Effects of inbreeding and selection in a closed line of hereford cattle
by Darrell Ian Nevins
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Animal Science
Montana State University
© Copyright by Darrell Ian Nevins (1986)
Abstract:
The objectives of this study were to estimate the effect of inbreeding on birth weight, weaning weight
and yearling weight in a closed line of Hereford cattle and to evaluate the selection index in use in this
line. The Havre Line 4 has been closed since 1976. Mean inbreeding was .15 and .14 for calves and
dams, respectively. Inbreeding of calf was increasing at a rate of .005 per year. Estimates of the effect
of inbreeding of calf and dam on birth weight were very small and not biologically significant.
Inbreeding of calf had no effect on weaning weight of male calves and a -.84 kg/% of calf inbreeding
effect on female calf weaning weight. Inbreeding of dam had no effect on weaning weight of female
calves and a -.64 kg/% of dam inbreeding effect on male calf weaning weight. Estimates of the effect of
inbreeding on yearling weight were very small and not biologically significant. Selection in the Havre
Line 4 is based on the index, I = Yearling Weight -3.2 Birth Weight. The purpose of the index is to
achieve an acceptable increase in yearling weight while minimizing the correlated increase in birth
weight. Genetic trends were estimated by use of frozen semen from sires born in 1975 and 1976 (group
1) and sires born in 1980 and 1981 (group 2) in a common tester herd. Estimates were -.2, 2.3 and 2.8
kg/yr for birth weight, weaning weight and yearling weight, respectively. The index is effectively
reducing the trend for larger birth weight but is not increasing yearling weight at the expected rate. EFFECTS
OF INBREEDING
AND SELECTION IN A CLOSED
LINE OF HEREFORD
CATTLE
by
Darrell Ian Nevins
A thesis submitted in partial fulfillment
of the requirements for the degree
or
Master of Science
in
Animal Science
MONTANA STATE UNIVERSITY
Bozeman, Montana
Decemher I 986
VIAIN LIB.
A/f/7
ii
APPROVAL
of a thesis submitted by
Darrell Ian Kevins
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College of Graduate Studies.
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Approved for the Major Department
Date
Head, Major Department
Approved for the College of Graduate Studies
Date
Graduate Dean
ill
STATEMENT OF PERMISSION TO USE
In presenting this thesis in partial fulfillment of the
requirements
University,
for
a m a s t e r ’s
degree
at
Montana
State
I agree that the Library shall make it available
to borrowers under rules of the Library. Brief quotations
from
this thesis are allowable without
special
permission,
provided that accurate acknowledgement of source is mad e .
Permission for extensive quotation from or reproduction
of this thesis may be granted by my major professor, or in
his/her absence,
by the Director of Libraries when, in the
opinion of either, the proposed use of the m aterial is for
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in
this thesis for financial gain shall not be allowed without
my written permission.
I
,
XV
ACKNOWLEDGEMENTS
I
thank my father and mother,
They wanted more for me than they had.
to Kathy Hanford.
Her patience,
Roland and Jessie Nevins.
A special thank you
statistical
com put or skills made my analyses possible.
Don
Kress.
About
four years
ago
breeding cows at Havre.
He said no.
into graduate school.
He said yes.
I asked
ability and
Last I thank Dr.
him
for
a job
I asked if I could get
About a year later
I
found out that Animal Breeding has something to do with the
genetics of livestock.
This thesis is the result.
V
TABLE OF CONTENTS
Page
LIST OF T A B L E S ...................................... ..
. •vii
.LIST OF F I G U R E S .............................................. X
A B S T R A C T .....................'.............................. xi
I N T R O D U C T I O N ........................................
I
PART I
THE EFFECT OF INBREEDING ON BIRTH WEIGHT,
WEANING WEIGHT AND YEARLING W E I G H T .....................
5
LITERATURE REVIEW ...............
6
; ......................
The Effect of Inbreeding on Birth Weight ..........
6
The Effect of Inbreeding on Weaning Weight .......... , 9
The Effect of Inbreeding on Yearling. W e i g h t ........... 12
S u m m a r y ............. .. ............................. .
13
MATERIALS AND M E T H O D S .....................
.15
Site D e s c r i p t i o n ........................... ............ 15
. 15
Experimental A n i m a l s .................................
Selection and Mating System ...............................15
. 16
M a n a g e m e n t ..............
D a t a ..................................................... 17
Statistical A n a l y s i s ................................... 17
RESULTS AND D I S C U S S I O N .............. ' .................... 20
I n b r e e d i n g ...............................................20
Birth W e i g h t ................ ............................ 20
Weaning Weight .............................
. . . . . .
24
Yearling Weight ......................................... 28
S u m m a r y .................................................. 3 2
vi
TABLE OF CONTENTS - Continued
Page
PART II
THE EFFECT OF SELECTION FOR AN INDEX ON BIRTH
WEIGHT, WEANING WEIGHT AND YEARLING WEIGHT .............
33
LITERATURE REVIEW . . ......................................3%
34
38
Response to Selection for Growth .
Summary ..........................
40
MATERIALS AND METHODS
• •
Site D e s c r i p t i o n s ............. •
S i r e s ........................
Test Dams ............................
D a t a ..................................
P r o g e n y .......................... .. •
Preliminary Analysis of Weaning Weight
of Calves Produced at Red Bluff . . .
Preliminary Analysis of Weaning Weight
of Calves Produced at Bozeman . . . .
Statistical A n a l y s i s ................
.
.
.
.
.
. 46
. 50
. 5.1
54
RESULTS AND DISCUSSION
Gestation Length . .
Birth Weight . . . .
Calving Difficulty .
Weaning Weight . ..
Yearling Weight . .
Heritability . .. .
S u m m a r y ..........
LITERATURE CITED
Literature Cited
40
41
42
43
45
.
.
.
.
54 .
55
57
59
. ,61
. 65
. 65
67
68
vii
LIST OF TABLES
Table
1
The effect
of inbreeding
on birth weight .........
2
The effect
of inbreeding
on weaning weight . . . .
11
3
The effect
of inbreeding
on yearling weight . . . .
13
4
Least-squares analysis of variance
for birth weight
^
5
8
................ 21
Least-squares means for main effects
affecting birth weight ( k g ) ....................
.22
6
Partial regression values of birth
weight on inbreeding of calf,
inbreeding of dam and day of b i r t h ................. 23
7
Least-squares analysis of variance
for weaning w e i g h t ........... .. • • • ........... 24
8
Least-squares means for main effects
affecting weaning weight . . . .............. ..
25
Partial regression values of weaning
weight on sex x inbreeding of calf,
sex x inbreeding of dam and day of
b i r t h .................................
27
9
10
Least-squares analysis of variance
for yearling w e i g h t ........................... ..
11
Least-squares means for main effects
affecting yearling weight . . ..................
12
. 29
30
Partial regression values of yearling
weight on inbreeding of calf, sex x
inbreeding of calf, inbreeding of dam,
sex x inbreeding of dam and age at
yearling w e i g h t ........... ........................ BI
13
I
Page
,
Responses and correlated responses
to selection for growth . .. . . .................. 39
I
V.
viii
LIST OF TABLES - Continued
Table
Pa£e
14
Least-squares analysis of variance for
1 9 84 weaning weight at Red B l u f f ................. 47
15
Least-squares means and standard
errors for implant treatment at
Red Bluff in 1984 ....................... ..
• • • • 47
16
Least-squares analysis of variance
for 19 85 weaning weight at Red B l u f f ............. 48
17
Least-squares means and standard
errors for fistulation treatment
at Red Bluff in 1 985 .................
18
I9
20
21
22
49
Least-squares analysis of variance
for weaning weight of progeny calves
at Red Bluff in 1984 and 19 85 ................. ..
. 50
Least-squares analysis of variance
for weaning weight at Bozeman .....................
Least-squares analysis of variance
for gestation length . . ........... ..
51
• •, • • . . 54
Least-squares means and standard errors
for main effects affecting gestation
length . . . ................................. . . . .
55
Least-squares analysis of variance
for birth w e i g h t .................
56
23
Least-squares means and standard errors
for main effects affecting birth weight . .. . . . 5 7
24
Least-squares analysis of variance
for calving difficulty score . . . .......... *
. . 58
*.
25
Least-squares means and standard errors
for main affecting calving difficulty
score ........................... . . . . . . . . .
58
ix
LIST OF TABLES - Continued
Table
26
Page
Least-squares analysis of variance for
.............
weaning weight . . . . . . . . . . .
60
27
Least-squares means and standard errors
for main effects affecting weaning
weight .............................................. 6 I
28
Least-squares analysis of variance
for steer yearling w e i g h t ..................
62
29
Least-squares means and standard errors
for main effects affecting yearling
w e i g h t ........... .. ........... . . . . ........... 6 2
30
Least-squares analysis of variance
for yearling weight of female progeny
born in 1 9 8 4 ....................................... 63
31
Least-squares analysis of variance
for yearling weight of female progeny
born in 19 85 .......................................
64
Least-squares means for female
yearling weight ....................................
64
32
33
Heritabilities of dependent variables . . . .
. . .65
34
Summary of response and correlated
responses to selection for yearling
w e i g h t ...................... ........................6 6
X
LIST OF FIGURES
Figure
Page
1.
Trend in inbreeding of calves over years . . . . . .
20
2.
Year x age of dam interaction for
weaning w e i g h t ....... .. . .........................26
xi
ABSTRACT
The o bjectives of this study were to estimate the
effect of inbreeding on birth weight, weaning weight and
yearling weight in a closed line of Hereford cattle and to
evaluate the selection index in use in this line.
The Havre
Line 4 has been closed since I 976.
Mean inbreeding was .15
and .14 for calves and dams, respectively.
Inbreeding of
calf was increasing at a rate of .0 0 5 per year.
Estimates
of the effect of inbreeding of calf and dam on birth weight
w e r e ver y
small
and not
biologically
significant.
Inbreeding of calf had no effect on w e a n i n g weight of male
calves and a -.84 kg/%
of calf inbreeding effect on female
calf w e a n i n g weight. Inbreeding of dam had no effect on
w e a n i n g w e i g h t of female calves and a -.64 k g / % of dam
inbreeding effect on male calf w e a n i n g weight.
Estimates
of the effect of inbreeding on yearling w e i g h t were very
small and not biologically significant.
S election in the
Havre Line 4 is based on the index, I = Yearling Weight 3.2 Birth Weight.
The purpose of the index is to achieve an
acceptable increase in yearling weight while minimizing the
correlated increase in birth weight.
Genetic trends were
e s t i m a t e d by use of frozen semen from sires born in I 97 5 and
1 976 (group 1) and sires born in 1 9 80 and 19 81 (group 2 ) in
a common tester herd.
Estimates were -.2, 2.3 and 2.8 kg/yr
for birth weight, w e a n i n g weig h t and year l i n g weight,
respectively.
The index is effectively reducing the trend
for larger birth weight but is not increasing yearling
weight at the expected rate.
I
INTRODUCTION
Animal
Breeding
is
the
science
genetics of d o m e s t i c livestock.
of
improving
Two procedures result in
changes in the genetic properties of a population,
of
parents
mated.
and
control
Control
of
of
the way
mating
the
may
in which
result
in
selection
parents are
inbreeding
(F a l co n e r , I 981).
