Leafy spurge (Euphorbia Esula L.) as a forage component for ewes and lambs
by Susan Jean Bartz
A thesis submitted in partial fulfillment of tne requirements for the degree of Master of Science in
Range Science
Montana State University
© Copyright by Susan Jean Bartz (1984)
Abstract:
Leafy spurge (Euphorbia esula L.) is an introduced perennial weed which is currently estimated to
infest over 200,000 hectares of rangeland in Montana. Leafy spurge's extensive root system and
reproductive modes make this weed extremely difficult to control. Because most methods of chemical
and biological control of leafy spurge have proven to be either ineffective or too costly, it has been
suggested that this weed be evaluated as a forage plant.
A research project was initiated in May of 1982 to determine the forage value of leafy spurge for sheep.
Average daily gains were determined for lambs and ewes grazing different treatment pastures. Diet
composition and forage intake of sheep were estimated, and production records of ewes having
consumed leafy spurge were examined.
The study area consisted of nine 1.66 hectare pastures -three replications of three treatment conditions.
Treatments were no spurge (control), light spurge (10-20 percent of the plant composition), and heavy
spurge (>20 percent of the plant composition). Five lamb/ewe pairs were randomly assigned to each
pasture. All sheep were weighed once every two weeks during the eight-week data collection period.
Ten 1.5 m^2 utilization cages were randomly located in each pasture, and the paired plot technique was
used to estimate the type and amount of forage removed.
Neither lambs nor ewes exhibited any deleterious effects due to the consumption of leafy spurge.
Average daily gains (ADG's) of lambs grazing heavy spurge pastures during 1982 were higher (P≤.05)
than average daily gains of lambs grazing light spurge and control pastures. ADG's of lambs grazing
heavy and light spurge-infested pastures during 1983 were higher (P≤.05) than ADG's of lambs grazing
control pastures. Estimates of forage removed and diet composition of sheep grazing the different
treatment pastures showed that leafy spurge comprised 41 percent of the diet of sheep selectively
grazing light spurge pastures and 55 percent of the diet of sheep selectively grazing heavy spurge
pastures. Performance records showed ewes exhibited no rebreeding or lambing difficulties the season
immediately following summer use of leafy spurge. LEAFY SPURGE; (EUPHORBIA ESULA L.) AS A
FORAGE COMPONENT FOR EWES AND LAMBS
by
Susan Jean Bartz
A thesis submitted in partial fulfillment
of tne requirements for the degree
of
Master of Science
in
Range Science
MONTANA STATE UNIVERSITY
Bozeman, Montana'
June 1984
APPROVAL
of a thesis submitted by
Susan Jean Bartz
This thesis has been read by each member of the thesis
committee and has been found to be satisfactory regarding
content, English usage, format, citations, bibliographic style,
and consistency, and is ready for submission to the College of
Graduate Studies.
[M.L
Chairperson, Graduate Committee
Approval for the Major Department
Date
Head, Major Department
Approved for the College of Graduate Studies
Date
Graduate Dean
•k-
iii
STATEMENT OF PERMISSION TO COPY
In presenting this thesis in partial fulfillment of the
requirements for a master's degree at Montana State University, I
agree that the Library shall make it available to borrowers under
the rules of the Library.
Brief quotations from this thesis are
allowable without special permission, provided that accurate
acknowledgement of source is made.
Permission for extensive quotation from or reproduction of
this thesis may be granted by my major professor,
or in his
absence, by the Director of Libraries when, in the opinion of
either,
the proposed
purposes.
financial
is for
scholarly
Any copying or use of the material in this thesis for
gain
permission. ■
Signature
use of the material
shall
not
be a l l o w e d w i t h o u t
my w r i t t e n
V .
ACKNOWLEDGEMENTS
Many people deserve a special thanks for their contribution
to the success of this research project. I would like to thank
Dr. Pete Fay and his associates for their time and effort in
setting up the different treatment pastures of the project and
also for enriching my weed science background.
I would like to
thank Eldon Ayers and Todd Walton for the excellent job they did
in putting up the many miles of fence which delineated the study
site.
A very sincere and heart-felt thanks is extended to the Ray
Gillespie family - Ray, Ellen, Donald, Bill, Ron, and Emmett for the donation of their land, equipment, time, and physical
labor. But, more importantly, I am forever grateful to them,for
their moral support and friendship. I love them all very much
and will never forget them and their unending generosity.
A deep appreciation is extended to the many friends and
fellow graduate students who at one time or another assisted me
during this project, with a very special thank-you going to my
roommate Julie for her endless hours of clipping, weighing,
laughing, and sharing. I will always treasure our friendship.
z
Many thanks, are expressed to Dr. Brian W. Sindelar and
Dr. Robert L. Blackwell for serving on my graduate committee and
for their helpful editing of this thesis.
Special gratitude is expressed to my friend and advisor Dr.
Kris Havstad for his many hours of help in designing, organizing,
implementing, and analyzing this research project, and for having
the faith in me to let me undertake this task.
And, to my Mom and Dad, I give my love and eternal gratitude
for their unending support, encouragement, and love. This is for
them.
'i.
vi
TABLE OF CONTENTS
LIST OF T A B L E S ...................
Page
vii
LIST OF FIGURES.....................................
Vlii
ABSTRACT.................................
ix
INTRODUCTION................ ............. ............'. .
I
LITERATURE REVIEW..........................................
3
Plant Characteristics ......................
Chemical Control......................................
Biological Control.........................
Sheep and Leafy Spurge. ..............
3
3
5
6
METHODS AND PROCEDURES ..............................
12
I
Description of the Study S i t e ........................
Sheep Analyses. ......................................
Forage Analyses ......................................
Statistical Analyses..................................
12
14
15
16
RESULTS. ..................................................
17
Sheep Weight Data ■.................
Forage D a t a .................
Ewe Performance......................................
17
18
20
DISCUSSION . ..............................................
23
SUMMARY.......................
31
LITERATURE CITED ................................
APPENDIX.....................
'33
38
vii
LIST OF TABLES
Table
1
2
3
4
5
6
Page
Average daily gains of lambs and ewes grazing
pastures with different proportions of leafy
spurge during the summers of 1982 and 1983. . . .
18
Estimated amounts of forage removed by sheep
grazing pastures with different proportions of
leafy spurge during the summer of 1983. . . . . .
19
Forage consumed as a percent of live weight of
sheep grazing pastures with different proportions
of leafy s p u r g e .......................... ..
20
Proximate analyses of leafy spurge and grass
harvest samples collected at three stages of the
data collection period during the summer of 1983.
21
Subsequent lambing performance of ewes which
grazed treatment pastures during the summers of
.1982 and 1983 ..................................
21
Species composition of the nine treatment
pastures. . . , . . . . .................... . .
39
viii
LIST OF FIGURES
Page
Figure
I
Diagram of the study site showing the size and
arrangement of the different treatment pastures
and locations of utilization cages............
)
Z■
13
ix
ABSTRACT
Leafy spurge, (Euphorbia esula L.) is an introduced perennial
weed which is currently estimated to infest over 200,000 hectares
of rangeland in Montana. Leafy spurge's extensive root system
and reproductive modes make this weed extremely difficult to
control. Because most methods of chemical and biological control
of leafy spurge have proven to be either ineffective or too
costly, it has been suggested that this weed be evaluated as a
forage plant.
A research project was initiated in May of 1982 to determine
the forage value of leafy spurge for sheep. Average daily gains
were determined for lambs and ewes grazing different treatment
pastures.
Diet composition and forage intake of sheep were
estimated, and production records of ewes having consumed leafy
spurge were examined..
The study area consisted of nine 1.66 hectare pastures three replications of three treatment conditions. Treatments
were no spurge (control), light spurge (10-20 percent of the
plant composition), and heavy spurge (>20 percent of the plant
composition). Five lamb/ewe pairs were randomly assigned to each
pasture. All sheep were weighed once every two weeks during the
eight-week data collection period.
Ten 1.5 m2 utilization cages
were randomly located in each pasture, and the paired plot
technique was used to estimate the type and amount of forage
removed.
Neither lambs nor ewes exhibited any deleterious effects due
to the consumption of leafy spurge. Average daily gains (ADG's)
of lambs grazing heavy spurge pastures during 1982 were higher
(P£.05) than average daily gains of lambs grazing light spurge
and control pastures.
ADG's of lambs grazing heavy and light
spurge-infested pastures during 1983 were higher (P<_.05) than
ADG's of lambs grazing control pastures.
Estimates of forage
removed and diet composition of sheep grazing the different
treatment pastures showed that leafy spurge comprised 41 percent
of the diet of sheep selectively grazing light spurge pastures
and 55 percent of the diet of sheep selectively grazing heavy
spurge pastures. Performance records showed ewes exhibited no
rebreeding or lambing difficulties the season immediately
following summer use of leafy spurge.
I
INTRODUCTION ■
Over 200,000 h e c ta r e s o f ra n g e la n d i n Montana a re c u r r e n tly
i n f e s t e d w ith an in tro d u c e d p e re n n ia l weed known a s l e a f y sp u rg e
(E uphorbia e s u la L.) (Noble e t a l . 1979).
T h is weed p o s s e s s e s an
e x tr e m e ly e x t e n s i v e r o o t sy s te m w h ic h m akes i t d i f f i c u l t t o
c o n tr o l and v i r t u a l l y im p o s sib le to e r a d ic a te (M essersm ith 1979)*
Because many a re a s o f le a f y spurge i n f e s t a t i o n go ungrazed
due t o n o x io u s r e a c t i o n s e x p e r i e n c e d by c a t t l e i n g e s t i n g t h i s
weed (Muenscher 1951), e f f o r t s have been made t o f i n d h e r b ic id a l
and b i o l o g i c a l m eans o f c o n t r o l l i n g t h e r a p i d s p r e a d o f l e a f y
sp u rg e.
S e v e ra l h e rb ic id e s have proven e f f e c t i v e i n c o n tr o l li n g
to p g ro w th f o r up to 3 y e a rs (Bowes and Molberg 1975; A lle y 1979;
A lle y
e t a l . 1 9 8 3 ), b u t r e p e a te d a p p l i c a t i o n s ,
w h ic h a r e
n e c e s s a r y t o k eep an i n f e s t a t i o n u n d e r c o n t r o l , a r e o f t e n to o
e x p e n s iv e
fo r
Kaufman 1979).
t h e a v e r a g e la n d o w n e r t o f i n a n c e
(R e illy
and
In a d d itio n , no h e r b ic id e s have been found w hich
e r a d i c a te l e a f y spurge because th e y c h e m ic a lly decompose b e fo re
th e d e e p l e a f y s p u r g e r o o t s a r e k i l l e d
M e s s e rs m ith 1983)„
(A lle y 1 979; Lym arid
B io a g e n ts a r e c u r r e n t l y b e in g i n v e s ti g a t e d
(B ru ck a rt 1983; C arlso n and L i t t l e f i e l d 1983).
