make up the birthcoat. This process
along with the reduction in blood flow to peripheral areas of the
b o d y ( v a s o c o n s t r i c t i o n ) i n r e s p o n s e t o c old e xposur e , ha s be e n f oun d
t o b e s t i m u l a t e d b y t he p r e se nc e o f c a t ec h o l a mi n e s i n a s i mi l a r w a y
t o w h i c h b r o w n a d i p o s e t i ss ue i s a ct i v at e d ( T h o m a s & P a l mi t er ,
1 9 9 7 ) . P e r i p h e r a l v a s o c o n s t r i c t i o n conserves heat by redirecting
b l o o d a w a y f r o m a r e a s o f t h e b o d y l i k e t h e f a c e a n d e a r s fr o m w h i c h
h e a t i s mo s t e a si l y l o s t .
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Chapter 1: Literature Review
1.4 PHYSICAL FACTORS AFFECTING COLD TOLERANCE IN LAMBS
L a mb s w i t h b i r t h w e i g h t s o u t s i de o f a n o p t i mu m r a n g e ( w h i c h
varies depending on the breed) suffer f r o m mor e d e a t h s f r o m e i t h e r
e x p o s u r e a n d / o r d y s t o c i a ( F i g u r e 6 - Pu r s e r & Y o u n g , 1 9 6 4 ; H i g h t &
J u r y , 1 9 7 0 ; S y k e s e t a l . , 1 9 7 6 ) . A t l o w b i r t h w e i g h t s , l a mb mo r t a l i t y
d u e t o e xp o s u r e i nc r e a se s b e c a u s e t he a b i l i t y o f a l a mb t o p r o d u c e
heat is proportional to its body we ight a nd the la mb’ s c a pa c ity to
l o s e h e a t i s p r o p o r t i o n a l t o s u r fa c e a r e a . U n f o r t u n a t e l y , s m a l l l a mbs
h a v e a g r e a t e r s u r f a c e a r e a per kilogram bodywe i ght (0.12 m - 2 / k g f o r
a 1 k g l a m b ) t h a n l a r g e r l a mb s ( 0 . 0 7 m - 2 / k g f o r a 4 k g l a mb )
( A l e x a n d e r , 1 9 7 4 ) . O t h e r f a c t o r s t ha t c ontr ibute to the e nha nc e d
s u s c e p t i b i l i t y o f l i ght l a mbs t o c o l d e xp o s u r e , i nc l u d e l o we r l e ve l s
of therma l insulation (wool and fat c o v e r ) , p l a s m a t h y r o i d h o r mo n e s
( V e r mor e l & V e r n e t , 1 9 8 5 ) a n d s mal l e r o r g a n s ( Al e x a n d e r , 1 9 8 4 ) .
Figure 6: Mortality of single (plain columns) and twin merino lambs
(shaded columns) relative to birth weight (Stevens et al.1982).
In contrast, at high bir th we ights , t h e i n c i d e n c e o f l a mb d e a t h
f r o m d y s t o c i a i nc r e a s e s ( S c a l e s e t al . , 1 9 8 6 ) . D y s t o c i a o c c u r s w h e n
t h e p a s s a g e o f t h e l a mb t h r o u g h t h e p e l v i s o f t h e e w e i s r e s t r i c t e d
d u r i n g t h e b i r t h i n g p r o c e s s a n d d e a t h c a n r e sult e ithe r dur ing or
i m me d i a t e l y a f t e r b i r t h ( D u f f e t a l . , 19 8 2 ) . I n a d d i t i o n , no n - f a t a l
d y stocia is thought to pr e dispose l a mb s t o d e a t h b y e x p o s u r e ( F i g u r e
2 ) . H a u g h e y ( 1 9 8 4 ) f o u n d t h a t l a mb mo r t a l i t y f r o m e x p o s u r e
i n c r e a s e d f r o m 1 7 % i n l a mbs w i t h n o b i r t h i n j u r i e s f r o m d y s t o c i a t o
2 1 % in lam bs that exhib ite d signs of birth injury. However, Duff e t
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Chapter 1: Literature Review
a l . ( 1 9 8 2 ) f o u n d t h a t s u c k l e d l a mb s wi t h s i g n s o f b i r t h i n j u r y h a d
t h e s a me m o r t a l i t y r a t e s a s suc k l e d l a m b s w i t h n o b i r t h i n j u r i e s .
T h i s w o u l d a p p e a r t o s u g g e s t t h a t n o n fa t a l d y s t o c i a a f f e c t s t h e
a p p e t i t e an d / o r v i go u r o f t h e l a mb , r e d u c i n g i t s d e s i r e/ a bil i t y t o s e ek
food and thus predisposing it to death by exposure. Dystocia can
a l s o c a u s e h y p o x i a w h i c h i n t u r n can result in the reduction of
t h y r o i d h o r mo n e p r o d u c t i o n , l e s s b l ood flow to muscles (thus
i n h i b i t i n g s h i v e ri n g) a n d t h e inhibition of BAT me tabolism
( V e r mor e l & V e r n e t , 1 9 8 5 ) .
T h e i n f l u e n c e o f b i r t h r a n k ( F i g u r e 6 ) , t h e a g e of t h e e w e a t
l a mbi n g a n d l a mb g e n d e r u p on l a mb m o r t al i t y i s p a r t i a l l y e x p l a i ne d
by variation in birth weight caused by these factors (Hight & Jury,
1 9 7 0 ; S mi t h , 1 9 7 7 ; N i c o l l et al., 1 9 9 9 ) . P r e v i o u s s t u d i e s h a v e
e s t a b l i s h e d t h a t ma l e l a mbs a r e b o r n o n a v e r a g e 0 . 2 0 t o 0 . 2 3 k g
h e a v i e r t h a n f e ma l e s ( P u r s e r and Young, 1964; Hight and Jury,
1 9 7 0; S mi t h, 1977; Wolff e t a l., 1987) a nd tha t the a ve r a ge bir th
weight of twins and triplets is 75% and 62% of the birth weight of
single lambs (Hinch et al., 1985). As a consequence, females and
m u l t i p l e bor n l a mbs g e n e r al l y h a v e h i ghe r mor t a l i t y r a t e s d u e t o
c o l d e x p o s u r e ( H i g h t & J u r y , 1 9 7 0 ; N i c o l l et al., 1 9 9 9 ) . T h e a v e r a g e
l i t t e r s i z e ( b i rt h r a nk ) a l s o i nc re a se s w i t h t he a ge o f t h e ewe a t
l a mbi n g ( P u r s e r & Y o u n g , 1 9 6 4 ) . B o t h b i r t h r a n k a n d e w e a g e a l s o
h a v e a s i g n i f i c a n t i n f l u e n c e o n t he mo t h e r i n g a bi l i t y o f t he e w e
( P a r k e r e t a l . , 1 9 8 7 ) . T h i s i s d e mo n s t r a t e d i n mul t i p l e l i t t e r s w h e r e
t h e d i l u t i o n e f f e c t o c c u r s a nd s in g l e l a mbs a r e a b l e t o c on s u me o n
a v e r a g e 35% mor e c o l u s t r u m t h a n t w i n a n d 6 0 % m o r e t h a n t r i pl e t s
( K a l l w e i t e t a l . , 1 9 85 ) . T h e c ol d r e si s t anc e o f mu l t i pl e b o rn l a mbs i s
f u r t h e r c o m p r o mi s e d b y p r e m a t u r i ty , l o w e r t h y r o i d h o r mo n e l e v e l s
a n d mor e d i f f i c u l t l a mbi n g s ( V e r mor e l & V e r n e t , 1 9 8 5 ; W o l l n e y et
a l . , 1 9 8 5 ) . P a r i t y ( n u mb e r o f l a mb i n g s ) o f t h e e w e w a s i d e n t i f i e d b y
P urser and Y oung (1959 ) a s ha vi ng a la r ge r inf lue nc e on la mb
mortality than ewe age.
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Chapter 1: Literature Review
1.5 THE GENETIC COMPONENTS OF COLD TOLERANCE.
R a p i d g e n e t i c i mp r o v e me n t i n a n y t r a i t i s d e p e n d e n t o n f i v e
f a c t o r s : a s h o r t g e ne r a t i o n i nt e r v a l , h i g h a c c u r a c y o f s e l e c t i o n , hi gh
s e l e c t i o n i n t e n s i t y , a l ar g e a m o u n t o f v a r i a t i o n p r e s e n t i n t h e t r a i t
from which to select from and a high heritability. Fortunately, cold
t o l er a n c e i s me a s u r e d w e l l b efo r e t h e an i ma l b e c o me s s e x u a l l y
ma t u r e a n d c o n s e q u e n t l y h a s n o ef f e c t u p o n t h e g e n e ration interval.
A c c u r a t el y s e l e ct i ng fo r n e o n a t a l l a mb c o l d t ol e ra n c e c a n b e
d i fficult ow ing to the vaga r ie s of t h e w e a t h e r a n d t h e u n c e r t a i n t y
o v e r t h e a u t o p s y me t h o d s c o m m o n l y u s e d . T h e u s e o f p r o g r e s s i v e l y
c o o l e d w a t e r b a t h s a p p e a r s t o o v e r c o me t h e s e d e fi c i e nc i e s b u t
unfortunately it is not suitable fo r w i de s p r e a d us e i n t he f i e l d . T h e
intensity of selection in any selective breeding program is entirely
d e p e n d a n t ( a s s u mi n g mi n i ma l n a t ur a l s e l e c t i o n ) u p o n t h e e mp h a s i s
p l a c e d u po n n e o n a t a l c o l d t o l e r a n c e c om p a r e d t o o t h e r t r ait s i n t h e
b r e e d i n g p r o g r a m m e . B y c o m p a r i s o n , t h e a mo u n t o f g e n e t i c
v a r i at i o n i s a l mos t e n t i r e l y i n fl u e n c e d b y n a t u r a l f a c t o r s l i k e t h e
a mo u n t o f n a t u r a l v a r i a t i o n p r e se n t i n t h e p o p u l a t i o n , t h e a m o u n t
n a t u r al s el e c t i o n ( oc c u r ri n g a s a r e s u l t o f p r e vi ou s ‘ b a d ’ w e a t h e r )
a n d i n d i r e c t s e l e c t i o n ( o c c u r r i n g t hr o u g h g e n e t i c c o r r e l a t i o n s w i t h
other traits).
I t h a s l o n g b e e n a c k n o w l e d g e d t h a t v a r i a t i o n e x i s t e d b e t we e n
b r e e d s i n t h e i r a b i l i t y t o withstand cold e x p o s u r e ( S y k e s e t a l . ,
1 9 7 6 ; S a ms o n & S l e e , 1 9 8 1 ; Wol f f e t a l . , 1987; Donnelly, 1983).
More recently, Slee (198 5) ha s a lso b e e n a b l e t o e s t a b l i s h v a r i a t i o n
in neonatal cold tolerance between lines of sheep within a flock
( F i g u r e 7), d e s p i t e t h e h e r i t a bi l i t y of la mb sur viva l be ing ve r y low
( 0 . 0 4 – L o p e z - V i l l a l o b o s & G a r r i ck, 1999). The heritability of
s e l e c t i o n f o r e n h a n c e d r e s i s t a n c e t o c o l d e x p o s u r e w a s e s t i ma t e d a s
0 . 2 7 , a l t h o u g h t h e o b s e r v e d t h e h e r i t a bi l i t y o f t h e l i n e s e l e c t e d f o r
r e d u c e d c o l d t o l e r a n c e w a s o n l y 0 . 0 1 , r e s u l t i n g i n v e r y little change
i n c o l d r es i s t a nc e of t h i s l i ne ( S l e e & S t o t t , 1 9 86 ) .
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Chapter 1: Literature Review
F i g u r e 7 : T h e r e s po n s e t o t hr e e y e a r s of upwa r d a nd downwa rd
s e l e c t i o n f o r c o l d r e s i s t a n c e , u s in g a w a t e r b a t h t e s t , i n n e w b o r n
l a mb s o f t h e S c o t t i sh B l a c k f a c e b r e e d ( S l e e , 1 9 85 ) .
Due the highly asymmetrical response to selection for and
a g a i n st c ol d r e si s t a n c e , t h e a c c u r a c y of t h e s e r e s u l t s h a ve b e e n
q u estioned. T his can be e xpla ine d b y t h e d i f f i c u l t y i n c a l c u l a t i n g t h e
heritability of low cold resistanc e i n a s t u d y l i k e t h i s . T h e a v e r a g e
c o l d r e si st a n c e me a s u r e d i n this breeding program was
a p p r o x i ma t e l y 3 0 mi n u t e s . T h e l o w e s t r e c or d e d c o l d r es i s t a n c e w a s
1 7 mi n u t e s , w h i c h i s c l o s e t o t h e a v e r a g e w h e n c o mpa r e d w i t h t h e
h i g h e s t c o l d r e s i s t a n c e ( 8 2 m i n u t e s) . C o n s e q u e n t l y t h e r e w a s v e r y
l i t t l e s c o pe for s e l ec t i o n b el ow t h e a v er a g e c o mpa r e d w i t h s e l e ct i o n
in the upward direction. The reason for the lack of phenotypic
v a r i a nc e b e l o w t h e me a n mi g h t a l s o b e e x p l a i n e d b y n a t u r a l
s e l e c t i o n . T h a t i s t h a t a n y l a m b s t o o f a r b e l o w t h e a v e r a ge a r e
n a t u r al l y u n l i k el y t o s u r v i v e , t h e r e f o r e t h e y a r e u n a b l e t o p a s s t h e i r
‘ l o w c o l d r e s i s t a n c e ’ g e n e ( s ) o n t o ma i n t a i n a l a r g e a mo u n t s o f
genetic variation below the mean.
15
Chapter 1: Literature Review
F r o m t h e r e s u l t s o f b r e e d i n g p r o g r a ms l i k e t h a t s h o w n i n f i g u r e
7 , g e n e t i c v a r i at i o n i n c o l d t o l e r an c e h a s b e e n s e p a r a t e d i n t o t h r e e
distinct groups (Slee, 1985):
1. P h y s i c a l ( ma i n l y i n s u l a t i v e ) c h a r a c t e r i s t i c s : b o d y w e i g h t ,
birthcoat type and skin thickness.
2. P h y s i o l o g i c a l a n d b i o c h e mi c a l c h a r a c t e r i s t i c s: Th y r o i d
h o r mo n e ( T 3 & T 4 ) l e v e l s , p e a k me t a b o l i c r a t e c a p a c i t y ,
b r o w n a d i p o s e t i ss ue a c t i v i t y a n d c o l d r e s i s t a n c e .
3. B e h a v i o u r a l c h a r a c t e r i st i c s : e ar ly vigour , suc kling dr ive ,
ma t e r n a l c a r e a n d ma t e r n a l b o n d i n g .
B r e e d i n g f o r o n e o r mor e o f t h e se t r a i t s c a n b e c o mp l i c a t e d b y
i n t er a c t i on s w i t h o t h e r t ra i t s . F o r e xa mple , in W e lsh Mounta in she ep
i t h a s b e e n f o u n d t h a t b o t h b i r t h w e i ght and birthcoat type are linked
g e n e t i c a l l y a n d i n s o me b r e e d s , f i n e b i r t h c o a t s ( l o w i n s u l a t i v e
v a lue) appear to be linked with b e t t e r a d u l t f l e e c e s a n d g r o w t h
( P u r s e r & K a r a m, 1 9 6 7 ) . S t o t t and Sle e ( 1987) a lso f ound tha t
s e l e c t i o n f o r e n h a n c e d c o l d t o l e r a nc e w a s g e n e t i c a l l y a s soc i a t e d
w i t h i n cr ea s e s i n s ki n t h i c k n es s , c o a t we i g h t p e r u n i t a r e a o f s k i n ,
total body insulation and the persistence of an enhanced metabolic
r a t e w h e n t h e l a mb s w e r e e x p o s e d t o c o l d . P h e n o t y p i c c o r r e l a t i o n s
w e r e a l s o d e t e c t e d be t w e e n c ol d t o l e r a nc e a n d i n c r e a s e d bi r t h
w e i g h t , c o a t d e p t h a n d h i g h e r l e v e l s o f c o l d i n d u c e d me t a b o l i c r a t e .
T h e h e r i t a b i l i t y o f s o me o f t h e se traits has been quantified and
is shown in table 1 (over page).
16
Chapter 1: Literature Review
Table 1: H eritability estima te s f or gen e t i c c o mp o n e n t s o f l a mb
c o l d t ol e ra n c e
Trait
Heritability (H 2 )
Breed(s)
Reference
0.2 - 0.3
Mer ino
McGuirk e t a l. , 1982
D ystocia
0.13
V ar ious
Smith , 1977
Matern al Beh av iour
0.15
V ar ious
Park er e t a l. , 1982
0.25 - 0.6
Mer ino
Gr egor y, 1982
Bir th w e ight
Sk in th ickne s s ( a t
15-16 mo n th s o ld)
Bir th co at le ng th
0.38
Mer ino crossbred s
W olff et al., 1987
Bir th co at typ e
0.66
Mer ino
Pon zon i e t a l. , 1995
0.75
Mu ltip le b irths*
0.102 – 0.139
Gr egor y, 1982
Ramb ou illet
Sh elton & Men z ies,
1970
L a mb surv iv a l to 7
0.02 – 0.04
Mer ino
McGuirk e t a l., 1982
0.27
S co t t ish B lac k f a c e
Slee & Sto tt, 1986
0.36
Mer ino crossbred s
W olff et al., 1987
d a ys
C o ld r es i s t an ce
(upw ard, measur ed in
a w a ter ba th).
* S e l ec t io n a g a in s t th i s t r a i t ( in o r d e r to enh an ce l a mb sur v i v a l) d ef ea ts the
ov erall purpo se o f th is research and f ar min g ( to r a ise la mb produ ction).
I n b r e e d i n g h a s b e e n f o u n d t o l e a d to an increased rate of lamb
mortality in field trials (Galal, 1981). However, further
i n v e s t i g a t i o n o f t h i s h a s s h o w n t ha t t he e f f e c t s o f h e t e r o si s a n d
i n b r e e di ng u p o n l a m b mor t a l i t y a r e r e l a t i v e l y sma l l a n d a p p e a r t o
a c t p r i ma r i l y t h r o u g h t h e g e n e s o f t h e l a m b ( L o p e z - V i l l a l o b o s &
Garrick, 1999).
17
Chapter 1: Literature Review
1.6 The Role of the 3 Adrenergic Receptor Gene in Cold
Tolerance
A s described in the pr e vious s e c t i o n s , c o l d t ol e r a n c e i s a n
e x t r e me l y c o mp l e x t r ai t t ha t i s i n f l u e n c e d b y a l a r g e n u mb e r o f
p h y s i c a l , p h y s i o l o g i c a l a n d e n d o c r i n e fa c t o r s . T h i s s u g g e s t s t h a t
c o l d t ol e ra n c e i s u nd e r t h e c on t r o l o f m u l t i pl e g en e s a n d t ha t g e n et i c
i mp r o v e m e n t i n r e s p o n s e t o s e l e c t i on f or this tr a it would be slow
(Alexander, 1984). Despite this, Slee (1985) was able to
s u c c e s s f u l l y e s t a b l i s h t w o l i ne s o f S c o t t i s h B l ac kfa c e s h e ep w i t h
d i v e r g e n t c o l d r e s i s t a n c e ( F i gu r e 7 ) .
I n t h e l ow c o l d r e si s t a nc e line, the progeny of one sire
e x h i b i t e d a n u n u s u a l r e a c t i o n t o n o r a d r e n a l i n e . Nor ma l l y t h e
e x o g e n o u s i n j e c t i o n o f n o r a d r e n aline causes an increase in
t h e r mo g e n e s i s o f a p p r o x i ma t e l y 200-250% in newborn lambs
( A l e x a n d e r & Wi l l i a ms , 1 9 6 8 ) , b u t i n t hi s s i r e l i ne , t h e p r oge n y
e x h i b i t e d n o t h e r mo g e n i c r e s p o n s e ( S l e e e t a l . , 1987) . Fur the r
ma t i n g s e s t a b l i s h e d t h a t t h i s e ffe c t w a s d u e t o a s i n g l e g e n e a n d t h a t
t h i s g e n e w a s i n h e r i t e d i n a d o mi n a n t , M e n d e l i a n f a s h i o n .
P h y s i o l o gi c a l s t u d i e s a l s o e st ab l i s h e d t h a t t h e B A T a n d t h e
mi t o c h o n d r i a w i t h i n t h e B A T w e r e s t i l l p r e s e n t i n n o r ma l n u mbe r s i n
t h e n o n - r e s p o n d e r l a mb s a n d t h a t t h i s genetic defect had no affect on
b i r t h w e i g h t , g r o w t h o r s u r v i va l , t h o u g h s u r v i v a l u n d e r f i e l d
c o n d i t i o n s w e r e n o t me a s u r e d . T h e se r e s u l t s l e a d t o t h e c o n c l u s i o n
t h a t a s i n g l e ma j o r g e n e a f f e ct i n g t h e r m o g e n e s i s e x i s t s i n t h e
c a t e c h o l a mi n e s t i m u l a t i o n p a t h w a y i n s h e e p ( S i mp s o n & S l e e , 1 9 8 8 ;
Slee & Simpson, 1991).
