Estimation of Stillbirth (Co)variance Components and Development of a Calving Ability Index

200420042006
J. B. Cole *, G. R. Wiggans, P. M. VanRaden, and R. H. Miller
Animal Improvement Programs Laboratory
Agricultural Research Service, USDA, Beltsville, MD
jcole@aipl.arsusda.gov
Estimation of Stillbirth
(Co)variance Components and
Development of a Calving Ability
Index

ADSA 2006: Stillbirth (co)variance components (2) Cole et al. 20042006
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.

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.

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.

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.

Sampling
 Six datasets ofSix datasets of ~250,000~250,000 records each wererecords each were
created by randomly sampling herd codescreated by randomly sampling herd codes
without replacement.without replacement.
 Datasets ranged fromDatasets ranged from 239,192239,192 toto 286,794286,794
observations, and all averagedobservations, and all averaged 7%7% stillbirths.stillbirths.
 A common pedigree file was used to facilitateA common pedigree file was used to facilitate
comparisons between sire and MGS solutions.comparisons between sire and MGS solutions.

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 emsBMBSPSYShyy +++++++= ijklnoprnplonlkjiijklnopr emsBMBSPSYShyy +++++++= ijklnoprnplonlkjiijklnopr emsBMBSPSYShyy +++++++=

(Co)variance components estimated by
Gibbs sampling
Var(Sire) Var(MGS) Cov(S-MGS)
Sample Mean SD Mean SD Mean SD
1 0.010 0.002 0.018 0.002 0.004 0.001
2 0.007 0.002 0.017 0.002 0.005 0.001
3 0.009 0.001 0.019 0.002 0.005 0.001
4 0.008 0.001 0.019 0.002 0.004 0.001
5 0.008 0.001 0.018 0.002 0.002 0.001
6 0.009 0.002 0.017 0.002 0.004 0.001
Mean 0.009 0.002 0.018 0.002 0.004 0.001

Heritabilities and Correlations
Heritability (%) Correlation
Method Statistic Direct Maternal MGS rD,M rD,MGS
GS Min 2.6 5.2 6.1 −0.25 0.18
Max 3.4 6.5 6.9 0.17 0.41
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 0.16 0.40
Mean 2.7 5.1 5.8 0.00 0.34

(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.

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)

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

Properties of the Calving Ability Index
Calving Ease Stillbirth
Paternal Maternal Paternal Maternal
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

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)

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 )

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.

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.

Acknowledgments
 Ignacy Misztal and Shogo Tsuruta,
University of Georgia
 Participants in Multi-State Project
S-1008
 John Clay, Dairy Records
Management Systems

Estimation of Stillbirth (Co)variance Components and Development of a Calving Ability Index

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