Sheep h a v e b een s u c c e s s f u l l y used, t o c o n t r o l l e a f y s p u rg e
(Muenscher 1930; H elgeson and Thompson 1939; Wood 1945; Jo h n sto n
and Peake 1960; Bowes and Thomas 1978; S t r a tt o n 1982), b u t th e r e
a re d isa g re e m e n ts c o n ce rn in g th e e f f e c t s o f l e a f y sp u rg e on sheep
(M uenscher 1930; Bakke 1936; C h r i s t e n s e n e t a l . 1938; H e lg e so n
2
and Thompson 1939; Wood 1945; Jo h n sto n and Peake 1960; B a rtik and
P isk a c 1981; L andgraf e t a l . 1983).
I f sheep a re used to c o n tro l
l e a f y sp u rg e , th en i t s fo ra g e v a lu e m ust be exam ined.
The o b je c tiv e s of t h i s stu d y w ere to : I) d e te rm in e th e r a t e
o f g a in o f lam bs and ewes g ra z in g d i f f e r e n t tr e a tm e n t p a s tu r e s ,
n am ely
no s p u r g e ,
p a s tu re s ,
lig h t
sp u rg e ,
an d heav y
s p u rg e -in fe s te d
2) e s t i m a t e d i e t c o m p o s itio n an d am o u n t o f f o r a g e
rem oved by s h e e p g r a z i n g d i f f e r e n t t r e a t m e n t p a s t u r e s ,
and
3) e s t i m a t e t h e e f f e c t s o f c o n s u m p tio n of. l e a f y s p u rg e on t h e
re b re e d in g and lam bing perform ance of ewes.
'f
3
LITERATURE REVIEW
P la n t C h a r a c te r is ti c s
Leafy spurge (E uphorbia e s u la L.) i s an in tro d u c e d p e re n n ia l
w eed w h ic h i s
c u rr e n tly e s tim a te d to i n f e s t o ver I m illio n
h e c t a r e s i n N o rth A m e ric a a n d m ore th a n 2 0 0 ,0 0 0 h e c t a r e s i n
M ontana (N oble e t a l . 1 9 7 9 ).
D i s t r i b u t i o n o f t h i s weed can be
la rg e ly
e x tre m e ly
a ttrib u te d
re p ro d u c tio n .
to
its
s u c c e s s f u l m odes o f
Leafy spurge can rep ro d u ce and s p re a d v e g e ta tiv e ly
fro m b o th r o o t s an d s e e d s .
R ip e s e e d pods c o n t a i n a s p e c i a l
e x p l o s i v e m ech an ism w h ic h h u r l s e e d s up t o 4.6 m e te r s (Bakke
1 9 3 6 ).
E x te n s iv e r o o t s y s te m s ,
p o s s e s s in g p r o p a g a tiv e buds
(H anson and Rudd 1 9 3 3 ), have b e en fo u n d a s d e e p a s 4.5 m e te r s
(M e sse rsm ith 1979).•
Many a r e a s o f l e a f y
s p u rg e
go u n g ra z e d due t o n o x io u s
r e a c tio n s e x p e rie n c e d by c a t t l e i n g e s t i n g t h i s w eed (M uenscher
1 9 5 1 ).
R e i l l y and Kaufm an (1979). r e p o r t e d t h a t t e s t s c o n d u c te d
n e a r B ozem an, M ontana show ed r e d u c t i o n s i n r a n g e la n d c a r r y i n g
c a p a c ity
a b ility
of
up t o
75 p e r c e n t a s a r e s u l t o f l e a f y
to i n h i b i t f o r a g e
p ro d u c tio n
and d e c re a s e
s p u r g e 's
c a ttle
u t i l i z a t i o n o f a s s o c ia te d g ra s s e s .
Chemical C o n tro l
%
C o n tro l m easures m ust be u t i l i z e d on ra n g e la n d s c o n ta in in g
l e a f y spurge to r e g u la te i t s s p re a d and r e t u r n i n f e s t e d a re a s to
t h e i r o r i g i n a l n a tiv e p la n t c o m p o sitio n .
T h e re fo re , e f f o r t s have
been made to f i n d h e r b i c id a l and b io lo g ic a l means of c o n tr o l li n g
■v
4
th e
ra p id
sp re ad
of
le a fy
sp u rg e .
S e v e ra l
h e rb ic id e s
can
e f f e c t i v e l y c o n tro l to p g ro w th o f l e a f y sp u rg e i f a p p lie d e v e ry I
to 3 y e a rs
1 9 8 3 ).
(Bowes and M o lb erg 1975; A lle y 1 9 7 9 ; A lle y e t a l .
H ow ever, t h e r e a r e no h e r b i c i d e s a v a i l a b l e w h ich c a n
e ffe c tiv e ly
e ra d ic a te
le a fy
sp u rg e
(A lle y 1 9 7 9 ).
■
>
In itia l
r e s e a r c h f o r ch em ical c o n tro l in v o lv e d in o rg a n ic h e rb ic id e s w hich
w e re e f f e c t i v e o n ly when h ig h r a t e s w h ic h s t e r i l i z e d t h e s o i l
w ere used (M essersm ith 1983a).
These e a r ly f a i l u r e s e s t a b l is h e d
j
j
/
t h e p r i n c i p l e t h a t l e a f y s p u rg e h ad a d e e p r o o t sy s te m w h ic h (
-*
I
co u ld s u rv iv e w ith o u t to p g ro w th f o r th r e e to f i v e y e a rs or m ore. ;
I
M odern h e r b i c i d e s , su c h a s 2 ,4 -D , d ic a m b a , g l y p h o s a te , a n d
J
p ic lo ra m ,
a re more e f f e c t i v e th a n o r i g in a l in o r g a n ic h e r b ic id e s
.
.
.
b u t b re a k down b e f o r e t h e d e ep l e a f y s p u rg e r o o t s d i e (Lym a n d
M essersm ith 1983).
C onsequently, re p e a te d an n u al a p p li c a t io n o f
‘
h e r b i c i d e s i s n e c e s s a r y t o d e p l e t e d e ep r o o t fo o d r e s e r v e s a n d
i n h i b i t ro o t r e g e n e ra tio n (M essersm ith 1983b).
Chem ical c o n tr o l of le a fy , sp u rg e m ight a ls o be h in d e re d by.
v a r i a b l e r e s p o n s e s o f d i f f e r e n t E u p h o rb ia s p e c i e s and t h e i r
v a r i e t i e s t o chem ical tr e a tm e n ts .
As many a s 12 d i f f e r e n t ta x a
have been a s s o c ia te d w ith l e a f y sp u rg e (Noble e t a l . 1979).
b ro a d p l a n t - e c o l o g i c a l d i v e r s i t y
h e lp s t o e x p l a i n ,
T h is
in p a r t ,
d is c r e p a n c ie s in th e l i t e r a t u r e re g a rd in g th e e f f e c tiv e n e s s o f
c e r t a i n c o n tro l m easures (Noble e t a l .
1979).
R esearch i s b e in g
conducted to ta x o n o m ic a lly d i s t in g u i s h s p e c ie s and v a r i e t i e s o f
th e genus E uphorbia and d e te rm in e why v a r i e t i e s o f le a f y spurge
j
i
«
I
i
j
|
\-
5
ap p ear to
resp o n d d i f f e r e n t l y
t o t h e sam e c o n t r o l m e a s u re s
(N ow ierski 1 9 8 4 ).
Because m ost c h e m ic a ls m ust be a p p lie d ev ery y e a r to keep an
i n f e s t a t i o n under c o n tr o l, i t has become e c o n o m ic a lly i n f e a s i b l e
fo r
th e
p ro g ra m .
a v erag e
ran c h er
to
fin a n c e
a le a fy
s p u rg e c o n t r o l
P r i v a t e la n d o w n e r s i n M ontana a r e e s t i m a t e d t o be
sp en d in g more th a n 2.5 m illio n d o l l a r s a n n u a lly to c o n tro l l e a f y
sp u rg e ,
an d a num ber o f r a n c h e r s h a v e w eed c o n t r o l e x p e n s e s
am ounting t o more th a n t h e i r la n d paym ents each y e a r (R e illy and
Kaufman 1 9 7 9 ).
B io lo g ic a l C o n tro l
B io lo g ic a l
c o n tro l
of
w eeds
in v o lv e s
u se
of
a liv in g -
o rg a n is m t o re d u c e t h e d e n s i t y o f t h e t a r g e t w eed below t h e
econom ic th r e s h o ld
(H a rris 1979).
Leafy spurge a p p e a rs to be an
e x c e l l e n t t a r g e t f o r b i o c o n t r o l b e c a u s e o f t h e l a r g e num ber o f
i n s e c t s p e c i e s w h ic h a t t a c k E u p h o rb ia i n E u ro p e ( H a r r is 1 9 7 9 ). 'i
In a d d itio n , some p la n t p ath o g en s a re bein g s tu d ie d to d e te rm in e
t h e i r p o t e n t i a l a s b i o l o g i c a l c o n t r o l a g e n ts f o r l e a f y s p u rg e
(B ru ck art 1983; C arlso n and L i t t l e f i e l d 1983).
H ow ever, t h e r e a r e p ro b le m s a s s o c i a t e d w i t h t h e u se o f
b io a g e n ts to c o n tro l l e a f y sp u rg e.
H o s t.s p e c i f i c i t y , s u r v iv a l ofx
t h e b i o a g e n t i n d i f f e r e n t e n v ir o n m e n ts , tim e r e s t r i c t i o n s , an d i
econom ic f e a s i b i l i t y a re some l i m i t a t i o n s r e q u ir in g c o n s id e r a tio n tj
( H a r r is 1 9 7 9 ).
The name " l e a f y s p u rg e " e n c o m p a s s e s a d i v e r s i t y
o f taxonom ic and b io lo g ic a l p la n t ty p e s .
T his range of b io ty p e s
-H-
6
and p h e n o ty p e s can c a u s e u n e x p e c te d p r o b l e m s - i n d e v e lo p in g a
h o s t - s p e c i f i c b io lo g ic a l c o n tro l o rg a n is m .
O rg a n ism s e f f e c t i v e
on one ty p e o f s p u rg e o f t e n w i l l n o t a t t a c k " o th e r " s p u r g e s .
C hanges i n c l i m a t e o r s p e c i e s may h i n d e r t r a n s l o c a t i o n o f an
org an ism to a n o th e r environm ent (H a rris 1979; Noble e t a l . 1979).
Some m o th s h av e b e en show n t o d e f o l i a t e l e a f y s p u rg e b u t n o t
enough
d am a g e
has
been
in c u rre d
r e g e n e r a t i v e a b i l i t y ( H a r r is 1 9 7 9 ).
to
re d u c e
th e
p l a n t 's
In a d d i t i o n , h ig h r a t e s o f
b i o a g e n t m o r t a l i t y hav e re d u c e d som e p o p u l a t i o n s t o t h e p o i n t
w h ere c o n t r o l i s n o n e x i s t e n t ( H a r r i s 1 9 7 9 ).
A new r o o t b o r in g
b e e t l e h a s h ad much s u c c e s s r e d u c i n g s p u rg e i n f e s t a t i o n s i n
Europe (H a rris 1979), b u t no r e s e a r c h h as y e t been conducted w ith
t h i s b e e t l e i n t h e U n ite d S t a t e s .
Tim e and money l i m i t a t i o n s
m ust a ls o be c o n sid e re d when exam ining th e use of a b io a g e n t to
c o n tr o l le a f y sp u rg e .