T h e  3 a dr e n e r gi c r e c e p t or ( A R ) i s a k e y c o mpo n e n t i n t he
c a t e c h o l a mi n e s t i m u l a t i o n o f B A T ( s e e F i g u r e 3 ) a n d i t h a s b e e n
p r o p o s e d t h e g e n e c o d i n g i t i s a l i k e l y c a n d i d a t e t o b e a ma j o r g e n e
i n f l u e n c i ng n e o n a t al c o l d t o l e r a n c e . T h i s r e c e pt o r i s p a r t o f t h e G p r o tein coupled receptor supe r f a mi l y t h a t i s r e s p o n s i b l e for t h e
me d i a t i o n o f t h e s y m p a t h e t i c c o n t r ol of va r ious me ta bolic pr oc e sses
18
Chapter 1: Literature Review
i n t h e di ge s t i ve t rac t , s k el e t al mu s c l e a n d a d i p o se t i s s ue (E mo r i n e et
a l . , 1989). It is in adipo se tissue tha t the  3 AR is found
p r e d o mi n a t e l y a n d w h e r e t h e y a r e t h o ug h t t o p l ay a ma j o r r o l e i n t he
r e g ulation of lipolysis (f a t use f o r e n e r g y ) a n d t h e r mo g e n e s i s .
T h e h y p o t h e s i s t h a t t h e  3 A R g e n e i s a ma j o r g e n e a f f e c t i n g
t h e e f f i c i e n c y o f t h e r mo g e n e s i s i n s he e p i s s u p po r t e d b y t h e r e c e pt o r
being recognised as having the unique ability to resist
desensitisation that occurs in response to prolonged exposure to
c a t e c h ol a mi n e s l i k e n o r a d r e n a l i n e ( S us u l i c e t a l . , 1 9 9 5 ; B o u v i e r ,
2000). This ability is unique to the 3 AR and does not occur in
e i t h er t h e  1 or  2 ARs (Strosberg, 1997). Thi s f i n d i n g h a s l e a d t o
t h e h y p o t h e s i s t h a t t h e p ri ma r y f u n c t i o n o f t h e  3 A R ma y b e t o
ma i n t a i n s i g n a l l i n g d u r i n g p e r i o d s o f s u s t a i n e d s y mp a t h e t i c
s t i mu l a t i on , s u c h a s t h a t w h i ch occurs in BAT during periods of
chronic cold exposure (Susulic et al., 1995; Bouvier, 2000).
T h e r e a r e s e v e r a l l i n e s o f e v i d e n c e f r om o t h e r sp e c i e s t h at
s u p p o r t t h e h y p o t h e s i s t h a t v a r i a t i o n i n t h e  3 A R g e n e ma y b e
linked with both neonatal lamb cold tolerance and reduced fat levels.
T h e g e n e h a s b e e n i d e n t i f i e d a nd sequenced from a number of
s p e c i e s , i n c l u d i n g h u ma n s , mi c e , r a ts, c a ttle , guine a pigs, monke ys ,
d o g s a n d h a ms t e r ( S t r o s b e r g & G e r h a r d t , 2 0 0 0 ) . I n h u ma n s a s i n g l e
a mi n o a c i d s u b s t i t u t i o n ( t h e t r p 6 4 a r g mu t a t i o n ) i n t h e  3 AR g e n e
w hich occurs in 10-50% of the popula tion ha s be e n f ound to be
a ss ociated w ith rapid w e ight ga i n , l o w me t a b o l i c r a t e a n d i m p r o v e d
fe r t i l i t y (Su s u l i c et al., 1 9 9 5 ; A r n e r & L o n n q v i s t , 2 0 0 0 ) . I t i s
i n t er e s t i ng t o n o t e t h a t t h i s m u t at i o n a c t u a l l y r e s t o r e s t h e a r g i n i n e
f o u n d i n m o s t a n i m a l s a t p o s i t i o n 6 4 i n t h e  3 AR gene, in the place
o f t h e t r y p t o p h a n n o r ma l l y f o u n d i n h u ma n s ( S t r o s b e r g , 1 9 9 7 ;
S t r o s b e r g & G e r h a r d t , 2 0 0 0 ) . T r a n s g e n i c mi c e w i t h t h e  3 AR gene
“ k n o c k e d o u t ” h a v e a n i mp a i r e d t h e r mo g e n i c r e s p o n s e t o c o l d a n d
i n c r e a s e d l e v e l s o f b o d y f a t ( S u s u l i c et al., 1 9 9 5 ) . Whi l e t h e e f f e c t s
o f t h e  3 A R gene knockout in mi c e a r e r e l a t i v e l y mi l d , t h e r e i s
19
Chapter 1: Literature Review
e v i d e n c e t h a t t hi s i s a r e s u l t of c o mpe n s a t o r y a c t i v i t y f r o m  1 a n d  2
A R s ( S u s u l i c et al., 1 9 9 5 ) .
Ani mal models bred to study gen e t i c obe s i t y a n d d i a b e t e s ( t h e
o b /ob and db/db mi ce re spe c tive ly) ha ve long be e n a c knowle dge d a s
b e i n g c o l d i n t o l e r a n t ( H i m m s - Ha g e n , 2 0 0 0 ) . F u r t h e r s t u d i e s h a v e
r e v e a l e d t h a t b o t h t h e n u mb e r a n d s i g na l l i n g e f f i c a c y o f t he  3 ARs
i n o b / o b mi c e i s d e c r e a se d , r e i n f o r c i n g t h e l i n k b e t w e e n obe s i t y a n d
i n a d e q u a t e c o l d t o l e r a n c e ( B o u v ie r , 2 0 0 0 ) . H o w e v e r i t i s d o u b t f u l
w h e t h e r t h e r e i s a l i n k b e t w ee n t h e  3 A R a n d d i a b e t e s , a s  3 ARs
have not been detected on the insulin secreting pancreatic  cells.
D e s p i t e t h i s , t h e r e i s e v i d e n c e t o s u g g e s t t h a t  3 A R s ma y s t i mu l a t e
w h i t e a d i p o s e t i ss ue t o s i g nal t h e p a ncr e a t i c  ce l l s t o i n du c e l ar g e
i n c r ea s e s i n i n s ul i n s e c r et i o n ( L o w e l l e t a l . , 2000).
R e c e n t l y , i t h a s be e n f o u n d t h a t v a r i a t i o n i n t h e f a t l e v e l of
l a mbs a p p e a r s t o b e c o r r e l ated with variation in the  3 AR gene
( F o r r e st e t a l . , 2 0 0 1 ) . F u r t h e r mo r e t h e c o r r e l at i on b e t w e e n t h i s t r ai t
a n d n e o n a t a l c ol d t ol e r a nc e a pp e a r s to be positive, so that genetic
progress in one will also lead to progress in the other. This finding
i s o f ma j o r i mp o r t a n c e t o t h e l a mb i n d u s t r y , a s l a mb i s p e r c e i v e d b y
c o n s u me r s a s h a v i n g t o o mu c h f a t a n d t h e r e f o r e l e s s v a l u a b l e
(Hammon d e t a l . , 1992). The inve stiga tion into the r ole of the  3 AR
i n l e a n mus c l e g rowt h i s p o t e n t i al l y ext r e me l y v a l u a b l e t o t h e s h e ep
industry.
G e n e t i c va r i at i o n be t w e e n t wo l i n e s o f S c o t t i s h B l a c k fa c e s h e e p
breed for high and low adult back fat, has been observed in neonatal
l a mb b e h a v i o u r ( D w y e r e t a l . 2 0 0 1 ) . L a m b s f r o m e w e s s e l e c t e d f o r
reduced levels of back fat were found to stand, suckle and play
e a r l i e r t ha n l a mbs f r o m e w e s s e l e c t e d f or inc r e a se d le ve ls of ba c k
f a t . T h e h i g h e r r a t e o f s u c k l i n g i n l a m b s i n t h e l e a n l i ne pe r s i st e d
f o r 3 d a y s , t h e a p p r o x i ma t e l e n g t h o f t i me t h a t B A T l a s t s ( u n d e r
good weather conditions) in starving lambs (Slee, 1979). These
20
Chapter 1: Literature Review
f i n d i n g s f i t i n w i t h t h e h y p o t h e s i s t h a t p o l y mo r p h i s m i n t h e g e n e
c o d i n g t h e  3 A R i s l i n k e d wi t h b o t h c o l d t o l e r a n c e a n d r e d u c e d f a t
l e v e l s . L a m b s f r o m t h e l i n e s e l e c t e d f o r l e a n ne s s a p p e a r e d t o b e a b l e
t o mo b i l i s e t h e i r b ro w n a d i p o s e t i ss ue fa s t e r , a l l ow i n g t h em t o s t a nd
a n d s u c k l e e a r l i e r t h a n t h e i r c o u n te r p a r t s f r o m t h e f a t l i n e . T h i s
study was carried out indoors and c o n s e q u e n t l y n o d i f f e r e n c e i n
l a mb mo r t a l i t y d u e t o c o l d e x p o s u r e w a s o b s e r v e d .
Fat is not only considered undesirable by the consumer but the
production of waste fat is also inefficient as it utilises energy that
would be able to be used for muscle growth (Cameron and Bracken
1992). With the development of in vivo fat measurement techniques
like ultrasound scanning, the inclusion of fat depth into selection
criteria has increased, particularly in terminal sire breeds. In terminal
sire breeds of sheep, selection can be focussed on production traits in a
small group of sheep that have a large influence on total lamb
production (Simm, 1987; Cameron & Bracken, 1992). As a result of
selection for these traits (and improved management), the average
weight of lambs slaughtered in New Zealand over the period of 198686 to 1999-2000, has increased from 13.2kg to 16.5kg (an increase of
25% - Meat and Wool Economic Service of New Zealand, cited in
Davison 2000).
I f t h e  3 AR gene is confirmed a s a m a j o r g e ne t h a t
s i g n i f i c a n t l y a f f e c t s n e o n a t a l l a mb c ol d t o l e r a n c e a n d / o r l e a n n e s s i n
s h e e p , i t ’ s p o l y mo r p h i c n a t u r e ( F o r r e s t e t a l . , 2 00 1 ) w i l l al l o w i t ’ s
u s e a s a ge n e t i c ma r k e r f o r t h e s e t r a i t s . T h i s w i l l p r o vi d e a l a r ge
n u mbe r o f a d v a n t a ge s t o t he f a r me r b e c a u s e t h e ge n e t i c i m p r o v e me n t
o f l a mb v i a b i l i t y s h o u l d b e p e r ma ne n t a n d c h e a pe r t o a c h i e v e t h a n
i mp r o v i n g s h e l t e r a n d / o r p r o v i d i n g mo r e i n t e n s i v e s h e p h e r d i n g
( S lee, 1985). A lso by using the  3 A R g e n e a s a g e n e t i c ma r k e r , t h e
i d e ntification of genetic a lly supe r i o r b r e e d i n g a n i ma l s s h o u l d b e
m o r e a c c ur a t e t h a n p r e v i o u sl y a c h i e v e d u s i n g o t h e r s e l e c t i o n
techniques.
21
Chapter 1: Literature Review
1.7 SUMMARY.
A h i g h l e v e l o f l a m b mo r t a l i t y i s h i g hl y d e t ri me n t a l t o t h e
p r o f i t a b i l i t y a n d s u c c e s s o f a n y s h e e p f a r mi n g e n t e r p r i s e . H o w e v e r
o w i n g t o t h e e x t re m e l y l o w he r i t a b i l i t y o f l a mb s u r v i v al , se l e ct i o n
f o r c o mp o n e n t s o f l a mb s u r v i v a l wi t h h i g h h e r i t a b i l i t i e s , l i k e c o l d
t o l e r a n c e i s p r e f e r a b l e . M u c h r e s e a r c h h a s b e e n c a r r i e d o ut
i n v e s t i g a t i n g t h e v a r i o u s b i o c h emi c a l , p h y s i o l o g i c a l a n d g e n e t i c
e f f e c t s i n f l u e n c i n g n e o n a t a l l a mb c ol d t o l er a n c e . T h e s e s t ud i e s h a v e
l e a d t o o u r h y p o t h e s i s t ha t t h e g e n e c o d i n g t h e  3 A R ma y b e a
ma j o r g e n e t h a t s i gn i fi c a n t l y i n f l u e n c e s n e o n a t a l l a mb c o l d
t o l er a n c e a n d t h a t i t ma y b e a b l e t o b e u s e d a s a g e n e t i c m a r k e r f o r
c o l d t ol e ra n c e .
R e s e a r c h i n o t h e r spe c i e s a nd mor e r e c e n t l y i n s h e e p h a s a l s o
l i n k e d v a r i a t i o n i n t h e  3 AR ge ne with va r ying l e v e l s o f f a t c o v e r .
T h e f a t c o n t e n t o f l a mb c a r c a s s e s i s a n e x t r e me l y i mp o r t a n t
e c o n o mi c t r a i t i n b o t h d u a l p u r p o se a n d me a t b r e e d s o f s h e e p . A s a
c o n s e q u en c e i t i s ho p e d t h a t n o t o n l y w i l l s i g n i fi c a n t s i r e l i n e
v a r i a t i o n i n n e o n a t a l c o l d t o l e r a nc e w i l l b e e s t a b l i s h e d a n d l i n k e d t o
v a r i a t i o n i n t h e  3 AR gene, but also that si g ni fi c a n t va r i a t i o n i n t h e
fa t l e v e l s o f l a mbs w i l l b e l i n k e d t o va r i at i o n i n t h e s a me g e n e .
22
Chapter 2: Sire Line Variation in Neonatal
Lamb Cold Mortality
Introduction
N e o n a t a l l a mb mor t a l i t y r e pre s e n t s a l a r g e e c o no mi c l o s s t o t h e
New Zealand sheep industry with an average of fifteen percent of
a l l l a mb s b o r n d y i n g b e f o r e we a n i n g e a c h y e a r ( M c C u t c h e o n e t a l .
1 9 8 1 ) . Fift e e n p e r ce n t o f t h es e d e a t hs a r e o n a v er a g e at t rib u t e d t o
c o l d e x p os u r e ( Gumbrell & Saville, 1986), although this can rise to
9 0 % u n d e r e x t r e me w e a t h e r c o n di t i o ns ( O b s t & D a y , 1 9 6 8 ) . F r o m
t h e s e f i g ur e s , t h e t ot a l e c o n omi c l o s s t o t h e N e w Z e a l a n d she e p
i n d u s t r y c a u s e d b y n e o n a t a l l a mb m o r t a l i t y f r o m c o l d e x p o s u r e
e q u a l s a pp r o x i ma t e l y 4 0 mi l l i o n d o l l a rs p e r a n n um ( s e e a pp e n d i x 1 )
and this figure is conservative, as it does not account for the loss
of selection potential incurred by lambs not surviving until
selection or the loss of production from those affected at sublethal levels. The losses also pose a welfare problem and
therefore a risk to the industry, especially during severe cold
weather when media attention in New Zealand frequently focuses
on lamb deaths.
R e s e a r c h h a s d e mo n s t r a t e d t h a t g e n e t i c v a r i a t i on i n n e o n a t a l
l a mb c o l d t o l er a n c e e x i s t s n ot o n l y between but also within breeds
o f sheep (Slee, 1985; Wolf f e t a l . , 1987) . Stott a nd Sle e ( 1987)
e s t i ma t e d t h e h e r i t a b i l i t y o f l a mb c o l d t o l e r a n c e t o b e 0 . 2 7 i n a
flock of Scottish Blackface, while Wol ff e t a l . ( 1 9 8 7 ) e s t i ma t e d t h a t
i t w a s 0 . 3 6 i n a f l o c k o f N Z M er i n o c r o s s b r e e d s. T h e s e r es u l t s
suggest that breeding for improved cold tolerance could be used
to improve neonatal survival in sheep. However, these results
were obtained using laboratory-based techniques to assess cold
tolerance and while they are considered indicative of a lamb’s
ability to survive cold exposure in the field (Slee et al. 1980;
Slee 1985), they are not suitable for use by commercial breeders.
23
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
By comparison, this study used simple field techniques that are
readily available to breeders with minimal or no training, to
evaluate the extent to which sire-line (lines within each
flock/breed separated according to sire) variation in cold
tolerance occurs and how this could be used to improve lamb
survival in a practical, or ‘on-farm’ situation.
2.1 Flocks Investigated & Lambing Locations
1999. Two flocks were used in 1999, a Hampshire flock
(comprising 90 ewes and five sire groups) and a Borderdale flock
(comprising 170 ewes and four sire groups). Lambing started on
the 11th of August for the Hampshire flock and 24th of August
for the Borderdale flock.
The lambing of the Hampshire flock was carried out on a
farm 4.72 km north of Temuka. This lowland farm possesses
extensive shelter from the south in the form of an established
macrocarpa (Cupressus macrocarpa) hedge. The pasture in these
paddocks was relatively new (sown in 1995) and consisted of
perennial ryegrass (Lolium perenne), and clover (Trifolium
pratense (red) and Trifolium repens (white)). The soil is
Wakanui silt loam and the stocking rate during lambing did not
exceed 30 ewes per hectare, though this varied as newborn lambs
and their mothers were separated from the flock after lambing.
The Borderdale flock was lambed at the Lincoln University
Research Farm. The paddock used for lambing this flock was
flat, contained established perennial ryegrass and white clover
pasture and was sheltered from south-east and the south-west by
a variety of young deciduous trees. The soil type is Templeton
silt loam and the stocking rate during lambing was approximately
25 ewes per hectare.
24
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
2000. Five flocks were used in 2000, the Hampshire flock (100
ewes, four sire groups), the Borderdale (135 ewes, 2 sire
groups), a Merino flock (150 ewes, 3 sire groups) and the Meat
Quality Flock (420 ewes, six sire groups). The Meat Quality
flock was comprised of Coopworth ewes mated to three Merino
and three Dorset Down sires. Expected lambing dates were the
7th of August for the Merino flock, 24th of August for the
Hampshire flock, 30th of August for Meat Quality Flock and the
4th of September for the Borderdale flock.
The Hampshire Flock was lambed on the same paddocks used
in the 1999 trial at a stocking rate of 35 ewes per hectare; the
Borderdale and Meat Quality flocks were lambed at the Lincoln
University Ashley Dene farm and the Merino Flock was lambed
at the Lincoln University Research Farm. The Borderdale
lambing paddock at Ashley Dene was flat, had Templeton silt
loam soils and consisted of established perennial ryegrass and
white clover pasture. This paddock was sheltered from the northeast by young gum trees (Genus Eucalyptus), from the south by a
large ditch, in which the animals could huddle out of the wind
and there was also limited easterly shelter from a mature
macrocarpa hedge adjacent to the paddock.
The Meat Quality lambing paddock was also flat, had
Templeton silt loam soils and the pasture consisted of
established perennial ryegrass and white clover. This paddock
had a large sheltered area provided by an established Douglas Fir
(Pseudotsuga menziesii) hedge on the southern boundary. The
stocking rate in this flock during lambing was maintained at
approximately 15 ewes per hectare, where possible. The Merino
lambing paddocks were the same paddocks that were used to
lamb the Borderdale flock in the 1999 trial (at the Research
Farm). The stocking rate for the Merinos was approximately 20
ewes per hectare.
25
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
2.2 Methods
Field Observations at Birth
The ewes were identified either by large plastic ear or neck
tags and/or individual brass ear tags with the exception of the
Merino flock, which only had coloured plastic eartags signifying
their sire group. All lambs were weighed and tagged at birth
using brass ear tags. All brass tags stated the flock name, year of
birth and a unique identification number for each animal.
The lamb tag number, dam tag number, sex of the lamb, date
of birth, birth rank, and birth weight were all recorded at tagging
(within 12 hours of birth). The probable cause of death was
diagnosed for all dead lambs and the date of death was recorded.
From the ewe tag numbers, the age of the ewe (with the
exception of the Merino trial) and the sire group that the lamb
belonged to was identified.
Lamb Death from Cold Exposure Diagnosis
The diagnosis of lamb death due to cold exposure was based
upon field observations during lambing, using a technique
similar to that used by Purser and Young (1964). Dead lambs
were classified as having died from cold exposure if they died
within four days of birth and no other cause of death was
obvious, such as swollen heads (dystocia), membranes over nose
(suffocation), unbroken feet membranes (stillborn) and birth
defects (poor development or mummification). Lambs that were
revived by artificial warming were classified as having died
from cold exposure.
26
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
C l imate O b s e rv a tio n s
Daily weather data was collected from the Lincoln
University Weather Station at the Research Farm and 9.15 km
from Ashley Dene. The weather data collected for the trial at
Temuka was collected from the National Institute of Weather and
Atmosphere (N.I.W.A.) weather station at Timaru Airport (10.55
km from the trial location). Variables recorded included
precipitation (mm/day), average temperature (C) and the total
wind run per day (km/day). Missing data were replaced with
long-term mean values for the month by N.I.W.A.
