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

ADSA 2006: Stillbirth (co)variance components (2)Cole et al Introduction  A national evaluation for stillbirth (SB) for Holstein will be implemented in August  (C o)variance components were required.  A calving ability index (CA$) which includes SB and calving ease (CE) was developed.

ADSA 2006: Stillbirth (co)variance components (3)Cole et al 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.

ADSA 2006: Stillbirth (co)variance components (4)Cole et al Data  7 million SB records were available for Holstein cows calving since  Calvings with unknown MGS were eliminated for VCE.  Records with sire and MGS among the 2,600 most-frequently appearing bulls were selected.

ADSA 2006: Stillbirth (co)variance components (5)Cole et al 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.

ADSA 2006: Stillbirth (co)variance components (6)Cole et al Sampling  Six datasets of ~250,000 records each were created by randomly sampling herd codes without replacement.  Datasets ranged from 239,192 to 286,794 observations, and all averaged 7% stillbirths.  A common pedigree file was used to facilitate comparisons between sire and MGS solutions.

ADSA 2006: Stillbirth (co)variance components (7)Cole et al 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.

ADSA 2006: Stillbirth (co)variance components (8)Cole et al (Co)variance Components Estimated by Quasi-REML SampleVar(Sire)Var(MGS)Cov(S-MGS) Mean

ADSA 2006: Stillbirth (co)variance components (9)Cole et al (Co)variance components estimated by Gibbs sampling Var(Sire)Var(MGS)Cov(S-MGS) SampleMeanSDMeanSDMeanSD Mean

ADSA 2006: Stillbirth (co)variance components (10)Cole et al Heritabilities and Correlations Heritability (%)Correlation MethodStatisticDirectMaternalMGSr D,M r D,MGS GSMin − Max Mean − REMLMin − Max Mean

ADSA 2006: Stillbirth (co)variance components (11)Cole et al (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.

ADSA 2006: Stillbirth (co)variance components (12)Cole et al 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)

ADSA 2006: Stillbirth (co)variance components (13)Cole et al Genetic Correlations Among Traits in Calving Ability Index Trait Calving EaseStillbirth SireDauSireDau Calving Ease Sire Dau Stillbirth Sire Dau1.00

ADSA 2006: Stillbirth (co)variance components (14)Cole et al Properties of the Calving Ability Index Calving EaseStillbirth PaternalMaternalPaternalMaternal Mean8888 SD Heritability, % Economic value, $4348

ADSA 2006: Stillbirth (co)variance components (15)Cole et al National Calving Trait Indices CntryPat CEMat CEPat SBMat SBModelMerit % DEU AM7 NLD S-MGS7 NOR03433 S-MGS3 SWE S-MGS12 CHE12 38 AM0 USA554500S-MGS4(2003) USA S-MGS6(2006)

ADSA 2006: Stillbirth (co)variance components (16)Cole et al 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$.

ADSA 2006: Stillbirth (co)variance components (17)Cole et al 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.

ADSA 2006: Stillbirth (co)variance components (18)Cole et al 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.

ADSA 2006: Stillbirth (co)variance components (19)Cole et al Acknowledgments  Ignacy Misztal and Shogo Tsuruta, University of Georgia  Participants in Multi-State Project S-1008  John Clay, Dairy Records Management Systems