A c c o rd in g t o H a rris (1979) a p p ro x im a te ly
20 y e a r s and 2 m illio n d o l l a r s w ould be re q u ir e d t o i n i t i a t e and
f u l l y d evelop an e f f e c t i v e b i o lo g ic a l c o n tro l program .
Sheep and L eafy Spurge
T h e re a r e r e p o r t s t h a t M ontana r a n c h e r s h a v e b een u s in g
s h e e p t o c o n t r o l l e a f y s p u rg e f o r m ore th a n 30 y e a r s ( S t r a t t o n
1982), b u t l i t t l e r e s e a rc h has been documented.
Muenscher (1930)
s u g g e s te d t h a t l a r g e a r e a s o r f i e l d s c o n t a i n i n g l e a f y s p u r g e
s h o u ld be s e e d e d t o
g r a s s an d f o l lo w e d by c o n tin u o u s c l o s e
p a s tu r in g w ith sheep f o r a t l e a s t 3 y e a rs .
H elgeson and Thompson
(1939) g r a z e d s h e e p f o r 2 y e a r s on unmowed an d mowed p a s t u r e s
7
i n f e s t e d w i t h l e a f y s p u rg e and fo u n d a r e d u c t i o n o f 68 p e r c e n t
(unmowed) and 31 p e r c e n t (mowed) i n th e num ber o f l e a f y s p u rg e
s ta lk s .
In a d d i t i o n , t h e t o t a l b a s a l a r e a o f t h e a s s o c i a t e d
b lu e g ra s s in c re a s e d 179 and 212 p e rc e n t i n th e mowed and unmowed
p a s tu r e s ,
r e s p e c tiv e ly .
Jo h n sto n and Peake (1960) used sh eep to
g raze a m ixed c r e s te d w h e a tg ra ss (A gropyron c r is ta tu m L.) - l e a f y
sp u rg e p a s tu r e .
A f t e r 5 y e a r s o f sum m er g r a z i n g t h e b a s a l a r e a
o f l e a f y sp u rg e d e c re a se d 98 p e rc e n t w h ile th e b a s a l a re a of th e
c r e s te d w h e a tg ra s s in c re a s e d 20 p e rc e n t.
Bowes and Thomas (1978)
found t h a t even though p ic ld ra m p ro v id e d c o n tro l o f l e a f y spurge
fo r
a m in im u m o f 3 y e a r s ,
s a tis fa c to ry
l o n g - te r m
c o n tin u o u s sh e e p g r a z in g gave
c o n tr o l o f le a f y sp u rg e .
V e g e t a ti v e
p o r t i o n s and num ber o f v i a b l e s e e d s i n t h e s o i l w e re g r e a t l y
/
red u ced .
A lthough v a rio u s r e p o r ts have s t a t e d t h a t sh eep can be used
to c o n tro l l e a f y sp u rg e , th e r e i s d isa g re e m e n t i n th e l i t e r a t u r e
c o n c e r n in g t h e r o l e o f l e a f y s p u rg e a s a f o r a g e an d i t s e f f e c t s
on s h e e p .
C o n s i d e r a t i o n m u st be g iv e n t o l e a f y s p u r g e 's l i f e
form , p ro d u c tio n c a p a b i l i t i e s , and n u t r i t i v e v a lu e .
L eafy sp u rg e i s a p e re n n ia l f o r b w hich e s t a b l i s h e s e a r ly and
resp o n d s r e a d ily to a v a ila b le m o is tu re .
New s h o o t s hav e b e e n
fo u n d a s t a l l a s 15 c e n t i m e t e r s by m id A p r i l , an d p l a n t s a r e i n
f u l l bloom by t h e f i r s t o f Ju n e (Bakke 1 9 3 6 ).
When t h e s o i l i s
m o is t t h e l e a v e s becom e l a r g e r an d m ore a b u n d a n t, b u t d u r in g
w a te r s t r e s s
( i . e . - l a t e sum m er) l e a f y spurge becomes dorm ant.
New f a l l reg ro w th i s s tim u la te d by c o o le r w eath er and r a i n f a l l i n
8
A ugust
or
e a rly
C o n s e q u e n tly ,
S e p te m b e r
le a fy
s p u rg e
(Lym
and
m a x im iz e s
M e s s e rs m ith
its
u se
of
1 9 8 3 ).
a v a ila b le
m o is tu re by p ro d u cin g la r g e am ounts o f green s u c c u le n t v e g e ta tio n
th ro u g h o u t th e grow ing season.
The b o t a n i c a l and n u t r i t i v e
d u r in g
th e
sum m er m u st a l s o
c o m p o s itio n o f sh e e p d i e t s
be e v a l u a t e d when c o n s i d e r i n g
u t i l i z a t i o n o f le a f y spurge a s a fo ra g e re s o u rc e .
Forage in ta k e
v a lu e s of sheep g ra z in g summer ran g e a ls o need to be e v a lu a te d t o
e s tim a te r e l a t i v e am ounts o f fo ra g e removed.
Cook e t a l .
(1967)
and Cook and H a rris (1968) found t h a t sheep g ra z in g m ountainous
summer ra n g e r e a d i l y a t e g r a s s e s b u t g e n e r a l l y consum ed m ore
f o r b s and b ro w se .
E a r ly i n th e s e a s o n b o th g r a s s e s an d f o r b s
w ere found t o be h ig h ly p a la ta b l e t o sheep.
As g r a s s e s d e c re a se d
i n p a l a t a b i l i t y d u r in g l a t e sum m er, f o r b u t i l i z a t i o n re m a in e d
fa irly
h ig h
c o n s u m p tio n .
and w as a c c o m p a n ie d
by an i n c r e a s e , i n
b ro w se
B uchanon e t a l . (1972) fo u n d t h a t sh e e p g r a z i n g
h ig h m o u n ta in ra n g e i n s o u t h w e s t e r n M ontana d u r i n g 2 sum m ers
av eraged 24 p e rc e n t g ra s s and 76 p e rc e n t fo rb s i n t h e i r d i e t .
e a rlie r
s tu d y by Cook e t a l .
An
(1956) n o te d t h a t d u r in g e a r l y
summer s te m s c o m p ris e d 60 p e r c e n t o f t h e a v a i l a b l e f o r a g e b u t
o n ly 34 p e r c e n t o f d i e t .
a v a ila b le fo ra g e
L e a v e s c o m p ris e d 40 p e r c e n t o f t h e
b u t 66 p e r c e n t o f t h e d i e t .
s u b s t a n t i a t e s f i n d i n g s o f Van Dyne e t a l .
T h is s t u d y
(1980) t h a t a m a jo r
co m p onent o f a n im a l p r e f e r e n c e i s th e p r e s e n c e o f g re e n l e a f
m a t e r i a l.
Van Dyne e t a l .
(1980) a l s o su m m a riz e d d a t a c o l l e c t e d by
Cook e t a l . d u r in g th e sum m er o f 1956 w h ic h e s t i m a t e d f o r a g e
in ta k e o f sheep g ra z in g seed ed p a s tu r e s i n th e f o o t h i l l s o f Utah.
R e s u l t s o f t h i s s e r i e s o f g r a z in g ' s t u d i e s show ed t h a t w e t h e r s ,
a v e r a g in g 59 k i lo g r a m s , consum ed 2.4 ± 0.77 p e r c e n t t h e i r body
w e ig h t i n f o r a g e on a d ry . m a t t e r b a s i s .
T h is f o r a g e i n t a k e
in fo rm a tio n co u ld p ro v id e a b a s is f o r e s tim a tin g fo ra g e in ta k e of
sheep g ra z in g s i m i l a r s p e c ie s d u rin g a s i m il a r g ra z in g season.
T h e re i s good e v id e n c e t h a t s h e e p w i l l e a t l e a f y s p u rg e .
C h riste n s e n e t a l .
(1939) n o te d t h a t m ost lam bs f e d l e a f y sp u rg e
s i l a g e d id n o t consum e much t h e f i r s t d ay , b u t a f t e r a few d a y s
a l l b u t tw o w e re e a t i n g enough t o c o n tin u e t h e t e s t w i t h o u t
a p p a re n t i l l e f f e c t s .
H elgeson and Thompson (1939) r e p o rte d t h a t
s h e e p a t e b lo s s o m s an d s e e d s f i r s t an d l a t e r a t e l e a v e s a n d
stem s. They a ls o n p te d t h a t sheep w ould a l t e r n a t i v e l y g raz e l e a f y
s p u rg e and g r a s s , e a t i n g s p u r g e r a t h e r " g r e e d i l y " a t t im e s an d
th e n s h i f t i n g
to
g ra ss.
Wood (1 9 4 5 ) o b s e r v e d t h a t s h e e p
e x h i b i t e d a d e c id e d p r e f e r e n c e f o r l e a f y
sp u rg e ,
c r e s te d w h e a tg ra s s to w hich th ey had e q u al a c c e s s .
ev en o v e r
Jo h n sto n and
P eake (1960) n o te d t h a t s h e e p p r e f e r r e d y o u n g e r l e a f y s p u rg e
p l a n t s and a v o id e d m ore m a tu re p l a n t s .
L a n d g ra f e t a l . (1983)
concluded t h a t a f t e r a 2 to 3 week a d ju s tm e n t p e rio d sheep w ould
s e l e c t i v e l y consume up to 40 to 50 p e rc e n t o f t h e i r d i e t a s l e a f y
sp u rg e .
P r e v io u s e x p o s u re t o l e a f y s p u rg e d i d n o t i n f l u e n c e
s e l e c t i o n o f th e p la n t d u rin g a d i f f e r e n t g ra z in g t r i a l (L andgraf
e t a l . 1983)
-tU.
10
A lth o u g h t h e r e i s e v id e n c e s h e e p w i l l s e l e c t i v e l y consum e
l e a f y sp u rg e ,
th e r e i s d isa g re e m e n t i n th e l i t e r a t u r e c o n ce rn in g
th e
of le a fy
e ffe c ts
C h ris te n s e n e t a l.
s p u r g e on s h e e p .
(1 9 3 8 ),
Wood (1 9 4 5 ),
M u en sch er (1 9 3 0 ),
and L a n d g ra f e t a l .
(1983) a l l found t h a t sheep e x h ib ite d no d e le te r i o u s e f f e c t s from
consum ing l e a f y sp u rg e.
Bakke (1936) s t a t e d t h a t n e i t h e r s h e e p
nor c a t t l e would e a t le a f y sp u rg e because o f i t s a c r i d l a t e x , b u t
t h a t sheep w ould e a t l e a f y sp u rg e i f s ta rv e d on t o i t .
However,
no d o cu m en tatio n was c i t e d to v a l i d a t e t h i s s ta te m e n t.
H elgeson
and Thompson (1939) fo u n d t h a t s h e e p e x p e r i e n c e d no h a rm fu l
e f f e c t s fro m e a t i n g l e a f y s p u r g e w i t h t h e e x c e p t i o n o f a few
lam bs w hich sco u red .
However, no docum ented e x a m in a tio n of th e
sc o u re d
c ite d
la m b s
w as
to
a ttrib u te
th is
c o n d itio n
to
consum ption o f l e a f y spurge.
