Environmental factors affecting milk yield traits of Brown Swiss cows raised at Ulas State Farm and phenotypic correlations between milk yield and fertility traits

Abstract

This experiment was done to study environmental factors affecting milk yield traits of Brown Swiss cows raised at the Ula degrees State Farm and phenotypic correlations between milk yield and fertility traits. The least-square means of 305-day milk yield, lactation duration and dry period were found as 4527 kg, 308 days and 102 days respectively. The effect of calving year on milk yield traits was found statistically significant. The effect of calving age on all milk yield traits was also statistically significant. The effect of calving season on 305-day milk yield was statistically significant. Phenotypic correlations between 305-day milk yield and lactation duration (0.38), between lactation duration and dry period (-0.16), between 305-day milk yield and calving interval (0.16), between lactation duration and calving interval (0.12) were significant.