Inbreeding
is the mating together
of
individuals that
are related to each other by ancestry (Falconer,
primary
effect
19 81).
The
of inbreeding is to increase the probability
that the two alleles at a particular locus in an individual
are identical by descent.
proportion
This causes an increase in the
of h o m o z y g o u s
(Brinks and Knapp,
loci
in
the
inbred
individual
1 975).
Increased homozygosity is associated with a decline in
performance traits such as reproduction,
rate (Brinks and Knapp,
the
coefficient
(1922).
that
the
identical
1 975).
survival and growth
The measure of inbreeding is
of inbreeding
(Fx)
developed
by
Wright,
The coefficient of inbreeding is the probability
two
genes
by descent
Grow t h traits,
at any
locus
(Falconer,
in an
individual
are
1981).
from birth to wea n i n g in beef cattle,
are affected by both the genotype of the offspring and the
maternal
environment
environment,
lactation,
provided
by
the
dam
(uterine
and other less well-known factors)
2
(Brinks and Knapp, 1975).
Yearling
individual
dam
weig h t
and
is affected
affected
Therefore,
by
the genotype
of
the
there is the possibility that inbreeding of
could have a carryover
offspring.
by
both
effect
growth
the
on yearling weight
traits may
inbreeding
of
of
be concurrently
the
dam
and
the
inbreeding of the offspring.
Under
dominance
theory
the
relationship
between
inbreeding (homozygosity) and the level of performance for a
trait such as weaning weight should be linear.
A non-linear
relationship would indicate an epistatic interaction between
loci
(Falconer,
linear
and
1981).
a quadratic
Analyzing
effect
inbreeding
provides
some
as
both
a
indication
whether dominance theory explains the effects of inbreeding.
Artificial
choice
of
selection is the process resulting from
parents.
offspring.
Only
the
selected
parents
The response to selection is meas u r e d
change in the population mean,
the
produce
by the
the difference between the
offspring of selected parents and the parental generation
(Falconer,
1981).
Many early
allow
studies of selection were not designed to
separation of genetic
changes (Dalton and. Baker,
1 979).
the genetic
trends in beef
random
control
bred
changes from
phenotypic
Techniques of evaluating
cattle
population,
the
include
maintaining
repeat matings,
a
intra-year
comparisons of sire or dam progeny groups and semen storage
3
with
evaluations
on
a common
tester
herd
(Koch
et
a l .,
1 9 8 2 ).
Selection for higher growth rate has been advocated to
increase
efficiency
in
beef
production
(Barlow,
I 97 9).
Dickerson et al. (1974) studied selection criteria including
carcass
composition,
meat quality,
at slaughter of calves,
mature
optimum economic weight
size,
milk production and
calving difficulty of cows to improve efficiency of beef
production.
An index (I) of I = Yearling Weight - 3.2 Birth
Weight was suggested.
Dickerson
et
al.
(1974)
predicted
the
result in 56% less increase in birth weight
index
should
while reducing
increase in yearling weight 10% as compared to selection for
yearling weight
alone.
This should
be possible
since
the
genetic correlation between birth weight and yearling weight
is about
.6 (W ol deh aw aria t et al., 1 977).
Selection for faster growth (among bulls) will increase
birth
weights
(Dickerson
et
of
calves
al.,
before
I 9 7 4).
it
Birth
increases
weight
is
cow
size
the
most
i mportant factor affecting calving difficulty (Bellows et
al., 1971).
Tw o- year- ol d-d am s that experience dystocia wean
fewer calves and as 3-yr-olds wean fewer and lighter calves
than 2-yr-old dams
that do not
experience
dystocia
(Brinks
et al., I 973).
The
Herefords.
data
for
this
study
are
from
the
Havre
Line
4
The Havre Line 4 is a closed line and herd sires
are selected by the index,
Weight.
Therefore,
I = Yearling Weig h t -3.2 Birth
genetic
change
in
this
line
may
be
affected by both inbreeding and selection.
The objectives of this study are to estimate the effect
of inbreeding on birth weight,
weaning weight and yearling
weight in the Havre Line 4 and to evaluate
selection
weaning
based on the
weight
and
selection
yearling
the ^ffect
of
index on birth weight,
weight.
To
evaluate
the
selection index a progeny test was performed through the use
of frozen semen in a c o m m o n tester herd.
5
PART I
THE EFFECT OF INBREEDING ON BIRTH WEIGHT,
YEARLING WEIGHT
WEANING WEIGHT AND
6
LITERATURE REVIEW
This
section
effects of
of literature
focuses
on
the
inbreeding of calf (Fx) and i nbreeding of dam
(Pd) on birth weight,
beef
review
weaning weight and yearling weight in
cattle.
The Effect of Inbreeding on Birth Weiaht
Swiger et al.
ford lines,
inbreeding
dams.
(1961) pooled 283 records from
two Here­
one Angus line and one Shorthorn line.
coefficients
Partial
were
regression
.13 for
values
calves
of
and
birth
Mean
.10
weight
for
on
inbreeding in kilograms per percent inbreeding were -.17 for
Fx and -.01
for Pd.
At a separate location 677 records from
ten Hereford lines and two Angus lines were
pooled.
The
me a n inbreeding coefficient of calves was .05 and the mean
inbreeding
coefficient
of dams was .03.
Partial regression
values were -.03 kg/% Fx and ,06 kg/% Fd for birth weight on
inbreeding.
either
Significance
levels
were
not
reported
for
analysis.
Swiger et al. (1962) pooled 647 records from Hereford
Angus and Shorthorn lines.
calves
and
Mean inbreeding
dams were .09 and .08,
coefficients of
respectively.
Partial
r egression values of. birth weight on i nbreeding were -.03
k
kg/% Fx and .06 kg% Fd.
Significance levels were not
reported.
7
Nelms and Sratton (1967) analyzed 302 records from one
Hereford line.
Mean inbreeding coefficients were .11 for
calves and .05 for dams.
weight
Partial regression values of birth
on inbreeding were -.0 2 kg/ % Fx and -.03 kg/ 56 Fd.
Neither Fx or Fd were significant sources of variation in
birth weight.
Sutherland and Lush (1962) analyzed 1008 records from a
line of Hol steins.
Mean inbreeding of calves was .10.
inbreeding of dams was not reported.
Mean
Simple regression
values of birth weight on inbreeding of calf were -.10 kg/%
Fx
of
male
calves
and
-.14
kg/%
Fx
for
female
calves.
Simple r egression values of birth weight on inbreeding of
dam were -.12 kg/% Fd for male calves and -.13 kg/% Fd for
female
calves.
Brinks et al.
Hereford records.
and
.12,
(1965) analyzed 2027 Mil e s City Line I
Mean inbreeding of calf and dam were .16
respectively.
Partial
regression
values
for
inbreeding of calf on birth weight were -.06kg/% Fx in males
and -.18 kg/% Fx in females.
Values for inbre e d i n g of dam
on birth weight were .004 kg/% Fd and .04 kg/% Fd for m a l e s
and females,
respectively.
Significance levels were not
reported.
Anderson
Hereford lines.
(1966)
analyzed
640
records
from
three
Mean inbreeding of calf and dam were .15
and .09, respectively.
Partial regression values were .01
kg/% Fx for m a l e s and -.03 kg/% Fx for f e m a l e s when birth
8
weight was regressed on inbreeding of calf. Values for birth
weight on
and
.06
inbreeding
kg/ %
Fd
of dam
for
were .17 kg/%
females.
Only
Fd
Fd for
for males
males
was
a
significant source of variation in birth weight.
Brinks and Knapp (1975) pooled records from 48 inbred
lines
in
the
western
United
States.
Mean
inbreeding
calves was .19 and mean inbreeding of dams wa s .12.
only
the linear
partial
effect
regression
of inbreeding
coefficients
was
of
When
considered
birth
of
weight
the
on
inbreeding were -.0 4 kg/% Fx and -.10 kg/% Fd for mal e s and
-.03 kg/% Fx and .001 kg/% Fd for females.
and females were
weight.
When
Fx for both males
significant sources of variation in birth
bo t h
linear
and
quadratic
effects
of
inbreeding were fitted no partial regressions of inbreeding
of
calf or dam
were
significant
sources of variation in
birth weight.
Table I . The effect of inbreeding on birth weight.
Swiger et
Swiger et
Swiger et
Nelms and
a l . (1961)
al. (1961)
a l . (I 962)
Stratton (1967)
Brinks (1965)
Anderson (1966)
Brinks and Knapp (1975)
b (kg/% Fx)
b (kg/% F d )
- .17
- .03
- .09
- .02
m al e female
— .18
- .06
.01
-.03
- .04
-.03
. -.01
.06
-.03
-.03
mal e
female
.004
.04
.17
.06
-.10
.001
b (kg/% Fx) = partial regression of birth weight on
inbreeding of calf
b (kg/% Fd) = partial regression of birth weight on
inbreeding of dam
9
The Effect of Inbreeding on Weaning Weight
Koch
(1951)
Herefords.
Mean
inbreeding
weaning
7 45
inbreeding
of dam was .06.
weight
kg/% Pd.
analyzed
of
records
calf
from
was
a
.12
line
and
Partial regression
mean
values
on inbreeding were -.22 kg/% Fx
of
and
of
-1.15
Significance levels were not reported.
Burgess
Hereford
et al .
lines.
(1954) pooled 546 records from several
Mean inbreeding of calf and dam were
and .06, respectively.
.12
Partial regression values of weaning
weight on inbreeding were -.81 kg/% Fx and -.52/kg% Pd. Both
Fx
and Fd were significant sources of variation in
weaning
weight.
McCleery
from
to
Blackwell (1954) analysed
one line of Herefords.
1455
records
Calf inbreeding ranged from 0
.25 and dam inbreeding ranged from 0
regression
kg/%
and
to
.16.
Partial
values of weaning weight on inbreeding were -.54
Fx and .43 kg/% Pd.
Fx and Fd were both
significant
sources of variation in weaning weight.
In the study of Swiger et al. (1961) partial regression
Values of weaning weight on inbreeding were -.65 kg/% Fx and
-.02
kg/% Fx at two locations.
regressed
kg/% Pd.
on
-.05
inbreeding of dam were -.07 kg/% Fd
weight
and
.02
Significance levels were not reported.
Anderson
weaning
Values for weaning
(1966)
found partial
regression
values
weight on inbreeding of -.12 kg/% Fx for males
kg/% Fx
for females.
Values for weaning
weight
of
and
on
inbreeding of dam were -.78 kg/% Fd for males and -.07
Fd for females.
The
Only Fd of males was significant.
study of Nelms and Stratton (1967)
regression
weaning
kg/%
values
of
-.47
weight on inbreeding.
found
kg/% Fx and .27
partial
kg/%
Only Fx was
a
Fd
for
significant
source of variation in weaning weight.
Brinks
et al .
(1965) found partial regression
values
for weaning weight on inbreeding of calf of -.21 kg/% Fx for
males
and
weight
-.20
-.77 kg/% Fx for females.
Values
for
weaning
on inbreeding of dam were -.85 kg/% Fd for males and
kg/%
Fd for females.
reported.