A l t e r n a t i v e l y , J o h n s to n an d P e a k e (1960) a t t r i b u t e d d e a th s
o f an unknown num ber o f s h e e p t o c o n s u m p tio n o f l a r g e m a tu re
l e a f y s p u rg e p l a n t s .
P o s t-m o rte m e x a m in a tio n s i n d i c a t e d t h a t
l e a f y sp u rg e was re s p o n s ib le f o r th e p o iso n in g l o s s e s , b u t th e s e
e x am in a tio n s w ere undocumented and d id n o t e x p la in th e means by
w h ic h l e a f y s p u rg e c o n t r i b u t e d t o th e d e a t h s . • H ow ever, when
s h e e p w e re p u t i n t h e p a s t u r e a t an e a r l i e r d a te an d a llo w e d t o
g raze im m ature p la n ts no l o s s e s w ere re p o rte d .
B a r tik and P is k a c
(1981) s t a t e d t h a t E uphorbia e s u la L. and c lo s e ly r e l a t e d s p e c ie s
p o ss e s s a p o iso n o u s w h ite l a t e x w hich a f f e c t s a lm o s t a l l an im al
s p e c ie s ,
to s h e e p .
b u t f a i l e d t o s u b s t a n t i a t e th e s e f in d in g s a s p e r ta in in g
11
A lth o u g h t h e r e a r e o b s e r v a t i o n s t h a t s h e e p can c o n t r o l
i n f e s t a t i o n s o f l e a f y spurge by g ra z in g th e to p g ro w th ,
th e r e i s
co n cern t h a t sheep may sp re a d t h i s weed to p r e v io u s ly u n in fe s te d
a r e a s by p a s s i n g v i a b l e s e e d s .
R ip p ey e t a l . (1983) fo u n d t h a t
seed v i a b i l i t y was reduced from 25 to 14 p e rc e n t when seed s w ere
exposed to a 48-hour in c u b a tio n i n sheep rumen f l u i d .
Com plete
l o s s o f v i a b i l i t y o c c u rre d when se e d s w ere exposed to an in v i t r o
rumen and sm a ll i n t e s t i n e tr e a tm e n t.
Seeds re c o v e re d from sheep
m an u re show ed g e r m i n a t i o n r a t e s r a n g in g fro m 7 t o 3.0 p e r c e n t .
Even th o u g h g e r m i n a t i o n s u c c e s s w as s i g n i f i c a n t l y lo w e r e d i n
s e e d s d i g e s t e d by s h e e p , o n ly a s m a ll am ount o£ v i a b l e s e e d s i s
s u ffic ie n t
to
sp re a d le a f y
sp u rg e .
S u g g e s tio n s t o
c o n tro l
d e p o s itio n o f v ia b le se ed s to u n in f e s te d a r e a s in c lu d e h e a v ily
g ra z in g l e a f y spurge b e fo re seed s e t to p re v e n t se ed developm ent,
o r i s o l a t i n g s h e e p i n a h o l d in g a r e a f o r 7 d a y s t o a llo w f o r
v o i d in g
v ia b ility
of le a fy
s p u rg e
(Rippey e t a l .
seed
w h ic h
may h a v e
re ta in e d
its
1983).
C o n sid e ra b le d isa g re e m e n t s t i l l e x i s t s w i t h in th e l i t e r a t u r e
re g a rd in g th e r o le o f l e a f y sp u rg e a s a fo ra g e and i t s e f f e c t s on
sheep.
I f s h e e p a r e u se d t o c o n t r o l l e a f y s p u r g e , i t s f o r a g e
v a lu e m ust be exam ined to d e te rm in e w hether sheep w i l l b e n e f i t
from i t s use a s a fo ra g e .
'h
12
METHODS AND PROCEDURES
D e s c rip tio n o f th e Study S ite
The re s e a rc h s i t e was lo c a te d n e a r th e w e s te rn s lo p e s o f th e
T obacco R oot M o u n ta in s i n
s o u t h w e s t e r n .M ontana on t h e
Ray
G i l le s p i e ran ch 9.7 k ilo m e te r s s o u th of W h ite h a ll, Montana.
The
r e s e a r c h s i t e w as l o c a t e d i n J e f f e r s o n C ounty ( S e c tio n 6 , T1S,
R4W). on t h e J e f f e r s o n R iv e r f l o o d p l a i n . The s tu d y a r e a w as a
s h a llo w -to -g ra v e l
ran g e
s ite
in
a 27
to
36
c e n tim e te r
p r e c i p i t a t i o n zo n e (M ontana C l i m a t o l o g i c a l D ata - 1972 - 1982)
and had been seeded t o t a l l fe s c u e (F e stu c a a ru n d in a ce a) i n 1974.
S in ce t h a t tim e s e v e ra l o th e r g ra s s s p e c ie s a p p ea re d on th e s i t e ,
i n c l u d i n g v a r i o u s A g ro p y ro n s p p . ,
K e n tu c k y
b lu e g ra s s
(Ppa
p r a t e n s i s ) , and s c a t t e r e d p a tc h e s o f c h e a tg ra s s (Byomus te c to ru m )
(Appendix - T able 6).
In 1976 l e a f y sp u rg e (E uphorbia e su la ) was
a c c i d e n t l y i n t r o d u c e d and g r a d u a l l y i n f e s t e d t h e a r e a u n t i l i t
com prised 10 to 50 p e rc e n t of th e p la n t c o m p o sitio n .
The r e c ta n g u la r e x p e rim e n ta l a re a m easured 274 m e te rs by 549
m e te r s
(15 h e c t a r e s ) an d w as d i v i d e d i n t o
p a s tu re s ,
p i n e 1.66 h e c t a r e
e a c h m e a s u rin g 61 m e t e r s by 274 m e t e r s (F ig u re I ) .
P a s t u r e s w e re d e s i g n a t e d on th e b a s i s o f t h e i r l e a f y s p u r g e
c o m p o s itio n ,
w ith
th re e
p a s t u r e s o f e a c h t r e a t m e n t b e in g
d e s ig n a te d by one of th e f o llo w in g l e a f y sp u rg e i n f e s t a t i o n s :
I)
c o n tro l
of
- no s p u rg e
(o n ly
g rasse s
p re s e n t)
as
a re s u lt
s p r a y i n g T ordon a t 0.56 (tilo g ra m s p e r h e c t a r e , 2) l i g h t - a n
o c u la r e s tim a te of 10 to 20 p e rc e n t c o m p o sitio n (canopy cover) o f
Control
Control
Control
H-H4
■'■Each pastu re = 1.66 ha
•Gage lo c a tio n
Figure I . Diagram of the study s i t e showing th e s iz e and arrangement of the d iffe re n t
treatm ent pastu res and lo c a tio n s of u tiliz a tio n cages.
14
l e a f y s p u r g e , and 3) heavy - an o c u l a r e s t i m a t e o f g r e a t e r th a n
20 p e rc e n t c o m p o sitio n (canopy cover) o f l e a f y sp u rg e .
E le c tric
fen ce s e p a ra te d th e tr e a tm e n t p a s tu r e s .
Sheep A nalyses
F orty-^five ewes w ith s in g le lam bs w ere random ly s e le c te d f o r
e a c h r e s e a r c h p e r i o d fro m a r a n g e / h e r d e r o p e r a t i o n a t M ontana
S ta te U n iv e r s ity 's Red B lu ff R esearch S ta tio n .
Ewes w ere 2 to 6
y e a r o fd F in n c r o s s e s w h ic h had b e en b re d t o S u f f o l k ram s a n d
w e ig h e d an a v e r a g e o f 60 k i lo g r a m s .
Lambs a v e r a g e d 70 d a y s o f
ag e a t th e b e g in n in g o f th e s tu d y an d w e ig h e d a n a v e r a g e o f 21
k ilo g ra m s.
F ive lam b/ew e p a i r s w ere random ly a s s ig n e d t o each
p a s tu r e d u rin g th e second week o f June (each summer) and a llo w e d
t o s e l e c t i v e l y g raz e. A nim als w ere a llo w e d f r e e a c c e s s t o t r a c e
m i n e r a l i z e d s a l t . 'a n d w a t e r w a s p r o v i d e d
in
each p a s tu re .
F o u rte en days a f t e r sheep' w ere p la c e d i n p a s tu r e s b o th lam bs and
ew es w e re w e ig h e d .
S heep w e re w e ig h e d o n ce e v e ry tw o w eeks
d u r in g t h e e ig h t- w e e k sum m er d a t a c o l l e c t i o n p e rio d t o m onitor
and compare w e ig h t g a in s of a n im a ls u sin g th e d i f f e r e n t tre a tm e n t
p a s tu r e s .
B re e d in g and la m b in g r e c o r d s o f ew es w h ic h g ra z e d l e a f y
s p u r g e - in f e s te d p a s tu r e s d u rin g th e summers o f 1982 and 1983 w ere
e x a m in e d t o d e te r m in e w h e th e r l e a f y s p u rg e c o n s u m p tio n c a u s e d
a b n o r m a litie s in p ro d u c tio n e f f i c ie n c y of ewes.
R ebreeding and
la m b in g s u c c e s s , num ber o f la m b s , s i z e o f la m b s , and h e a l t h o f
newborn lam bs w ere a n aly ze d .
15
Forage A nalyses
Ten 1.5
p a s tu re
u t i l i z a t i o n cages w ere random ly lo c a te d i n each
( F ig u r e I ) .
The p a i r e d
p lo t
te c h n iq u e
w as
u se d
e s tim a te th e amount and ty p e of fo ra g e removed (NRC 1962).
to
Two I
p l o t s w e re h a r v e s t e d a t e a c h c a g e l o c a t i o n - on e i n s i d e t h e
cag e and one o u t s i d e t h e c a g e .
random ly d e te rm in e d .
L o c a tio n s o f u n c a g e d p l o t s w e re
V e g e ta tio n o f each p l o t was h a rv e s te d and
s e p a r a t e d i n t o i t s l e a f y s p u rg e an d g r a s s c o n s t i t u e n t s .
O th e r
f o r b s o c c u rre d in o nly n e g li g i b le am ounts and w ere n o t in c lu d e d
in th e h a rv e s t c o ll e c t io n s .
Spurge and g ra s s sam p les w ere bagged
s e p a r a te ly and a i r - d r i e d w e ig h ts w ere d eterm in ed .
T h re e p a s t u r e s ( c o n t r o l , l i g h t and heavy) w e re h a r v e s t e d
ev ery week b e g in n in g J u ly 5, 1983. P a ire d p l o t s w ere h a rv e s te d
/■
fro m e a c h cag e l o c a t i o n , and c a g e s w e re r e p l a c e d t o c o v e r
h a r v e s t e d u n c ag e d p l o t s t o m e a s u re r e g r o w th o f g r a z e d p l a n t s .
B e g in n in g J u l y 2 6 , 1983 a s e c o n d r o t a t i o n o f h a r v e s t s w as begun
w i t h t h r e e p a s t u r e s , one o f e a c h t r e a t m e n t 'c o n d i t i o n .
H a rv e s t
d a ta w ere used to e s tim a te amount and ty p e of fo ra g e removed by
sh eep , g r a z i n g t r e a t m e n t p a s t u r e s .