Combined Weather Variable Calculation
T h e i mp a c t o f t h e cl i ma t i c c on d i t i o ns du r i n g t he n e o n a t al
p e riod w as represented by a single f i g ur e i n di c a t i n g t h e a ve r a g e r a t e
o f h e a t l os s ( H L ) pe r u n i t o f s u r f a c e a r e a b y a l a m b u n d e r g i v e n
w e a t h e r co n d i t i o ns . T h e p r e d i c t e d ra t e o f h e a t l os s for e i t he r t h e
d a y of birth or day of de a th ( if a p p l i c abl e ) w a s ca l c u l a t e d u s i n g t h e
following equation derived by Coronato (1999), from the work of
Mount and Brown (1982). The equation is:
H L = 4 0 . 3 8 – ( 2 . 1 2  T) + ( 5.84  W) + ( 0 . 7 3  P )
Whe r e : HL = The average predicted rate of heat loss per unit of
surface area by a lamb under given weather conditions.
Measured in Watts per square metre (W m - 2 ).
T
= A v e r a g e da i l y t e mp e r a t ur e . M e a s u r e d i n C e l s i us ( C) .
W = A v e r a g e da i l y w i n d s p e e d . M e a s u r e d i n me t r e s p e r
second (m s-1).
P
= T h e d a i l y p r e c i pi t a t i o n . M e a su r e d i n mi l l i me t r e s
(mm) .
27
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
S t a t i s t i cal A n a l ysi s
The strength of the univariate relationships between
potential predictors and lamb mortality due to cold exposure was
assessed using Chi-square tests (categorical variables) and Ttests (continuous variables). Given the strong potential for interrelationships among the predictors of lamb mortality, which
could lead to unstable parameter estimates in a multivariate
analysis, the inter-relationships between the predictor variables
was evaluated using Chi-square, 1-way ANOVA and correlation
tests. Predictor variables without strong inter-relationship(s) and
showing some association with lamb mortality due to cold
exposure were retained for subsequent analysis using logistic
regression, along with the most significant variable of any
related pairing. The Logistic Regression model used was:
Logit(mortality) = Mean +HL +BW + Sire 1
L o g i s t i c r e g r e s s i o n w a s u s e d t o c a lc u l at e s i r e l i ne v a r i a t i on i n
l a mb mo r t a l i t y d u e t o c o l d e xp o s u r e b e c a u s e i t c a n a c c o m m o d a t e a
b i n a r y d ep e n d e n t va r i a bl e (la mb c o l d d e a t h ) a nd mul t i p l e p r e d i ct o r
v a r i a bl e s t h a t ca n be e i t he r m e t ri c ( b i r t h w e i g h t , p r e d i c t e d r a t e o f
h e a t l o s s ) a n d n o n - me t r i c ( s i r e ) ( H a i r e t a l . , 1998). In SPSS
(Version 10.0, SPSS Incorporated, Chicago), the true accuracy of the
logistic regression models was calculated from the difference
between how accurately the model predicted lamb mortality from
cold exposure and the percentage of lambs born that did die from
cold exposure.
1
a breed/location/year variable was also introduced for the combined dataset analysis.
28
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
2.3 Results
O f t h e 1 6 9 2 l a mb s b o r n i n t h i s s t u d y ( 4 4 4 i n 1 9 9 9 a n d 1 2 4 8 i n
2000), a total of 22.5% died (all causes) which included an outbreak
of T o x o p l a s m a g o n d i i i n t w o o f t h e t r i a l s . T h i s o u t b r e a k w a s
detected when the a larger number of dry ewes and stillbirths
than usual was observed in the Hampshire trials in 1999 and
2000. The presence of T. gondii was confirmed by an
independent autopsy (M. Colson 2 pers. comm. 1999, see appendix
2) of some of the dead lambs. The affected trials were removed
from the analysis to prevent the effects of T. gondii from further
c o n f o u n d i n g t h e r e s u l t s . A s a c o n s e q u e n c e , t h e t o t al l a mb
m o r t a l i t y a c r o s s t h e r e ma i n i n g t r ials dropped to an average of
1 6 . 5 % o f a l l l a mbs b o r n .
Table 2: Total lamb mortality in each trial.
Hampshire
Borderdale
Meat Quality
Merino
Year
No. of Lambs Born
% Total Mortality
1999
2000
1999
2000
2000
2000
169
133
275
267
728
153
27
47
16
17
20
25
Effect of Climatic Conditions on Cold Induced Lamb Mortality
L a mb m o r t a l i t y d u e t o c o l d e xp o s u r e i n e a c h t r i al f o l l o w e d a
s i mi l a r t re n d t o t h e p r e d i ct e d r a t e o f he a t l os s i n t h e B o r de r d a l e
2000 (p=0.000), Meat Quality (p=0.002), and Merino trials (p=0.035
– Figure 8), but not in th e Bor d e r d a l e 1 9 9 9 t r i a l ( p = 0 . 2 3 0 – F i g u r e
9 ) e v e n w h e n t h e d a t a w e r e c or r e c t e d f o r t h e e f f e c t s o f s i r e a n d
b i r t h w e i g h t u s i n g l o g i s t i c r e g re s s i o n . T h e B o r d e r d a l e 1 9 9 9 t r i a l
was observed to have been exposed to considerably less severe
c l i ma t e co n d i t i o ns t h a n t h e ot h e r t r i a l s. A l l t ri a l s w i t h t h e e x c e p t i on
o f t h e M e r i n o ( p = 0 . 1 7 8 ) , e x h i b i t ed s i r e - l i n e v a r i a t i o n i n t h e
predicted rate of heat loss (p<0.001).
2
Aorangi Veterinary Services Limited, Geraldine
29
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
F i g u r e 8 : T h e a v e r a g e p r e di c t e d d a i l y h e a t l os s a n d t h e c ol d
m o r t a l i t y o n e a c h t r i a l d a y a t t h e L i n c oln s i t e i n 20 0 0 .
Figure 9: The average predicted daily heat loss and the cold
mortality on each trial day at the Lincoln site in 1999.
30
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
Effect of Lamb Birth Rank and Birth Weight on Cold
Induced Lamb Mortalit y
A s t h e n u m b e r o f l a m b s i n e ac h l i t t er (bi r t h r a n k) i n c re a s ed ,
t h e r e w a s a s i g n i f i c a n t i n c r e a s e i n t h e n u mbe r o f l a mbs d y i n g f r o m
c o l d e x p o s u r e i n t h e M e a t Qu a l i t y ( p = 0 . 0 0 5 ) a n d M e r i n o t r i a l s
( p = 0 . 0 1 0 - F i g u r e 1 0 ) b u t n o t i n e it h e r B o r d e r d a l e t r i a l ( 1 9 9 9 –
p=0.402, 2000 – p=0.056). Further analysis revealed that as the
n u mbe r o f l a mbs i n e a c h l i t t e r i nc r ea s e d, t h e b i r t h w e i g h t o f e a c h
i n d i v i d u a l l a mb d e c r e a s e d ( p < 0 . 0 0 1 ) .
F i g u r e 1 0 : T h e i n f l u e n c e o f b i r t h r a n k u p o n l a m b mo r t a l i t y d u e t o
cold exposure. Lamb death percentages that are
s i g n i f i c a n t l y d i f f e r e n t ( p <0 . 05 ) a r e r e pr e s e n t e d by
d i f f e r e n t a l p h a b e t i c s u b s c r i pt s a t t he t op o f e a c h b a r .
A s b i r t h w e i g h t d e c r e a s e d t h e r at e o f l a mb m o r t a l i t y d u e t o
cold exposure increased signifi c a n t l y ( p < 0 . 0 5 - F i g u r e 1 1 ) , t h o u g h
t h i s e ffe c t w e r e n o t p r e s e n t i n e i t her o f t h e B o r d er d a l e t ri a l s a ft e r
the data was corrected for the influence of sire line and the
p r e d i c t e d r a t e o f h e a t l o s s . Thi s t re n d w a s p a r t i cu l a rl y s i gni fi c a n t
o n c e t h e r a w b i r t h w e i g h t d e c r eased below 2.5 (Merino) – 4 kg
(Borderdale 2000). Further analysis revealed sire line variation in
b i r th w eight (p<0.001) i n al l t r i a l s w i t h t h e e x c ep t i o n o f t h e
M e r i n o s ( p = 0 . 1 2 3 ) . L a mb s f r o m o l d e r e w e s w e r e f o u n d t o b e h e a v i e r
( p < 0 . 0 5 ) t h a n t h o s e f r o m y o u n g e r e w e s a n d ma l e l a mbs w e r e
o b s e r v e d t o b e h e a v i e r a t b i r t h t ha n f e ma l e s ( p < 0 . 0 5 ) i n a l l t r i a l s
with the exception of the Merino (p=0.168).
31
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
F i g u r e 1 1 : The influence of birth weight ( r a w ) u p o n l a mb m o r t a l i t y
d u e t o c o l d e x p o s u r e i n e a c h o f t h e f o u r t r i a l s a na l y s e d .
Effect of Dam age and Lamb Gender on Cold Induced Lamb Mortality
T h e r e a p p e a r e d t o b e n o r e l a t io n s h i p ( p > 0 . 0 5 ) b e t w e e n t h e a g e
o f t h e d a m a t l a mb i n g a n d l am b mor t a l i t y d u e t o c o l d e x pos u r e ,
d e s p i t e t h e r e l a t i o n s h i p b e t we e n d a m a g e a n d b i r t h w e i g h t . N o
difference was observed in the numb e r o f l a mb s d y i n g f r o m c o l d
e x p o s u r e i n e a c h g e n d e r ( p > 0. 0 5 ) e v e n t h o u g h g e n d e r w a s a l s o
observed to influence birth weight.
Sire line Variation in Cold Induced Lamb Mortality
L a mb m o r t a l i t y d u e t o c o l d e xposure accounted for 11.2% of all
l a mbs b o r n a n d 6 8 % o f a l l d e a d l a mbs i n t h i s s t u d y . Wh e n s i r e - l i n e s
w e r e c o m p a r e d for t h e i n ci d en c e o f l am b mor t a l i t y d u e t o c o l d u s i ng
C h i - s q u a r e me t h o d o l o g i e s , s i r e e f f e c t s w e r e s i g n i f i c a n t a t t h e 5 %
level within the Coopworth – Dorset Down, Merino and 1999
B o r d e r d a l e t ri a l s ( Ta b l e 3 ) . Va r i at i o n be t w e e n s i re - l i n e s w as
s i g n i f i c a nt a t t h e 1 0% l e v e l f o r a l l t r i a l s a n a l y s e d .
32
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
When the data was corrected for the influence of birth weight
a n d t h e cli ma t i c c o n d i t i o ns pr e s e n t a t b i r t h/ d e ath , s i r e l i ne v a r i a t i on
was observed in the Meat Qual i t y ( p = 0 . 0 1 5 ) a n d M e r i n o ( p = 0 . 0 0 5 )
t r i a l s a n d i n a c o mb i n e d d a t a s e t o f a l l t h e t r i a l s ( p < 0 . 0 0 1 ) , t h o u g h
n o t i n e i t h e r B o r d e r d a l e t ri a l ( 1 9 9 9 – p = 0 . 1 1 6 & 2 0 0 0 – p = 0 . 8 5 9 ) . I t
w a s a l s o n o t e d t h a t t h e b i r t h d a t es o f t h e l a mb s i n e a c h s i r e l i n e
w e re not evenly distribute d ove r t h e l a m b i n g p e r i o d i n a l l o f t h e
t r i a l s ( p < 0 . 0 0 1 ) w i t h t h e e x c e p t i on of the Merino trial (p=0.178).
T a b l e 3 : T h e l a mb m o r t a l i t y c a u s e d b y c o l d e x pos u r e f o r e a c h s i r e line. Significant differences (p<0.05, univariate analysis)
b e t w e e n si r e s w i t h i n t r i a l s i n l a mb d e a t h d u e t o c o l d
exposure are represented by different alphabetic subscripts
for t h o s e t r i a l s s h owi n g s i g ni fi c a n t si re - l i n e e ffe c t s . ( B =
B orderdale, M = Me r ino, DD = Dor se t Down)
Ewe Breed
Borderdale
Borderdale
Coopworth
Year
1999
2000
2000
Coopworth
Merino
2000
Sire (Breed)
Number of
% Lambs that died
Lambs Born
from Cold Exposure
4/97 (B)
76
14a
25/94 (B)
60
3b
16/95 (B)
72
13a
82/95 (B)
59
7ab
263/98 (B)
63
8
266/98 (B)
166
17
8512 (M)
150
11a
8255 (M)
121
11a
8585 (M)
89
8b
129/97 (DD)
128
5a
238/97 (DD)
97
3a
122/98 (DD)
157
13b
26 (M)
54
6a
132 (M)
43
33b
356 (M)
51
25b
33
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
Accuracy of the Logistic Regression Models
The accuracy of the logistic regression models varied by
between 0 and 5.6% depending upon the trial (Table 4), though
there were minimal errors in the logistic regression models
prediction of which lambs would die from cold exposure (0
errors in Borderdale 1999 & Meat Quality, 3 in Borderdale 2000
& 5 in Merino). The errors were mainly confined to the
prediction of which lambs would survive cold exposure (26
errors in Borderdale 1999, 17 in Borderdale 2000, 61 in Meat
Quality, 26 in Merino).
Table 4: The Accuracy of the Logistic Regression Models.
Trial
Year
Logistic Regression
Prediction
90.3%
91.3%
Difference
1999
2000
Actual
Survival
89.05%
85.7%
Borderdale
Meat Quality
2000
91.3%
91.6%
0.3%
Merino
Pooled Data
2000
-
79.7%
88.9
79.7%
89.1%
0%
0.2%
0.95%
5.6%
34
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
2.4 Discussion
T h e a v e r a g e n e o n a t a l l a mb m o r t a l i t y o f t h i s st u dy w a s 1 6 . 5 %
c o mp a r e d w i t h t h e pr e v i o u sl y r e p o r t e d a v e r a g e o f 1 5 % f o r N e w
Z e aland flocks by McC utc he on e t a l . (1981), suggesting that this
s t u d y a c c u r a t e l y r e p l i c a t e d l a mb m o r t a l i t y f o u n d u n d e r t y p i c a l N e w
Z e a l a n d f a r mi n g c o n d i t i o ns . L a mb m o r t a l i t y f r om c o l d e x p o s u r e
a c c o u n t e d f o r 1 1 . 2 % o f a l l l a mb s b o rn i n t h i s s t u d y ( 6 8 % o f t o t a l
l a mb d e a t h s ) . T h i s w a s mu c h h i g h e r t ha n mo s t r e s u l t s r e po r t e d i n
the literature, including those of Purser & Young (1964), who used
a s i mi l a r me t h o d f o r t h e d i a g n o s i s o f c o l d d e a t h . T h e mo r t a l i t y
b e f o r e 1 4 d a y s c l a s s ( s i mi l a r t o t h e l a mb d e a t h f r o m c o l d e x p o s u r e
classification in this study) used by Purser & Young contained 46%
o f a l l l a mbs d y i n g o n t w o f a r ms i n S c o t l a n d & N o r t h Wa l e s . T o p u t
Purser & Young’s work in context, the overall mortality in their
s t u d y w a s 1 3 % o f a l l l a mb s b o r n , c o mp a r e d w i t h 1 6 . 5 % i n o u r s t u d y
a n d they used breeds of she e p not f ound in Ne w Ze a la nd ( Sc ottish
B l a c k f a c e & We l s h M o u n t a i n ) . T h e str e ngth of the c old c ha lle nge
was not measured by Purser & Young, which prevented a
c o mpa r i s o n o f t h e e n v i r o n me n t a l conditions between studies.
A s i mi l a r l a mb mor t a l i t y s t u d y w a s c a r r i e d o u t b y U p r e t i
( 1 9 8 9 ) 1 1 y e a r s p r e v i o u s l y o n t h e s a me f a r m ( L . U . R e s e a r c h f a r m)
a s s o me o f t h e t r i a l s i n t h i s s t u d y . T h e t o t a l mor t a l i t y o f t h e l a mbs
b o r n o u t s i d e i n U p r e t i ’ s s t u d y ( 29% ) wa s highe r tha n tha t r e por te d
h e r e , d e s p i t e U p r e t i s t u d y i n g h i gh f e c undity Boor oola Coopwor th
cross ewes which are acknowledged as having lower survival rates
( d u e t o l a r g e r l i t t e r s i z e s) t h a n o t h e r bre e d s ( H i nc h e t a l . , 1985).
F i ft y t h r ee p e r c e nt o f t h e l a m b mo r t a l i t y i n U p r e t i ’ s w o r k w a s
a t t r i b u t e d t o s t a r v a t i o n - e x p o su r e u s i n g t h e a u t o p s y me t h o d
o r i g i n a l l y d e v e l o p e d b y M a c F a r l a n e (1965). This result is surprising
c o n s i d e r i n g t h e c o r r e l a t i o n be t w e e n birth rank and sus c e pt i b i l i t y t o
c o l d e x p o s u r e ( H i n c h e t a l . , 1985) and the use of an autopsy
t e c h n i q u e t h o u g h t t o u n d e r e s t i ma t e d e a t h s f r o m c o l d e x p o s u r e .
35
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
V a r i a t i o n b e t w e e n t r i a l s w a s fo u n d t o e x i s t i n t h e a c c u r a c y o f
t h e l o g i s t i c r e g r e s s i o n mo d e l u s e d t o a na l y s e si r e l i n e v ar i at i o n i n
n e o n a t a l l a mb m o r t a l i t y d u e t o c o l d e x p o s u r e . W h i l e t h e m o d e l s
w e r e e x t r e me l y a c c u r a t e a t pr e d i ct i n g l a mb mor t a l i t y d u e t o c o l d
e x p o s u r e , c o n s i d e r a b l e v a r i a t i o n w a s f o u n d i n t he i r a b i l i t y t o
p r e d i ct l am b s u r v i v a l . T h i s wa s t h e re sul t o f mor e l a mbs d y i n g t h a n
w a s e x p e c t e d a f t e r a n a l y s i n g t h e c o mbi n e d e f f e c t s o f s i r e , bi r t h
weight and the predicted rate of heatloss. This has been previously
o b served by A lexander (1984) , who f o u n d t h a t a c o r e l e v e l o f l a mb
l o s s e s r e ma i n e v e n u n d e r i d e a l w e a t h e r c o n d i t i o n s a n d o p t i ma l
ma n a g e m e n t .
The variation in lamb mortality b e t w e e n t r i a l s o b s e r v e d i n t h i s
study prevented any between breed comparisons from being carried
o u t , t h o u g h t h e h i g h e s t r a t e o f l a mb mo r t a l i t y d u e t o c o l d e x p o s u r e
was observed in the Merino trial. Previous work has shown that
c o n s i d e r a b l e v a r i a t i o n i n n e o n a t a l l a m b c o l d t ol e r a n c e d oe s e x i st
between certain breeds of sheep (Sykes e t a l . , 1 9 7 6 ; S a ms o n & S l e e ,
1 9 8 1 ; D o n n e l l y , 1 9 8 3 ; Wo l f f e t a l . , 1 9 8 7 ) . A p a r t f r o m b r e e d / g e n e t i c
v a r i a t i o n , o t h e r s o u r c e s o f i n t er - t r i a l v ar i at i o n a s s u me d t o b e
p r e s e n t i nc l u d e d t he e f f e c t i ve n e s s o f t h e s h e l t e r p r e s e n t dur i n g
l a mbi n g ( d u e t o i t s o r i e n t a t i o n t o t h e p r e v a i l i n g w i n d s a n d p o r o s i t y )
a n d v a r i a t i o n i n i n fe c t i o n s t a t u s b e t w e e n t r i a l s . V a r i a t i o n b e t w e e n
t h e c l i ma t e c o n d i t i ons p r e s e nt d u ri n g l a m b i n g i n e a c h t r i a l w a s
o b s e r v e d d u e t o d i ffe r e n c e s i n l a mbi n g d a t e s . F o r e x a mp l e t h e w o r s t
w e a t h e r c o n d i t i o ns e n c o u n t e r e d b y t h e B o r d e r d a l e 1 9 9 9 t r i a l w a s
1 5 0 W/ m 2 whereas the same fl ock in 2000 had two weather incidents
a b o v e t h i s l e v e l ( o n e s u c h inc ide nt r e a c he d 248 W/ m 2 ) .
F i x e d E f f e c t s : D am A g e a n d L a m b G e n d e r
D a m a g e a p p e a r s t o i n f l u e n c e a l a r ge nu mbe r o f f a c t o r s t ha t c a n
i n f l u e n c e n e o n a t a l l a mb m o r t a l i t y c a u s e d b y c o l d e x p o s u r e . P u r s e r
a n d Y oung (1964) found tha t the f r e que nc y of twinning inc r e a se d
w i t h e w e a g e , r e s ul t i n g i n a n i n c r ea s e i n n e o n a t a l l a mb c o l d
36
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
m o r t a l i t y . T h i s a s s oc i a t i o n w a s n o t o b s e r v e d b y S mi t h ( 1 9 7 7 ) , w h o
f o u n d t h a t l a mb b i r t h w e i g h t i n c r e a se d w i t h e w e a g e , o r b y P a r k e r et
a l . ( 1 9 8 7 ) , w h o f o u n d t h a t ma t e r n a l behaviour improves as ewes get
o l d e r , b o t h f a c t o r s l e a d i n g t o i mp r o v e d n e o n a t a l l a mb c o l d
t o l e r a n c e . A l t h o u g h l a mb b i r t h w e i g h t w a s a l s o f o u n d t o i n c r e a s e
w i t h e w e a g e , i mp r o v e d l a mb c o l d t ol e r a n c e d u e t o e w e a ge w a s n o t
o b s e r v e d i n t h i s s t u d y o r i n t h e w o r k o f H i n c h e t a l . (1985).