Significance levels
were
not
Inbreeding of calf had a larger effect on weaning
weight of females.
Inbreeding of dam had a larger effect on
weaning weight of males.
Brinks et al. (1963) hypothesized
that males have a greater growth potential and therefore are
affected less by inbreeding of calf.
of
dam
males
Conversely,
is associated with decreased
milk
inbreeding
production
having greater growth potential are affected more
and
by
inbreeding of dam.
Dinkel
Hereford
inbreeding
et al.
lines.
of
(1968) analyzed 860 records
from
four
Mean inbreeding of calf was .20 and
mean
dam was .09«
Partial regression values
of
weaning weight on inbreeding were -.61 kg/% Fx for males and
-.36. kg/% Fx for females.
Values for inbreeding of dam were
-.23 kg/% Fd for males and -.73 kg/% Fd for females.
of
males
and
Fd of females were
significant
Only Fx
sources
of
variation
the
in weaning weight.
hypothesis of
Brinks et al .
analysis,
inbreeding
quadratic
effect.
and
Fd
as
These results disagree
was
(1963).
In
fitted as both a
a
with
separate
linear
and
a
Only Fx as a quadratic effect for males
a linear effect for
females
were
significant
sources of variation in weaning weight.
Brinks and Knapp (1975) found partial regression values
of
kg/%
weaning
Fd
females.
weight on inbreeding of -.29 kg/% Fx
for males and -.31 kg/% Fx and -.24
and
kg/%
-.40
Fd
for
Each of the partial regressions was a significant
source of variation in weaning weight.
quadratic
effects
quadratic
effect
When both linear and
of inbreeding were fitted only Fd
as
was a significant source of variation
a
in
weaning weight.
Table 2. The effect of inbreeding on weaning weight.
b (kg/% Fx)
Koch (1951)
Burgess et al. ( 1954)
McCleery and Blackwell (1954)
Swiger et al. (1961)
Swiger et a l . (1961)
Nelms and Stratton (1967)
Anderson (1966)
Brinks et al. (I 96 5)
Dinkel et al. (1968)
Brinks and Knapp (I 97 5)
male
-.12
-.21
-.61
-.29
I .20
— .81
-.54
— .65
— .02
-.47
female
-.0 5
-.77
-.36
-.31
b (kg/% F d )
' — .22
- .52
.43
- .07
.02
.27
male
female
— .07
-.7 8
.20
- .85
.73
-.23
- .24
-.40
b (kg/% Fx) = partial regression of birthweight on
inbreeding of calf
b (kg/% Fd) = partial regression of birthweight on
inbreeding of dam
The Effect of Inbreeding on Yearling Weight
Several
researchers
have
studied
the
effect
of
inbreeding on final weight off postweaning gain test.
Final
weight
since
they
may be a different trait in males and females
are
managed separately and fed to gain
at
different
rates.
Brinks
et
al.
(1965)
analyzed
final
weight
po stweaning gain test of males and 12-mo weight of
Partial
regression
values
for final weight
of
females.
males
inbreeding were -1.04 kg/% Fx and -.39 kg/% Fd.
off
on
Values for
12-mo weight of females on inbreeding were -1.38 kg/% Fx and
-.10 kg/% Fd.
Nelms
and
po stweaning
regression
kg/%
Significance levels were not reported.
Stratton (1967) analyzed final
gain
test
of
males
and
weight
females.
Partial
values for final weight on inbreeding were
Fx and .50 kg/% Fd.
off
-.15
Neither Fx or Fd were significant
sources of variation in final weight.
Dinkel
et
al.
po stweaning gain test.
weight
(1967)
analyzed
final
weight
off
Partial regression values for final
on inbreeding were -1.09 kg/% Fx and -.004
kg/%
Fd
for males and -.53 kg/% Fx and -.61 kg/% Fd for females.
Fx
and Fd for males and Fd for females were significant sources
of
variation
quadratic
females
in final weight.
effects
as
both
of
When both the
inbreeding were fitted
a linear and quadratic
sources of variation in final weight.
were
linear
only
Fd
and
of
significant
13
Anderson
final
for
found partial
regression
values for
weight on inbreeding of -.61 kg/% Fx and -.65 kg/% Fd
males
None
(1966)
of
and -.17 kg/% Fx and -.19 kg/% Fd
the
regressions
were
for
significant
females.
sources
of
variation in final weight.
Brinks and Knapp (1975) found partial regression values
for final weight on inbreeding of -.44 kg/% Fx and -.31 kg/%
Fd
for males and -.25 kg/% Fx and .13 kg,/% Fd for
Only
final
Fx of males was a significant
weight.
females.
source of variation
When both linear and quadratic
effects
in
of
inbreeding were fitted only Fd of males as a quadratic was a
significant source of variation in final weight.
Table 3. The effect of inbreeding on yearling weight.
b (kg/% F x )
Nelms and Stratton (1967)
Brinks et a l . ( 1 965)
Dinkel et al. (1967)
Anderson (1966)
Brinks and Knapp (1975)
b (kg/% Pd)
-.15
male
female
-1 .04
-I .38a
-1.09
-.53
-.61
-.17
-.44
-.25
mal e
-.39
-.004
-.65
-•31
.50
female
-.IOa
-.61
-.19
.13
b (kg/% Fx) = partial regression of yearling weight on
inbreeding of calf
b (kg/% Pd) = partial regression of yearling weight on
inbreeding of dam
a 12-mo weight
Summary
Inbreeding
weight.
of calf and dam,have little effect on birth
Inbreeding
of
calf
has
a
fairly
large
(approximately
weight.
is
The
usually
Inbreeding
-.5 kg/% Fx) detrimental effect
on
weaning
effect of inbreeding of dam on weaning weight
detrimental
of
and
varies
greatly
calf has a fairly large
with
line.
(approximately
-.6
kg/% Fx) detrimental effect on yearling weight.
Inbreeding
of
kg/%
dap
has
detrimental
a
(approximately
increased inbreeding varies greatly between inbred lines
of
beef
be
greatly
manner
affected
or
differences
no
Growth
The
Pd)
to
cattle.
on yearling weight.
-.14
response
is
effect
smaller
traits of a particular line
by inbreeding in a positive
may not be affected.
or
The explanation
in response to inbreeding is not known.
strong evidence for a quadratic growth
inbreeding (Brinks and Knapp, 1975).
may
negative
for
sex
There
response
to
MATERIALS AND METHODS
The data for this part of the study were collected at
the Northern Agricultural Research Center (NARC) near Havre,
Montana from 1 97 6 to 1 983.
Site Description
NARC is located 13 km SW of Havre.
plains
with
an approx i m a t e
precipitation
1980).
averaged
2 97
The area is rolling
elevation
mm
fr o m
of
1951
819
m.
Annual
to
1 980
(US D C ,
The pastures at NARC are mixed praire grasslands
containing Aeroovron desertorum. Stioa
gracilis (crested w heatgr ass,
comata
and Bouteloa
needle and thread and blue
grama) as the major forage species.
Experimental Animals
Data were collected on 594 Havre Line 4 Horned Hereford
calves.
Line I.
The Havre Line 4 is a subline of the Miles City
Foundation
cows were purchased from
the Livestock
and Range Research Station at Fort Keogh in I 96 2 and 1 963.
The Havre Line 4 consists of a p p r o x i m a t e l y 100 cows.
The
line was closed in 1976.
Selection and Mating System
Each year
utilizing
two
sires are selected w i t h i n
the following
index,
I = Yearling
nI
the line
by
Weight - 3.2
16
Birth
Weight.
Yearling
weight
and
birth
weight
are
corrected for age of dam and yearling weight is corrected to
365 d of age.
herd data.
yr-olds.
Correction factors are calculated from within
Sires are used for breeding as yearlings and 2As
yearlings,
sires
replacement heifers and cows.
are
randomly
mated
with
Two-yr-old sires are repeat-
mat e d to half the dams that produced their offspring the
preceding year.
To limit the rate of increase in inbreeding
half-sib and son-dam matings are excluded and the two sires
selected each year cannot be half-sibs.
All yearling heifers are exposed to breeding and those
becoming pregnant are retained in the herd.
Dams are culled
on Most Probable Producing Ability for p r e w e a n i n g gain of
calves.
Cows which are not pregnant In the fall are culled.
Management
Breeding is by natural
I.
After
the
breeding
service for 45 d beginning June
season
the
four
sire
groups
are
pastured together on improved pastures for the rest of the
year.
Winter feed for the cow herd consists of grass hay
and corn silage.
W e a n i n g occurs on Oct. I.
After a 2 - w k w a r m u p period
bull calves go on a 168-d gain test. . The ration consists of
corn silage,
grass hay and an oat-barley concentrate mix.
Average gain is 1.1 kg per d.
For 6 - wk after w e a n i n g heifer calves are pastured on
17
hay field a fter m a t h and then go on a 14 0 - d gain test.
The
ration consists of corn silage, second cutting alfalfa and
barley.
Average gain is .6 kg per d.
Data
The
data
weaned from
collected
the
594
Havre
Line
1 976 to 1983 included birth date,
sex of calf, age of dam,
final
on
weight
4 calves
birth weight
sire of calf, w e a n i n g weight and
off postw e a n i n g gain test.
I nbreeding was
calculated by an algorithm developed by Quaas (1 976).
Statistical Analysis
To esti m a t e the effect of calf and dam inbreeding on
birth weight, w e a n i n g weight and yearling weight the data
were
analyzed
by
(Harvey, 1 977).
inbreeding
interest
of
in
fixed
model
I east - squares
procedures
The effects of inbreeding of calf (Fx) and
dam
the
(Fd)
were
analysis.
the v a r i a b l e s
The
other
of
primary
variables
an d
interactions were fitted to account for k n o w n sources of.
variation
and
inbreeding.
allow
better
estimates
of
the
effects
of
The model used to analyze birth weight was as
follows:
Y1 Jki = u + Yri + Sx j + Ak + Slti) + Yr x S x i J + Yr x A ik +
Sx x A j k + B ijkl + F x ijkl + F d ijkl
Fdijkl + Gijkl
where
+ SXj x F x ijkl
+ Sxj x
Yijk I = an observation
z
u = the overall mean
Yri = the fixed effect of the ith year
SXj = the fixed effect of the j th sex
Ak = the fixed effect of the kth age of dam
’I ( i)
the
fixed
effect of the Ith sire nested
within the ith year
Yr x SxiJ = the
interaction of the
ith
year and
the j th sex
Yr x A ik = the interaction of the ith year and the
kth age of dam
Sx x Ajk = the
interaction of the j th sex and the
kth age of dam
B ijkl = tlie effect of day of birth
Fx iJki = the effect of inbreeding of calf
Fdfjki " the effect of inbreeding of dam
Sxj x Fx i^jki " the
interaction of the
j th sex of
calf and inbreeding of calf
Sx • x F d 1
-^ vi = the
J
IJ K J.
interaction of the
j th sex of
calf and inbreeding of dam
eijki = random error.
The same model
variable was
with w e a n i n g weight as the dependent
used to analyze w e a n i n g weight.
model was used to analyze yearling weight.
A similar
Final weight off
po stweaning gain test was the dependent variable and age at
yearling weight was included as a covariate.