R e p r e s e n t a t i v e s a m p le s o f
t h e s e h a r v e s t d a ta w e re a n a ly z e d t o d e te r m in e f o r a g e q u a l i t y .
Forage q u a l i t y was d e fin e d on th e b a s is of v a lu e s o b ta in e d from
p ro x im a te a n a ly s e s o f le a f y spurge and g ra s s h a r v e s ts .
Samples
f o r a n a ly s e s w ere c o lle c te d d u rin g th r e e s ta g e s o f p h o n o lo g ic a l
d e v e lo p m e n t, i n c l u d i n g i n i t i a l s t a n d i n g c ro p , g razed reg ro w th ,
an d f i n a l
s t a n d in g
c ro p .
P ro x im a te a n a l y s e s w e re c o n d u c te d
fo llo w in g AOAC (1980) p ro c e d u re s t o d e te rm in e cru d e p r o te in , a sh .
16
a c i d d e t e r g e n t f i b e r (ADF), and l i g n i n f r a c t i o n s o f t h e s p u rg e
and g ra s s sam ples on a p e rc e n t dry m a tte r b a s is .
S t a t i s t i c a l A nalyses
D ata w ere a n aly ze d u sin g a random ized c o m p lete blo ck d e sig n .
One f a c t o r a n a l y s i s o f v a r i a n c e
(ANOVA) w as u s e d t o co m p are
av erag e d a ily g a in s o f lam bs and ewes and e s tim a te d am ounts and
ty p e s o f fo ra g e removed by lam b/ew e p a i r s g ra z in g th e d i f f e r e n t
- t r e a tm e n t p a s t u r e s .
in c lu d e d a g e,
v a ria tio n .
t im e ,
The s t a t i s t i c a l m odel f o r w e ig h t g a in s
tre a tm e n t,
and y e a r a s f ix e d s o u rc e s of
The s t a t i s t i c a l m odel f o r f o r a g e r e m o v a ls i n c l u d e d
a g e , t i m e , an d t r e a t m e n t a s f i x e d s o u r c e s o f v a r i a t i o n .
Means
w e re s e p a r a t e d u s in g a l e a s t s i g n i f i c a n t d if f e r e n c e (LSD) t e s t ,
w ith s i g n i f i c a n c e b e in g d e te r m in e d a t P.1.05 ( S t e e l a n d T o r r i e
1 9 6 0 ).
Lambing perfo rm an ce of e x p e rim e n ta l ewes was a ls o a n aly ze d .
Data from 1983 and 1984 lam bing se a so n s w ere a n a ly z e d s e p a r a te ly .
A G-t e s t (Sokal and R o h lf .1981) w a s•used to t e s t f o r independence
betw een th e th r e e tr e a tm e n ts a g a in s t s in g le and m u ltip le b i r t h s .
S i g n i f i c a n c e w as d e te r m in e d a t P I .O5.
Lamb b i r t h w e ig h ts w e re
n o t a n a ly z e d because th e e x p e rim e n ta l d e sig n was n o t ad eq u ate to
allo w fo r s t a t i s t i c a l a n a ly s is o f th e s e d a ta .
17
RESULTS
The fo llo w in g r e s u l t s w i l l p r e s e n t s t a t i s t i c a l a n a ly s e s o f
sheep and fo ra g e d a ta c o lle c te d d u rin g t h i s r e s e a r c h p r o j e c t. . A
s e p a r a te d is c u s s io n s e c tio n fo llo w s .
o f la m b an d ewe ADG1s .
Sheep d a ta in c lu d e a n a ly s e s
F o ra g e d a t a in c l u d e e s t i m a t e s o f f o r a g e
rem oval and d i e t c o m p o sitio n o f sh eep , and p ro x im a te a n a ly s e s o f
l e a f y s p u rg e and g r a s s s a m p le s .
Ewe p r o d u c t i o n d a ta p r o v id e
a n a l y s e s o f la m b in g p e rfo rm a n c e o f ewes w hich g raz ed d i f f e r e n t
tr e a tm e n t p a s tu r e s .
Sheep W eight D ata
A v erag e
d a ily
g a in s
(AtD C s)
of
la m b s an d ew es g r a z i n g
d i f f e r e n t tr e a tm e n t p a s tu r e s during, th e summers o f 1982 and 1983
a r e p r e s e n t e d i n !Table I .
Lambs g r a z i n g h e av y s p u rg e p a s t u r e s
d u rin g th e summer o f 1982. w ere found t o have s i g n i f i c a n t l y h ig h e r
(P<L.05) ADG1s d u rin g th e f i r s t w eig h in g p e rio d and f o r th e e n t i r e
s e a s o n th a n la m b s g r a z in g c o n t r o l an d l i g h t s p u r g e p a s t u r e s .
Lambs g r a z i n g l i g h t an d h eav y s p u rg e p a s t u r e s d u r in g t h e s e tw o
p e r i o d s i n 1983 w e re f o u n d .t o h av e s i g n i f i c a n t l y h ig h e r ADCs
th a n c o n tr o l tr e a tm e n t lam bs.
Ewe w e ig h t d a ta c o ll e c t e d i n 1982
show ed a s i g n i f i c a n t d i f f e r e n c e b e tw e e n ADCs o f ew es g r a z in g
■c o n t r o l and l i g h t s p u rg e p a s t u r e s d u r in g t h e s e c o n d w e ig h in g
p e rio d , and ADG1s of ewes g ra z in g l i g h t and heavy sp u rg e p a s tu r e s
f o r t h e e n t i r e s e a s o n w e re s i g n i f i c a n t l y h ig h e r th a n ADCs o f
c o n tr o l tre a tm e n t ewes.
A s i g n i f i c a n t d i f f e r e n c e w as o b s e r v e d
•'ii-
18
T ab le I . A v erag e d a i l y g a in s (kg) o f la m b s a n d ew es g r a z i n g
p a s t u r e s w i t h d i f f e r e n t p r o p o r t i o n s o f l e a f y s p u rg e
d u rin g th e summers o f 1982 and 1983.
T reatm ent
Lambs:
(1982)
(1983)
Ewes:
(1982)
(1983)
________ W eighing P e rio d ________
6 /2 4 -7 /8
7 /8 -7 /2 2
7 /2 2 -8 /5
0.19^
0.22a
0.26a
0.18a
- 0.23b
C o n tro l
L ig h t
Heavy
0.29b
0 . 2 ia
0.30b
0.35b
0.12a
0.12a
0.14a
0.24a
0.28a
0.25a
0.19a
0.21a
0.23a
0.21a
0.26b
0.28°
C o n tro l
L ig h t
Heavy
-0.03a
- 0 .12a
-0.03a
-0 .22a
-0.07b
-0.17ab
0 .0 0 a
0.07a
0.13a
-0 .0 8 a
-0.04°
- 0 . 0 2b
C o n tro l
L ig h t
Heavy
—
0 .05a ■
-0.02a
- 0 .06a
0.05b
-0 .0 4 a
• CUOla
0 .0 0 a
C o n tro l
L ig h t
Heavy
0.22a
E n tir e
Season
0 *2 1 u
0.03 a
0.05a
0.13a
O .l? ^
0 .0 0 ab
0.02a
1-Means within the same column followed by d ifferen t le t t e r s are
sig n ific a n tly d ifferen t ( P £ „ 0 5 ) .
d u r in g t h e t h i r d w e ig h in g p e r i o d i n 1983 b e tw e e n ADG's o f ew es
g ra z in g c o n tro l and l i g h t sp u rg e p a s tu r e s .
Forage D ata
Means o f d a ta c o ll e c t e d d u rin g th e summer of 1983 and used
t o e s t i m a t e t h e am ount an d ty p e o f f o r a g e re m o v e d . by s h e e p
g r a z i n g d i f f e r e n t t r e a t m e n t p a s t u r e s a r e l i s t e d i n T a b le 2.
A
s h i f t i n d i e t c o m p o s itio n w as o b s e r v e d i n t h e .,d ie ts o f s h e e p
g ra z in g le a f y - s p u r g e i n f e s te d p a s tu r e s .
Sheep g ra z in g l i g h t and
h eav y s p u rg e p a s t u r e s consum ed m ore l e a f y s p u r g e th a n g r a s s
" e a r l y " (Ju n e 28 th ro u g h J u l y 19) i n t h e d a ta c o l l e c t i o n p e r i o d
a n d m o re g r a s s t h a n l e a f y
sp u rg e
" la te "
(J u ly
20 t h r o u g h
'x .
19
T able 2 . E s t im a te d a m o u n ts o f f o r a g e removed^- by s h e e p g r a z i n g
p a s t u r e s w i t h d i f f e r e n t p r o p o r t i o n s o f l e a f y s p u rg e
d u rin g th e summer of 1983.
T reatm ent
C o n tro l
L ig h t
Heavy
E a rlv
P a s tu re G rass
Souroe
I
2
3
I
2
3
I
2
3
11.2
17.9
33.2
15.7
7 .6
6.2
9 .2
0
2 .8
O
O
O
11.7
18.2
4.3
17.9
16.3
0.5
G rass
1 6 .8
19.4
41.6
21.5
11.9
11.7
9 .3
7 .6
15.4
L ate
Spuroe
E n tir e Season
G rass Souroe
0
0
0
6 .6
11.4
3.1
13.0
9.4
7 .4
14.0
18.7
37.4
18.6
9.7
8.9
9 .2
3 .8
9 .1
0
0
0
9.1
14.8
3 .7
15.4
12.9
4 .0
-*-Mean v a lu e s o f 10 p a ir e d p l o t s f o r each p a s tu r e a re e x p re ss e d i n
kg (DM)/ p a s t u r e /d a y o f a i r - d r i e d fo r a g e .
A ugust 9) i n th e d a ta c o l l e c t i o n p e rio d .
D ie ts of sheep g ra z in g
l i g h t and heavy spurge p a s tu r e s e a r l y in th e seaso n c o n ta in e d 52
a n d . 61 p e r c e n t l e a f y
sp u rg e ,
re s p e c tiv e ly .
g r a z in g l i g h t and h e av y s p u rg e p a s t u r e s l a t e
D ie ts of sh eep
in th e seaso n
c o n ta in e d o n ly 31 an d 49 p e r c e n t l e a f y s p u r g e , r e s p e c t i v e l y .
These d e c re a s e s i n le a f y spurge consum ption w ere accom panied by
p r o p o r tio n a l in c r e a s e s in g ra s s consum ption.
E s tim a te s o f fo ra g e in ta k e w ere a ls o e x p re ss e d a s a p e rc e n t
o f t o t a l l i v e body w e ig h t p e r tr e a tm e n t.
i n T a b le 3.
These v a lu e s a re l i s t e d
Sheep g r a z i n g c o n t r o l p a s t u r e s consum ed t h e m ost
t o t a l f o r a g e a s a p e r c e n t o f l i v e w e ig h t f o r t h e e n t i r e s e a s o n
w h i l e s h e e p g r a z in g h e a v y s p u rg e p a s t u r e s consum ed t h e l e a s t
amount of t o t a l fo ra g e a s a p e rc e n t o f l i v e w eig h t.
