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2004
2004
2006
J. B. Cole *, G. R. Wiggans, P. M. VanRaden, and R. H. Miller
Animal Improvement Programs Laboratory
Agricultural Research Service, USDA, Beltsville, MD
Estimation of Stillbirth (Co)variance Components
and Development of a Calving Ability Index
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Introduction
A national evaluation for stillbirth (SB) for Holstein will be implemented in August 2006.
(Co)variance components were required.
A calving ability index (CA$) which includes SB and calving ease (CE) was developed.
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Stillbirth
Reported on a three-point scale:
Scores of 2 and 3 are combined.
1 = calf born alive,
2 = calf born dead,
3 = calf died within 48 h of parturition.
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Data 7 million SB records were
available for Holstein cows calving since 1980.
Calvings with unknown MGS were eliminated for VCE.
Records with sire and MGS among the 2,600 most-frequently appearing bulls were selected.
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Data (cont’d) Herds needed ≥10 calving records with
SB scores of 2 or 3 in the database to be included.
Herd-years were required to include ≥20 records and only single births were used.
Inclusion of all records for a cow was not guaranteed.
The final dataset included 2,083,979 calving records from 5,765 herds and 33,304 herd-years.
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Sampling
Six datasets of Six datasets of ~250,000~250,000 records each records each were created by randomly sampling were created by randomly sampling herd codes without replacement.herd codes without replacement.
Datasets ranged from Datasets ranged from 239,192239,192 to to 286,794286,794 observations, and all averaged observations, and all averaged 7%7% stillbirths. stillbirths.
A common pedigree file was used to A common pedigree file was used to facilitate comparisons between sire facilitate comparisons between sire and MGS solutions.and MGS solutions.
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Modeling and Estimation
A S-MGS threshold model was used.
Fixed: year-season, parity-sex, sire and MGS birth year;
Random: herd-year, sire, MGS.
Estimation was by quasi-REML and Gibbs sampling.
CBLUP90REML and THRGIBBS1.
ijklnoprnplonlkjiijklnopr e m s BM BS PS YS hy y ijklnoprnplonlkjiijklnopr e m s BM BS PS YS hy y ijklnoprnplonlkjiijklnopr e m s BM BS PS YS hy y
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(Co)variance components estimated by Gibbs sampling
Var(Sire) Var(MGS)Cov(S-MGS)
Sample
Mean SD
Mean SD
Mean SD
10.01
0 0.0020.01
8 0.0020.00
40.00
1
20.00
7 0.0020.01
7 0.0020.00
50.00
1
30.00
9 0.0010.01
9 0.0020.00
50.00
1
40.00
8 0.0010.01
9 0.0020.00
40.00
1
50.00
8 0.0010.01
8 0.0020.00
20.00
1
60.00
9 0.0020.01
7 0.0020.00
40.00
1
Mean0.00
9 0.0020.01
8 0.0020.00
40.00
1
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Heritabilities and Correlations
Heritability (%)Correlatio
n
Method
Statistic
Direct
Maternal MGS rD,M
rD,MG
S
GS Min 2.6 5.2 6.1−0.25
0.18
Max 3.4 6.5 6.9 0.170.41
Mean 3.0 5.8 6.5−0.02
0.33
REML Min 2.4 4.6 5.4−0.28
0.20
Max 3.1 5.7 6.3 0.160.40
Mean 2.7 5.1 5.8 0.000.34
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(Co)variance Components Summary
Heritability estimates were slightly lower than literature estimates.
Direct-maternal genetic correlations were much smaller than previous reports.
Mean Gibbs sampling estimates were used in the national evaluation.
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Economic Assumptions
Newborn calf value
Expenses per difficult birth (CE ≥4)
$450 for females
$150 for males
$75 labor and veterinary
$100 reduced milk yield
$75 reduced fertility and longevity
1.5% chance of cow death ($1800)
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Genetic Correlations Among Traits in Calving Ability Index
Trait
Calving Ease Stillbirth
Sire Dau Sire Dau
Calving Ease
Sire 1.00 0.46 0.67
0.25
Dau 1.00 0.29
0.63
Stillbirth
Sire 1.00
0.28
Dau
1.00
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Properties of the Calving Ability Index
Calving Ease StillbirthPatern
alMatern
alPatern
alMatern
al
Mean 8 8 8 8
SD 1.7 1.4 1.0 1.7
Heritability, % 8.6 4.8 3.0 6.5
Economic value, $ 4 3 4 8
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National Calving Trait Indices
Cntry Pat CE Mat CE Pat SB Mat SB Model Merit %
DEU 19 26 26 29 AM 7
NLD 33 17 33 17 S-MGS 7
NOR 0 34 33 33 S-MGS 3
SWE 12 38 12 38 S-MGS 12
CHE 12 12 38 38 AM 0
USA 55 45 0 0 S-MGS 4(2003
)
USA 25 15 15 45 S-MGS 6(2006
)
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Calving Ability Index
CA$ has a genetic correlation of 0.85 with the combined SCE and DCE values in 2003 NM$ and 0.77 with DCE in TPI.
Calving traits will receive 6% of the total emphasis in the August 2006 revision of NM$.
4 8 3 8 4 8 8 8(SCE ) (DCE ) (SSB ) (DS$ BCA )
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Breeds Other Than Holstein
Brown Swiss economic values are −6 for SCE and −8 for DCE.
Separate SB evaluations are not available.
CE values include the correlated response in SB.
Other breeds will be assigned CA$ of 0.
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Conclusions
SB evaluations can provide additional value beyond that of CE.
Mating programs should assign bulls selected for high NM$ with low and high PTA for service sire effects to heifers and to cows, respectively.
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Acknowledgments
Ignacy Misztal and Shogo Tsuruta, University of Georgia
Participants in Multi-State Project S-1008
John Clay, Dairy Records Management Systems