. In prelim i n a r y
were-fitted
as
analyses,
bo t h l i n e a r
inbreeding of calf and dam
and
quadratic
covariates.
Inbreeding of calf and dam as quadratic covariates were not
significant sources of variation in any a nalysis and were
not included in final models.
calf
The two-way
interactions of age of dam x inbreeding of
and
dam
age
preliminary
of
analy s e s .
significant for any
analyses.
x inbreeding
These
of dam
were
interactions
fitted
were
in
not
trait and were not included in final
20
RESULTS AND DISCUSSION
Inbreeding
Inbreeding
of dam
of .14. Inbreeding of
ranged from .06 to .31 with
calf
ranged
a mean
from .08 to .39 with a
mea n of .15. Inbreed ing of calf increased at a rate of .0 0 5
per
year.
The
trend
for
inbreeding
of calf is shown in
Figure I.
0 . 26 U-J
u °-20U-
O
0 . 16 -
Z
O
LU
UJ
0 . 10CO
Z
0. 06-
0 0 0 ----------- :---------- 1---------- :-----------:-----------1---------- 1
19 7 6
I 97 7
19 7 9
1 97 9
19 9 0
15 9 1
1
19 9 2
rTT
19 8 3
YEAR
Figure I. Trend in inbreeding of calves over years.
Birth Weight
The mean birth weight was 36.2 kg.
significantly
within
year.
affected
by all
The least-squares
main
Birth weight was
effects
analysis
of
except
sire
variance
of
birth weight is shown in Table 4 and the least-squares means
21
for main effects are shown in Table 5.
Table 4. Least-squares
weight.
analysis
Sour ce
df
Year
Sex
Age of dam
Sire/year
Year x sex
Year x age of dam
Sex x age of dam
'7
I
3
27
7
21
3
Regressions:
Day of birth
Inbreeding of calf
Sex x Inbreeding of calf
Inbreeding of dam
Sex x Inbreeding of dam
of
variance
birth
Mean square (kg2 )
392°
21
27
13
I
I
I
I
I
290 9°°
34a
45
29
II
519
Remainder
for
i
i
i
i
i
i
i
•i
i
CTt I
i
I
I
I
I
I
i
I
I
I
R2
r x •v i
P< .0 5
a P= .0 8
Year
weight
1983,
was
and
a
a significant source of variation
birth
means ranged from 34.3 kg in 1979 to 37.8 kg in
difference of 3.5 kg.
Burfening
in
and
This is in agreement
Kress (1 97 3) who found a
significant
with
year
effect in a study at the same location.
Sex
of
calf was a significant source of variation
in
birth weight and mean male calf birth weight was 37.3 kg and
mean female calf birth weight was 35.3 kg.
kg
heavier
than females at birth.
Males were
The sex difference
2.0
is
22
within the range given by Woldehawariat et al. (1977).
Table 5. Least-squares means
birth weight (kg).
for
main
effects
affecting
Mean
SE
36.3
±.« I6
64
69
65
68
68
77
88
95
36.0
36.4
35.5
34 .3
37.3
37.2
35.8
37.8
±. 55
±.45
±.45
±.47
±.47
±.44
±.46
±.40
Sex
Mal e
Femal e
302
292
37.3
35 .3
±.22
±.23
Age of dam
2
3
4
5-10
I40
I 27
83
244
33.6
36 .2
37.3
38.2
±.3 5
±.33
±. 4 0
±,2 5
Item
n
U
594
Year
1976
I 977
I 978
I 979
I 980
1981
1982
19 83
Age
birth
for
of
.
dam was a significant source of
weight and means were 33.6,
2-yr-old,
respectively.
3-yr-old,
4-yr-old
36.2,
and
variation
in
37.3 and 38.2
kg
5-10-yr-old
for
2-yr-olds,
increased with age to mature dams (5-1O-yr-old).
The effect
of
age
of
Birth weights were lightest
dams,
dam
on
birth
weight
is
in
agreement v with
Woldehawariat et al. (1977).
The
two-way
significant
source
interac ti on
year
x age
of
of va r i at i o n in birth weight.
dam
was
a
Year m e an s
23
for
age of dam subclasses changed
magnitude
from
year
to year.
erratically in rank
' The
explanation
and
of
this
interaction was not apparent.
Partial regression values are shown in Table 6.
birth
as a covariate was a significant source of
in birth weight.
day
increase
Day of
variation
Birth weight increased .06 kg for each one
in
the calving
season.
This
agrees
with
Burfening and Kress (1973).
Table 6. Partial
regression values of birth weight
on
inbreeding of calf,
inbreeding of dam and day of
birth.
Inbreeding of calf (kg/% Fx)
Inbreeding of dam
(kg/% Pd)
Day of birth
(kg/d)
oo
o
±.0001
±.00004
±.01
-.0001
- .0001
— .06
PC.01
PC.05
Inbreeding
of
SE
b
Regression
of calf approached significance as a
variation
significant.
in
birth
weight.
Inbreeding
of
source
dam
The partial regression values were -.0001 kg/$
inbreeding of calf and -.0001 kg/% inbreeding of dam.
small values lack biological significance.
little
effect
agreement
was
with
Inbreeding
on birth weight in this study.
several
studies which
These
have
This is
shown
had
in
little
effect of inbreeding of calf on birth weight (Swiger et al.,
1962; Brinks et al., 1965 and Brinks and Knapp,
1975).
This
24
study agrees with most previous studies where inbreeding
dam
has
shown
little effect on birth weight
(Brinks
of
and
Knapp, 1975).
Weaning Weight
The
was
mean weaning weight was 203.4 kg.
Weaning weight
significantly affected by all main effects except
within
year.
weaning
The least-squares analysis of
weight
is shown in Table 7 and
the
variance
sire
for
least-squares
means for the main effects are shown in Table 8.
Table 7. Least-squares
weight.
analysis
of
Source
df
Year
Sex
Age of dam
Sire/year
Year x sex
Year x age of dam
Sex x age of dam
7
I
3
27
7
21
3
Regressions:
Day of birth
Inbreeding of calf
Sex x inbreeding
Inbreeding of dam
Sex x inbreeding of dam
Remainder
s
I
I
1
I
I
519
variance
for
weaning
Mean square (kg2 )
12057OO
24683
375
396
934
691
59262°°
1678*
440
1507
355
t— I
VO B
R2
r N •u I
P < .0 5
Year
was a significant
source
of v a r i a t i o n in
w e an i n g
25
weight
and means for year ranged from 17 6.6 kg in
216.8
year
kg
in 1 977.
effect
Many studies have shown a
on weaning weight.
I 97 8
to
significant
Anderson (1966)
found
significant year effect of a similiar magnitude at the
a
same
location.
Sex
weaning
of
calf was a significant source of variation
weight
and mean weaning weight was
males and 192.0 for females.
207.7
kg
in
for
The 15.7 kg difference due to
sex is in agreement with Woldehawariat et a l . (1 977).
Table 8. Least-squares means
weaning weight (kg).
Item
n
for
main
Mean
effects
affecting
SE
5 94
199*9
±1.3
64
69
65
68
68
77
88
95
198.6
216.8
176.6
I 93.2
214.7
208.1
190.8
200 .0
±4.6
±3.5
±3.4
±3.0
±3.1
±3.7
±4.5
±3.0
Sex
Male
Female
302
292
207.7
192.0
±1 .7
±2.0
Age of dam
2
3
4
5-10
I40
I 27
83
244
176.6
198.3
210.3
217.8
±2.0
±1 .8
±2.2
±1.4
U
Year
1976
I 977
I 97 8
I 979
I 980
1981
I 982
19 83
26
Age
of
dam was a significant source of
variation
in
weaning weight and means were 177,
198,
210 and 218 kg for
2-yr-old,
and
5-10-yr-old
3-yr-old,
respectively.
This
4-yr-old
dams
effect of age of dam on weaning weight
is in agreement with Woldehawariat et al., (1977).
The
two-way
important
weights
interaction
year
x age of
source of variation in weaning
dam
weight.
was
an
Weaning
of calves from 2-yr-old dams were affected more
by
year than calves from mature dams as shown in Figure 2.
320_
A
X
280-
2-YR-OLD DAMS
5-10-YR OLD DAMS
240-
. X -- - • X'
200 -
(3 160120-
1980
1976
1982
1983
YEAR
Figure 2. Year x age of dam interaction for weaning weight.
Day of birth as a covariate was a significant source of
variation
in weaning weight.
Weaning weight increased .89
kg for each one day decrease in day of birth.
This
agrees
closely with the study of Urick (1958) at the same location.
Inbreeding
of
calf and dam when pooled over sex
were
27
not
significant
However,
the
sources of variation
in
weaning
weight.
two-way interactions sex x inbreeding of calf
and sex by inbreeding of dam were significant.
Male weaning
weight
increase
in
Female weaning weight decreased .84
kg
decreased
.64 kg for each one percent
inbreeding of dam.
for
each
one
percent
increase
in
inbreeding
of
calf.
Partial regression values are shown in Table 9.
Table 9. Partial
regression
sex x inbreeding of
and day of birth.
values
of weaning weight
on
calf, sex x inbreeding of dam
b
SE
CM
CM
±.30
.39
-.84
±.46
±.36
Regression
I
I
(kg/%
»
Sex x inbreeding of calf0
Mal e
Female
I
Inbreeding of calf (kg/56 F x )
Fx)
I
Day of birth00 (kg/d)
I Co
I VO
I
i
i
i i
— .65
.20
O
CM
Sex x inbreeding of dam° (kg/56 Pd)
Mal e
Female
■H
I
CM
CM
Inbreeding of dam (kg/56 F d )
±.2 9
±.28
. ±.07
r N .u I
P< .05
Inbreeding of calf had a detrimental effect on
weight
of females.
detrimental
effect
(Swiger et al.,
Several studies have found a
of
I 96 2;
inbreeding of calf
Dinkel et al.,
I965 and Brinks and Knapp,
I 97 5) .
on
weaning
sizeable
both
sexes
1 968, Brinks et al.,
Inbreeding of dam had a
28
detrimental effect on weaning weight of males.
found
a detrimental effect of inbreeding of dam on
weight of both sexes (Brinks et a l . ,
and Dinkel et al.,
Blackwell,
The
Studies have
1968),
of
Anderson,
1966
a positive effect (McCleery
1954) and no effect
response
1 965;
weaning
(Nelms and Stratton,
weaning weight
to
increased
and
1964) .
inbreeding
varies by line and selection criteria.
Weaning
inbreeding
greatly
Brinks
weight of males was more greatly
by
of dam while weaning weight of females was
affected by inbreeding of calf.
et al.
(1963).
expected because
I
affected
Hereford
This agrees
This similarity
Brinks et al.,
more
with
is probably to be
(1963) used Miles City Line
data and the Havre Line 4 is a subline
of
the
Line I.
Yearling Weight
The mean yearling weight was 350 kg.
were
significant
except
sire
variance
All main effects
sources of variation in yearling
within year.
The least-squares
is shown in Table 10 and the
weight
analysis
least-squares
of
means
for main effects are shown in Table 11.
