Genetic evaluation for milk production trait in crossbred Holstein dairy cattle separated by region of Thailnad using Random regression testday model

Abstract

The objective of this study was to genetic evaluation for milk production in crossbred Holstein dairycattle in different regions of Thailand. Data included 140,452 test-day milk yield records from 16,175 first parityHolstein crossbreds in Thailand. Test-day milk records were obtained from the Bureau of Biotechnology inLivestock Production, Department of Livestock Development under the Master Bull project during 1991 to 2008.Restricted Maximum Likelihood (REML) was used to estimate genetic parameters and genetic lactation curvesunder Random regression test-day model. The estimated heritability using combined data from all regions was 0.24. The estimated heritability from different regions ranged from 0.16 to 0.23. The estimated heritability over lactationfor each region was different. These results showed that the variation of milk production for each region partlydepended on gene expression was different. Permanent environmental variance ratios for each region ranged from0.54 to 0.65. These results indicated that the variation of milk yield depended more on the effects of environmentthan the effects of genetic. Genetic lactation curve for each region were also different in both sires and dams.Consequently, the selection of sires should be specific for each region and selective mating should be recommended.