S o me l a m b mor t a l i t y s t u d i e s h a v e f o u n d t h a t f e m a l e l a mb s
a p p e a r t o h a v e h i g h e r s u r v i v a l r at e s t han ma l e l am b s d e s p i t e r e s ul t s
t ha t s how t ha t ma l e l a mbs a r e bor n he a vi e r (Purser and Young, 1964;
Smith, 1977; Wolff et al., 1987) . M a l e l a mb s w e r e f o u n d t o h a v e
h i g h e r b i r t h w e i g h t s t h a n f e ma l e s i n t h i s s t u d y , t h o u g h n o
difference between ma le and fe ma le l a m b s u r v i v a l w a s o b s e r v e d .
Fixed Effects: Birth Ra n k a n d B i r t h W e i g h t
A s t h e n u m b e r o f l a m b s i n e a c h l i t t e r i n c r e a se d , t h e r e w a s a
c o r r e s p o n d i n g d r o p i n t h e a v e r a g e lamb birth weight leading to
d e c r e as e d n e o n a t al l a mb c o l d t o l er a n c e. T h i s e ffe c t w a s simi l a r t o
that found for total mortality in other studies (Purser & Young,
1 9 6 4 ; H i g h t & J u r y , 1 9 7 0 ; S t e v e n s et al., 1 9 8 2 ) a n d a p p e a r e d t o
c o mpl e t e l y e x p l a i n t h e r o l e o f b i r t h r a n k u p o n n e o n a t a l l a m b c o l d
mortality in this study. It was fo r t h i s r e a s o n t h a t b i r t h r a n k w a s
o mi t t e d fro m t h e l og i s t i c r e gr e s s i o n mo d e l , d e s pi t e h a vi n g a l a r ge
i n f l u e n c e u p o n n e o n a t a l l a mb m o r t a l i t y .
A ft e r c o r re c t i n g t h e d a t a for t h e i n f l u e nc e o f t h e c l i ma t e a n d
sire line, birth weight was iden t i f i e d a s t h e v a r i a b l e h a v i n g t h e
s i n g l e l a r g e s t i n f l u e n c e u p o n n e o n a t al l a mb c o l d mor t a l i t y i n t h e
M e a t Q u al i t y a n d M e r i n o t ri a l s . T h e t r e n d t h at , a s b i rt h w e i g h t
increased, there was a correspondi n g d e c r e a s e i n l a mb mor t a l i t y d u e
t o c o l d e x p o s u r e w a s t h e s a me a s t h a t o b s e r v e d b y P u r s e r & Y o u n g
( 1 9 6 4 ) , H i g h t & J u r y ( 1 9 7 0 ) a n d S y k e s e t a l . (1976). This trend
appeared to be particularly si g n i f i c a n t b e l o w 2 . 5 – 4 k g ( d e p e n d i n g
37
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
o n t h e b r e e d ) a n d w a s a l s o o b s e r v e d in the Borderdale trials, though
t h e r e w a s s i r e l i n e va r i at i o n i n b i r t h w e i g h t i n t h i s f l o c k , w h i c h
c a n c e l l e d o u t t h e e ff e c t o f b i r t h w e i g h t i n t h e l o g i s t i c r e g r e s s i o n
m o d e l . S i r e l i n e v a r i a t i o n i n b i r t h we ight wa s a lso obse r ve d in the
M e a t Q u al i t y t ri a l an d w a s s i mi l a r t o t h e r e s u l t s p r e v i o u sl y r e p o r t e d
i n M c G u i rk e t a l . (1982), Smi t h (1977) and Dwyer e t a l . (2001).
D u e t o t he l a r ge i nfl u e n c e o f b i r t h w ei g h t o n l am b mor t a l i t y
due to cold exposure, the question is raised whether selection for
b i r t h w e i g h t a s a me t h o d o f i mp r o v i n g l a mb s u r v i v a l w o u l d b e
b e t t er t h an s e l e ct i on fo r c o l d t o l er a n c e. T h i s a p pr o a c h ma y b e
f a v o u r e d b e c a u s e di r e c t s e l e c t i o n f o r b i r t h w e i gh t i s s i mp l e a n d
r e mo v e s t h e r e q u i r e me n t f o r a c o l d c h a l l e n g e , w h i c h i s i mp o s s i b l e
t o s t a n da rd i s e a cr o ss a l l l a mb s i n a c o mme r c i a l fl o c k ( H a l ey e t a l .
1 9 8 7). H ow ever, selection f or highe r bir th we ight in a n a tte mpt to
i n c r e a s e l a mb s u r v i v a l i s c onf ounde d by the la r ge numbe r of
interactions between bi r t h w e i g h t a n d t h e p r e s e nc e o f d i s e a s e a n d / or
i n f e c t i o n , b i r t h r a n k , l a mb g e n d e r , ma t e r n a l a g e , s i z e a n d p a r i t y
( A l e x a n d e r 1 9 7 4 ) . La mb s w i t h h i g h b i r t h w e i g h t s ( a n d t h u s m o r e
c o l d t ol e ra n t ) ar e als o p r e d i s po s ed t o d e a t h f r o m d y s t o c i a ( S c a l e s et
a l . 1986).
Fixed Effect: Climate
O b s t & D a y ( 1 9 6 8 ) a n d C o r o n a t o ( 1 9 9 9 ) f o u n d t h a t c l i ma t e h a d
a l a r g e i n f l u e n c e u p o n n e o n a t a l l a mb m o r t a l i t y s i mi l a r t o o u r
f i n d i n g s i n t h e B o r d e r d a l e 20 0 0 , M e a t Q u a l i t y a n d M e r i n o t r i a l s .
W h i l e t h e B o r d e r d a l e 1 9 9 9 t r i a l f o l l o we d t h e s a me t r e n d a s t h e
o t h e r s , t h e t r e n d wa s n o t s i g n i f icant, apparently due to the low
a v e r a g e pr e d i c t e d r a t e o f h e a t l o s s i n t h i s t ri al . A s a c o n s e q u e n c e
t h e c o l d c h a l l e n g e ma y n o t h a v e been sufficient to cause enough
l a mb d e a t h s f r o m c o l d e x p o s u r e t o e s t a b l i s h v a r i a t i o n b e t w e e n s i r e
l i n e s i n t hi s t ri al .
38
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
The presence of variation in col d e x p o s u r e b e t w e e n s i r e l i n e s
w i t h i n t r i a l s ma y h a v e s l i g h t l y c o n f o u n d e d t h e r e s u l t s , d e s p i t e t h e
e f f e c t b e i n g a c c o u n t e d f o r i n t h e l o gistic regression analysis. This
i ssue could have been avoide d b y s y n c h r o n i s i n g e q u a l n u m b e r s o f
e w e s p e r r a m t o b e ma t e d e a c h w e e k ( o r o t h e r a pp r o p r i a t e t i me
p e riod) during the joinin g pe r iod. As a r e s u l t a s i mi l a r n u m b e r o f
l a mb s p e r s i r e w o u l d h a v e b e e n b o r n a t a n y g i v e n t i me .
C o r o n a t o f o u n d t h a t t h e c l i ma t i c c o n d i t i o n s i n the two weeks
p r i o r t o b i r t h h a d a l a r g er i n flu e n c e u p on l a mb m o r t al i t y t ha n t h e
c o n d i t i o n s a t t h e t i me o f b i r t h , t h o u g h t h i s o b s e r v a t i o n w a s ma d e i n
C e n t r a l Pa t a g o n i a w h e r e t h e a v e r a g e p r edicted rate of heat loss from
a l a mb r a r e l y e x c e e d e d 5 0 W/ m 2 . O b s t a n d E l l i s ( 1 9 7 7 ) f o u n d t h a t
o n c e t h e pr e d i ct e d ra t e o f h e a t l o s s e xc e e d e d 5 7 W/ m 2 , s i g n i f i c a n t
l a mb mor t a l i t y i n M e r i n o a n d C o r r ie d a l e s o c c u r r e d . B y c o m p a r i s o n ,
l a mb mor t a l i t y d u e t o c o l d e xp o s u r e i n t h i s t r i a l i n c r e a se d ma r k e d l y
once the predicted rate of heat loss exceeded 97 (Borderdale 1999),
1 0 5 ( B o r d e r d a l e 2 0 0 0 a n d M e a t Quality) and 108 W/ m - 2 ( M e r i n o ) .
The wind chill index was first developed by Siple and Passel
( 1 9 4 5 ) f o r h u ma n s w o r k i n g i n A n t ar c t i c a . T h i s i n d e x w a s d e s i g n e d
t o me a s u r e t h e a mo u n t o f h e a t l ost by huma n bare skin from wind
s p e e d a n d t e mp e r a t u r e a n d h a s b e e n s u b s e q u e n t l y f o u n d t o b e
i n v a l i d f o r w o o l l y ( o r h a i r y ) a n i ma l s, pa r tic ula r ly a t wind ve loc ities
g r e a t e r t h a n 4 0 k m p e r h o u r ( A me s & I n s l e y , 1 9 7 5 ) . F u r t h e r
i n a c c ur a c y w a s i n t r o d u c e d b y t h e f a i l ur e t o a c c o unt f o r t h e c h i l l i n g
e f f ects of precipitation, though Sykes e t a l . ( 1 9 7 6 ) s t a t e d t h a t t h i s
i s o f r e d u c e d i mp o r t a n c e f o r n e w b o r n l a mb s a s t h e y a r e a l r e a d y w e t
f r o m a mn i o t i c f l u i d s .
Sensitivity analysis of the Cor o n a t o ( 1 9 9 9 ) w i n d c h i l l mod e l
r e f l e c t s t he r e d u c e d i mp o r t a n c e o f p re c i p i t a t i o n i n c o o l i n g l a mbs . I n
t h e C o r o n a t o mo d e l , t h e g r e a t e s t v ar i a t i o n i n t h e p r e d i c t e d r a t e o f
39
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
h e a t l o s s i s i n d u c e d b y w i n d , w h i l e t e mpe r a t u r e h a s a s l i g h t l y l e s s
i n f l u e n c e . B y c o mp a r i s o n , t h e i n f l u e n c e o f p r e c i p i t a t i o n i s a l mo s t
n e g l i g i b l e ( C o r o n a t o , 1 9 9 9 ) , s imi l a r t o t h e i n f l u e n c e o f
p r e cipitation on the w in d c hill mo d e l d e r i v e d b y N i x o n S m i t h ( 1 9 7 2 ,
cited in Donnelly, 1984) and used by Donnelly (1984) and Upreti
( 1 9 8 9 ) . The C o r o n a t o mo d e l a s s u me s t h a t t h e e w e i s l a mbi n g i n a n
o p e n f i e l d , w i t h r a n d o m o r i e n t a ti o n t o w i n d r a i n a n d s u n ( M o u n t
a n d B r o w n , 1 9 8 2 – f r o m w h o m t h e C o r o n a t o mo d e l w a s d e r i v e d ) .
T h i s c a n i n t r o d u c e e r r o r , a s S y k es ( 1 9 8 2 ) o b s e r v e d t h a t t h e l a mb
w a s p a r t i c u l a r l y a d e p t a t c r e a t i n g a mo r e f a v o u r a b l e mi c r o c l i ma t e
t h a n i s des c r i b e d by t r a di t i on a l me t e o r o l o g y . La mb s c a n a c h i e v e
t h i s b y s e e k i n g s h e l t e r a n d / o r b y h u d d l i n g w i t h t h e i r mot h e r / o t h e r
l a mbs. B e cause of these be ha vi o u r a l a l t e r a t i o n s , me t e o r o l o g i c a l
r e c o r d s l i k e t h o s e u s e d i n t h i s s t u d y o f t e n d e s c r i b e mo r e s e v e r e
conditions than actually expe r i e n c e d b y t h e l am b , t h o u g h i t i s
a s s u me d t h a t t h i s e f f e c t i s u n i f o r m a n d d o e s n o t i n f l u e n c e t h e
validity of our results.
S i re L ine V ariation in Ne onat al Lam b Cold M or t alit y
S i r e l i n e v a r i a t i o n i n l a mb m or t a l i t y due t o c o l d e x p o s u r e w a s
d e t e ct e d i n a l l o f t he t ri a l s u nt i l t h e d at a w a s c o r re c t e d for t h e
i n f l u e n c e o f b i r t h w e i g h t a n d t h e p r edicted rate of heat loss using
logistic regression. Sire line variation was not observed in either
Borderdale trial after accounting for these fixed effects, though it
w a s s t i l l o b s e r v e d w h e n t h e t r i a l s w e re c o mbi n e d i n t o o n e d a t a s et
and analysed. Previous studies by Slee (1985), Slee et al. (1987)
a n d Wol f f e t a l . ( 1 9 8 7 ) have detected evidence of sire line variation
i n l a mb c o l d t o l e r a n c e , t h o u g h these studies used laboratory
techniques as opposed to the field technique used here. Unfor t una t el y,
t h e r e a p pe a r s t o b e n o p r e v i ou s w o r k t h a t u s e s fi e l d t r i a l s a n a l y si n g
g e n e t i c v a r i a t i o n i n c o l d i n d u c e d l a mb m o r t a l i t y in conjunction with
t h e c l i ma t e ( t h e c h a l l e n g e ) f o r c o mpa r i s o n w i t h t h e s e r e s ul t s .
40
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
The studies by S lee ( 1985) a nd Sle e e t a l. ( 1987) a lso f ound
e v i d e n c e t h a t t h e r e ma y b e a ma j or g e n e i n f l u e n c i n g n o n - s h i v e r i n g
t h e r mo g e n e s i s ( a n d h e n c e n e o n a t a l cold tolerance). In two of the
t r i a l s a na l y s e d i n t hi s s t u d y , si r e- l i ne va r i a t i o n i n c o l d mo r t a l i t y
i n d ependent of birth w eight wa s d e t e c t e d , s u g g e s t i n g t h a t o t h e r
f a c t o r ( s ) o t h e r t h a n b ir t h w e i g h t w e r e r e s p o n s i b l e f o r t h e i n c r e a s e d
n e o n a t a l c o l d t o l e r a n c e . L i n k i n g a l l of this toge the r c ould be the
r e c e nt f i n d i n g t h a t v a r i a t io n i n t h e g e ne c o d i n g t h e  3 a d r en e r g i c
r e c e pt o r ha s b e e n l i n k e d w i t h v ar i a t i o n i n c o l d t o l e r a nc e ( R .
F o r r e s t , pe rs. comm. ) . T h e  3 a d r e n er gi c r ec e p t or i s a k ey
c o mp o n e n t i n t h e c a t e c h o l a mi ne stimula tion of br own a dipose tissu e
(Strosberg, 1997), which is the principle site of non-shivering
t h e r mo g e n e s i s i n t h e n e w b o r n l a mb ( A l e x a n d e r & Wi l l i a ms 1 9 6 8 ) .
T h e r e a r e ma n y r e a s o n s w h y s i r e l i n e v ar i at i o n i n l a mb
m o r t a l i t y c a u s e d b y c o l d e x po s u r e w a s d e t e ct e d i n a l l t ri al s w i t h t h e
e x c e p t i o n o f t h e t w o B o r d e r da l e t r i al s . T h e u s e o f f i e l d t r i a l s ma d e
i t d i f f i c u l t t o s t a n da r d i s e t h e c o l d c h a l l e n g e e x pe r i e nc e d b y a l l
l a mbs , p a r t i c u l a r l y a s t h e bi r t h d a t e s o f e a c h s i r e l i n e w e r e n o t
e v e n l y d i s t r i b u t e d a c r o s s t h e l a mbi n g p e r i o d , l e a d i n g t o s o me s i r e
l i n e s e x p er i e n ci n g w o r s e c o ndi t i o ns t ha n o t h e rs . T h e d a t a i n t h i s
st udy w as partially standa r dise d for the strength of the cold
c h allenge, through the u se of l o g i s t i c r e g r e s s i o n , w h i c h a l s o
a d justed the data for varia tion in b i r t h w e i g h t . Th e s t r e n g t h o f t h e
c o l d c h a l l e n g e mu s t a l s o b e s u f f i c ie n t t o c a u s e h i g h l a mb m o r t a l i t y .
I n s i t ua t i o n s w h e r e t h e r e i s l o w mo r t a l i t y , t h e e f f e c t o f g e n e s
d e t e r mi n i n g r e s i s t a n c e t o c l i ma t i c s t r e s s c a n b e ma s k e d a mo n g s t
n o r ma l l a m b d e a t h a n d d e t e r mi n i n g v a r i a t i o n b e t w e e n s i r e l i n e s c a n
b e c o me v e r y d i f f i c u l t ( H a l e y e t a l . 1987).
F i e l d t r i al s a l s o ma k e i t v er y d i ffi c u l t t o l i mi t t he e ffe c t s o f
m o t h e r i n g b e h a v i o u r a n d l a mb f e e d i n g a b i l i t y o n n e o n a t a l l a mb c o l d
t o l e r a n c e . T h e s e f a c t o r s a r e m ai n l y ma t e r n a l a n d c o n f o u n d t h e
r e s u l t s o f s i r e l i n e a n a l y s e s l i k e t h i s . Th e p r o g e n y g r o u p s i z e i n t h e
41
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
B o r d e r d a l e t ri a l s wa s s ma l l e r t h a n t h o se i n t h e Me a t Q u a l i t y a n d
M e r i n o t r i a l s . T h i s w o u l d h a v e ma d e i t m o r e d i f f i c u l t t o d e t e c t a n y
variation between sire lines and to show that this was a significant
difference.
T he overall population siz e of the Bor de r da le br e e d in NZ is
c o n s i d e r a b l y s ma l l e r ( n = 1 5 0 0 - N Z S h e e p b r e e d e r s A s s o c i a t i o n ,
2 0 0 0 ) t h a n t h e M e r i n o b r e e d ( n = 3 mi l l i o n – M e a t & Wo o l E c o n o mi c
S e r v i c e o f N Z , 1 9 9 9 ) . T h i s p o t e n t i a l l y r e d u c e s t h e a mo u n t o f
g e n e t i c v a r i a t i o n ( i n c l u d i n g v a r i a t io n i n c o l d t o l e r a n c e ) p r e s e n t i n
t h e B o r d e r d a l e br e e d c o mpa r e d t o t h e M e r i n o bre e d o r t he M e a t
Q u a l i t y pro g e n y , w h i c h a r e o f c r o s s b r e ds . T h e c o l d t o l e r a n c e o f t h e
B o r d e r d a l e s i s c o n s e q u e n t l y m o r e likely to be negatively affected
b y i n b r e e d i n g a s r e p o r t e d b y Galal (1981) and Lopez-Villalobos &
Garrick (1999). T h e s e r e s e a r c h e r s h av e b o t h r e p or t e d t h a t t h e e f f e c t
o f i n b r e e d i n g o n n e o n a t al l am b s u r v i v a l i s r e l a t i v e l y s ma l l a n d
i n c o n s i s t e n t . Lopez-Villalobos & Garrick (1999) also found that the
effect of inbreeding appeared t o d i r e c t l y i n f l u e n c e t h e l a mb s ’
survival and not act through the ewe.
T h e d i a g n o s i s o f l a m b d e a t h d u e t o c o l d e x p o s u r e i s ma d e
d i f f i c u l t be c a u s e o f t h e i nt e r ac t i o n s w i t h i n f e c t i on , b i r t h we i g h t ,
dystocia, starvation, birth injury and birth coat which can
p r e d i s p o s e l a mb s t o d e a t h f r o m c o l d e x p o s u r e ( Al e x a n d e r , 1 9 8 4 ) .
T h i s s t u d y u s e d a t e c h n i q u e t h a t ruled out other causes of death
rather than actually diagnosing cold death. It is thought that while
t h i s t e c h n i q u e ma y s l i g h t l y o v e r e s t i ma t e l a mb d e a t h s d u e t o c o l d
e x p o s u r e i t i s s t i l l m o r e a c c ur a t e t h a n o t h e r me t h o d s .
42
Chapter 2: Sire Line Variation in Neonatal Lamb Mortality
2.5 Conclusions
U n d e r c o n d i t i o ns t ha t w e r e r ep r e s e n t a t i v e o f t y p i c a l N e w
Z e a l a n d f a r mi n g c o n d i t i o ns , t h i s s t u d y s h o w e d t h a t v a r i a t i o n
b e t w e e n si r e s i n n eo n a t a l c o l d t o l er a n ce e x i st s w i t h i n a r an g e o f
b r e eds, given sufficiently la r ge sir e g r o u p s a n d g e n e t i c v a r i a t i o n .