Year
was a significant source of variation in yearling
weight and means for
1978
yearling
to 381 kg in 1980.
weight ranged from 316 kg in
This 65 kg variation due to
year
agrees with Anderson (1966).
Sex
of
calf was a significant
source
of
v a ri at ion
in
29
yearling
weight and mean yearling weight for males was
kg and mean yearling weight for females was 298 kg.
kg
a
The 100
difference due to sex is larger than the range given
Woldhawariat et al .
combination
managed
( 1 977).
by
Sex effect in this analysis is
of sex and environment.
separately
398
The two sexes
and males are fed to gain at
a
are
higher
rate.
Table 10. Least-squares
w el ght.
analysis of
variance for
yearling
Mean square (kg2 )
Sour ce
df
Year
Sex
Age of dam
Sire/year
Year x sex
Year x age of dam
Sex x age of dam
7
I
3
27
7
21
3
15620%;
1047412
26626 00
2020
3716°°
726
1650
I
I
I
I
I
96437;;
6 120
87 5
2016
6196**
Regressions:
Age at yearling weight
Inbreeding of calf
Sex x inbreeding of calf
Inbreeding of dam
Sex x inbreeding of dam
841
4 93
Remainder
.82
R2
oo
PC.01
Age
of
dam was a significant source of
yearling weight and means were 332,
2-yr-old,
3-yr-old,
4-yr-old
variation
in
347, 357 and 359 kg for
and 5-10-yr-old
dams.
The
30
weaning weight differences due to age of dam were maintained
through yearling weight.
The t w o - w a y interaction year x sex was a significant
source of v ariation in yearling weight.
Male
means were
mo r e
Males
apparently
varied
than
means
for
females.
respond differently to e n v i r o n m e n t a l
differences of year
than females.
Table 11. Least-squares means for
yearling weight (kg).
effects
affecting
SE
Mean
n
568
347 .7
1+
•.
Item
main
62
. 67
56
. 65
68
75
83
92
335 .5
344 .4
316.2
345.8
381 .1
355.1
345.5
357.9
±4.9
±4 .0
±4.3
±4.2
±4.1
±3.9
±4 •I
±3.5
Sex
Male
Female
284
284
397.7
2 97 .7
±2.0
±2.0
Age of dam
2
3
4
5-10
I24
124
82
238
324.0
345 .7
358.7
362.3
±3.2
±2.9
±3.5
±2.2
U
Year
1976
I 977
I 978
I 979
I 980
19 81
I 982
19 83
Age
variation
value
at
in
yearling
weight was a significant
yearling weight and
was 1.2 kg/day.
the
partial
source
of
regression
Each I day increase in age resulted
BI
in
a 1.2 kg increase in yearling
calf
was
weight. '
Fx,
a
significant
weight.
Inbreeding
source of variation
in
yearling
The partial regression value is small, -.001
and lacks biological significance.
individual
would decrease only .I
of
kg/%
A completely inbred
kg in
yearling
weight.
Regression values are shown in Table 12.
Table 12. Partial
regression values of yearling weight on
inbreeding
of
calf, sex x inbreeding
of
calf,
inbreeding of da m , sex x inbreeding of dam and age
yearling weight.
Regression
b
Inbreeding o f .calf00
(kg/%
(kg/%
— .001
Fx)
Inbreeding of dam (kg/56 F d )
Sex x inbreeding of dam00
Male
Female
(kg/%
two-way
also significant.
kg/%
Fd
and
-.002
kg/%
significance.
Selection
Line
±.0003
— .002
.0004
±.0006
±.0004
I .2
±.1
dam
was
The partial regression values were - .0008
Again
Havre
-.0003
interaction sex x inbreeding of
respectively.
the
±.0007
±.0006
Fd)
Age at weaning weight00 (kg/d)
The
±.0005
co
O 1—
O O
O O
I I
Sex x inbreeding of calf
Male
Female
Fx)
SG
these
Fd
for
males
small values
and
lack
females,
biological
for increased yearling weight
4 may be masking the
possible
effect
in
of
32
inbreeding
on. yearling weight.
Previous studies
of
the
effect of inbreeding on yearling weight have generally found
a detrimental effect (Brinks and Knapp,
1975).
Summary
The
on
effect of inbreeding of calf and inbreeding of dam
bir-th weight,
weaning, weight and yearling
estimated in the Havre Line 4 Herefords.
and
calf
weight.
a
-.84
kg/% Fx decrease
were
Inbreeding of calf
dam had little effect on birth weight.
caused
weight
in
Inbreeding
female
of
weaning
Inbreeding of dam caused a -.64 kg/% Fd decrease in
male weaning weight.
Inbreeding of calf and dam had little
effect on yearling weight.
33
PART II
THE
EFFECT
OF
SELECTION
FOR
AN
INDEX
ON
BIRTH
WEANING WEIGHT AND YEARLING WEIGHT
WEIGHT,
34
LITERATURE REVIEW
This
section
of
literature
review
focuses
response to selection for the growth traits,
and year l i n g weight,
on
the
weaning weight
and the correlated response in birth
weight in beef cattle.
Response to Selection for Growth
Flower
three
et
closed
sequential
al.
lines
(1964)
of
selection
studied
selection
H e r e f ords.
for
Sire
increased
response
selection
weaning
in
was
weight
by
and
p o s t w e a n i n g w e i g h t gain f o l l o w e d by progeny testing in a
common
tester
line.
Genetic
subtracting e n v ironmental
trends
genetic
increases
estimated
by
trends (calculated from repeat
matings) from phenotypic trends.
the
were
were
.33
After 6 yr of selection
and
1.91
kg/yr
for
birth
weight and weaning weight, respectively.
Brinks
et
al.
(1965)
studied
selection for increased weights,
the
effectiveness
gains and
of
confo r m a t i o n
score in the Miles City Line I.
Repeat matings wer e used to
estimate environmental
Sires used in the line were
selected
on
performance
trends.
weaning
weight
and
conformation
during a postweaning gain test and
progeny test.
score,
(usually)
a
After 25 yr of selection genetic trend for
birth weight was .19 kg/yr and genetic trend for w e a n i n g
weig h t
was
.56
kg/yr.
Due
to
small
numbers
of
repeat
35
matings
for
estimated
p o s t w e a n i n g traits,
for
them.
It
was
genetic trends
concluded
that
were not
substantial
genetic progress was obtained for growth traits.
Newman et al.
for
greater
lines
of
deviations
(1973) studied
the response to selection
unadjusted yearling weight
Shorthorns.
from
Genetic
unselected
trends
control
in two replicate
were
measured
line means.
as
Ten yr of
selection resulted in genetic responses of 4.8 and 4.1 kg/yr
in male yearling weight in the two lines.
Genetic response
in female year l i n g weight in the two lines was 3.3 and 2.3
kg/yr,
respectively.
It was concluded that selection was
highly effective in changing yearling weight.
Koch et al.
(1974) studied selection response in three
lines of Herefords selected for increased w e a n i n g weight,
yearling weight and an index of yearling weight and muscling
score.
Genetic trends were measured
on selection in parents.
were
.18,
1.05 and
After 8 of selection genetic trends
2.5 8 kg/yr
wei g h t
and year l i n g weight,
weight
line.
were .23,
.77
The
and
responses
3.09
index line
was
for
birth
in
for
birth
.68
and
weaning
in the w e a n i n g
the yearling
respectively.
.23,
weight,
respectively
kg/yr
weight and yearling weight,
in the
by offspring regression
weight
weight,
line
weaning
Genetic response
2.37 kg/yr
for
birth
weight, weaning weight and yearling weight, respectively. It
was
concluded
that
genetic
traits are fairly large.
correlations
between
Applying negative
growth
selection on
36
birth weight to decrease death loss associated with large
birth weight was suggested.
Chevraux
and
Bailey
(1977)
studied
the
response
to
selection for increased postweaning gain in a closed line of
Herefords.
Genetic changes were estimated by regression on
dam birth year.
After 19 yr of selection genetic change was
2.6 kg/yr for w e a n i n g weig h t and 4.5 kg/yr for p o s t w e a n i n g
gain.
Frahm et al. ( 1 985) studied selection response in two
lines of Heref or ds.
Single trait selection was applied for
increased weaning weight and yearling weight.
Angus line was maintained as a control.
measured
as
crossbred
deviations
progeny
from
test
the
using
An unselected
Genetic trends were
control
frozen
line
semen
and
by
from
a
tw o
foundation sires and two selected sires born in the sixth yr
of selection.
sires were
sires.
Due to small n u m b e r s of progeny, selected
considered a group and compared to foundation
Selected sire progeny minus foundation
sire progeny
differences were .28, 2.2 and 4.01 kg/yr for birth weight,
w e a n i n g weight and yearling weight, respectively.
weaning
weig h t
line
deviations from
the
genetic
trends
were
control line and were
In the
e stimated
.3,
1.0 and
as
.6
kg/yr for birth weight , weaning weight and yearling weight,
respectively.
In the yearling weight line genetic trends
were .2, .9 and 1.0 kg/yr for birth weight,
and yearling weight, respectively.
wean i n g wei g h t
It was concluded that
37
substantial
result
and
increase
for
growth
rate
had
occurred
as
a
of selection for weaning weight and yearling weight
some
attention
should
be
given
to
minimizing
the
correlated response of increased birth weight.
Irgang et al.
(1985)
studied
the response
to single
trait selection for increased weaning weight and postweaning
gain in two lines of Herefords.
was
used
as
a
control.
A nonselected Hereford line
Estimated
genetic
responses
in
weaning weight were 1.1 and .6 kg/yr
for bulls and heifers,
respectively
line
kg/yr
in
in
the w e a n i n g
the
weig h t
postweaning
gain
and
line.
1.4 and
1.2
Responses
in
p o s t w e a n i n g gain was .0 and .2 kg/yr for bulls and heifers,
respectively,
in the weaning weight line.
and .3 kg/yr for
bulls and heifers,
Responses were .9
respectively,
in the
postweaning gain line.
Anderson
et al. (1985) s t u d i e d the r e s p o n s e to
,
\
selection for the index, I = Yearling W e i g h t - 3.2 Birth
.
Weight
in the Havre Line 4.
from repeat matings.
were
-.4,
3.2
and
Genetic trends were estimated
Increases
1.6
kg/yr
due
for
to the
birth
weight, and yearling weight, respectively.
that
through
improvement
can
be
the
use
of
the
whi l e
the
weight,
correlated
weaning
It was concluded
selection
in weaning weaning weight
realized
selection index
index,
some
and yearling weight
increase
in
birth
weight can be retarded.
Aaron
et al.
(1986)
s t u d i e d the r e s p o n s e
to s e l e c t i o n
38
for w e a n i n g weight,
yearling w e i g h t and a c o m b i n a t i o n of
weaning weight and progeny weaning weight in three lines of
Angus cattle.
An unselected Angus line was maintained as a
control. In the weaning weight line after 16 yr of selection
e s t i m a t e d responses
were .2,
1.0 and
1.8 kg/yr for
birth
weight, w e a n i n g weight and year l i n g weight, respectively.
In the yearling weight line estimated responses were .4, 1.3
and 3.0 kg/yr for birth weight,
weaning weight and yearling
weight,
15
respectively.
