| dc.description | The objective of this study was to estimate genetic parameters for milk production and reproduction traits using phenotypic and pedigree information from the Dairy Overo Colorado breed from southern Chile. Single- and multi-trait mixed models were used to analyze the data. Analyses were performed using ASReml software. The heritability estimates for milk yield, fat yield, protein yield, fat content, protein content, age at first calving and calving interval were 0.29 ± 0.04, 0.34 ± 0.04, 0.30 ± 0.04, 0.56 ± 0.04, 0.56 ± 0.04, 0.01 ± 0.07 and 0.002 ± 0.02, respectively. The genetic correlations between yield traits were high and positive (≥ 0.81). The genetic correlations of milk yield with fat content (-0.32) and protein content (-0.34) were unfavorable. The genetic correlation estimates between age at first calving and yield traits were negative, ranging between -0.71 and -0.29. The phenotypic correlations between calving interval and milk yield traits were slightly positive (0.06-0.09), suggesting a weak relationship between reproduction and yield in this population. Genetic variation was significantly greater than zero for milk production traits. Genetic improvement for age at first calving and calving interval may be slow because small differences between animals and low reliabilities are expected for estimated breeding values for these traits due to heritabilities close to zero. The design of an efficient breeding program for yield traits based on artificial insemination for this population is feasible using either progeny testing or genomic breeding value prediction to select sires. | |
