title: Multiple-trait multiple-country genetic evaluations for udder health traits.
abstract: International genetic bull evaluations of somatic cell counts (SCC) from 8 different Holstein populations and clinical mastitis from 3 of these populations were inferred simultaneously using a multiple-trait-multiple-country evaluation (MT-MACE) model. This model considered effective independent weighting factors and multivariately deregressed national genetic evaluations for countries with multiple-trait national models. Predictions of genetic merit from MT-MACE and their reliabilities were compared with the corresponding results from 2 separate single-trait-multiple-country evaluations (ST-MACE) for different groups of bulls. The assumed heritabilities for clinical mastitis (h(2) = 0.02 to 0.05) were substantially lower than the heritabilities for SCC (h(2) = 0.08 to 0.27). The predictive ability of MT-MACE was essentially equal to or better than the predictive ability of ST-MACE for all country-trait combinations, but both methods yielded effectively unbiased and consistent consecutive predictions (correlation > 0.93). Both sets of predictions also agreed well with future national genetic evaluations for bulls receiving additional daughter information (correlation > 0.96), except for evaluations for which within-country correlations were utilized internationally, but not nationally (correlation = 0.86 to 0.97). The reliabilities for MT-MACE were essentially equal to or higher than reliabilities for ST-MACE, depending on the trait and group of bulls in question. Reliabilities increased most for young bulls, and for clinical mastitis in countries that did not use the within-country correlations with SCC in the national evaluation (up to a 23% increase in average reliability).
authors.affiliation: Interbull Centre, Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 7023, 750 07 Uppsala, Sweden. thm@kvl.dk
authors.forename: T
authors.initials: T
authors.lastname: Mark
authors.forename: P G
authors.initials: PG
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics*; D003612:Dairying / Q000379:methods*; D005260:Female; D014943:Global Health; D008297:Male; D008321:Mammary Glands, Animal / Q000502:physiology*; D008414:Mastitis, Bovine / Q000235:genetics*; D008957:Models, Genetic; D015233:Models, Statistical; D010375:Pedigree; D015203:Reproducibility of Results; D013223:Statistics as Topic