After
yr
of
selection
in the
combi n a t i o n line e s t i m a t e d responses were .3, I .7 and 2.2
kg/yr for birth weight,
respectively.
It was
weaning weight and yearling weight,
concluded
that
selection for yearling
weight was most effective in increasing both.weaning weight
and yearling weight and some attention should be given to
minimizing the correlated increase in birth weight.
Summary
Selection for increased w e a n i n g wei g h t and yearling
weight is effective in beef cattle.
growth
Selection for these two
traits results in genetic improvement.
increases
as
a
correlated
increased growth.
response
Selection for
the
genetic
correlation
selection
for
increased yearling weight
while limiting increase in birth weight
since
to
Birth weight
between
should
birth
be possible
weight
and
yearling weight is about. .6 (W ol d eh aw ari a t et al., I 977).
The study of Anderson et al., ( 1 9 85) used Havre Line 4 data
39
and concluded that the selection index,
- 3.2 Birth Weight,
I = Yearling Weight
increased yearling weight while limiting
the increase in birth weight.
Table 13. Responses and correlated responses to selection
for growth.
Selection criteria
Response (kg/yr)
T ------ T
WW and PWG
Flower et a l . (1964)
Brinks et al. ( 1965)
WWf, CS and PWG
YW
Newman (1973)
YW
Newman (1973)
YW
Koch et al. ( 1974)
WW
Koch et al. ( 1974)
YW and MS
Koch et al. (I 97 4)
PWG
Chevraux and Bailey (1977)
YW -3.2 BW
Anderson et aI (1985)
WW
Frahm et al . (198.5)
YW
Frahm et a l . (1985)
YW and WW
Frahm et al . (1985)
WW
Aaron et a l . (1986)
YW
Aaron et al . (1986)
WW and PWW
Aaron et al. (1986)
BW
.3
.2
.2
.2
.2
-.4
.3
.2
.3
.2
.4
.3
WW
I .9
.6
.8
I .0
.7
2.6
3.2
1.0
.9
2.2
I .0
1.3
I .7
YW
PWG
3.9
3.2
3.1
2.6
2.4
4.5
I .6
.6
1.0
4.0
.8
3.0
2.2
BW = birth weight, WW = w e a n i n g weight, YW = yearling
weight, PWG = p o s t w e a n i n g gain, CS = condition score, MS =
muscling score and PWW = progeny weaning weight
/
40
MATERIALS AND METHODS
The
during
data
1984
for
and
Norris,
Montana
Center,
Bozeman,
the Department
this
1985
and
part
at
the
the
the
Red
study
Bluff
were
collected
Research
Ranch,
Montana State University Livestock
Montana.
of Animal
of
Both facilities
are operated
and Range Sciences,
by
Montana State
University.
Site Descriptions
The Red Bluff Research Ranch is located near Norris,
Montana
5 6 km
west
of Bozeman,
slope of the Madison range.
to 1,900
mm,
Montana on the northwest
The elevation ranges from I ,400
m arid the annual precipitation averages 350 to 406
USDA-SCS
(I 97 6).
A^jzssxilSjQ -SJBi-LiLii and
idahoensis (Blue bunch Wheatgrass and Idaho Fescue)
account
for 7 0% of the principle plant c o m m u n i t y (Turner,
1 9 85).
The
Montana
State
University
Livestock
Center
is
located on the southwest edge of B o z e m a n in the Gallatin
V alley.
The
elevation
is
about
1370
precipitation averages 406 to 457 mm,
m
and
the
annual
USDA-SCS (I 97 6).
The
subirrigated improved pastures include Zfla pratensis. Bromus
iflflZSifl,
LoZfls
corniculatus
(Kentucky Bluegr ass,
and
Onobrvcbis
viaiafoiia
Smooth B r o m e, Birdsfoot trefoil and
Sainfoin) as the major forage species.
41
Sires
The si res used in this study were Havre Line 4 Horned
Herefor ds from
near Havre,
Miles
the Northern Agricultural
Montana.
City Line
I.
Research
Center
The Havre Line 4 is a subline of the
The Line 4 has
been
closed
at Havre
since 1976. Two herd sires per year were selected within the
line based on the selection index,
Birth Weight
(Dickerson et al.,
I = Yearling Weight - 3»2
1 974).
Yearling weight and
birth weight are adjusted for age of dam and yearling weight
is corrected to 365 d of age. Use of the index was initiated
for sires born in 1 975.
Eight
sires were used through frozen semen to measure
genetic progress r esulting from the selection index.
eight
sires were considered two groups.
The
The first group
consisted of the four sires selected in 1975 and 1976 and
the
second
1980 and
group consisted of the four sires selected in
1981.
Calving occurred in March
Agricultural
within
24
h
Research
of
birth,
po stw eaning gain test.
gain
test
after
Center.
at
All
weaning
at the Northern
calves
and
wer e
at
the
weighed
end
of
Male calves were placed on a I6 8 - d
weaning.
approximately 1.1 kg/d
and April
Male
calves were
(Anderson et al., 19 85).
fed to gain
42
Teat Dams
The Montana State University cow herd wa s m anaged by
the
Red
Bluff
University
Research
Livestock
Ranch
Center.
and
the
Three- year- old
Montana
State
and older
dams
were maintained at Red Bluff and replacement heifers and 2yr-old dams were maintained at Bozeman.
Female replacement
calves were trucked to Bozeman after weaning.
At
the
Montana
State
University
Livestock
Center
replacement females were wintered on mixed grass-alfalfa hay
ad
libitum
and .9 kg of
ground
barley
per
head per
day.
R e p l a c e m e n t f e m a l e s weighed a p p r o x i m a t e l y 330 kg at the
beginning of the breeding season,
ended June
30.
Bred
yearling
which began May 20 and
heifers
were
summered
on
improved pastures.
The pregnant replacement females were wintered on mixed
grass-alfalfa hay provided ad libitum.
to calving,
Beginning 60 d prior
.9 kg of ground barley per head per day was fed.
Second cutting alfalfa ad libitum and
.3
per head we r e fed for 45 d post calving.
kg of ground barley
Calves were weaned
in mid-November.
After weaning their first calves the 2-yr-old-dams were
moved to Red Bluff.
on
range
and
At Red Bluff
supplemented
restricted grazing.
the cow herd was wintered
grass
hay
when
snow
cover
Beginning 45 d prior to calving .9 kg
of barley pellets per head per day were fed.
Alfalfa hay ad
libitum and 1.8 kg of barley pellets per head wer e fed for
43
45 d post
calving.
The
breeding
season
began June
I and
ended July 15.
The
cow
herd
consisted
of
Angus,
Hereford and Tarantaise X cows.
sires were used.
Hereford,
Angus
X
In I 979 and 19 80 Tarantaise
In other years Angus and/or Hereford sires
were used to produce the test dams used in this study.
Yearling replacement
heifers at Bozeman were randomly
assigned to the eight Havre Line 4 sires with i n breed type
( A n g u s , Angus
X Hereford,
Hereford,
T a r a n t a i se
X and
Simmental X (a Simmental sire was used at Bozeman from 19 82
to
I 9 84 ).
The
older
cows
at Red B l u f f
were
randomly
assigned to the eight Havre Line 4 sires within age of cow.
Data
The data
Red Bluff
weight,
collected on the 169
and B o z e m a n
included
calving difficulty
progeny calves born at
sire,
score,
day
age
of
of
dam,
birth
W e a n i n g weight was taken on I 59 progeny calves.
weight
was
calculated
All
birth
and sex.
Yearling
taken on 149 progeny.
Gestation length was
from
day
calves
breeding
date
and
of
birth.
born at B o z e m a n were from 2-yr-old dams.
Age of dam at Red Bluff was pooled into 3, 4, 5-10 and 11
and older age groups.
Birth weights were taken within 24 h of birth.
difficulty was scored from I to 5 where
I = No difficulty,
no assistance
Calving
2 = Minor difficulty,
some assistance
3 = Major assistance, mechanical assistance
4 = Caesarean
5 = Abnormal presentation.
Calving difficulty
scores of 5 were
analysis of calving difficulty.
not been
not
included
in the
Abnormal presentations have
shown to have a genetic relationship with
calving
difficulty (BIF, 1981).
Weaning weights for the 1 984 progeny calves were taken
November
I and
respectively.
November
2 at
Bozeman
and
Red
Bluff,
In 1 985 weaning weights were taken October 17
at Bozeman and October 18 at Red Bluff.
Weaning age of the 20 progeny calves weaned at Bozeman
averaged 241 d in 1984.
The 21 progeny calves weaned at Red
Bluff averaged 231 d of age at weaning in 1 984.
in 1985
averaged
212 d for 66
progeny
Weaning age
calves at B o z e m a n
while 52 progeny calves at Red Bluff averaged 21 5 d of age
at weaning.
Age
at
yearling
averaged 375 d.
April
weight
of
the
progeny
steers
Yearling weight of stocker steers was taken
I in I 985 and March 8 in 1 9 86.
feedlot
85
steers w as
taken April
Yearling weight of
I in 1985
and
April
5 in
I 986 .
Age
at
yearl i n g
weight
averaged
3 83
d
for
the
12
progeny fema l e s in 1 985 and 389 d for the 52 progeny f e m a l e s
in 1 986.
Yearling w e i g h t s were taken April I in I 9 85 and
45
April 5 in 1986.
In both 1 984 and 1 985 the steer progeny were split into
two
groups
postweaning.
The
43
steer
progeny
produced
during the 2 years by 2-yr-old dams at Bozeman were wintered
on 8.2 kg of grass hay per head per day and gained .5 kg per
day.
The 42 steer progeny produced during the 2 yr by older
dams at Red Bluff were finished in a feedlot.
After a 2 I d
adjus t m e n t period they were placed on full feed for I 80 d
before slaughter.
The ad libitum ration was 85% concentrate
consisting of 20% beet pulp and 80% barley.
up 15% of the
diet
and
consisted
Roughage made
of grass hay.
Average
daily gain was 1.5 kg.
Postweaning in 1984 the 12 female progeny
were placed
on a barley and grass hay ration and fed to gain .6 kg per
head per day.
a nutrition
In 1 985 the 52 female progeny were placed in
study for 60 d.
Three
rations
daily gains were small (.007 to .01 kg/d).
wer e
fed and
F o l l o w i n g the
study the heifers were placed on growing rations of hay and
corn or hay and distillers dried grains.
Daily gains were
1.3 kg per head per day.
Progeny
One hundred sixty nine progeny were born (44 in 1984
and
125
evaluate
from
in
1 985)
and
the
progeny
the sire selection index.
data were
analyzed
to
Calving dates ranged
February 20 to March 11. The progeny were raised on
46'
pasture
without
creepfeed.
The
progeny
Bluff were included in growth implant
and 1985.
produced
at Red
studies in both 1984
Preliminary analyses were performed to determine
if a d j u s t m e n t s were needed to correct w e a n i n g weight to a
non implant
basis.
Preliminary Analysis of Weaning Weight of Calves Produced at
Red Bluff
The 115 calves produced at Red Bluff in 1 984 included
22 progeny
were
test
randomly
treatments;
calves.
The 1984
assigned
negative
to. one
control,
calves from
of
four
Red Bluff
growth
implant
1/4 dose " S t eer-oid"^, 1/2
dose "Steeer-oid" and full dose "Steer-oid".