T h i s s t u d y e s t a b l i s h e d t ha t fi e l d t r i a l s u t i l i s i n g s i mpl e d e a t h f r o m
c o ld exposure diagnosis a r e suf f ic ie n t t o d e t ec t v a r i at i o n i n t h e
p r e s e n c e o f a d e q u a t e c o l d c ha l l e n ge . T h i s c o u l d p r o v i d e a b a s i s f o r
s e l e ct i o n fo r i mp r o v i n g t h e nu mb e r o f l a mb s s u r v i v i n g a n d t h u s
r a ising the efficiency of la mb p r o d u c t i o n , p a r t i c u l a r l y i n f l o c k s
s u f f e r i n g l a r g e l o s se s p r i or t o we a n i n g w h i c h i s a t t r a c t i v e b e c a u s e
t h e c o s t s i n v o l v e d a r e s ma l l a n d n o n - r e c u r r e n t i n c o n t r a s t t o t h e
a l t e r n a t i v e o f i mp r o v i n g n u t r i t i o n , shelter or incr e a s i n g t h e a mo u n t
o f s h e p h e r d i n g ( H a l e y e t al . 1987). The variation between sires was
l a r g e e n o u g h t o b e d e t e c t e d i n o n e g e n e r a t i o n , w h i c h me a n s t h a t
l a r g e ge ne t i c ga i n s c a n b e m a d e o v e r o n e g e n e r a t i o n b y t h e
s e l e c t i o n o f ‘ s u p e r i o r ’ p a r e n t s . T hi s i s e s p e c i a l l y r e l e va n t t o
b r e e d i n g p r o g r a ms u t i l i s i n g t e r mi n a l s i r e s w h e r e b e n e f i t s n e e d t o b e
exhibited by the progeny.
Lamb birth weight had a large influence on lamb mortality
due to cold exposure and was largely responsible for the
influence of rank on lamb mortality due to cold exposure. Birth
weight was also found to be correlated with the age of the ewe at
lambing and lamb gender, though neither of these factors were
found to influence lamb mortality due to cold exposure. These
results suggest that further investigation into the genetic factors
that influence neonatal lamb cold tolerance may be warranted. In
particular, research relating to the detection of the possible
major gene detected by Slee (1985) and Slee et al. (1987)
(Chapter 3).
43
Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
Chapter 3: The Role of Polymorphism in the  3
Adrenergic Receptor Gene in Cold
Tolerance and Lean Muscle Growth
Introduction
Previous studies have i n d i ca t e d t h a t t he r e i s a m a j o r g e ne
i n fl u e n c i ng n e o n a t al l a mb c o l d t o l er a n ce v i a t he c a t e c h ol ami n e
s t i mu l a t i o n o f n o n - s h i v e r i n g t h e rmo g e n e s i s ( Si m p s o n & S l e e , 1 9 8 8 ;
Slee & Simpson, 1991). The gene that codes the 3-adrenergic
r e c e pt o r ( 3 - A R ) i s t h o u g h t t o b e a l i k e l y c a n d i d a t e f o r t h i s ma j o r
g e n e a s 3 - A R s a r e t h o u g h t t o b e t h e ma j o r me d i a t o r s o f t h e
l i p o l y t i c a n d t h e r mo g e n i c e f f e c t s o f h i g h c a t e c ho l a mi n e
concentrations.
V a r i a t i o n i n t h e g e n e c o d i n g t h e  3 AR ha s be e n f ound in
h u ma n s . T h i s c o n si s t s o f a si n g l e a mi n o a c i d s ub s t i t ut i o n ( t h e
t r p 6 4 a r g m u t a t i o n ) i n t h e  3 AR gene and has been associated with
r a p i d w e i g h t g a i n , l o w me t a b o l i c r a t e a n d i mp r o v e d f e r t i l i t y
( S u s u l i c et al . , 1 9 9 5 ; A r n e r & L o n n q v i s t , 2 0 0 0 ) . F u r t h e r m o r e , i n
r o d e n t  3-AR gene knockout models ther e i s a m a r k e d r e d u c t i o n i n
the thermogenic response to cold and an increase in fat deposition
( S u s u l i c et al ., 1995).
S i x a l l e l e s o f t h e g e n e c o d i n g t h e o v i n e  3-AR, which
s e g r e g a t e i n a M e n d e l i a n f a s h i o n , h a v e b e e n i d e n t i f i e d b y F o r r e s t et
a l . ( 2 0 0 1 ) . T h e s e a l l e l e s w e r e l i n k e d t o v a r i a t i o n i n l e a n mu s c l e
g r ow th and although a cor r e la tion wit h n e o n a t a l l a mb c o l d t o l e r a n c e
w a s n o t d e t e c t e d , t h i s w a s a t t r i b u te d t o i n s u f f i c i e n t c ol d c h a l l e n g e .
F u r t h e r s t u d i e s h a v e r e v e a l e d a n a s s o cia t i o n i n on e s i r e l i ne
b e t w e e n 3 - A R a l l el e s a n d n eo n a t a l l am b mor t a l i t y d u e t o c o l d
44
Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
e x p o s u r e ( R . H . F o r r e s t pers. comm. ) . T h e l i n k b e t w e e n v a r i a t i o n i n
t h e g e n e c o d i n g t h e o v i n e  3 - A R a n d l e a n mu s c l e g r o w t h i s
p o t e n t i a l l y v e r y i mp o r t a n t t o t h e p r i me l a mb i n d u s t r y a s l a mb i s
p e r c e i v e d b y c o n s u me r s a s b e i n g o v e r fa t a n d t h e r e f o r e i s l e s s
v a l u a b l e ( H a mmo n d e t a l . , 1992) a nd the pr oduc tion of wa s t e f a t is
i n e f f i c i e n t i n t e r ms o f t h e e n e rg y u s e d ( C a me r o n & B r a c k e n 1 9 9 2 ) .
S e l e c t i o n f o r i mp r o v e d l e a n m u s cl e g r o w t h i n l a m b s h a s b e e n
ma d e m o r e a c c u r a t e t h r o u g h t h e u s e o f u l t r a s o u nd s c a n n i ng .
U l t r a s o u n d s c a n n i n g a l l o w s t h e q u a n t i t a t i v e me a s u r e me n t o f t i s s u e
( mu s c l e a n d f a t ) d e p t h s o v e r t h e 1 3 t h rib in live sheep and is now
w i d e l y u s e d i n N e w Z e a l a n d , p a r t i c u l a r ly in te r mina l sir e br e e ds of
s h e e p ( B i n n i e e t al ., 1 9 9 7 ) . G e n e t i c i m p r o v e me n t i n l e a n m u s c l e
g r o w t h o f t e r mi n a l s i r e b r e e d s i s p e r ma n e n t , c u m u l a t i v e , r e l a t i v e l y
c h e a p a n d c a n b e c o n c e n t r a t e d o n a n u me r i c a l l y s ma l l g r o u p o f
a n i ma l s t h a t c a n h a v e a l a r g e g e n e t i c i n f l u e n c e u p o n o v e r a l l l a mb
( me a t ) p r o d u c t i o n ( S i m m , 1 9 8 7 ; C a me r o n & B r a c k e n , 1 9 9 2 ) .
A study linking neonatal lamb cold tolerance to sire variation
i n t h e g e n e c o d i n g t h e o v i n e  3- AR is de sc r ibe d in this c ha pte r . Th e
l e a n mu s c l e g r o w t h w o r k o f F o r r e s t e t al . ( 2001) is a lso r e plic a te d
u s i n g a t e r mi n a l s i r e b r e e d o f s heep (the Ha mpshire) and ultrasound
s c a n n i n g . T h i s w a s i n t e n d e d t o t e s t t h e v i a b i l i t y o f t h e  3-AR gene
a s a ma r k e r g e n e f or c o l d t o l e r a nce and/or lean muscle growth.
45
Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
3.1 Animals Investigated
C o l d T o l e r a n c e : The flocks used to anal yse sir e line va r ia tion
i n n e o n a t a l c o l d mor t a l i t y , d e s c r i b e d i n c h a p t e r 2 , w e r e a l s o u s e d t o
a n a l y s e t he r o l e o f t h e  3 - A R i n n e o n a t a l l a mb c o l d t o l e r an c e .
L e a n M u s c l e G r o wt h: T h r e e s i r e g r o u p s f r o m t h e B l u e v i e w
H a mp s h i r e S t u d F l o c k w e r e u s e d t o a s s e s s t h e r o l e o f t h e  3 -AR in
l e a n mus c l e g r o w t h i n l a mbs b e f o r e w e a n i n g . T h e l a mbs w e r e
weaned on the first of Dece mber (2 0 0 0 ) w h e n t h e a v e rage age of the
l a mbs w a s 8 9 d a y s . A f t e r l a m b i n g , t h e e w e s a n d l a mbs w e r e
ma i n t a i n e d i n o n e m o b o n p e r e n n i a l r y e g r a s s ( L o l i u m p e r e n n e ) a nd
c l o v e r ( Trifolium pratense & T r i f o l i u m r e p e n s ) p a s t u r e wi t h n o
a r t i f i c i a l s u p p l e me n t s .
3.2 Methods
Blood Collection, DNA Pu rification and Extraction
Whole blood was collected from the sires involved in the cold
t o l er a n c e t r i a l s a n d fr o m t h e p ro g e n y i n t h e H a m p s h i r e f l o c k t h a t
w e r e me a s u r e d f o r l e a n mus c l e g r o w t h . T h i s w a s a c h i e v e d e i t h e r v i a
v e n o p u n c t u r e o r b y t a k i n g a s ma l l n o t c h o u t o f t h e e a r o f t h e a n i ma l
a n d c o l l e c t i n g s o me b l o o d o n t o F T A  c a r ds ( Lif e Te c hnologie s,
G a i t h e r s b u r g , U . S . A . ) . T h e b l o o d w a s t h e n a l l o we d t o d r y o n t h e
c a r d a n d w a s s t o r e d i n d a r k n e s s a t r o om t e mp e r a t u r e u nt i l a n a l ys i s .
The DNA on the FTA  c a r d s w a s t h e n p u r i f i e d a c c o r d i n g t o
ma n u f a c t u r e r ’ s i n st r u ct i o n s ( s e e A p p e n d i x 3 ) .
A m p l i f i ca t i o n o f G e n e C o d i n g t h e  3 Adrenergic Receptor.
From the purified DNA on the FTA cards, a 225 base pair
r e g ion w ithin the single la r ge int r o n w hi c h i nt e rr u p t s t h e c o d i n g
s e q u e n c e o f t h e o v i n e  3 - A R g e n e w a s a mp l i f i e d u s i n g t h e
P o l y me r a s e C h a i n R e a c t i o n ( P C R ) .
46
Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
T h e p r i me r s u s e d i n t h e P C R w e r e d e s i g n e d f r o m t h e o v i n e  3 AR gene sequence (Forrest & Hickford, 2000; GenBank accession
n o . A F 1 0 9 9 2 8 ) . T h e p r i me r s e q u e n c e s u s e d w e r e a s f o l l o w s :
F o r w a r d p r i me r 5 '- T C T T A C C ATCACGCGAGCT GGCT-3 ' and
r e v e r se p r i me r 5 '- A C T C C A A C C C G A C C C G C T T C - 3 '. F o r e a c h
s a mpl e , a 2 0  L r e a c t i o n c o n t a i n i n g 1 PCR buffer and 1 U of Taq
p o l y me r a s e ( Q i a g e n , G mB H , H i l d e n , G e r ma n y ) , 1 0 0 M d N T P s , 2 5 0
nM o f e a c h p r i me r a n d 1 0 0 n g o f o v i n e g e n o mi c D N A ( s t a n d a r d s ) o r
o n e F T A p u n c h e s ( s a mp l e s ) w e r e a mp l i f i e d u s i n g 3 0 c y c l e s o f 9 4 C
f o r 3 0 s ( d e n a t u r a t i o n ) , 6 5C f o r 3 0 s ( a n n e a l i n g ) , a n d 7 2  C for 30s
( e longation). T he P C R pr oduc ts we re then confirme d on a 1%
a g a r o s e ge l i n 1  T B E ( 8 9 mM T r i s b o r a t e , 8 9 mM B o r i c a c i d & 2
mM Na 2 EDT A (pH 8.0)), whic h wa s r un f or 30 mi nute s a t 5 volts
p e r c e nt i me t r e .
Detection of  3 Adrenergic Recept or Pol ymorphism.
PC R -Single S trand Conf or ma tion Polymorphism (PCR-SSCP)
w a s u s e d t o s c r e e n f o r p o l y m o r p h i s m a t t h e o v i n e  3 -AR locus using a
me t h o d s i mi l a r t o F o r r e s t e t al . ( 2001) . A 3 L a l i q u o t o f e a c h
p r o d u c t wa s mi x e d w i t h 1 4 L o f l o a d i n g d y e ( 9 5 % f o r ma mi d e , 2 0
mM E D T A , 0 . 0 5 % b r o mo p h e n o l b l u e , 0 . 0 5 % x y l e n e c y a n o l ) ,
denatured for 5 mi n at 95 C a nd the n a pplie d to a 11%
p o l y a c r y l a mi d e : b i s a c r y l a mi d e ( 3 7 . 5 : 1 ) g e l ( 1 6  1 8 c m, 1 . 0 m m
s p a c e r s , 20 w e l l c om b ) c o n t a i n i n g 1 % f o r ma mi d e a n d 2 % g l y c e r ol .
T h e s a mp l e s w e r e s e p a r a t e d a t 2 2 0 V f o r 1 7 h o u r s u s i n g a Pr o t e a n I I
c e l l ( B i o R a d , H e r c u l e s C A , U S A ) . E l e c t r o p h o r e s i s w a s p e r f o r me d i n
a 1 0C r o o m w i t h 1 2  C wa te r c ir c ula ting thr ough the c e ll c or e . Gels
w e r e s i l v e r - s t a i n e d a c c o r di n g t o t h e me t h o d o f S a n g u i n e t t i e t a l .
( 1 9 9 4 ) a n d t h e b a n d i n g p a t t e r n s c o mpa r e d to the sta ndards identified
b y F o r r e s t e t a l . (2001). These standards wer e d e r i v e d f r o m M e r i n o
a n d B o r d e r d a l e a n i ma l s i d e ntified by PCR-SSCP as being
h o mo z y g o u s f o r e a c h o f t h e  3 - A R a l l el e s .
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
DNA Se q uencing and Analysis
N o a n i ma l s f r o m t h e H a mps h i r e b r e e d h ad p r e v i o us l y b e e n
t y p e d f o r t h e  3 - A R g e n e , s o f r o m 4 a n i ma l s i d e n t i f i e d b y P C R SSCP as being homozygous, the 225bp region of the 3-AR intron
w a s s e q u e n c e d t o c on f i r m a l l e l e i d e nt i t y . T h e s eq u e n c e f o r e a c h
f r a g me n t w a s d e t e r mi n e d d i r e c t l y from PCR products. Se quencing
was performe d by the Wa ikato DNA Se q u e n c i n g F a c i l i t y , U n i v e r s i t y
of Wa ikato, New Ze aland. Electroni c c o p i e s o f t h e s e q u e n c e s w e r e
e d i t e d us i n g t h e p r i n t e d e l e c t r o p h e ro g r a ms . M u l t i - a l l e l e a l i g n me n t s
(DNA) we re carried out using DNAM AN™ (Lynnon BioSoft,
version 4.0).
Cold Mortalit y & Climate Data
T h e c o l d m o r t a l i t y a n d c l i ma t e d a t a u se d i n t hi s s e c t i o n w a s t h e
s a me a s t h a t u s e d t o a n a l y s e s i r e l i n e va r i at i o n i n n e o n a t al c o l d
mortality (Chapter 2).
Measurement of Lamb Lean Muscle Growth
T h e l a mb s w e r e w e i g h e d a t b i r t h a n d t h e n a g a i n a t w e a n i n g ,
w hen ultrasound scannin g a lso took p l a c e . L a mb g r o w t h r a t e w a s
c a l c ul a t ed b y t h e fol l o w i n g eq u a t i o n:
G r o w t h R a t e = We a n i n g w e i g h t ( k g ) – b i r t h w e i g h t ( k g )
Age a t we a ning ( da ys)
U l t r a s o u n d s c a n n i n g u s i n g a n Aloka SSD 210DX Echo Ca mera
( A l o k a C o . L i mi t e d , T o k y o , J a p a n ) w a s u s e d t o me a s u r e t i s s u e
d e p t h s ( f a t a n d mu s c l e ) a b o v e t h e 1 3 t h r i b o f e a c h l a mb . T h e a g e o f
t h e e w e , b i r t h r a n k a n d l a mb g e n d er w a s a l s o r e cor d e d a t bi r t h .
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
S t a t i s t i cal A n a l ysi s
C o l d T o l e r a n c e : T he c o l d mo r t al i t y a nd c l i ma t e d a t a fr o m
c h a p t e r 2 w a s c o mb i n e d i nt o o n e d a t a s e t a n d a n a l y s e d i n SPSS
(Version 10.0, SPSS Incorporated, Chicago). Th e p r e d ic t or v a r ia b l es
i d e n t i f i e d i n c h a p t e r 2 a s i n f l u en c i n g l a mb m o r t a l i t y d u e t o c o l d
e x p o s u r e ( b i r t h w e i g h t , c l i ma t e , s i r e ) a n d t h e c o r r e s p o n d i n g s i r e  3 A R g e n o t y p e f o r e a c h l a mb w a s a n a l ys e d a g a i n st e a c h o t h e r u s i n g
chi-square, 1-way ANOVA, correlati on a nd T- te st te c hnique s to
q u a n t i f y t h e r e l a t i o n s h i p b e t w e e n the m. Logistic r e gr e ssion wa s
u s e d t o c a l c u l a t e t he c o mbi n e d e f f e c t s o f s i r e g e n o t y p e , b i r t h
w e i g h t , t h e p r e d i c t e d r a t e o f he a t l o s s a n d t r i a l u p o n c o l d i n d u c e d
l a mb mor t a l i t y . T h e a c c u r a c y o f t h e l o gi s t i c r e gr e s s i o n mod e l s w a s
c a l c ul a t ed i n a s i mi l a r ma n n e r t o t h at d es c r i b e d i n c h a p t er 2.
L e a n M u s c l e G r o wt h : T h e e f f e c t o f s i r e , d a m a g e , l a mb
g e n d e r , b i r t h r a n k a n d l a mb  3 - AR ge notype we r e a na lyse d a ga inst
t h e c o mpo n e n t s o f l e a n mus c l e g r owth ( bir th we ight, gr owth r a te ,
m u s c l e a n d f a t d e p t h ) u s i n g c h i - squa r e ( c a te gor ic a l va r ia ble s) a nd
1 - w a y A N O V A ( c o n t i n u o u s v a r i a bl e s ) me t h o d o l o g i e s i n SPSS.
F r o m t h e s e a n a l y se s, t h e v a r i a b l e s t ha t h a d a s i g ni f i c a n t i n f l u e n c e
u p o n l e a n mu s c l e g r o w t h w e r e e s t ablished. The relationship between
t h e s e v a r i a b l e s w a s t h e n q u a nt i f i e d u s i n g c h i - s q u a r e , 1 - wa y
A N O V A , correlation and inde pe nde nt s a mpl e s T - t e st t ec hn i q u e s .
T h o s e v a r i a b l e s w i t h n o s t r o n g i n t errelationship(s) were retained for
s u b s e q u e n t a n a l y s i s a l o n g w i t h t h e mos t significant variable of any
r e l a t e d p a i r i n g . C o m p a r i s o n o f t h e mo s t c o m mo n a l l e l e
c o mb i n a t i o n s ( n > 1 0 ) u p o n b i r t h w e ig h t , g r o w t h r a t e , mu s c l e d e p t h
a n d f a t d e p t h w a s a n a l y s e d u s in g a G e n e r a l Li n e a r M o d e l ( G L M )
w h i c h i n c l u d e d t h e p r e d i c t o r v ar i a b l e s i d e n t i f i e d a b o v e a s
i n f l u e n c i n g l e a n mu s c l e g r o wt h .
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
3.3 Results
Lamb Mortality due to Cold Exposure
P C R - S S C P a n a l y s i s o f t h e 1 5 s i r e s ( f r om f o u r t r i a l s ) r e v e al e d
six different alleles in ten differ e n t c o m b i n a t i o ns ( T a b l e 4) .
T a b l e 4 :  3 - A R g e n o t y p e o f a l l t h e s i r e s u s e d i n t h e c o l d t o l e r a nc e
study.
Flock
Year
Sire
3-AR genotype
Number of Progeny
Borderdale
1999
16-95
AC
59
1999
82-95
AA
72
1999
25-94
BF
60
1999
4-97
AA
76
2000
226-98
AF
166
2000
263-98
AB
63
Meat
2000
8585
DE
89
Quality
2000
122-98
EF
157
2000
8512
EF
150
2000
238-97
AA
97
2000
8255
AE
121
2000
159-97
AC
126
2000
GLD26
CC
54
2000
R356
DE
51
2000
EN132
CD
43
Merino
L o g i s t i c re g r e s si o n a n a l y si s of l a mb m o r t al i t y d ue t o c o l d
exposure and the sire 3-AR genotype revealed that there was
v a r i a t i o n b e t w e e n s i r e  3 - AR ge notype s ( p= 0.001) . Chisqua r e
a n a l y s i s s h o w e d t h a t l a mbs f r o m s i r e s w i t h t h e C D  3 - A R g e n o t y p e
h a d t h e h i g h e s t mor t a l i t y a n d l amb s f r o m s i r e s w i t h t h e B F  3 -AR
g e n o t y p e h a d t h e h i g h e s t mor t a l i t y ( Fi g u r e 1 4 ) .