R e p r e s e n t a t i v e s a m p le s o f l e a f y s p u rg e and g r a s s h a r v e s t s
w ere exam ined to d e te rm in e t h e i r fo ra g e q u a l i t y d u rin g th e summer
20
T able 3 . Forage-^- consum ed a s a p e r c e n t o f l i v e w e ig h t o f s h e e p
g ra z in g p a s tu r e s w ith d i f f e r e n t p r o p o r tio n s o f le a f y
sp u rg e .
E a rly
T reatm ent____________G rass Spurge
_____ L ate
„ E n tir e Season
G rass Spurge
G rass Spurge
----------------------------------------------------------------------------------- % --------------------------------------------------------------------------------------- -----
C o n tro l
L ig h t
Heavy
5 .0
2 .5
1 .0
0
2 .8
2 .7
6 .0
3 .4
2 .2
0
1 .6
2 .1
5 .4
2 .9
1 .6
0
2 .2
2 .4
1A ir-d ry b a s i s .
g ra z in g se aso n .
R e s u lts o f p ro x im a te a n a ly s e s a r e p re s e n te d in
T a b le 4.
T h ro u g h o u t t h e g ro w in g s e a s o n l e a f y s p u r g e c o n ta in e d
\
m ore c ru d e p r o t e i n and l i g n i n b u t l e s s a s h and a c i d d e t e r g e n t
f i b e r (ADF) th a n g ra s s ;
G razed re g ro w th sam ples o f b o th s p e c ie s
w ere h ig h e r i n crude p r o t e i n and a sh and lo w er i n ADF and l i g n i n
th a n t h e i r c o r r e s p o n d in g i n i t i a l a n d s t a n d i n g c r o p s , b u t th e
m agnitude of th e s e d if f e r e n c e s was l a r g e r and more v a r i a b le f o r
l e a f y sp u rg e th a n i t was f o r g ra s s .
Ewe Perform ance
B reeding and lam bing re c o rd s w ere m o n ito red f o r ewes having
g razed d i f f e r e n t tre a tm e n t p a s t u r e s d u r in g t h e sum m ers o f 1982
an d 1983.
sh o w e d
Red B l u f f Ranch R e s e a rc h S t a t i o n la m b in g r e c o r d s
th a t
no
ew es
e x p e rie n c e d
re b re e d in g
or
la m b in g
d i f f i c u l t i e s th e seaso n im m e d ia te ly fo llo w in g summer use of le a f y
s p u rg e -in fe s te d p a s tu re s .
L am bing p e rfo rm a n c e o f ew es w h ic h
g r a z e d d i f f e r e n t t r e a t m e n t p a s t u r e s d u rin g th e summers of 1982
and 1983 i s p re s e n te d i n T able 5.
No s i g n i f i c a n t d if f e r e n c e was
21
T able 4 . P ro x im ate a n a ly s e s o f l e a f y spurge-1- and g r a s s 2 h a rv e s t
sam ples c o ll e c t e d a t th r e e s ta g e s of th e d a ta c o l l e c t i o n
p e rio d d u rin g th e summer of 1983.
Foraae
Growth S taae
DM
- - - Dry M a tte r B a sis - - Crude
ADF
P r o te in Ash
L ia n in
- -% -
L eafy sp u rg e :
I n i t i a l S tan d in g
Crop
G razed Regrowth
F in a l S tan d in g
Crop
93.6
93.6
12.2
20.6
7.3
9 .8
38.0
23.2
8.8
4 .8
92.8
8.4
6 .8
42.3
9.6
I n i t i a l S tan d in g
Crop
G razed Regrowth
F in a l S tan d in g
Crop
94.8
94.3
7 .3
11.9
11.6
13.6
41.8
36.4
4.6
3 .0
94.1
7 .0
12.8
40.8
4 .0
G rass:
x
-I-Mean v a lu e s o f sam ples from l i g h t and heavy spurge p a s tu r e s . .
2 Mean v a l u e s o f s a m p le s fro m c o n t r o l , l i g h t , a n d h e av y s p u rg e
p a s tu r e s .
T able 5 . S u b s e q u e n t la m b in g p e rf o r m a n c e o f ew es w h ic h ' g ra z e d
tre a tm e n t p a s tu r e s d u rin g th e summers o f 1982 and 1983.
Number
o f Ewes
*
Lambs
/Ewe
Year
T reatm ent
19821
C o n tro l
L ig h t
Heavy
8
9
11
1 .9 a
I - 5?
1 .4 a
19832
C ontrol
L ig h t
Heavy
13
11
11
1 .5 a
1 .4 a
1 .7 a
3
!R e c o rd s w e re fo u n d f o r o n ly 28 ew es b e c a u se o f c u l l i n g and
p r e d a tio n l o s s e s .
2R e c o rd s w e re fo u n d f o r o n ly 35 ew es b e c a u s e o f c u l l i n g a n d
p r e d a tio n l o s s e s .
3Means w ith in th e same column fo llo w e d by d i f f e r e n t l e t t e r s 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 i..0 5 ).
22
o b serv ed among mean l i t t e r
tr e a tm e n t p a s tu r e s .
s i z e s o f ewes w hich g raz ed d i f f e r e n t
A ll lam bs w ere born h e a lth y and e x p e rie n c e d
no changes i n t h e i r g e n e ra l h e a lth w hich could be a t t r i b u t e d to
l e a f y s p u r g e c o n s u m p tio n by t h e i r m o th e rs (J o rd a n 1 9 8 4 ).
Mean
b i r t h w e ig h ts o f lam bs born to 1982 e x p e rim e n ta l ewes ranged from
4.4 t o 4.9 k i lo g r a m s .
Mean b i r t h w e i g h ts o f la m b s b o rn t o 1983
e x p e rim e n ta l ewes ranged from 3.9 to 4.3 k ilo g ra m s.
S ig n ific a n c e
among b i r t h w e ig h ts o f lam bs born to ewes w hich g raz ed d i f f e r e n t
tr e a tm e n t p a s tu r e s was n o t s t a t i s t i c a l l y d e te rm in e d .
Confounding
f a c t o r s su c h a s b r e e d , s e x , ag e o f ew e, an d l i t t e r
s i z e w ould
n e e d t o h av e b e en c o n s i d e r e d b u t w e re n o t a c c o u n te d f o r i n t h e
e x p e rim e n ta l d e s ig n .
23
DISCUSSION
T h is d is c u s s io n s e c tio n w i l l exam ine d a ta a n a ly s e s p re s e n te d
i n th e r e s u l t s and a tte m p t to e x p la in t h e i r s ig n if ic a n c e .
Data
w i l l be d i s c u s s e d i n t h e sam e o r d e r th e y w ere p r e s e n t e d i n t h e
r e s u l t s s e c tio n .
S easo n -lo n g ADG1s of e x p e rim e n ta l lam bs ranged from 0.17 to
0.23 kg i n 1982 an d fro m 0.21 t o 0.28 kg i n 1983 (T a b le I ) .
A
t y p ic a l range lam b born w eighing 4.5 kg and weaned 120 days l a t e r
w e i g h i n g 3 6 .3 kg w o u ld h a v e a s e a s o n - l o n g ADG o f 0 .2 6 kg
(H aresig n 1983).
Based on th e s e s i m i l a r i t i e s ADG's o f ex p erim en t
lam bs w ere c o n sid e re d com parable to an ADG of a lam b i n a s i m il a r
r a n g e la n d s i t u a t i o n .
S i g n i f i c a n t d i f f e r e n c e s w e re o b s e rv e d betw een se a so n -lo n g
ADG's. o f e x p e rim e n ta l lam bs.
In 1982 se a so n -lo n g ADG's o f heavy
sp u rg e tr e a tm e n t lam bs w ere 0.05 and 0.06 kg h ig h e r th a n se aso n l o n g ADG's o f l i g h t
s p u rg e and
r e s p e c t i v e l y (T a b le I ) .
c o n tro l
t r e a t m e n t la m b s ,
In 1983 s e a s o n - lo n g ADG's o f l i g h t and
h eav y s p u rg e t r e a t m e n t la m b s w e re 0.05 and OTO7 kg h i g h e r ,
r e s p e c tiv e ly ,
(T a b le I ) .
re tu rn s ,
th a n se a s o n -lo n g ADG's o f c o n tr o l tr e a tm e n t lam bs
B e c a u se h e a v i e r la m b s p r o v id e h i g h e r
it
is
im p o rta n t to
e x a m in e w h a t f a c t o r s
fin a n c ia l
p o s s ib ly
c o n tr ib u te d to d if f e r e n c e s betw een ADG's of e x p e rim e n ta l lam bs.
At 2 to 4 weeks o f age a lam b consum es 4 to 6 p e r c e n t of i t s
body w e ig h t a s f o r a g e (C hurch 1 9 8 0 ).
A t 8 w eeks o f a g e a la m b 's
s to m a c h i s p h y s i o l o g i c a l l y d e v e lo p e d a n d t h e sam e s i z e a s an
24
a d u l t 's
(Church 1976).
w eeks o ld
E x p erim en tal lam bs w ere a p p ro x im a te ly 10
w hen a s s i g n e d
p h y s io lo g ic a lly
to
tre a tm e n t p a s tu r e s
m a tu re enough t o
(A n so teg ui 1984).
a n d w e re
s u b s i s t s o l e l y on h e rb a g e
Lambs w ere o b serv ed consum ing some m ilk , b u t
on t h e b a s i s o f d i r e c t o b s e r v a t i o n s i t w as c o n c lu d e d t h a t lam b
d i e t s w ere composed l a r g e l y of fo ra g e .
Milk consum ption had no
e f f e c t on ADG's a f t e r th e f i r s t w eighing p e rio d .
E nvironm ental s t r e s s can a f f e c t ADG's.
However, because a l l
s h e e p w e re e x p o se d t o t h e sam e e n v ir o n m e n ta l c o n d i t i o n s i t was
c o n c lu d e d t h a t c h a n g e s i n th e e n v iro n m e n t d i d n o t d i r e c t l y
c o n tr ib u te t o d if f e r e n c e s among tr e a tm e n t ADG's.
D iffe re n c e s among ADG's of e x p e rim e n ta l lam bs w ere based on
t h e q u a l i t y and q u a n t i t y o f f o r a g e a v a i l a b l e t o s h e e p i n t h e
tr e a tm e n t p a s tu r e s .
A ccording t o NRC re q u ire m e n ts (1975) a 21 kg
lam b needs a p p ro x im a te ly 11.7 p e rc e n t crude p r o t e i n i n i t s d i e t
t o g a in 0.26 kg p e r d ay .
E a r ly (Ju n e 28 th r o u g h J u l y 19) i n th e
summer o f 1983 le a f y spurge c o n ta in e d 12.2 p e rc e n t cru d e p r o te in
w h ile g r a s s c o n ta in e d o n ly 7.3 p e r c e n t (T a b le 4 ).
L a te i n th e
summer a 32 kg lam b n e e d s o n ly 8.2 p e r c e n t c ru d e p r o t e i n i n i t s
d i e t t o g a in 0.23 kg (NRC 1 9 7 5 ).
M a tu re la m b s c an m e e t t h e i r
n u t r i e n t r e q u i r e m e n t s by c o n su m in g l a r g e r a m o u n ts o f lo w e r
q u a l i t y fo ra g e .
la te
L eafy sp u rg e fu r n is h e d 8.4 p e rc e n t cru d e p r o te in
(Ju ly 20 th ro u g h August 9) in th e g ra z in g se a so n w h ile g ra s s
f u r n i s h e d o n ly 7.0 p e r c e n t (T a b le 4 ).
