Genomic evaluation of gestation length in Holstein cattle
The model for prediction of genomic breeding values for gestation length (GL) was developed in Holstein cattle. GL was calculated as a difference between the date of calving and the date of the last service in 881 thousand of Holstein cows calved in 2011–2019. Mean GL was 277 days, and it ranged from 254 to 303 days with SD of 5.2 days. We employed animal model with maternal effect for genetic evaluation. The model included the fixed effects of month of conception, herd-year-season of calving, parity of dam, sex of calf, and the random direct genetic, maternal genetic and permanent environmental effects. The estimated heritabilities were 0.48 for direct genetic effect and 0.05 for maternal effect. The genetic correlation between both effects was 0.12. Two genomic matrices were set up: (1) based on SNP genotypes of 4,383 Holstein sires; (2) based on SNP genotypes of Holstein sires and domestic Holstein cows (28,975 animals, most of them born between 2017 and 2021). Genomic breeding values (GEBV) were predicted with single-step GBLUP method for 1.39 and 1.47 million animals for matrix 1 and 2, respectively, based on 3-generation pedigree. Estimates of fixed effects showed that GL was 0.9 longer in multiparous compare to primiparous cows. GL was 1, 6 and 2 days shorter in female calves, multiple births and calves of unknown sex (mostly stillborn) compare to male calves. GEBV for direct effect ranged from -10 to +17 days, with SD about 2.5 days. GEBV for maternal genetic effect ranged from -6 to +5 days with SD about 0.8 days. Genomic prediction achieved the same mean reliability (52% for direct and 28% for maternal GEBV) with both genomic matrices. Mean reliabilities of prediction increased from 0.55 to 0.91 (direct GEBV) and from 0.33 to 0.60 (maternal GEBV) in genotyped bulls. The inclusion of female genotypes helped to increase their own GEBV reliabilities, from 0.61 to 0.78 in females with known phenotype and from 0.30 to 0.70 in females with unknown phenotype. The genetic trend indicated the shortening of GL in recent years, which was partly compensated by the increase in maternal component.
|Projekt||Dlouhodobý koncepční rozvoj výzkumné organizace, Navýšení spolehlivosti celostátního genomického hodnocení dojeného skotu zařazením krav s domácí užitkovostí do genotypované referenční populace|
|Oddělení||Genetika a šlechtění hospodářských zvířat|
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