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
Figure 14: T h e u n c o r r e c t e d a m o u n t o f l amb mor t a l i t y d u e t o c o l d
e x p o s u r e f o r e a c h s i r e 3-AR genotype. Percentages that
a r e s i g n i f i c a n t l y d i f f e r e n t (p<0.05) are represented by
t h e d i f f e r e n t a l p ha b e t i c s u b sc ri pt s a t t h e t o p o f e a c h b a r .
Accuracy of the Logistic Regression Model Predicting Lamb Mortality
The accuracy of the logistic re g r e s si o n m o d e l u s ed t o a n a l ys e
t h e v a ri a t i o n b e t w ee n s i r e g en o t y p e s i n l a mb m o r t al i t y due t o c o l d
exposure was 0.1%, though there was very little error in the logistic
r e gression model predic tion of whi c h l a m b s w o u l d d i e f o r m c o l d
e x p o s u r e . T h e e r r o r w a s c o n f i n e d ma i n l y t o t h e p r e d i c t i o n o f w h i c h
l a mbs w o u l d s u r v i ve c o l d e x pos u r e ( 1 46 s u c h e r r o r s c o mpa r e d t o 6
in the prediction of which lambs would die from cold exposure).
T h i s w a s t h e r e s u l t o f mor e l am b s d y i n g t h a n w a s e x p e c t e d a f t e r
a n a l y si n g t h e c o mbi n e d e f f e c t s of sir e , bir th we ight a nd the
predicted rate of heatloss.
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
Lean Muscle Growth
U n i v a r i a t e a n a l y si s r e v e al e d s i r e l i n e v a r i a t i o n i n l a mb g r o w t h
r a t e ( p = 0 . 0 0 4 ) b u t n o t i n b i r t h weight (p=0.416), muscle depth
(p=0.061) or in fat depth (p=0.888). Sire pair comparison revealed
t h a t t h e p r o g e n y o f 3 2 1 / 9 8 h a d f a s t e r growth rates than the progeny
o f either 984/97 (p=0.002) a nd 309/ 9 8 ( p = 0 . 0 0 6 - T a b l e 5 ) . Wh e n
t h e d a t a w a s c o r r e c t e d f o r t h e a g e o f t h e d a m, b i r t h r a n k a n d l a mb
gender using a general linear model, sire line variation was only
de t e ct e d in gr owt h r a t e (p=0.046), though a t r e n d wa s obs e r ve d i n
mus c l e dept h (p=0.096). No va r i at i on be t we e n si r e l i ne s wa s
o b s e r v e d i n e it h e r b i r t h wei gh t (p=0.448) o r fa t d e p t h (p=0.906)
w h e n t h e d a t a w a s c o r r e c t e d u s i n g t h e g e n e r a l l i n e a r mo d e l .
T a b l e 5 : S i r e l i n e v a r i a t i o n i n l e a n mu s c l e g r o w t h . S i g n i f i c a n t l y
d i f f e r e n t me a n s ( p < 0 . 0 5 ) i n e a c h c o l u mn a r e r e p r e s e n t e d
by different alphabetic subscripts.
Sire
Sire
Genotype
309/98
321/98
984/97
BE
EE
BE
Number
of
Progeny
19
11
26
Birth
Weight
(kg)
4.890.54
5.220.92
5.190.96
Average
Growth
Muscle
Rate
Depth
(kg/day)
(mm)
0.3450.07a 23.532.70
0.4260.06b 25.631.69
0.3340.08a 24.192.20
Fat
Depth
(mm)
3.841.89
4.091.22
3.961.43
PC R -SS C P analysis of the  3 - A R g e n e r e v e a l e d t h a t 4 d i f f e r e n t
a l l el e s i nh e r i t e d i n t y p i c al Me n d e l i a n fa s h i o n w er e p r e se n t i n t h e
p r o g e n y o f t h e l e a n m u s c l e t r i a l (Figure 15). Of these 4 alleles,
a l l el e s E a n d B w e r e i n h e ri t ed fr o m t h e s i r es a nd a l l el e s A a n d C
w e r e o b s e r v e d i n h e t e r o z y g o u s p r o g e n y ( s o me o f w h i c h a r e n o t
shown in Figure 15). The overall fr e que nc y of the a lle le s A, B, C
and E in the Ha mpshire flock was 0.02, 0.30, 0.05 and 0.63
r e s p e c t i v e l y , w h i l e t h e g e n o t y p e f r e que nc ie s we r e 0.414 ( EB) , 0.36 0
(EE), 0.108 (CE), 0.072 (BB), 0.018 (AB) and 0.018 (AE).
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
Animal:
Alleles: A
Standards
B C D
E
Sire
Progeny
.
F BE AB BE EE EE BB BE BB BE BE EE EE BB BE
Figure 15: P C R - S S C P g e l s c o n t a i n i n g t h e o v i n e  3 A R a l l e l e
s t a n d a r d s a n d s o me o f t h e p rogeny of 984/97. The genotype of
t w i n s i s un d e r l i n e d s o t h a t t h e i n h e r i t a n c e c a n b e o b s e r v e d .
Sequence analysis of the homozygous 3 AR genotypes present
i n t h e l e an mus c l e t r i al ( T a b l e 7 ) r e ve al e d t h at t he s e q u e n ce s o f
a l l el e s E a n d B w e r e i d e n t i c al t o t he s t a n d a r d s i d e nt i fi e d b y F o r r e s t
e t a l . (2001). The effect of i n h e r i t i n g e i t h e r o f t h e s e a l l e l e s ( i . e . B E
v s . E E – t h e o n l y g e n o t y p e s p r e s e nt i n mo r e t h a n 6 p r o g e n y ) u p o n
t h e c o mp o n e n t s o f l e a n mu s c l e g r o w t h w a s a n a l y s e d . N o d i f f e r e n c e
( p < 0 . 0 5 ) b e t w e e n w h i c h a l l e l e w a s inhe r ite d wa s obse r ve d in bir th
w eight, grow th rate, mus c le de pth o r f a t d e p t h e v e n w h e n t h e d a t a
w a s c o r r e c t e d f o r t h e a g e o f t h e d a m, b i r t h r a n k a n d l a mb g e n d e r
u s i n g a g e n e r a l l i n e a r mo d e l ( T a b l e 6 ) .
T a b l e 6 : V a r i a t i o n b e t w e e n  3 A R g e n o t y p e s i n l e a n mu s c l e g r o w t h .
T h e s t a n da r d d e v i a t i o n f o r e a c h me a s u r e me n t i s s h o w n .
3 AR
Genotype
Number of
Progeny
BE
EE
Overall
22
20
42
Birth
Weight
(kg)
5.080.95
5.170.78
5.120.86
Average
Growth
Muscle
Rate
Depth
(kg/day)
(mm)
0.3520.090
24.452.36
0.3700.071
24.502.48
0.3610.080
24.482.39
Fat
Depth
(mm)
3.771.57
4.101.48
3.931.52
53
Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
T a b l e 7 : DNA sequ ences of the ovine  3 - AR a lle le sta nda r ds a nd
t h e t w o m o s t c o m m o n a l l el e s p r e s e n t i n t h e l ea n mus c l e
g r o w t h t ri a l
Allele
Allele
560-00
566-00
Allele
Allele
Allele
321-98
554-00
Allele
A TCTTACCATCACGCGAGCTGGCTTTGACTTGCCGAGACTAGAGGGCAACC 50
B -------------------------------------------------- 50
-------------------------------------------------- 50
-------------------------------------------------- 50
C -------------------------------------------------- 50
D -------------------------------------------------- 50
E --------------------------------T---------.------- 49
--------------------------------T---------.------- 49
--------------------------------T---------.------- 49
F -------------------------------------------------- 50
Allele
Allele
560-00
566-00
Allele
Allele
Allele
321-98
554-00
Allele
A CCCCATTCCCTGCCCCACCCCATCCCCGCGCCAGTCCCCAAGCCTTCGGG 100
B -------------------------------------------------- 100
-------------------------------------------------- 100
-------------------------------------------------- 100
C -------------------------------------------------- 100
D ------C-------------------------C----------------- 100
E -------------------------------------------------- 99
-------------------------------------------------- 99
-------------------------------------------------- 99
F ------------T------------------------------------- 100
Allele
Allele
560-00
566-00
Allele
Allele
Allele
321-98
554-00
Allele
A CTCAGTTCTGGTTTCTTTGGAAAGTCTGATAGCCCCGAAGGTGAGGATTC 150
B -------------------------------------------------- 150
-------------------------------------------------- 150
-------------------------------------------------- 150
C -------------------------------------------------- 150
D -------------------------------------------------- 150
E -------------------------------------------------- 149
-------------------------------------------------- 149
-------------------------------------------------- 149
F -------------------------------------------------- 150
Allele
Allele
560-00
566-00
Allele
Allele
Allele
321-98
554-00
Allele
A GCTTCCGGAATGAAGGCTAGCGGGGCTGAGGAAGCTGCGAGTGCGAATTC 200
B ---------------------A---------------T------------ 200
---------------------A---------------T------------ 200
---------------------A---------------T------------ 200
C ---------------------A---------------T------------ 200
D ---------------------C---------------------------- 200
E ---------------------A---------------T------------ 199
---------------------A---------------T------------ 199
---------------------A---------------T------------ 199
F ---------------------A---------------T------------ 200
Allele
Allele
560-00
566-00
Allele
Allele
Allele
321-98
554-00
Allele
A
B
C
D
E
F
TTCCCCAGTAGGAAGCGGGTCGGGTTGGAGT
--A-T---------------------------A-T---------------------------A-T-----------------------------T-----------------------------------------------------------T-----------------------------T-----------------------------T-----------------------------T--------------------------
231
231
230
230
231
231
230
230
230
231
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
M a l e l a m b s w e r e i de n t i fi e d as h a v i n g h i g h e r g r o w t h r a t e s t h a n
f e ma l e l a m b s ( p = 0 . 0 0 7 ) a n d a t r e n d t h a t l a mbs b o r n t o o l d e r e w e s
a l s o grew faster (p=0.062) wa s detected. No diffe rence (p<0.05)
b e t w e e n ma l e s a n d f e ma l e s o r b e t w een ewes of different ages was
o b s e r v e d i n b i r t h w e i g h t , mu scle depth or fat depth.
3.4 Discussion
Lamb Mortality due to Cold Exposure
V a r i a t i o n b e t w e e n t h e s i r e  3 A R g e n o t y p e s i n l am b mo r t a l i t y
due to cold exposure was observed until the data was corrected for
the influence of birth weight and the predicted rate of heat loss.
S i r e g e n o t y p e v a r i a t i o n w a s n o t o b s e r ve d i n t h e B o r d e r d a l e t ri a l
a f t e r a c c ou n t i n g f o r t h e s e f i xe d e f fe c t s , t h o u g h i t w a s s t i l l o b s e r v e d
w h e n t h e c o mbi n e d d a t a s e t w a s a n a l ys e d .
T h e a c c u r a c y o f t h i s a n a l y si s i s q u e s t i o n a b l e , a s t h e ma j o r i t y o f
t h e s i r e  3 genotypes w er e only r e pr e se nte d by a single sir e , thus
ma k i n g i t i mp o s s i b l e t o d i f f e r e n t i a t e t he e f f e c t s o f e a c h s i r e  3
g e n o t y p e f r o m g e n e r a l s i r e e f f e c t s . The environment would not have
been standardised for the genotypes that were only represented by a
s i n g l e s i r e , a s t h e y o n l y r e p r e s e n t e d one trial out of four. Therefore,
t h e v a r i a t i o n b e t w e e n s o me o f t h e s i r e g e n o t y p e s i n l a mb m o r t a l i t y
d u e to cold exposure could ha ve be e n due to va r ia tion be twe e n
trials.
P r e v i o u s w o r k b y F o r r e s t e t a l . ( 2 0 0 1 ) h a s f o u n d t h a t l a mb
d e a t h s o c c u r r i n g wi t h i n t h e f i r s t week of birth could not be
a t t r i b u t e d t o t h e i nh e r it a n c e o f a p a r t i c u l a r  3 - a d r e n e r gi c r e c e pt o r
a l l e l e , t h ou g h t h i s w a s t h o u g h t t o b e be c a u s e t he r e w e r e i n s u f f i c i e n t
cold deaths to ascertain the affect of  3 A R a l l e l e s o n c o l d s u r v i v al
( F o r r e st e t a l . 2 0 0 1 ) . T h i s w o r k u t i l i se d s e g r e g a t i o n a n a l y s i s ,
w h i c h i s a mu c h mo r e p o w e r f u l e x p er i me n t a l d e s i g n t h a n t h a t u s e d
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
h e r e , t h o u g h i t r e q u i r e s t h e g e n o t y p e of a ll of the pr oge ny ( de a d a n d
a l i v e ) f r o m h e t e r o z y g o u s s i r e s t o be recorded. Se gr egation analysis
me a s u r e s t h e v a r i a t i o n b e t w e e n t he t wo a l l e l e s i n h e r i t e d f r o m a
h e t e r o z y g o u s s i r e . T h e l o g i s t i c r e g r e s s i o n mo d e l s w e r e r e a s o n a b l y
a c c u r a t e a t p r e di c t i n g l a mb m o r t a li t y d u e t o c o l d e x p o s u r e , t h o u g h
s i mi l a r t o t h e l o g i s t i c r e g r e s s i o n mo d e l s d e s c r i b e d i n c h a p t e r 2 ,
l a mb mor t a l i t y d u e t o c o l d e x p o s u re w as p r e d i ct ed b e t t er t h a n l a mb
survival.
P C R - S S C P a n a l y s i s o f t h e 1 5 s i r e s ( f r om 4 t r i a l s) r e v ea l e d t h a t
a l l o f t h e s i x  3 - A R a l l el e s pre v i o u s l y i d e n t i fi e d b y F o r r e s t e t a l .
( 2 0 0 1 ) w e r e p r e s e n t i n t h e l e a n mu s cl e g r o w t h t r i a l . T h e s i x a l l e l e s
w ere arranged in 10 diffe r e nt genotype s, with AA be ing the most
c o m m o n g e n o t y p e ( fo u n d i n 3 s i r e s ) a n d a l l e l e C t h e o n l y a l l e l e
f o u n d i n a l l t r i a l s . Th e r e w e r e 4 d if f e r e n t a l l e l e s i d e n t i f i e d i n t h e
s i r e s o f t he B o r d e r da l e t r i al s ( b o t h y e a r s ) , 5 i n t h e M e a t Qu a l i t y
t r i a l a n d 3 i n t h e M e r i n o . Thi s d i f f e r e n c e i n g e n e t i c v a r i a t i o n
b e t w e e n t r i a l s i s e xp e c t e d c on s i de r i n g t h e n u mb e r o f s i r e s i n e a c h
t r i a l a n d r e l a t i v e p o p u l a t i o n s i z e s of each breed in New Ze aland.
T h e overall population s iz e of the Bor de r da le br e e d in NZ is
c o n s i d er ab l y s ma l l e r t h a n t he M er ino br e e d, whic h pote ntia lly ha s
l a r g e i mp l i c a t i o n s u p o n t h e a mo u n t o f v a r i a t i o n p r e s e n t i n  3 -AR
l o c u s w i t h i n t h e se b r e e d s . The Me a t Q u a l i t y t ri a l i s ma d e u p o f
c r o s s b r e d p r o g e n y , w h i c h a r e c o n s e q u en t l y mo r e g e n e t i c a l l y d i v e r s e
than pure-breds.
Lean Muscle Growth
V a r i a t i o n b e t w e e n s i r e l i n e s w a s f o u n d i n l a mb g r o w t h r a t e , b u t
n o t i n b i r t h w e i g h t , m u s c l e d e p t h o r i n fa t d e p t h w h e n a u n i v a r i a t e
a n a l y si s of t h e d a t a w a s c a r r i ed o u t . Wh e n t h e d a t a w a s c o r r e c t e d
f o r t h e a g e o f t h e d a m, r a n k a n d l a mb g e n d e r u s i n g a g e n er a l l i n e ar
m o d e l , s i re l i n e va r i a t i o n w a s s t i l l o n l y d e t e c t e d i n g r o w t h r a t e a n d
not in birth weight, muscle depth or fat depth. Previous studies have
56
Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
f o u n d g e n e t i c v a r i a t i o n i n l e a n mus c l e g r o w t h i n c l u d i n g s i r e l i n e
v a r i a t i o n i n b i r t h w e i g h t o b s e r v e d i n t he B o r d e r da l e a n d Me a t
Q u a l i t y t ri a l s i n t h e l a mb mor t a l i t y st u dy . B r e e d i n g p r o g r ams b y
S i m m a n d D i n g w a l l ( 1 9 8 9 ) , C a me r o n a n d B r a c k e n ( 1 9 9 2 ) a n d C l a r k e
e t a l . (1998) established tha t t h e r e i s si g n i f i c a nt g e n e t i c v a r i a t i o n i n
g r o w t h r a t e , mu s c l e d e p t h a n d f a t d e p t h ( me a s u r e d u s i n g u l t r a s o u n d
s c a n n i n g ) f o r p r o g r e s s t o ma d e b y s e l e c t i n g f o r t h e s e t r a i t s .
Heritabilities of between 0.20 and 0.30 for growth rate (reviewed in
P a rratt and Simm, 1987; Cr oston e t al . 1983), between 0.22 and
0 . 43 for m uscle depth an d be twe e n 0.16 a nd 0.35 f or f a t de pth ha ve
b e e n e s t i ma t e d i n t y p i c a l t e r mi n a l s i r e b r e e d s ( Su f f o l k s - S i m m a n d
D i n g w a l l , 1 9 8 9 ; T e x e l O x f o r d c r o s s b r e d s - C a me r o n a n d B r a c k e n ,
1 9 9 2 a n d L a n d c o r p “ L a mb S u p r e me ” c o m p o s i t e s - C l a r k e e t a l .
1998).
P C R -SS C P analysis of the  3 - A R g e n e r e v e a l e d t h a t 4 d i f f e r e n t
a l l el e s i nh e r i t e d i n t y p i c al Me n d e l i a n fa s h i o n w er e p r e se n t i n t h e
l e a n mus c l e t r i a l a nd s e q u e n c e a n a lysis r e ve a le d tha t the se que nc e s
o f a l l e l es E a n d B w e r e i de n t i c a l t o t h e s t a n d a r d s i d e n t i f i e d b y
Forrest et al. (2001). The overall frequency of the alleles was quite
different to that observed by Forrest et al. (2001) in 25 unrelated
New Zealand Merino rams . The high frequencies of the B and E
a l l el e s i s n o t s u r p ris i n g a s t he fl oc k is r e a sona bly inte r r e la te d a nd
these were the only alleles detected in the sires.
The effect of inheriting the B allele versus inheriting an E
a l lele (i.e. B E vs. E E ) o n the var i o u s c o mp o n e n t s o f l e a n m u s c l e
g r o w t h w a s a n a l y s e d . N o d i f f e r e nc e ( p > 0 . 0 5 ) b e t w e e n w h i c h a l l e l e
w as inherited w as observ e d in bi r t h w e i g h t , g r o wt h r a t e , m u s c l e
d e p t h o r fa t d e p t h e v e n w h e n t h e d a t a w a s c o r r e c t e d f o r t h e a g e o f
t h e d a m, b i r t h r a n k a n d l a mb g en d e r u s i n g a g e n e r al l i n e ar m o d e l .
Age of da m, birth rank and lamb g e n d e r a r e a l l fa c t o r s t h a t h a v e
b e en identified as influenc ing l e a n mu s c l e g r o wt h ( A l e x a n d e r ,
1974). In this study, ma le lambs we r e f o u n d t o g r o w f a s t e r a n d a
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
t r e n d w a s d e t e c t e d s h o w i n g t h a t l ambs did likewise. No effe ct due
to birth rank was found and none of the factors were found to
i n f l u e n c e m u s c l e a n d f a t d e p t h s . I t w a sn’ t p o s si bl e t o c or r e c t
m u s c l e d e p t h a n d f a t d e p t h f o r w e ig h t i n t h e g e n e r a l l i n e a r m o d e l ,
a s t h e c orr e l at i o n be t w e e n t he t r ai t s wa s t o o h i gh .
