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

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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) …

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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  • 1. 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
  • 2. 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.
  • 3. ADSA 2006: Stillbirth (co)variance components (3) Cole et al. 20042006 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.
  • 4. ADSA 2006: Stillbirth (co)variance components (4) Cole et al. 20042006 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.
  • 5. ADSA 2006: Stillbirth (co)variance components (5) Cole et al. 20042006 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.
  • 6. ADSA 2006: Stillbirth (co)variance components (6) Cole et al. 20042006 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.
  • 7. ADSA 2006: Stillbirth (co)variance components (7) Cole et al. 20042006 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 +++++++=
  • 8. ADSA 2006: Stillbirth (co)variance components (9) Cole et al. 20042006 (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
  • 9. ADSA 2006: Stillbirth (co)variance components (10) Cole et al. 20042006 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
  • 10. ADSA 2006: Stillbirth (co)variance components (11) Cole et al. 20042006 (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.
  • 11. ADSA 2006: Stillbirth (co)variance components (12) Cole et al. 20042006 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)
  • 12. ADSA 2006: Stillbirth (co)variance components (13) Cole et al. 20042006 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
  • 13. ADSA 2006: Stillbirth (co)variance components (14) Cole et al. 20042006 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
  • 14. ADSA 2006: Stillbirth (co)variance components (15) Cole et al. 20042006 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)
  • 15. ADSA 2006: Stillbirth (co)variance components (16) Cole et al. 20042006 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 )
  • 16. ADSA 2006: Stillbirth (co)variance components (17) Cole et al. 20042006 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.
  • 17. ADSA 2006: Stillbirth (co)variance components (18) Cole et al. 20042006 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.
  • 18. ADSA 2006: Stillbirth (co)variance components (19) Cole et al. 20042006 Acknowledgments  Ignacy Misztal and Shogo Tsuruta, University of Georgia  Participants in Multi-State Project S-1008  John Clay, Dairy Records Management Systems