Phenotypic and genetic characterization of the milk yield and calving interval in buffalo of the Murrah breed

Abstract

The objective of this work was to estimate the correlations, heritabilities, repeatabilities, phenotypic and genetic trends, and to evaluate the univariate and bivariate distributions of the milk yield and calving interval of Murrah breed buffalo, calved from 1982 to 2003. The genetic and phenotypic trends were estimated by regressions of the dependant variables on year of the animals calving, based on two methods: linear regression and articulated polynomial regression. The heritabilities estimates were 0.21 and 0.02, and the repeatabilities 0.32 and 0.06, for milk yield and calving interval, respectively. The genetic, phenotypic and environmental correlations were -0.22, 0.01 and 0.03, respectively. Genetics trends (linear regression) were significant and equal to 1.57 kg per year and 0.085 day per year, and the phenotypics trends were 27.74 kg per year and 0.647 day per year, for milk yield and calving interval, respectively, being significant just for milk yield. The negative genetic correlation suggests that there is a favorable relationship between milk yield and calving intervals, thus it is possible to select animals of high breeding values for milk yield and with low breeding values for calving intervals.