Phenotypic correlations of productive and reproductive traits of Simmental cows

Research included 3.461 first calving Simmental cows in control, with lactations concluded within one year. All first calving cows were reared by private/individual farmers on the territory of the Republic of Serbia. Phenotypic correlations between following milk and fertility traits have been investigated: duration of lactation DL, milk yield MY, milk fat content MFC, milk fat yield MFY, yield of 4% FCM, age at first calving AFC and duration of service period DSP. Results of the investigation of phenotypic correlations are obtained using mixed models LSMLMW (Harvey 1990). This method enables optimal consideration of numerous effects on investigated traits (bull sires, region, calving season, and calving year). Phenotypic correlation of traits in cattle breeding relates to presence of mutual positive or negative covariance which is result of the effect of genetic and factors of the environment. Information on phenotypic correlations between milk and fertility traits can be of great importance in selection of cows, since it provides possibility to choose/select heads based on several traits at the same time. .