Weaning weight
of all 115 calves was analyzed by fixed model least-squares
procedures (Harvey,
implant
treatment.
1 977) to estimate the effect of
Implant
variation in weaning weight.
tested
by
linear
was a significant
Implant
orthogonal
"Steer-oid" treatment differed
three
treatments
weaning
weight.
r eceiving
implant
the full
basis
by
and
of
The
full
dose
significantly from the other
in
weights
dose implant
subtracting
source
treatment means were
contrasts.
resulted
Weaning
growth
a 9•1
of
were
9.1
kg.
kg
the
increase
five
corrected
The
in
progeny
to a non
analysis
of
variance for 19 84 weaning weight and least-square means for
implant treatment are presented in Tables 14 and 15.
1 Anchor, 20 mg estradiol benzoate and 200 mg progesterone
47
Table
14.
Least-squares
analysis of
weaning weight at Red Bluff.
variance
for
Mean Square (kg2)
Sour ce
df
Sex
Age of dama
Implant level
I
6
3
538
Regressions:
Birth weight
Age at weaning
Weight at implant
I
I
I
?6 !°°
16548
70
101
Remainder
I 9 84
117
.85
R2
55
P<.01
a age of dam groups were 3,4,5,6,7,12 and 13
Table 15. Least-squares
means and
standard
errors
implant treatment at Red Bluff in 1984.
Treatment
Negative
control
1/4 dose
1/2 dose
Full dose
a »b means
level
The
one
of
oidn,
calves,
Total
no.
No. progeny
test calves
29
28
29
29
5
7
5
5
with
differing
Weaning weight (kg)
±. standard error
231 .5
230.5
230.2
239.8
superscripts
differ
±
±
±
±
at
2.1 a
2.3*
2.3*
2 . Ib
the .01
1 985 Red Bluff calf crop was randomly assigned
three growth implant treatments;
1/2
dose
nSteer-Oidn and
for
1/4 dose
nRalgron2.
52 were progeny test calves.
Of
to
nSteerthe
124
Weaning weight of all
2 International Minerals & Chemical Corporation,
zeranol
48
I 24
calves
was
analyzed
by
fixed
model
least-squares
procedures (Harvey, 1977) to esti m a t e the effect of growth
implant treatment.
Implant treatment was not a significant
source of variation in weaning weight.
Analysis of variance
of 1 985 weaning weight and least-squares means are presented
in Tables 16 and 17.
Table
16.
Least-squares
analysis of
weaning weight at Red Bluff.
Source
variance
I
1 924°°
3*°%
5
2
Regressions :
Birthweight
Age at weaning
Weight at implant
Remainder
1985
Mean squares (kg2 )
df
Sex
Age of dama
Implant level
Fistula
for
I
'13OO
2822
I
I
I
641OO
5979OO
30324
241
III
.76
R2
a age of dam groups were 3*4,5.,6,7 and 8
In 1 9 85 , 1 6 dams of Red Bluff
calves rece i v e d r u m e n
fistulae as part of a nutrition study.
produced progeny test calves.
produced offspring from
was
included
as
an
Ten fistulated dams
Seven of the eight test sires
these dams.
independent
Fistulation treatment
variable
in
the
wean i n g
weight analysis to estimate the effect of dam fistulation on
49
calf weaning weights.
Fistulation was a significant source
of variation in weaning weight.
Fistulation treatment means
were tested by linear orthogonal contrasts.
fistulated dams weaned 15.1 kg
intact
Offspring of
heavier than offspring of
dams.
Table 17. Least-squares
mea n s and
standard errors
fistulation treatment at Red Bluff in 1985.
for
Weaning weight
(kg)
Total
no.
Treatment
16
108
Fistulated dams
Intact dams
a,k
No. progeny
test calves
10
42
means
level
with differing superscripts differ at
In
further
progeny
a
analysis of all
a
weights
progeny
the
calves
corrected for implant) weaning weight was
by mixed model least-squares (SAS,
as
252.5 ± 4 .2a
237.4 ± I .6b
main effect was not
were
1982).
significant.
.001
(1984
analyzed
Fistulated dams
Therefore,
not corrected for effect of dam
weaning
fistulation.
This analysis of variance is presented in Table 18.
50
Table 18. Least-squares analysis of variance
for weaning
weight of progeny calves at Red Bluff in 19 84 and
I 985 .
Mean squares (kg2 )
df
Source
Group
Sire/group
Sex
Year
Age of dama
Fistula
Calving dificulty
"
Regressions:
Gestation length
Birth weight
Day of birth
Remainder
I
6
I
I
4
I
3
1492
494
2427
16O
1249
67
862
I
I
I
7614.
'I M S o o
376 I00
416
133
.49
„2
* P<.05
PC.01
a age of dam groups were 2,3,4,5-10 and 11
Preliminary Analysis
of
Weaning
Height of Proaenv
Calves
Produced at Bozeman
The
1 985
Bozeman
steer
nRalgro".
if
progeny were not implanted in
progeny at Bozeman were
implanted
1984.
twice
In
with
A preliminary analysis was performed to determine
adjustments were needed to correct 1 985 Bozeman
weaning
weights to a non implant basis.
Weaning
weight
of Bozeman calves for both years
progeny were produced in 1984 and 66 were produced in
(20
1985)
was analyzed by mixed model I east-square procedures (Harvey,
1977).
The two-way interaction of sex by year was fitted to
51
estimate, effect of I 985 implants on weaning weight.
by
year
was
not
Therefore
the
difference
variation.
heifer
1 985 .
significant
interaction
a
source
between
adjusted.
progeny
weaning
weights for
of
steer
and
1984
and
were
not
calves was not significantly different in
Steer
The sex
1985
Analysis of variance is presented in Table 19.
Table 19• Least-squares analysis
weight at Bozeman.
of
variance for
Mean square (kg2 )
df
Source
weaning
Year
Sex
Group
Sire/group
Sex x Year
I
I
I
6
I
1105
407
180,
870
54a
Regressions:
Birthweight
Age at weaning
I
I
4202.0
• 2304
377
71
Remaihder
.35
„2
a
oo P < .05
PC.01
a P= .71
Statisloal Analysis
The progeny calf data were pooled and analyzed by mixed
model I east-squares procedures,
(Harvey,
1 97 7) •
The basic
model was as follows:
Yijklm = u + G1 + Sj(i) -6- Sxk + Yr1 + ADffl + eIjklm
where
52
1Ijklm = an observation
u = the overall mean
G i = the fixed effect of the ith sire group
S j(i)
=
the random effect of the j th sire within
the
ith
sire group
Sxk =
the fixed effect of
the kth sex
Yri =
the fixed effect of
the Ith year
ADffi =
the fixed effect of
the mth age of
dam
eIjklm = randoin error.
Group
of
sire
was
tested for
significance
by
the
sire/group mean square term.
All other effects were tested
against
the
The basic model was
analyze
gestation length.
analyzed
were
weight,
day
Calving
birth weight,
of
calving
used
dependent
difficulty,
weaning
Birth weight was analyzed by
birth as a covariate to
Weaning
length
weight
covariate
to
analyzed
to
the
basic
the
basis
model
as
a
was analyzed by adding day of
the basic model.
model.
weight
born in 1985
was
analyzed
within
and
covariates.
birth
Steer yearling weight
with age at yearling weight added as a
yearling
to
variables
difficulty was analyzed by adding birth weight
gestation
females
The other
and yearling weight.
adding
Female
error term.
as
a
was
covariate.
year.
For
the two nutrition regimes were
added
of sire (group I = sires born in 1975 and
1976,
as main effects.
Group
group
2 = sires born in 1980 and 1981) was the
independent
53
variable
of primary interest in these analyses.
variables
were
variation
and
group
fitted
to account
for
known
to allow better estimates of the
of sire.
The other
sources
of
effect
of
Because of the small number of records all
two-way interactions were assumed to be nonsignificant.
Age
of dam and location were completely confounded in these data
since all 2-yr-old dams were located at Bozeman.
of age of dam,and location can not be estimated
Therefore,
separately.
location was omitted from the model.
Heritability
sib
The effect
procedure,
(h2 ) was estimated by the paternal
(Falconer,
1981).
half-
Heritability
calculated as four times the sire variance component
sibs
by
have one-fourth their sires' genes in common)
the
sire
variance
component
plus
the
was
(half-
divided
environmental
variance component
V
Postweaning
between
management
years and sexes.
+ °e
varied
Therefore,
estimated for yearling weight
greatly
within
heritability was
and
not
54
RESULTS AND DISCUSSION
Gestation Length
The mean gestation length was 281 d.
The I east- squares
analysis of variance is presented in Table 20 and leastsquares means are presented in table 21.
Table 20. Least-squares
length.
analysis of variance for gestation
Mean square (d2 )
df
Sour ce
50 a
150
I
6
I
I
4
Group
Sire/group
Sex of calf
Year
Age of dam
Remainder
112.
II
15
155
.16
R2
a P=. I 2
Sex
variation
of
calf
and year
were
significant
affecting gestation length.
sources
of
Male calf gestation
length was I .3 d greater than female calf gestation
length.
This
(1971).
agrees
with
the study of
Bellows
et
al.,
Gestation length in 1 984 was 1.9 d greater than in 1 985.
55
Table 21. Least-squares means and standard errors for main
effects affecting ge station length.
Mean ±. SE (d)
Effect
n
Sex of calf
Mal e
Female
94
75
282.2 ± .8
280.9 ± .8
44
125
282.5 + .8
280.6 ± .8
88
81
281 .0 ± .8
2 82.2 ±. .8
Year
1984
1985
Group
I
2
Group of sire was not an important
in
gestation
(sires
born
length.
The I east-squares mean for group
in 1981 and 1982) was 1.2 d greater
least-squares
I 976).
source of variation
mean for group
I
(sires born
This suggests a positive genetic
length.
Dickerson et
selection
index,
al.
(1974)
in
2
than
the
1975
and
trend for gestation
predicted
I = Yearling Weight - 3•2 Birth
that the
Weight,
would result in a shorter gestation period.
Birth Weight
The
analysis
mean
of
birth
weight was 37.1
variance
kg.
Least- squares
is presented in Table 22
and least-
squares means are presented in Table 23.
Sex
variation
greater
and
in
than
age
of
dam
birth weight.
female
were
significant
Male birth weight
birth weight.
This
sources
was
agrees
2
of
kg
with
56
Woldehawariat
et
al .
(1977).
confounded with location.
old
Age
of
dam
means
were
The least-squares means for 2-yr-
dams at Bozeman cannot be compared with means for other
age groups at Red Bluff. The age of dam effect for Red Bluff
dams is in agreement with the study of Kress et al.
Table 22. Least-squares
weight.
Source
analysis
of
df
variance
I
6
I
I
4
Ia
186
2271
42 V
554
Regression:
Day of birth
I
29
154
129
R2
for
birth
Mean square (kg2 )
Group
Sire/group
Sex of calf
Year
Age of dam
Remainder
(1979).
.57
Group of sire was not an important source of
in birth weight.
progeny
variation
The group I (sires born in 1975 and 1976)
were .5 kg heavier than group 2 (sires born in 1980
and
1981) progeny.