T h e l a c k o f r e s p o n s e t o v a r i a t i o n i n  3 -AR genotype in this
s t u d y c o n t r a s t s w i t h t h e f i n d i n g s o f F o r r e s t et al. ( 2 0 0 1 ) w h e r e
segegration analysis wi t h i n o n e B o r d e r d a l e s i r e l i n e ( g e n o t y p e A C )
e s t a bl i s h ed t h a t t h e i n h e ri t a n ce o f a p a rt i c ul a r  3 - A R a l l e l e ( A ) w a s
a s s o c i a t e d w i t h d e c r e a s e d t i s su e d e p t h o v e r t h e t h i r t e e n t h r i b ( G R ) ,
c o mp a r e d t o p r o g e n y t h a t i n h e r i t e d t h e o t h e r si r e a l l el e ( C ) . T h e G R
me a s u r e m e n t u s e d by F o r r e s t e t a l . ( 2001) wa s ba se d upon a
s u b j e c t i v e me a s u r e me n t ma d e b y f e e l ing the a mount of f a t c ove r ing
t h e mus c l e o n a l a m b ’ s r i b . F o r r e s t e t a l . (2001) also found that the
i n h e r i t a n c e o f a p a r t i c u l a r s i r e a l l ele did not a f f e c t bir th we ight or
growth rate in either the Merino or Borderdale lines, nor did it
a f f e c t G R a t w e a n i ng i n t h e M e r in o l i n e s . T h e u s e o f s e g r e g a t i o n
a n a l y si s w a s n o t p o s s i b l e i n t hi s st u dy b e c a u s e t h e n u mb e r o f
progeny from the heterozygous sires was not sufficient.
G e n e s w i t h ma j o r e f f e c t s ( r e s p o n s i bl e for mor e t h a n 2 0 % o f t h e
o b s e r v e d p h e n o t y p e ) h a v e b e e n p r e vi o us l y i d e nt i fi e d i n s he e p .
T h ese genes have m ainly be e n r e str ic te d to those inf lue nc ing
fecundity (Booroola (Fec B ) , I n v e r d a l e ( F e c X ) a nd Ja va ne se ( Fe c J )),
t h o u g h t he C a l l i p yge a n d C a r w e l l g e ne s a r e be l i e v e d t o be t h e f i r st
ma j o r g e n e s d i s c o v e r e d i n s h e e p t h a t i n f l u e n c e l e a n mu s c l e g r o w t h .
T h e C a l l i p y g e a n d C a r w e l l g e n e s a p p ea r t o c a u s e ma r k e d i n c r e a s e s
i n mus c l e ma s s a n d a d e c r e a s e i n o v e ral l c ar c a ss fa t n e s s . G e n e s w i t h
s i mi l a r m a j o r e f f e c t s h a v e a l r e a d y b e e n i d e n t i f i e d i n c a t t l e a n d p i g s
( F a h my , 1 9 9 9 ) .
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Chapter 3: T h e R o l e o f  3 A d r e n e r g i c R e c e p t o r G e n e P o l y m o r p h i s m i n C o l d
Tolerance and Lean Muscle Growth
T h e e w e s i n t h e l e an mus c l e g r o w t h t ri a l w e r e e xp o s e d t o
t o x o p l a s mo s a g o n d i i (Appendix 1) during p r e g n a n c y . T h i s h a d a
n e gative effect on the numbe r of la mbs pr e se nt a t we a ning a nd
c o nsequently reduced the numbe r of l a m b s me a s u r e d f o r l e a n mus c l e
g r o w t h . T h i s w o u l d h a v e ma d e i t mo r e d i f f i c u l t t o d e t e c t a n y
v a r i a t i o n b e t w e e n l a mb g e n o t y p e s a nd to show tha t this wa s a
significant difference. It is possible that the variation in genotypes
ma y h a v e a l s o b e e n r e d u c e d b y t h e s e d e a t h s .
O n e a v e n u e o f r e s e a r c h n o t p u r s u e d h e r e w a s t h e c o mp a r i s o n o f
 3 - A R g e n o t y p e s w i t h e s t i ma t e d b r e e d i n g v a l u e s ( E B V s ) f o r a n y o f
t h e t r a i t s s t u d i e d . Whi l e t h er e i s n’ t any reported trials using EBVs
t o s e l e c t for n e o n a t a l l a mb c o l d t o l e r a n c e , t h e i r u s e i n b r e e d i n g
p r o g r a ms s e l e c t i n g f o r l e a n m u s c l e growth is well established. The
b e n e f i t s o f c o mp a r i n g  3 -AR genotypes with EBVs in a trial like this
i s t h a t E B V s mor e a c c u r at e l y r e p re se n t t h e t r u e “ g e n e t i c v al u e ” o f
a n i n d i vi dua l t h a n t h e r a w data used in this study.
3.5 Conclusions
G e n e s o f ma j o r e f f e c t h a v e b e e n previously detected in sheep,
t h o u g h n o n e h a v e b e e n i d e n t i f i e d t ha t i n f l u e n c e n e o n a t a l l a mb c o l d
t o l e r a n c e . S l e e f o u n d e v i d e n c e t h a t one existed in the catecholamine
s t i mu l a t i o n o f b r o w n a d i p o s e t h e r mo g e n e s i s a n d t h e r e i s e v i d e n c e
t h a t i n d i ca t e s t h a t t h e  3 - A R g e n e i s a l i k e l y c a n d i d a t e . Ho w e v e r ,
t h i s h y p o t h e s i s w a s n o t c o n f i r med i n t h i s s t u d y , t h o u g h i t a p p e a r s
t h a t the results w ere conf ounde d b y a n u n s u i t a b l e e x p e r i me n t a l
d e s i g n . The r o l e o f t h e  3 - A R g e n e i n l e a n mu s c l e g r o w t h i n l a mb s
w a s a l s o i n v e s t i g a t e d . Wh i l e v a r i at i o n w a s f o u n d b e t w e e n s i r e l i n e s
i n l a mb g r o w t h r a t e , v a r i a t i o n b e t w e e n l a mb g e n o t y p e s w a s n o t
o b s e r v e d . S o w h i l e i t a p p e a r s t h a t the r e sults we r e c onf ounde d by
e x p e r i me n t a l d e s i g n , t h e r e i s e v i d e n c e t h a t i n f l u e n c e o f
p o l y mo r p h i s m i n t h e o v i n e 3 A R g e n e o n n e o n a t a l l a mb m o r t a l i t y
a n d / o r l e a n mu s c l e g r o w t h i s n o t s u ffi c i e n t t o b e c o n s i d er ed a ma j o r
gene effect.
59
Chapter 4: General Summary and Future Directions
N e o n a t a l l a mb s u r v i v a l h as an e x t r e me l y l o w h e ri t a bi l i t y ,
r e s u l t i n g f r o m t h e l a r g e n u m b e r o f e n v i r o n me n t a l a n d g e n e t i c
f a c t o r s t h a t i n f l u e n c e i t ( A l e x a n d e r , 1 9 8 4 ) . Co n s e q u e n t l y t h e r a t e
o f i mp r o v e me n t i n l a mb s u r v i v a l h a s b e e n r e a s o n a b l y l o w . B y
f o c u s s i n g u p o n a n i m p o r t a n t c o mp o n e n t o f l a mb s u r v i v a l ( n e o n a t a l
c o l d t o l e r a n c e ) w i t h a h i g h e r h e r it a b i l i t y ( e s t i ma ted at around 0.3
( Slee & Stott, 1986, Wolff et al., 1987) ) , mu c h f a s t e r i mp r o v e me n t
i s possible.
Under conditions that were representative of typical New
Zealand farming conditions, this experiment was sufficient to
show that there was phenotypic variation between sire lines
v a r i at i o n i n n e o n a t a l l a mb c o l d t o l e r an c e . T h i s i n d i c at e s t h a t s i r e
selection is sufficient to breed cold tolerant lambs provided
there are sufficiently large sire groups and genetic variation.
Lamb birth weight was also found to have a large influence on
lamb mortality due to cold exposure and was also found to be
largely responsible for the influence of birth rank on lamb
m o r t a l i t y d u e t o c o l d e x p o s u r e ( Cha pt e r 2) .
T h e s e f i n d i n g s h a v e g r e a t i m p l i ca t i o n s f o r t h e s h e e p i n d u s t r y .
T h e p r e s enc e o f s i re l i n e va r i a t i o n i n ne o n a t al l am b c o l d t o l e r a nc e
me a n s t h a t s i r e s e l e c t i o n c a n b e u s e d t o b r e e d c o l d t o l e r a n t l a mb s
a n d r e d u c e r e p r o d u c t i v e w a s t a g e . T h i s i s o f p a r t i c u l a r i mp o r t a n c e
t o f a r me r s i n a r e a s t h a t a r e r e g u la r l y e x p o s e d t o a d v e r s e w e a t h e r
c o n d i t i o ns l e a di n g t o h i g h n e o n a t a l l a m b mor t a l i t y a n d t o b r e e d s o f
s h e e p t h a t a r e mor e s u s c e p t i b l e t o c o l d e x p o s u r e t h a n o t h e r s . T h e
o p t i o n o f i mp r o v i n g l a mb v i a b i l it y b y g e n e t i c s e l e c t i o n i s
a t t r a c t i v e b e c a u s e t h e c o s t s i n v o l v ed a r e s ma l l a n d n o n - r e c u r r e nt i n
60
Chapter 4: General Summary and Future Directions
c o n t r a st t o t h e a l t e rna t i v es o f i mp r o v i n g n u t r i t i o n , s h e l t e r o r
i n c r e a s i n g t h e a mo u n t o f s h e p h e r d i n g ( H a l e y e t al . 1 9 8 7 ) .
Low birth weight was found to have a large influence on
n e o n a t a l l a mb c o l d t o l e r a n c e d u e t o c o l d t o l e r a n c e i n t h i s s t u d y .
Genetic variation in birth weight has also been observed by other
r e sear chers ( M cGui rk e t a l . , 1982; Smith, 1977; Dwye r e t a l . ,
2001) and in parts of this study . A l t h o u g h l a mbs w i t h h i g h b i r t h
w e i g h t s a r e p r e d i s p o s e d t o d y s t o c i a ( S c a l e s e t a l ., 1 9 8 6 ) , t h i s
r e s ult suggests that genetic va r ia t i o n i n b i r t h w e i g h t ma y b e w o r t h y
o f f u r t h e r s t u d y a s a me t h o d o f r e d u c i ng n e o n a t a l l a mb mo r t a l i t y .
D i r e c t se l e c t i o n for t h i s t r ai t i s p o s s i b l e , a n d t h e r e i s n o
r e q uireme nt for an unpre dic ta b l e c o l d c h a l l e n g e ( H a l e y et al .
1 9 8 7 ) . T h e i n f l u e n c e o f b i r t h w e ig h t o n n e o n a t a l l a mb mor t a l i t y
d u e t o c o l d e x p o s u r e h a s ma j o r i mp l i c a t i o n s f o r t h e h i g h f e c u n d i t y
b r e e d s l i k e t h e B o o r o o l a M e r i n o and Finnshe e p. Due to the la r ge
litter size of these breeds, the offspring are generally lighter than
l a mbs f r o m o t h e r b r e e d s a n d c o n s e q u e n t l y mor e s u s c e p t i b l e t o
d e a t h f r o m c o l d e x p o s u r e ( Hi n c h e t al . 1 9 8 5 ) . B e c a u s e o f t h e s e
fa c t o r s , fu r t h e r i n v e s t i g a t i o n i n t o t h e g e n e t i c f a c t o r s i n f l u e n c i n g
birth weight and hence neonatal lamb cold tolerance is
warranted. However, the birth weight of lambs is dependent
upon a large number of factors (maternal disease, birth rank,
sex, parental breed, maternal age, size and parity (Alexander,
1974)), making genetic improvement difficult, although direct
s e l e c t i o n f o r t h i s t r a i t i s p o s s i b l e ( Ha le y e t a l . 1987).
S i r e l i n e a n a l y s i s l i k e t h a t us e d t o a n a l y s e n e o na t a l l a mb
m o r t a l i t y d u e t o c o l d e x p o s u r e may n o t b e a s p o w e r f u l a s o t h e r
me t h o d s o f a s s e s s i n g t h e g e n e t i c v ar i a t i o n o f p a r t i c u l a r t r a i t s , b u t
i t ’ s s t u d y i s o f p a r t i c u l a r i mp o r t a n t a n c e t o c o m me r c i a l b r e e d i n g
p r o g r a ms u t i l i s i n g t e r mi n a l s i r e s . T e r mi n a l s i r e s a r e e x p e c t e d t o
p a s s o n g e n e s c o n f e r r i n g a n i m me d i a t e i mp r o v e me n t i n
61
Chapter 4: General Summary and Future Directions
p e r f o r ma n c e , w h e r e a s i mp r o v e me n t t h a t o c c u r s a c r o s s ma n y
g e n e r a t i on s a s i s a c c e p t a bl e i n s e l f - r e p l a c i n g f l o c k s .
D e t a i l e d i n v e s t i g a t i o n o f t h e ef f e c t s o f v a r i a t i o n i n t h e g e n e
c o d i n g t h e  3 A R on cold tole r a nc e a nd le a n mu s c l e g r o wt h s h o w e d
t h a t polym orphism in sir e  3 AR ge notype s is linke d with c old
m o r t a l i t y ( C h a p t e r 3 ) . G e n e s o f maj o r e f f e c t h a v e b e e n p r e v i o u s l y
d e t e c t e d i n s h e e p , t h o u g h n o n e h a v e been previously i d e n t i f i e d t h a t
i n fl u e n c e n e o n a t al l a mb c o l d t o l er a n c e . Wh i l e t he r e i s e v i d e n c e
t h a t p o l y m o r p h i s m i n t h e  3 -AR gene influences neonatal lamb
c o l d t o l e r a n c e , t h i s h y p o t h e s i s wa s not c onf ir me d in this study.
The results were confounded, however, by an unsuitable
e x p e r i me n t a l d e s i g n . A s i mi l a r l a c k o f r e s p o n s e t o v a r i a t i o n i n t h e
 3 - A R g e n e f r o m l e a n mu s c l e g r o w t h w a s a l s o d e t e c t e d . W h i l e
v a r i a t i o n b e t w e e n s i r e l i n e s i n l a mb g r o w t h r a t e w a s f o u n d ,
v a r i a t i o n b e t w e e n l a mb g e n o t y p e s i n a n y o f t h e c o mp o n e n t s o f l e a n
m uscle grow th w as not obse r ve d. Consequently there is no
e v i d e n c e t h a t t h e use o f t h e  3 A R g e n e a s a g e n e t i c ma r k e r f o r
e i t h er c o l d t o l er a n ce o r l ea n m u s c l e g ro w t h i n l am b s i s p o s s i b l e .
Marker assisted selection would have increased the rate of genetic
p r o g r e s s a n d r e mov e d t h e n e e d f o r l a m b s t o b e cha l l e n ge d w i t h
c o l d i n ord e r t o se l e c t for r esi s t a nc e . Th u s t h e u se o f ma r k e r
a s s i s t e d s e l e c t i o n c a n r e d u c e o r e v e n e l i mi n a t e t he c o s t s i nv o l v e d
with the loss of production during such challenges and the
p h e n o t y p i c me a s u r e me n t o f t h e t r ai t s , as w e l l a s b e i n g mor a l l y
acceptable (Garrick & Spelman 1996, Davis & DeNise 1998).
I n a n i d eal s i t ua t i o n, t h e r e sul t s o f t h i s e x p e r i me n t n e e d t o b e
r e p l i c a t e d t o e n s u r e t h e i r a c cu r a c y . T he a c c u r a c y o f t h i s s t u d y
w o u l d a l s o b e n e f i t f r o m s o m e i mp ro v e me n t i n e x p e r i me n t a l d e s i g n .
Difficulties arising from the use of field trials, inadequate progeny
group sizes and flocks with low ge n e t i c v a r i a t i o n a r e d i s c u s s e d i n
62
Chapter 4: General Summary and Future Directions
t h e e x p e r i me n t a l c h a p t e r s . S ome o f t h e s e d i f f i c u l t i e s w o u l d b e e a s y
t o r e ct i fy i f a d e q u a t e r e s o u r c es w e r e a va i l a bl e . Wa t e r s pr a ye r s
( ‘ a rt i fi ci al r ai n ’ ) a nd fa n s ( ‘ ar t i fi ci a l wi n d ’ ) ca n b e u s e d t o mi mi c
a d v e r s e e n v i r o n me n t a l c o n d it i o n s d u r i n g l a mb i n g , t h u s
s t a n d a r d i si n g a n d gua r a n t e e i n g s u f f i c i e n t c o l d cha l l e n ge a c r o s s a l l
l a mbs involved in the tria l. W h e t h e r i t w o u l d b e mor a l l y a n d
e c o n o mi c a l l y a c c e pt a b l e t o de v i s e o r t o d e l i b e r a t e l y t o l e r a t e s u c h
c o n d i t i o ns l e a di n g t o h i g h m o r t al i t y i n o r d e r t o p e r mi t g e n e t i c
s e l e c t i o n i s d o u b t f u l , p a r t i c u l a rl y i n a c o m me r c i a l f a r mi n g
e n t e r pr i se ( H a l e y et al. 1 9 8 7 ) . E w e s c o u l d h a v e a l s o b e e n
s y n c h r o n i s e d i n g r o u p s t o e n s u r e t h a t r o u g h l y e q u a l n u mb e r s o f
e w e s w e r e l a mb i n g t o e a c h s i r e o v e r a gi v e n t i me p e r i o d ( e g. o n e
w e e k ) o f t h e t r i a l p e r i o d . T h i s would ha ve the dua l e f f e c ts of
h e l p i n g t o e l i mi n a t e t h e v a ri a t i o n b et w ee n s i r e l i ne s i n t he se v e r i t y
o f t h e w e a t h e r c o nd i t i o ns e nc o u n t e r e d a n d e n s u r i n g t h a t r o u g h l y
e q u a l n u m b e r s o f l a m b s w e r e b ei n g b o r n a t a n y g i v e n t i me ( a n d
w e a t h e r co n d i t i o n) w i t h i n t he t r i a l .
T o r e mov e t h e e f f e c t s o f i nsul a t i o n ( bi r t hc o a t an d s k i n
thickness) and behaviour (lamb a n d m a t e r na l ) fro m l a mb c o l d
t o l e r a n c e , t h e u s e o f t h e p r o g r es s i v e l y c o o l e d w a t e r b a t h m e t h o d
developed by Sa ms on and Slee (1981) w o u l d h a v e b e e n i d e a l . T h i s
me t h o d w o u l d h a v e b e e n p a r t i c u l a r l y suita ble f or a na lysing the r ole
o f p o l y mo r p h i s m i n t h e o v i n e  3 A R g e n e i n n e o n a t a l l a m b c o l d
t o l e r a n c e ( C h a p t e r 3 ) , a s i t w o u l d h a v e o n l y me a s u r e d t h e
t h e r mo g e n i c r e s p o n s e o f t h e l a mb .
T h e mos t l i mi t i n g f a c t o r i n t h i s s t u d y w a s t h e s ma l l s i z e o f t h e
si r e lines. L arger sire line s would h a v e ma d e i t e a s i e r t o d e t e c t a n y
v a r i a t i o n b e t w e e n s i r e l i n e s a nd to show tha t the dif f e r e nc e
b e t w e e n si r e l i n e s w a s a s i gni f i c a n t di f f e r e n c e . U s i n g m o r e
c r o s s b r e d a n i ma l s c o u l d h a v e a l s o i nc r e a s e d t he g e n e t i c v ar i a t i o n
63
Chapter 4: General Summary and Future Directions
w i t h i n t h e s t u d y , t h o u g h i t w o u l d h a v e b e e n i mp o s s i b l e t o e s t a b l i s h
a n y w i t h i n b r e e d ge n e t i c e f f e c t s .
V a r i a t i o n b e t w e e n si r e l i n e s i n n e o n a t al l a mb c o l d mor t a l i t y
d u e to cold exposure w ithin br e e ds wa s de te c te d, sugge sting tha t
s i r e l i n e se l e ct i o n i s s u ffi c i en t t o i nc r e a s e n e o na t a l l a mb c o l d
t o l e r a n c e . B i r t h w e i g h t w a s f o u n d t o p l a y a ma j o r r o l e i n n e o n a t a l
l a mb c o l d t o l e r a n c e a n d f u r t h e r s t udy into the r ole of bir th we ight
i n n e o n a t a l c o l d t o l e r a n c e a p p e a r s to be wa r r a nte d, though c a r e
m u s t b e t a k e n t o a v o i d i n c r e a s i n g t h e i n c i d e n c e o f d y s t o c i a . Whe n
t h e r o l e o f p o l y mo r p h i s m i n t h e o v i n e  3 A R g e n e o n n e o n a t a l
l a mb mor t a l i t y a n d / o r l e a n mus cl e g r o w t h w a s i n v e s t i g a t e d , t h e
results suggest that influence of  3 A R g e n e o n n e o n a t a l l a mb
m o r t a l i t y a n d / o r l e a n mu s c l e g r o w t h i s n o t s u f f i c i e n t t o b e
c o n s i d e r e d a ma j o r g e n e e f f e c t . Fur the r study is justif ie d howe ve r
o w i n g t o s o me o f t h e e x p e r i me n t a l d i f f i c u l t i e s e n c o u n t e r e d i n t h i s
study.
64
Acknowledgements.
