Genetic parameters for test-day model with random regressions for production traits of Czech Holstein cattle
Zavadilova, L.(Vyzkumny Ustav Zivocisne Vyroby, Prague (Czech Republic))E-mail:[email protected] | Jamrozik, J.(University of Guelph (Canada). Centre for Genetic Improvement of Livestock) | Schaeffer, L.R.(University of Guelph (Canada). Centre for Genetic Improvement of Livestock)
Multiple-lactation random regression model was applied to test-day records of milk, fat and protein yields in the Czech Holstein breed. Data included 9,583 cows, 89,584, 44,207 and 11,266 test-day records in the first, second and third lactation, respectively. Milk, fat and protein were analysed separately and in a multiple-trait analysis. Linear model included herd-test date, fixed regressions within age-season class and two random effects: animal genetic and permanent environment modelled by regressions. Gibbs sampling method was used to generate samples from marginal posterior distributions of the model parameters. The single- and multiple-trait models provided similar results. Genetic and permanent environmental variances and heritability for particular days in milk were high at the beginning and at the end of lactation. The residual variance decreased throughout the lactation. The heritability (0.13-0.52) increased with parity.
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