Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2006
Publication Date: July 9, 2006
Citation: Cole, J.B., Wiggans, G.R., Van Raden, P.M., Miller, R.H. 2006. Stillbirth (co)variance components for a sire-maternal grandsire threshold model [abstract]. Journal of Dairy Science. 89(Suppl. 1):273(abstr. 339). Technical Abstract: (Co)variance components for stillbirth in US Holsteins were estimated under a sire-maternal grandsire threshold model using subsets of data from the national calving ease database, which includes over 7 million calving records with associated stillbirth scores. Stillbirth was coded as a binomial trait indicating whether or not the calf was alive 48 h postpartum; 10.8% of calves born to heifers were stillborn, versus 4.8% of calves born to cows. Records were selected from calves with sire and maternal grandsire (MGS) among the 2600 most-frequently appearing bulls (2578 distinct sires and 2586 distinct MGS). Herd-years were required to contain at least 20 records and only single births were used. After edits, the dataset included 2,083,979 calving records from 5765 herds and 33,304 herd-years. Six sample datasets of approximately 250,000 records each were created by randomly selecting herd codes. Quasi-REML and Gibbs sampling approaches were used to estimate (co)variance components from each sample. The model included fixed year-season, parity-sex, birth year group of sire, and birth year group of MGS effects and random herd-year, sire, MGS, and residual effects. Quasi-REML point estimates fell within the corresponding Gibbs sampling 95% confidence intervals for all samples, indicating good agreement between the two estimation procedures. Marginal posterior means (and standard deviations) averaged 0.0085 (0.0015), 0.0181 (0.0020), 0.0872 (0.0538), and 0.00410 (0.0001) for sire, MGS, and herd-year variances and the sire-MGS covariance, respectively. Mean direct and MGS heritabilities were 0.030 (0.003) and 0.016 (0.001), respectively, and the genetic correlation between direct and MGS effects was 0.331 (0.079). Heritability estimates were lower than some literature results, but the genetic correlation between direct and MGS effects was larger than previous estimated correlations of direct with pure maternal effects. Economic values of sire and MGS effects for stillbirth are less than for calving ease, and all four traits may be combined into a calving index.