This suggests a negative genetic
for
birth weight.
Anderson et al.,
genetic
trend
(1985) estimated
the
trend for birth weight in the Havre Line 4 by
the
repeat mating method and found it to be negative.
57
Table 23. Least-squares
means and standard
main effects affecting birth weight.
Effect
n .
errors
for
Mean ±. SE (kg)
Sex of calf
Mal e
Female
94
75
37.6 ±
35.6 ±.
Age of dam
2
3
4
5-10
II
94
2
11
58
4
36 .3
35.4
38.3
38.5
34.3
Group
I
2
88
81
36.9 ±.
36.4 ±
.7
.8
±
.5
± 2.4
± I .1
±. .5
±. 1.8
.7
.7
Calving Difficulty
Mean
difficulty
calving
difficulty
score
was
scores of 5 were not included in
1.2*
Calving
the
analysis.
The least-squares analysis of variance is presented in Table
24 and least-squares means are presented in Table 25.
Male
progeny
calving
difficulty score was
.2
units
greater than female progeny calving difficulty score.
This
agrees with the study of Bellows et al ., (1971).
dam means are confounded with location.
The age Of
The 2-yr-old
dams
at Bozeman did experience more calving difficulty than older
dams at Red Bluff.
This agrees with Laster et al ., (1973).
58
Table 24. Least-squares
difficulty.
analysis
Source
df
of
variance for
Meansquare (scored)
Group
Sire/group
Sex of calf
Year
Age of dam
I
6
1
I
4
I .47
•0 I
10.64
Regressions
Gestation length
Birth weight
I
I
.14
4.11
.0 8a
VO
CO
Remainder
calving
148
R=
.48
a P= .62
o
PC.05
OO
PC .01
Table 25. Least-squares
means and standard errors for main
effects affecting calving difficulty score.
SI3 (score)
Sex of calf
Mal e
Female
93
71
1.3
I .1
Age of dam
2
3
4
5-10
II
92
2
10
56
4
Group
I
2
85
79
±
±
±
.1
.1
O
n
CM
Mean
Effect
± .1
1 .1 ± .4
.8 ± .2
.9 ±. .1
I .1 ± .3
1.18
I .22
±
±.
.2
.2
59
Birth
weight
was an important source of variation
calving difficulty score.
units
per kg was .05.
caused
a
The partial
regression value in
Each I kg increase on birth
.05 unit increase in
calving
in
weight
difficulty
score.
Tjhis is in agreement with Bellows et al. (1971).
Group of sire was not a significant source of variation
in calving difficulty score.
Group 2 sires progeny calving
difficulty score was .04 units greater than group I
calving
difficulty score.
progeny
This is hot consistent with the
trend for heavier birth weight in group 2 progeny.
Weaning Weight
The mean weaning weight was 250 kg.
analysis
of
variance
is
presented
The least-squares
in
Table
26
and
least-squares means are presented in Table 27.
Sex
of calf and age of dam were significant sources of
variation
in
weaning weight.
heavier than female progeny.
Male progeny were
(1977).
251 .1,
27 3.9 , 255.2 and 241.5 kg for 2-yr-old,
location
Age of dam least squares means were 230.6.
5-10-yr-old
respectively.
the
Because
and
of
I I-yr-old
at weaning.
and
3-yr-old, 4older
confounding of age of
mean for 2-yr-olds cannot
means for older dams.
heaviest
kg
This agrees with Woldehawariat
et al .
yr-old,
13.4
be
dams,
dam
compared
and
with
The progeny of 4-yr-old dams were the
Most studies (Woldehawariat et
al.,
(1977) have found that 5 to 10-yr-old dams wean the heaviest
60
calves.
sampling
The different result in this study may be caused by
error
because
only
10
4-yr-old
dams
produced
progeny.
Table 26.. Least-squares
weight.
analysis of
Source
variance
df
for
weaning
Mean square (kg2 )
Group
Sire/group
Sex of calf
Year
Age of dam
I
6
I
I
4
1259a
*66
6524
120
6 4 85
Regression:
Day of birth
I
2499°°
144
Remainder
499
.35
R2
« p = -I 5
O
T W
r\
I-
Day
weaning
-.43
of birth was a significant source of variation
weight.
kg per d.
The partial
regression
Each I d increase
coefficient
in day of birth
a .43 kg decrease in weaning weight.
in
was
caused
This agrees with
the
study of Anderson ( 1966) .
Group of sire was not a significant source of variation
in
weaning weight.
progeny
born
Group 2 (sires born in 1980 and
were 5.7 kg heavier at weaning than group I
in 1975 and 1976) progeny.
genetic trend for weaning weight.
This suggests a
Anderson et al .,
1981)
(sires
positive
(1985)
61
found a positive trend in the Havre Line 4.
Table 27.
Least-squares
means and standard errors for main
effects affecting weaning weight.
Effect
n
Mean ±. SE (kg)
Sex of calf
Mal e
Female
89
70
2 57 .2 ±
2 43 *8 ±
Age of dam
2
3
4
5 - T0
11
86
2
I0
58
3
230.6
251 .1
273.9
255 .2
241 .5
Group
I
2
84
75
247 .6
253.3
4.7
5.1
±
2.9
16 .1
7 .7
3.2
13.4
±
±
4.8
5.0
±
±
.±
±
Yearling Weight
Mean yearling weight of steer progeny was 372 kg.
least-squares analysis
is presented in Table 28
The
and least-
squares means are presented in table 29.
Age
affecting
of
dam
yearling
was the only
main
weight of steer progeny.
location and postweaning management are
progeny
effect
significantly
Age of
confounded.
Steer
from 3-yr-old and older dams at Hed Bluff were
out to slaughter.
dam,
fed
The yearling weight of Red Bluff progeny
steers was 131.1 kg heavier than yearling weight of
progeny steers which were wintered on
grass.
Bozeman
62
Table 28. Least-squares
analysis
yearling weight.. .
Source
of
variance
for
df
MeanSquare
Group
Sire/group
Age of dam13
Year
I
6
I
I
950 a
809
294286
148
Regression:
age at yearling
weight
I
5170°
Remainder
74
steer
(kg2;)
I 278
R2
.81
® P=.39
D age of dam groups were 2 and 3-13
**P<.01
PC.05
Table 29. Least-squares
means and standard errors for main
effects affecting yearling weight.
Effect
.
n
Mean ±. SE (kg)
Age of dam
2
3-11
43
42
3 07.6 ± 6.1
438.7 ± 6.3
Group
I
2
42
43
36 9.6 ± 5.7
376 .7 ± 6.4
Age at yearling
weight
was a
variation in steer yearling weight.
value
was . .72
kg
per d.
significant
source
of
The partial regression
Each I d increase
in
age
at
yearling weight caused a .72 kg increase in yearling weight.
Group
of
sires
was
not
a
significant
source
of
63
variation
group
in
steer yearling weight.
weight
of
2 progeny was 7.1 kg heavier than yearling weight
of
group I progeny.
Yearling
This suggests that the genetic trend
yearling weight is positive.
for
This agrees with the study of
Anderson et al . (1985).
Female
progeny
yearling
weight was
analyzed
within
year.
Mean yearling weight was 338 kg in 19 85 and 311 kg in
1986.
Least-squares
is
presented
analyses of variance for the two years
in Tables 30 and 31 and
group
least-squares
means are presented in Table 32.
Table 30. Least-squares analysis of variance for
weight of female progeny born in 1984.
Sour ce
df
yearling
Mean square (kg2)
Group
Sire/group
Age of dama
I
3
2
16
140
1330
Regression:
Age at yearling
weight
I
170 8
Remainder
4
1049
R2
.49
a age of dam groups were 2 and 3-13
None
variation
of the main effects was a significant
in
yearing
weight
of
females
born
source
in
of
1984.
Yearling weight of group I female progeny was 3.5 kg heavier
than yearling weight of group 2 progeny.
64
Table 31. Least-squares analysis of variance for
weight of female progeny born in 1985.
Source
df
yearling
Mean square (kg2 )
Group
Sire/group
Age of dama
Nutrition trial I
Nutrition trial 2
I
6
3
2
I
40
75
510
306
15679°°
Regression:
Age at yearling
weight
I
33
37
I 96
Remainder
R2
.76
^ age of dam groups were 2,3,4 and 5-9
#oP<.01
Table 32. Least-squares means for female yearling weight.
Year
n
1984
Group I
Group 2
5
7
1985
Group I
Group 2
32
20
The
weight
only
of
number
±
SE (kg)
346.3 ± 29.1
342.8 ± 16.7
317.9 ± 5.6
317.1 ± 6.2
significant source of variation in
female
nutrition trial.
were
Mean
progeny
born in
1 985
was
the
Yearling weight of group I female
.8 kg heavier than group 2 female progeny.
of
differences
female progeny born in 1984 and
of
female
progeny
born
in
yearling
the
1985
second
progeny
The small
management
prevent
6 5.
meaningful sire group comparisons.
Heritabilltv
Heritabilities
for
gestation
length,
birth
weight,
calving difficulty and weaning weight are presented in Table
33.
The
heritability estimates are much lower than
those
usually reported (Woldehawariat et al ., 1977).
Table 33. Heritabilities of dependent variables.
Trait
h2 ± SE
Gestation length
Birth weight
Calving difficulty
Weaning weight
r
.01
.03
-.04
.05
±
±.
±
±
.11
•I2
.11
.15
Summary
The purpose of the selection index, I = Yearling Weight
-3.2
Birth Weight,
is to achieve an acceptable increase in
yearling weight while minimizing the correlated increase
in
birth weight.
The estimates of the genetic trends were -.2,
2.3
kg/yr for
and
yearling
2.8
weight
(steer
Anderson et al., ( 1985)
kg/yr
birthweight,
progeny
found
increased
respectively.
only),
estimates
and 1.6 kg/yr for birth weight,
yearling weight,
weaning
weight
and
respectively.
of — .4 kg/yr, 3*2
weaning
weight
and
Single trait selection for
yearling weight has resulted in genetic trends of
66
about
2.9 kg/yr with
of about .3 kg/yr.
a correlated response
in birth weight
The wei ght ed average respons es of this
study and And erson et al. ( 1 9 85) are -.4, 2.7 and 1.8 kg/yr
for
bir thweight,
we a n i n g
wei gh t
and
yea rl in g
weight,
respectively.
Therefore,
the selection index is very effective in
minimizing the trend for larger birth weight
but results in
a smaller than expected response in yearling weight.
Table 34. Summary of response and
correlated responses to
selection for yearling weight (kg/yr).
Anderson et al . (1985)
Progeny testa
Weighted average of
Anderson et al . (1985)
and progeny testb
Average from literature0
Expected response^
YW
BW
WW
-.4
- .2
3.2
2.3
I .6
2.8
- .4
.3
.3
2.7
I .0
I .8
I .8
2.9
3.6
and YW = yearling
BW = birth weight,
WW = weaning weight
weight
a group 2 - group I means / 5 x 2
b weighted by number of observations
0 unconnected mean
d h2 x selection intensity x phenotypic standard deviation,
based on Woldehawariat
et al. (1 977)
67
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I
68
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