This thesis couldn’t have been w r i t t e n w i t h o u t t h e h e l p o f t h e
f o llow ing people. Mum a nd Da d f or you know wha t whic h r e sulte d
i n me , p u t t i n g u p w i t h me a t h o me f o r 1 8 y e a r s a n d s t i l l l e t t i n g me
i n the door w hen I need a br e a k, f or f unding my s t udie s a nd f or
r e c o r d i n g t h e d a t a o n a n d p r o v i d in g a c c e s s t o o ne o f t h e r e s e a r c h
f l o c k s u s e d i n t h i s s t u d y . I w o u l d a l s o l i k e t o t h a n k my s i s t e r ,
A n g e l a f o r g i v i n g me s o me w h e r e t o l i v e f o r a c o u p l e o f y e a r s a n d
m y u n c l e , D r A n d r e w B r a y f o r a ll o f h i s a d v i c e , g u i d a n c e a n d t i me
s p e n t p r o o f - r e a d i n g . T h a n k s a l s o t o a l l t h e ot h er me mb e r s o f my
e x t e n d e d f a mi l y f o r t h e i r s u p p o r t .
I would like to acknowledge the generous grant I received from
t h e S i n c l a i r C u m mi n g s T r u s t a n d t he s c h o l a r s hi p I r e c e i v e d f r o m t h e
S u p r e me G r a n d R o y a l A r c h C h a p t e r Ju b i l e e M e m o r i a l S c h o l a r s hi p
fund, whi c h have greatly assiste d i n f u n d i n g my p o s t g r a d u a t e
studies.
I w o u l d l i k e t o t h a n k t h o s e p eo p l e a t Lin c o l n U n i v e r s i t y w h o
h a v e a s s i s t e d me i n m y s t u d i e s . M y s u pe r v i s or s , D r J o n H i c k f o r d
a n d P r o f . A n d r e w S y k e s , f o r a l l o f t h e i r g u i d a n c e , e n c o u r a g e me n t
a n d a d v i c e . O t h e r me m b e r s o f M o l e c u l a r B i o t e c h n o l o g y g r o u p
( S a n d y , G r a n t , A n d r e a , M a r i o , T u l a y , H u i t o n g a n d C a r me l ) f o r t h e i r
h e l p , s u p p o r t a n d a d v i c e , i n p a r ti c u l a r R a c h a e l Fo r r e s t w i t h o u t
w h o s e h e l p I w o u l d n ’ t h a v e b e e n c o mpl e t e l y l o s t . T h a n k s m u s t a l s o
go to Chris Logan, John Dunnet and Nigel Jay for all their help
c o l l e c t i n g t h e d a t a f o r a n a l y s i s , C h r i s Fr a mp t o n , w i t h o u t w h o m I
w o u l d h a v e b e e n l o s t i n a h u g e pi l e o f n u mb e r s a n d S u e W i n t e r f o r
k e e p i n g t r a c k o f t h e a d mi n i s t r a t i ve n i g h t ma r e t h a t I ’ v e u n d o u b t e d l y
c a u s e d ( a n d f o r t h e s u p p l y o f h u mo r o u s e ma i l s ) ) . I w o u l d a l s o l i k e
t o t h a n k a l l o f t h e o t h e r p o s t g r ad u a t e s i n t h e d e p a r t me n t w h o s e
w o r k / l i fe I ’ v e d i s t ur b e d a t s ome t i me o r a n o t h er . I n p a r t i cu l a r , t h e
65
i n h abitants of M Y o f f i c e ( I w a s t h e r e f i r s t ! ) , H a nn i e s , M ar i o ,
F r i d a y , K a t h y r n , Th a y i l a n i a n d T a ma n n a a n d t h e t h i r d f l o o r
r e s i d e n t s , B r a d l e y a n d L u c i n d a . T h a n k s t o t h e 4 t h f loor te a - r oom
n e w s p a p e r s u p p l i e r a n d o t h e r “ t h i n k t a n k ” me m b e r s . M a y y o u o n e
d a y s o l v e a l l o f t h e w o r l d s p r o b l e ms ( a t l e as t i n t h e o r y ) fr om g l o b a l
c o o l i n g t o w h y w e k n o w mo r e a b o u t inte r na tiona l spor t tha n those
who have played it!
I w o u l d l i k e t o t h a n k t h e f o l lo w i n g l o c a l g r o u p s f o r p r o v i d i n g
s o me r e l e a s e f r o m m y s t u d i e s : E l l e s m e r e C o n c e r t B a n d , S p r i n g s t o n
Dogs Rugby Team and Springston B Cricket team. Thanks also to
t h e E c o l o g y S o c i a l g r o u p f o r n o t b e i n g a c o mpl e t e g r o u p o f t r e e
h u ggers and being a good gr oup of gu ys to hang out with. In
p a r t i c u l a r t h a n k s t o t h e M a n s i o n ( an d i t ’ s i n h a b i t a n t s ) f o r b e i n g t h e
s c e n e o f ma n y o f m y c r i me s . T h a n k s t o my ma n y o t h e r f r i e n d s , i n
p a rticular H ayden, Mick ( a nd br othe rs), Eric (and Mrs), Jack, Rob
a n d my f l a t ma t e s J a n e a n d G a v i n .
A s muc h a s I w o u l d l i k e t o t h i n k tha t this the sis c ouldn’ t ha ve
b e e n w r i t t e n w i t h o u t me , I k n o w t ha t i t c o u l d n ’ t h a v e b e e n w r i t t e n
without the help of the you guys , it was a team effort, all credit to
you, it was a thesis of four chapters that required a lot of
c o m mi t me n t f r o m a l l p a r t i e s , i t s been a long and hard road to
c o mp l e t i o n b u t t h e t h e s i s w a s t h e w i n n e r o n t h e d a y .

If I’ve forgotten anyone, I sincerely apologise and your help was most appreciated.
66
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A l e x a n d e r , G . ( 1 9 6 2 ) . T e mp e r a t u r e r e g u l a t i o n i n t h e n e w b o r n l a mb .
I V . T h e e f f e c t o f w i n d a n d e v a p o r a ti on o f w a t e r fr o m t h e c o a t i n
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P o n z o n i , R . W. G r i ms o n , R . J . J a e nsch, K.S. Smi t h, D.H. Gifford,
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T u r r e t f i e l d s h e e p b r e e d i n g p ro j e c t : me s s a g e s o n p h e n o t y p i c a n d
g e n e t i c p a r a me t e r s f o r S o u t h A u s t r a l i a n M e r i n o S h e e p . P r o c e e d i n g s
of the Australian Association o f A n i m a l . B r e e d i n g a n d G e n e t i c s . 1 1
: 303 – 313.
P u r s e r , A. F . & K a r a m, H . A . ( 1 9 6 7 ) . L a mb s u r v i v a l , g r o w t h a n d
fleece
production
in
relation
to
b i r t hc o a t
type
among
welsh
m o u n t a i n s h e e p . Ani m a l P r o d u c t i o n 9 : 7 5 - 8 5
P u r s e r , A . F . & Y o u n g , G . B . ( 1 9 6 4 ) . Mo r t a l i t y a m o n g t w i n a n d
s i n g l e l a m b s . A n i m a l P r o d u c t i o n 6 : 321-329.
S a ms o n , D . E . & S l e e , J . ( 1 9 8 1 ) . F a c t o r s a f f e c t i n g r e s i s t a n c e t o
i n d u c e d b o d y c o o l i n g i n n e w b o r n l a mb s o f 1 0 b r e e d s , Animal
P r o d u c t i o n. 3 3 : 5 9 – 6 5 .
Sanguinetti, C. J., Neto, E. D. & Simpson, A. J. G. (1994). Rapid
s i l v e r s t a i n i n g a n d r e c o v e r y of PCR products seperated on
p o l y a c r i l a mi d e g e l s . B i o T e c h n i q u e s 17 : 9 1 5 - 9 1 9 .
S c a l e s , G .H . B u r t o n , R . N . & M o s s , R . A . ( 1 9 8 6 ) . L a mb m o r t a l i t y ,
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712 - 713.
S i m m , G . ( 1 9 8 7 ) . C a r c a s s e v a l u a t i o n i n s h e e p b r e e d i n g p r o g r a ms . I n
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S i m m , G . & D i n g w a l l , W. S . ( 1 9 8 9 ) . S e l e c t i o n i n d i c e s f o r l e a n me a t
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R e s e a r c h ( C a m b r i d g e ). 5 1 : 6 5 - 6 9 .
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S h e e p. E d s . J . M . M . C u n n i n g h a m, J . T . S t a mp & W . B M a r t i n .
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References
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( e d s ) F a cto r s A f f ec t i n g t h e S ur v i val. of New Born Lambs.
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S l e e , J . S i m p s o n , S . P . & Woo l l i a ms , J . A . ( 1 9 8 7 ) . M e t a b o l i c r a t e
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S t e v e n s D . A l e x a n de r G & L yn c h J . J . ( 1 9 8 2 ) . L a m b mo r t a l i t y d u e t o
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References
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L o ndon. T aylor and Franc is.
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Targeted disruption of the  3 a d r e n e r g i c r e c e pt o r g e n e . T h e J o u r n a l
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S y kes, A .R . G riffiths, R.G. & Sle e , J . ( 1 9 7 6 ) . I n f l u e n c e o f b r e e d ,
birth weight and weather on the b o d y t e mpe r a t u r e o f n e w b o r n
l a mb s . A n i m a l P r o d u c t i o n . 22 : 395 – 402.
S y k e s , A . R . ( 1 9 8 2 ) . T h e s h e l t e r r e q u i r e me n t s o f t h e n e w - b o r n l a mb .
P r o c e e d i ng s o f t h e N e w Z e a l a n d S o c i e t y o f A n i ma l P r o d u c t i o n . 4 2 :
7 – 11.
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me t a b o l i c p h e n o t y p e s o f mi c e l a c k in g n o r a d r e n a l i n e a n d a d r e n a l i n e .
Nature 387 : 94 – 97.
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F e c u n d i t y F l o c k . U n p u b l i s h e d M a s t e r s t h e s i s . Lin c o l n U n i v e r s i t y ,
Lincoln, New Zealand.
78
References
V e r mo r e l , M . & V e r n e t , J . ( 19 8 5 ) . M a j o r f a c tor s a f f e c ting
t h e r mo g e n e s i s a n d c o l d r e si st a n c e . I n : G . A l e x a n d e r J . D . B a r k e r &
J . S l e e ( e d s ) F a c t or s A f f e c t i n g t h e S u rv i v a l of N e w B o r n L a m b s .
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Wolff, J.E. Baker, R.L. Dobbie, P.M. Ford, A.J. & Jordan, R.B.
( 1 9 8 7 ) . G e n e t i c a s p e c t s o f c o l d resistance in newborn lambs.
P r o c e e d i ng s o f t h e N e w Z e a l a n d S o c i e t y o f A n i ma l P r o d u c t i o n . 4 7 :
9 3 – 98.
W o l l n y , C . Wa s s mu t h , R . M e i n e c k e - T i l l ma n , S . & D z a p o , V . ( 1 9 8 5 ) .
E n d o c r i n e a n d e n z y me a c t i v i t y a n d ma t e r n a l e f f e c t s i n r e l a t i o n t o
l a mb s u r v i v a l . A g ric u l t ur e - F a c t o r s a f f e c t i n g t he s urvival of new
b o r n l a mb s . E d s : G . A l e x a n d e r , J . D . B a r k e r a n d J . S l e e . B r u s s e l s ,
C o m mi s s i o n o f t h e E u r o p e a n C o m mu n i t i e s : 63-77.
79
Appendix 1: Cost of Neonatal Lamb Mortality due to
Cold Exposure
Number of Lambs Born 1
(Meat and Wool Economic Service of N.Z., 2001a)
=
 15%
15% of all lambs born die before weaning each year
(McCutcheon et al. 1981)
=
=
806 000 dead lambs
due to cold exposure
 $49.81
Average price of a lamb
(Meat and Wool Economic Service of N.Z., 2001b)
1
5.37 million dead
lambs
 15%
15% of all dead lambs die of cold exposure
(Gumbrell & Saville, 1986)
Cost of neonatal lamb mortality due to cold
exposure in New Zealand per annum.
35.8 million lambs
=
$ 40 million
All values are for the 2000 lambing season
80
Appendix 2: Hampshire Autopsy Report (3/9/1999)
¢
~
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Mis Rand
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R and M Gudex
Factory Rd
R.D .
R.D.
Temuka
Dear Ray and Margaret
Margar~t
re<:unls rr~s
ult s of
o f the
ror your recunls
0sults
samples collected on the 18.8.9
lR . 8.99,
9.
lamb abortion
inv
estij!;ation nn
nil
i nvestigation
background wlwn
wllt!n yo
.'l twn
two tooth . .1~
youu bagged
bagg e d the ewe
ewe~s there were !l
:; ix tuuth,
(lflC
'<)5 ewe:
.lI1U three '94
were empty.
empty . W
We
:;ix
tuoth, (lilt!
i!.WC: .1I1d
'9 ,~ ewes that IVcre
e
assumed they !tilU
ill I be
been
~here wa
nonc~ lVi th
'latE" '
had aJ
en tupped as (here
wass non!?
rh 'latp
~rayon and these
thc~e dr
dryy numbe
yo ni c death .,
crayon
numberr s suggested early emhr yonic
As
AS
ut the beginning of ;\ugust aand
laml""
Abortion starleu
starll:u <.Il
nd in aillllI 16 lamh
,)'J . the
~ tart of la
mbing (t
hree hd
hu vt'
v€'
had died by the :;~ sS ." ·q~.. ')'J.
t/1e official start
lambing
(three
died since) .
o th ewes
\dc~i
nat e d each year WI
wl th Tnxovax
vaccine0
'f wD
wo to
tooth
ew~ s hud Iltcn
Ilten 'dL
c inated
Toxovax vaccin
'fwo
On autopsy the
"1IlIhs sugge
tlt e! LlIlIhs
s ugge s ted death had occurred
close to being expelled ., Samples wcre
were collected.
in utero vu
ve,'v
ver- v\'
R~SJnT~
R~SJ1U:>
Toxoplasma
Stomach
contt;lltss
no
S tomach content
110
isolates .
significant isolates.
DI
QI SCUSS
~P1.S..S_ ION
I.9~
Th;-h'i'ghThe high -numlieJ'
numlii!r Lluff dr y
isolation of Toxuplasma
Toxupl.isma
plasma attack throughout
pos
i tive x 2 (titre
positive
( titre level
c.lmpylobacter,
Campylobacter,
no
1 : 128)
Salmonella ,
no
othe r
other
animals,
animals , despite tupp i ng marks , and thl!
th e
in two aborted lambE
lamb~ does
dot' s suggest Tow the pregnancy.
Toxo
s e abortion
dbortion any time during the pregnancy and the
Tuxo will cau se
th e
~IIYs
ctbOlled
dl
ys probabl y abol
dbol
It;d celliy
Cell I yin
y in lheir
the i r pregnancy . The aborted foetu :~
would have been too small to see.
that. you have regularly used Toxova~
lTliis
l,is is alarming 1l!5ult
Je s uit g i ven that
vaccint! liver
P.l s t yea
yearr s and the flock should he
ht,
vact:ine
uver Ule
tlie P.lst
immune .
hl' immune.
was very high
There is always a possibility that the Toxo attack wa:>
hi g h
....lilt.!
accine (you did comment that yoU!' neigh wc..! this overwhelmed the vvaccine
L~ster Mulligan had
hac..! a heavy dose of abortion in his
hiR ewes).
ewes) .
huur Lester
81
Appendix 2: Hampshire Autopsy Report 3/9/1999
-2~e v ertlil;)less
:-ieverlilidess
:-ieverlllldess
technique .
WI::
Wt:
JIlU~t
must
re 'l'/v icw
iew
vaccination
handling,
timing
and
Toxovax is a H!ry
,cry se nsitive
nsitivc \'vaccine
accine to heat and sunlight, it is 11
liv\::
livC;! val:cine
vaccine ulill
ullll
uuu L!xpircs.
cxpires, or goes off,
off . very quickly ., Recommenda
Recommenda-linns
tillns suggest I"
I:; ;,
"l1o
llOUld
ulu be: us
used
ed wi
within
thin 5 days (If
(1f arrival at 'the
th e
clinic Until it is
i~ time Ll)
l,) use tlie
tile vaccine keep it refrigerated .
Tox o,uxx Lllncent!d
l:ll ncent! 'dtc
tc vigorously
vigorousl y during preparation.
preparation .
Slluke the Toxu\<l.
Siluke
En/,
En/;
ure the gull
En!,ure
gu ll dod
dllll tubing
tubi:l!; iiss free o f material s cg
meths etc that could harm the live vaccine.
djsinfectant~
disinfectant~ .
Use
immediatelyy after preparing and mixing.
l' ~e immediatel
't
It should .Q!,).!
Q9J he
bl! u,eu
u;;eu wi
witliin
Lhin
thin four weeks of tupping hut can be used
mu..:h earlier if
j f cL'
cU lIven
ll venien
cg. OCL:cmbcl'
Oc..:cmbcl· January
Januar y,. Vaccine immunit'
immuni n·1'
mUL:h
ie n t eg.
should last the life of the animal.
animal .
Hope this is
0"
sume help
Yours sincerely
r . M.Colson S.V
. Se .
B.V.Se
B.V.St:
82
Appendix 3: Manufacturers Instructions for FTA
Card Purification.
~card'
Cat. No.: 10786-010
Lot No. 1074184
lIFE~TEO-NOLOGIE5_
LlFE~TEO-NOLOGIES_
Size: 100 cards
Store at room temperature.
Description:
FT A Cards are designed for the convenient collection, storage, and
subsequent DNA purification
puritication of blood samples for DNA analysis,
databanking, and genomics. The specimen area is constructed from FT A
paper, which is impregnated with a proprietary formulation. The card is
constructed of materials that will not aUect
atTect the DNA analysis of a blood
sample. A cover sheet protects the samples and allows the card to stand on
its own while drying the sample. The FT A Card can be used in conjunction
with the ULTRABARRlERTM
ULTRABARRIERTM Pouch and desiccant for shipping or long term
storage of blood specimens .
Quality Control:
FTA Cards are inspected tor
for product integrity and uniformity.
!i
I
I
.----- -
Protocols:
Application of blood sample
sample::
Spot peripheral blood directly on the FTA Card.
overnight before processing further.
Caution : Universal Precautions should be used
Caution:
potentially infectious human-source blood products.
S
&
I
Allow to dry II h to
when
handling
any
Extraction of peripheral blood DNA for PCR * analysis:
When the cells are lysed in blood stains on FTA paper, the nuclear DNA
from the white blood cells is immobilized within the matrix of the paper.
Heme and other inhibitors of PCR amplification
amplitication can be removed by
washing. After processing, the immobilized DNA is amplified directly on
the FTA paper in the presence of the appropriate amplification mix.
®
Doc.
Doe. Rev ..:: 10/05/99
IO/OS/99
This product is distributed for laboratory research only_
only. CAUTION : Not for diagnostic
d iagnostic use. The
safety
s afety and efficacy of this product in diagnostic or
o r other clinical uses has nol
not been established
established..
For
TeeM-LINEsM (800) 828-6686
F o r technical Questions about this product . call the Ufe Technologies TecH-LtNEsM
V
II..
Using a clean I to 33-l11m
-111111 punch. remove a sample from the middle of the
stain and place it into an amplitication tube whose minimum capacity is
300 ~L1.
~Ll.
Purification Reagent to each tube. Cap each tube
2. Add 200 ~d of FT A Puritication
and vortex 1-2 s at low speed.
33.. Allow the tubes to sit for
tor 5 min at room temperature with a second brief
vortex halfway through the incubation.
4. After the 5-min
5-l11in incubation. vortex for
tor a third time and then carefully
remove as much of the reagent as possible.
S.
5. Repeat steps 2 through 4 an additional two times for
tor a total of three
washes with the FT A Purification
Puritication reagent.
6. After FT A Puritication
Purification Reagent has been removed tor the third time,
add 200 ~L1
~d ofTE [10 mM Tris-HCI (pH 8.0),
8 .0), 0.1
O. lmM
mM EDTA). Cap each
tube and vortex 1-2 s at low speed.
77.. Allow the tubes to sit for
tor 5 min
mill at room temperature with a brief vortex
half way through the incubation.
8. Pour off
ofT the TE and replace with an additional 200 III
j.ll of TE . Cap each
tube and vortex 1-2 s at low speed.
99.. Allow the tubes to sit for
tor 5 min
mill at room temperature with a brief vortex
halfway through the incubation
incubation..
10. Pour off
oft' the TE and allow the FT
A paper punch to completely air dry.
FTA
This will require approximately I h at room temperature . Alternatively.
the drying can be accelerated by placing the tube with the punch at 60°C
for
tor 30 min.
11. The complete PCR amplification
amplitication mix is directly added to the punch
containing the puritied immobilized DNA.
DNA . It is recommended that
50-~d reaction volumes be used with all PCR amplitication mixes.
sO-~d
83
//
,I
"Welcome little [ella
fella ...
. . . -'fiJfab
·~r"ab a decent feed, lea/~
t'swim, like the cold, an' in 14 weeks we'll eat yer!"
yerl"