| Summary: | Data on 8948 pedigree, breeding and performance records of a purebred herd of Sahiwal cattle maintained at the Livestock Experiment Station Jahangirabad district Khanewal (Pakistan) during the period 1939-98 were analysed. The phenotypic, genetic and residual correlations between first lactation milk yield and some first lactation and lifetime traits were estimated, using Bivariate REML analysis. Phenotypic, genetic and residual correlations between first lactation milk yield and age at first calving were 0.67, 0.61 ± 0.30 and 0.73; between first lactation milk yield and first lactation length were 0.35, 0.48 ± 0.38 and 0.31; between first lactation milk yield and first calving interval were 0.39, 0.46 ± 0.46 and 0.39; between first lactation milk yield and first dry period were 0.35, 0.49 ± 0.46 and 0.30; between first lactation milk yield and lifetime milk yield were 0.02, 0.01 ± 0.77 and 0.05. Positive and high genetic correlation between first lactation milk yield and age at first calving indicated that the selection for higher first lactation milk yield would increase the age at first calving, which is not advantageous.
|
|---|
