Genetic model comparison between homogeneous and heterogeneous residual variance in Thai crossbred Holsteins using random regression test-day model

Abstract

The objective of this research was to compare the genetic models of homogeneous and heterogeneous residual variances in crossbred Thai-Holstein dairy cattle. The data included 398,805 test-day milk yield records from 27,133 first-three lactations. The test-day milk records were obtained from the Bureau of Biotechnology in Livestock Production, Department of Livestock Development under the Master Bull project during the years 1991 to 2008. Bayesian analysis via Gibbs sampling and best linear unbiased prediction under random regression test-day model were used to estimate genetic parameters and breeding values, respectively. The results showed that the adjusted heterogeneity of residual variance had no effect on additive variance whereas it had effects on permanent environmental  variance and heritability. In addition, in a comparison between both models, the model with heterogeneous residual variance had rank correlation of breeding value estimates (0.92-0.96) and coefficients of determination (R2) (0.90-0.96)  higher than the model with homogeneous residual variance. Therefore, the adjustment for heterogeneity of residual variance could be appropriate for increasing the selection accuracy of dairy cattle.