L e a fy s p u rg e p r o v id e d a
h ig h e r q u a l i t y fo ra g e th a n g ra s s th ro u g h o u t th e grow ing seaso n .
25
E s tim a te s o f fo ra g e d isa p p e a ra n c e showed t h a t sheep i n heavy
an d l i g h t p a s t u r e s s e l e c t i v e l y consum ed p a r t o f t h e i r d i e t a s
l e a f y sp u rge (Table 2).
o n ly g r a s s .
p a s tu re s
Sheep g ra z in g c o n tro l p a s tu r e s consumed
C o n s e q u e n tly , h ig h e r ADG1s o f la m b s g r a z i n g s p u rg e
w e re a t t r i b u t e d
to
th e a v a i l a b i l i t y
consum ption of a h ig h e r q u a l i t y d i e t .
D iffe re n c e s w ere observed
among s e a s o n - lo n g ADG1s o f ew es i n 1982
m a g n itu d e o f
d iffe re n c e s
t h e s e ADG1s an d t h e i r
w e re n o t
c o n s id e re d
an d s e l e c t i v e
(T a b le I ) ,
c o r r e s p o n d in g
la rg e
enough t o
b u t th e
tre a tm e n t
be deem ed
b i o lo g i c a l ly s i g n i f i c a n t .
E s t im a te d a m o u n ts o f f o r a g e rem oved by e x p e rim e n ta l sheep
s u g g e s te d a s h i f t i n d i e t c o m p o s itio n o f sh e e p g r a z i n g l e a f y
sp u rg e - i n f e s t e d p a s tu r e s .
E a rly in th e seaso n a l a r g e r p o rtio n
of sheep d i e t s c o n s is te d o f le a f y sp u rg e .
L a te i n t h e s e a s o n
more g r a s s was p r o p o r tio n a lly consumed (Table 2).
d i e t c o m p o s itio n c o r r e s p o n d s
c lo s e ly
to
th e
T h is s h i f t in
p h e n o lo g ic a l
developm ent and p ro d u c tio n c a p a b i l i t i e s o f le a f y sp u rg e.
Leafy
sp u rg e e s t a b l i s h e s and p ro d u ces l a r g e am ounts of g ree n , s u c c u le n t
l e a f m a t e r i a l e a r l y i n t h e g ro w in g s e a s o n (Bakke 1 9 3 6 ).
The
e x h i b i t e d p r e f e r e n c e o f s h e e p f o r l e a f y s p u rg e e a r l y i n th e
seaso n may be d i r e c t l y r e l a t e d t o th e p re se n c e of la r g e amounts
o f t h i s more s u c c u le n t v e g e ta tio n .
McClymont (1967) n o te d t h a t
s tu d i e s on g ra z in g sheep have shown a n im a ls w i l l s e l e c t fo ra g e s
w i t h h ig h n u t r i t i o n a l v a l u e s .
ste m s,
L e a v e s w i l l be s e l e c t e d o v e r
g ree n m a te r ia l over dead m a t e r i a l, and young le a v e s over
o ld le a y e s (McClymont 1967).
Sheep w ere o b serv ed consum ing a l l
26
th e to p g ro w th of young l e a f y spurge p l a n t s b u t th e y s e le c te d only
l e a v e s and b lo s s o m s o f m ore m a tu re p l a n t s .
L a te i n t h e s e a s o n ,
a f t e r l e a f y s p u rg e had b e en h e a v i l y g r a z e d and o n ly b a r e , woody
stem s rem ain ed , in c re a s e d consum ption of g ra s s was o b serv ed .
If
a n a n im a l i s u n a b le t o s a t i s f y i t s fo o d n e e d s w i t h p r e f e r r e d
s p e c i e s i t may consum e f o r a g e p r e v i o u s l y r e j e c t e d
1 9 6 7 ).
(McClymont
S heep may have s e l e c t i v e l y consum ed m ore g r a s s l a t e i n
th e seaso n to av o id consum ing woody s t a l k s of m atu re l e a f y spurge
p la n ts .
Forage in ta k e was e x p re sse d a s a p e rc e n t o f t o t a l l i v e body
w e ig h t p e r tr e a tm e n t (Table 3).
Sheep, g ra z in g c o n tr o l p a s tu r e s
consum ed m ore f o r a g e a s a p e r c e n t o f l i v e w e ig h t th a n sh e e p
g r a z i n g s p u r g e p a s t u r e s (T a b le 3 ).
D i f f e r e n c e s b e tw e e n i n t a k e
v a l u e s w e re a t t r i b u t e d t o d i f f e r e n c e s i n q u a l i t y o f a v a i l a b l e
fo ra g e .
T h is r e p o r t w i l l base i t s d e f i n i t i o n o f fo ra g e " q u a lity "
o f le a f y sp u rg e and g ra s s on d a ta d e riv e d from p ro x im a te a n a ly se s
o f t h e s e f o r a g e s (T a b le 4 ).
O nly t h e f o r a g e q u a l i t i e s o f l e a f y
s p u rg e and g r a s s s a m p le s c o l l e c t e d d u r in g t h i s s tu d y w i l l be
compared.
H ig h -q u a lity fo ra g e s a r e g e n e r a lly more d i g e s t i b l e th an low - .
q u a l i t y fo ra g e s and p a ss th ro u g h th e d ig e s tiv e t r a c t more ra p id ly
(NRC 1 9 7 5 ).
A n im a ls may e a t m ore b io m a s s b u t a c t u a l l y r e q u i r e
s m a lle r am ounts o f h i g h - q u a l i t y f o r a g e t o m e e t t h e i r n u t r i t i v e
need s.
L o w - q u a lity f o r a g e s p a s s th r o u g h t h e d i g e s t i v e t r a c t
slo w ly , b u t a n im a ls a c tu a lly , need to consume l a r g e r q u a n t i t i e s to
m eet t h e i r n u t r i t i o n a l re q u ire m e n ts (Church 1980).
L eafy spurge
27
c o n tr ib u te d s u b s t a n t i a l amounts o f p r o t e i n to sheep d i e t s b u t may
a ls o have c o n tr ib u te d to lo w e r in ta k e v a lu e s by slo w in g d ig e s tio n
r a t e s w i t h i t s h ig h l i g n i n c o n t e n t (T a b le 4 ) .
S heep g r a z in g
c o n t r o l p a s t u r e s n e e d e d t o consum e m ore t o t a l f o r a g e t o m e e t
t h e i r n u t r i e n t re q u ire m e n ts .
G rass c o n ta in e d l e s s p r o t e i n th a n
l e a f y s p u rg e b u t s h e e p c o u ld e a t m ore o f i t
b ecau se i t s
low
l i g n i n c o n te n t f a c i l i t a t e d d ig e s tio n .
Forage in ta k e v a lu e s f o r a l l tr e a tm e n ts w ere c o m p a ra tiv e ly
h ig h e r th a n v a lu e s d e riv e d from s i m i l a r docum ented summer g ra z in g
e x p e rim e n ts (Cook e t a l . 1956).
One f a c t o r p o s s ib ly c o n tr ib u tin g
t o t h e s e d i s s i m i l a r i t i e s w as t h e u se o f an a g ro n o m ic te c h n iq u e
i n s t e a d o f a d i r e c t a p p ro a c h t o e s t i m a t e th e am o u n t an d ty p e o f
fo ra g e removed from th e tr e a tm e n t p a s tu r e s .
A nother f a c t o r w hich
m u st be c o n s i d e r e d w as t h e i n c r e a s i n g f o r a g e c o n s u m p tio n by
la m b s .
R e s e a rc h h a s show n t h a t h e rb a g e c o n s u m p tio n i n c r e a s e s
p r o p o r t i o n a l l y w i t h d e c r e a s e d m ilk c o n s u m p tio n a n d i n c r e a s i n g
body w e ig h t (P e n n in g an d G ibb 1 9 7 9 ).
E a r ly i n t h e s e a s o n lam b s
w e re c o n su m in g o n l y .s m a l l a m o u n ts o f f o r a g e b e c a u s e o f t h e i r
s m a ll body s i z e .
As t h e s e a s o n p r o g r e s s e d ,
h o w e v e r,
lam b s
consumed g r e a te r am ounts of fo ra g e to keep up w ith p ro p o rtio n a l
i n c r e a s e s i n t h e i r body s i z e .
To g a in an a v e r a g e o f 0.23 kg p e r
day a 32 k ilo g ram re p la c e m e n t lam b m ust consume 4.9 p e rc e n t i t s
body w eig h t a s fo ra g e - a lm o st tw ic e a s much fo ra g e a s a ewe on a
m a in te n a n c e
ra tio n
(NRC 1 9 7 5 ) .
T h is i n c r e a s e
in
fo ra g e
c o n s u m p tio n by lam b s p o s s i b l y c o n tr i b u te d to h ig h e x p e rim e n ta l
in ta k e v a lu e s .
D uring th e seaso n g ra z in g p re s s u re in c re a s e d from
28
5 an im al u n i t s p e r p a s tu r e t o a p p ro x im a te ly 7.5 an im al u n its p e r
p a s tu r e .
P ro x im ate a n a ly s e s of l e a f y spurge arid g ra s s sam ples showed
t h a t l e a f y s p u rg e c o n s i s t e n t l y m a i n t a i n e d a h i g h e r n u t r i e n t
c o n t e n t th a n g r a s s .
L e a fy s p u r g e 's h ig h c ru d e p r o t e i n l e v e l s
w ere a t t r i b u t e d to th e c h a r a c t e r i s t i c h ig h crude p r o te in co riten t
o f f o r b s and t h e e x t e n s i v e l e a f p r o d u c t i o n o f t h i s s p e c i e s .
L e a fy s p u r g e 's h ig h l i g n i n c o n t e n t w as a t t r i b u t e d t o i t s woody
ste m and p o s s i b l e c o n ta m i n a ti o n o f t h e l i g n i n f r a c t i o n by t h e
m ilk y l a t e x i n s p u r g e .
L e a fy S p u rg e a l s o c o n ta in e d a lo w e r ADF
f r a c t i o n th a n g ra s s d u rin g m ost o f th e summer, and ash f r a c t i o n s
f o r b o th f o r a g e s w e re c o n s i d e r e d a d e q u a te t o m e e t n u t r i t i o n a l
re q u ire m e n ts .
The m a g n itu d e o f d i f f e r e n c e
i n n u t r i e n t l e v e l s b e tw e e n
grow th s ta g e s of b o th fo ra g e s was c o n sid e re d im p o rta n t.
Grazed
reg ro w th sam ples of b o th fo ra g e s p o ss e s se d h ig h e r n u t r i e n t l e v e ls
th a n c o r r e s p o n d in g i n i t i a l an d f i n a l s t a n d i n g c r o p s .
R eg ro w th
sam ples c o n s is te d o f young s u c c u le n t v e g e ta tio n w hich c o n ta in e d
h ig h a m o u n ts o f p r o t e i n an d a s h a n d low a m o u n ts o f -ADF an d
lig n in .
