Estimation of variance components of milk, fat, and protein yields of Tunisian Holstein dairy cattle using Bayesian and REML methods

摘要

A multi-trait repeatability animal model under restricted maximum likelihood (REML)and Bayesian methods was used to estimate genetic parameters ofmilk, fat, and protein yields in Tunisian Holstein cows. The estimates ofheritability for milk, fat, and protein yields from the REML procedure were0.21 ± 0.05, 0.159 ± 0.04, and 0.158 ± 0.04, respectively. Thecorresponding results from the Bayesian procedure were 0.273 ± 0.02,0.198 ± 0.01, and 0.187 ± 0.01. Heritability estimates tended to belarger via the Bayesian than those obtained by the REML method. Genetic andpermanent environmental variances estimated by REML were smaller than thoseobtained by the Bayesian analysis. Inversely, REML estimates of the residualvariances were larger than Bayesian estimates. Genetic and permanentcorrelation estimates were on the other hand comparable by both REML andBayesian methods with permanent environmental being larger than geneticcorrelations. Results from this study confirm previous reports on geneticparameters for milk traits in Tunisian Holsteins and suggest that amulti-trait approach can be an alternative for implementing a routinegenetic evaluation of the Tunisian dairy cattle population.