D i f f e r e n c e s i n n u t r i e n t l e v e l s b e tw e e n g ro w th s t a g e s
w e re g e n e r a l l y l a r g e r f o r l e a f y S p u rg e , i n d i c a t i n g t h a t l e a f y
s p u rg e c o u ld p ro d u c e h i g h e r q u a l i t y f o r a g e th a n g r a s s e a r l y in
th e seaso n even a f t e r b e in g g razed .
le a fy
s p u r g e 's
fo rag e
m a in ta in e d a f a i r l y
q u a lity
L ate i n th e se a so n , how ever,
d ro p p e d d r a m a t i c a l l y .
c o n s is te n t fo ra g e
q u a lity
d u rin g
G ra ss
th e
29
e n t i r e s e a s o n and c o n s e q u e n tly p r o v id e d a b e t t e r f o r a g e th a n
sp u rg e l a t e i n th e seaso n .
C hanges i n f o r a g e v a l u e s o f l e a f y s p u rg e and g r a s s c l o s e l y
c o in c id e d w i t h t h e i r p r e s e n c e i n d i e t s o f s h e e p g r a z i n g l e a f y
sp u rg e p a s tu r e s .
E a rly in th e seaso n when l e a f y sp u rg e p ro v id ed
a h ig h e r q u a lity
fo ra g e
p e rc e n ta g e o f sh eep d i e t s .
th a n
g ra ss
it
com posed a h ig h e r
As l e a f y s p u rg e m a tu re d i t s f o r a g e
v a lu e d e c lin e d and sheep consumed more g r a s s .
Lambing re c o rd s o f e x p e rim e n ta l ewes w ere exam ined to see
w h e th e r c o n s u m p tio n o f l e a f y
s p u r g e m ig h t a d v e r s e l y a f f e c t
su b seq u en t lam bing p erfo rm an c e s.
lam bs.
B irth
A ll b red ewes d e liv e r e d h e a lth y
Lamb b i r t h w e ig h ts w ere c o n s id e re d av erag e (Jo rd an 1984).
w e i g h ts o f la m b s b o rn t o
e x p e r i m e n t a l ew es w e re n o t
s t a t i s t i c a l l y a n a ly z e d because to o many v a r i a b le s
(which needed
t o be c o n s id e r e d ) w e re n o t a c c o u n te d f o r i n t h e e x p e r i m e n t a l
d e s ig n .
L itte r
s iz e s
of
ew es w h ic h g r a z e d d i f f e r e n t t r e a t m e n t
p a s t u r e s w e re a n a ly z e d (T a b le 5 ).
No s i g n i f i c a n t d i f f e r e n c e s
w e re fo u n d b e tw e e n mean l i t t e r s i z e s o f c o n t r o l t r e a t m e n t an d
s p u r g e t r e a t m e n t e w es.
I t was c o n c lu d e d t h a t c o n s u m p tio n o f
l e a f y spurge by e x p e rim e n ta l ewes th e summer p r i o r to being b red
d id n o t a d v e rs e ly a f f e c t t h e i r su b se q u e n t lam bing p erfo rm an c e s.
A lthough, l e a f y sp u rg e has been c l a s s i f i e d a s a noxious weed
re s u lts
fro m
th is
s tu d y
in d ic a te
c l a s s i f i e d a s a fo ra g e f o r sheep.
th a t le a fy
s p u rg e
can
be
Sheep s e l e c t i v e l y consumed a s
much a s 55 p e rc e n t of t h e i r d i e t a s l e a f y sp u rg e and e x h ib ite d no
)
30
h a rm f u l s i d e e f f e c t s .
H e lg e so n and Thompson (1939) a t t r i b u t e d
th e p r e s e n c e o f s c o u r s i n a few la m b s t o c o n s u m p tio n o f l e a f y
sp u rg e .
J o h n s to n and P eak e (1960) a t t r i b u t e d t h e d e a th s o f an
unknown number of sheep to p o iso n in g r e s u l t i n g from consum ption
o f m atu re l e a f y spurge p la n ts .
In t h i s stu d y sheep w ere a llo w ed
to s e l e c t i v e l y consume l e a f y sp u rg e th ro u g h o u t i t s
p h o n o lo g ic al
d e v e lo p m e n t a n d no d e a t h s o r s i c k n e s s w e re r e c o r d e d .
s p u r g e t r e a t m e n t la m b s w e re c o m p a ra b le t o
t r e a t m e n t la m b s ,
and s p u rg e
ADG1s o f
th o s e , o f c o n t r o l
t r e a t m e n t ew es p ro d u c e d lam b s
com parable i n s iz e and number t o lam bs of c o n tro l tr e a tm e n t ewes.
On th e b a s is o f th e s e r e s u l t s l e a f y spurge was c o n s id e re d a good
i f n o t b e t t e r fo ra g e f o r sheep th an g ra s s .
31
SUMMARY
B ecau se c o n s id e r a b le d is a g re e m e n t e x i s t s w ith in th e
l i t e r a t u r e re g a rd in g th e r o le o f l e a f y sp u rg e a s a fo ra g e and i t s
e f f e c t s on s h e e p , a r e s e a r c h p r o j e c t w as i n i t i a t e d i n May, 1982
t o d e te r m in e i t s f o r a g e v a lu e .
L am b/ew e p a i r s w e re ra n d o m ly
a s s i g n e d t o t r e a t m e n t p a s t u r e s c o n t a i n i n g no s p u rg e ( c o n t r o l ) ,
l i g h t sp u rg e , or heavy sp u rg e and a llo w e d t o f r e e l y g raz e d u rin g
t h e sum m ers o f 1982 and 1983.
U t i l i z a t i o n c a g e s an d t h e p a i r e d
p l o t te c h n iq u e w e re u se d t o e s t i m a t e t h e am ount a n d ty p e o f
f o r a g e rem o v ed by s h e e p .
Sheep w e ig h t g a in s w e re r e c o r d e d and
ewe p erfo rm an ce re c o rd s w ere exam ined t o e s tim a te th e n u t r i t i o n a l
c o n tr ib u tio n o f le a f y spurge to sheep d i e t s .
N e i th e r la m b s n o r ew es e x h i b i t e d any d e l e t e r i o u s e f f e c t s
r e s u l t i n g fro m c o n s u m p tio n o f l e a f y s p u r g e .
ADG's o f s p u rg e
t r e a t m e n t la m b s w e re fo u n d t o be c o m p a ra b le t o a n d , i n some
cases,
h i g h e r th a n ADG's o f c o n t r o l t r e a t m e n t la m t)s.
Sheep
s e l e c t i v e l y consumed from 40 to 60 p e rc e n t of t h e i r d i e t a s le a f y
sp u rg e .
fo rag e
L e a fy s p u rg e c o n s i s t e n t l y p r o v id e d a h i g h e r q u a l i t y
th a n
g rass.
P r o d u c tio n
c a p a b ilitie s
of
ew es w h ic h
consumed l e a f y spurge th e summer im m e d ia te ly p r i o r to bein g bred
showed no a b n o r m a litie s i n su b seq u e n t lam bing p erfo rm an ce.
A ll
b red ewes produced h e a lth y lam bs.
R e s u l t s o f t h i s s tu d y i n d i c a t e t h a t l e a f y s p u rg e can be
c l a s s i f i e d a s a good f o r a g e f o r s h e e p .
T h ro u g h o u t t h e g ro w in g
seaso n le a f y spurge p ro v id e d a h ig h e r q u a l i t y fo ra g e th a n g ra s s .
32
Sheep s e l e c t i v e l y consumed a la r g e p o r tio n o f t h e i r d i e t a s le a f y
s p u rg e and e x p e r ie n c e d no h a rm f u l s i d e e f f e c t s fro m c o n su m in g
l e a f y spurge th ro u g h o u t i t s p h en o lo g ic a l developm ent.
F u tu re re s e a rc h on sheep use o f l e a f y sp u rg e m ig h t in c lu d e
m ore e x t e n s i v e e x a m in a tio n s o f v i a b i l i t y o f l e a f y s p u rg e s e e d s
p a s s e d by s h e e p .
I f s h e e p a r e t o be u se d t o c o n t r o l th e s p r e a d
o f l e a f y s p u rg e i t i s i m p o r t a n t t o p r e v e n t t r a n s p o r t o f v i a b l e
se ed s to u n in fe s te d a re a s .
A lso, a s d i f f e r e n t v a r i e t i e s o f le a f y
sp u rg e a r e ta x o n o m ic a lly i d e n t i f i e d i t m ight prove b e n e f i c i a l to
d e te rm in e t h e i r c o rre sp o n d in g fo ra g e p o t e n t i a l s .
LITERATURE CITED
34
' L IT E R A T U R E
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APPENDIX
T ab le 6 . S p ecies co m p o sitio n 1 o f th e n in e tre a tm e n t p a s tu r e s .
S c i e n t i f i c B inom ial
G ra ss e s:
A lopecurus p r a t e n s i s
A aropyron rep en s
Aaropyron s m ith ii
A aropyron spicatum
A aropyron trich o p h o ru m
A q ro s tis sp p .
Bromus in e rm is
Bromus tecto ru m
D a c ty lis a lo m e ra ta
F e stu c a a ru n d in a ce a
Hordeum jubatum
Poa p r a t e n s i s
S tio a comata
G r a s s lik e P la n ts :
Carex sp p .
F o rb s:
A s c le p ia s sp .
C irsiu m c a n a d e n sis
E quisetum spp.
E uohorbia e s u la
M e lilo tu s o f f i c i n a l i s
H a lf-S h ru b s:
A rtem esia f r i a i d a
P a s tu r e s
5
6
H
C
Common Name
I
C
2
L
3
C
4
L
meadow f o x t a i l
q u a c k g ra ss
w e ste rn w h e atg rass
bluebunch w h e atg rass
p u b e sc e n t w h e atg rass
2
2
4
3
I
I
3
2
I
7
. I
3
3
13
15
11
smooth brome
c h e a tg ra s s brome
o rc h a rd g ra s s
t a l l fe s c u e
f o x t a i l b a rle y
Kentucky b lu e g ra s s
n e e d le a n d th re a d
T o ta l
I
3
I
68
2
9
59
I
12
9
I
57
7
9
95
82
2
2
sedge
milkweed
Canada t h i s t l e
h o rs e ta il
l e a f y spurge
y ellow sw eet c lo v e r
T o ta l
f r in g e d sagew ort
I
I
3
__
3
I
I
13
.JL
16
7
8
H
H
9
L
6
I
6
3
15
6
2
15
33
I
13
10
5
49
I
4
I
32
37
I
10
36
I
21
2
3
90
37
I
5
JL
77
28
I
15
3
8
72
92
77
71
86
7
3
2
7
I
5
3
4
I
15
I
I
22
I
21
3
I
20
I
10
20
23
22
24
11
I
I
I
3
15
I
3
1 S p e c ie s c o m p o s itio n w as d e te r m in e d by t h r e e 5 0 - p o i n t s t e p / p o i n t t r a n s e c t s ran d o m ly
l o c a t e d i n e a c h p a s t u r e . D ata c o l l e c t e d by H a t f i e l d (1982). V a lu e s a r e e x p r e s s e d a s a
p e rc e n t o f th e t o t a l co m p o sitio n .
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