Effect of a successive lactation and its stages on milk performance of Jersey and Polish Holstein-Friesian cows

摘要

The aim of the study was to analyze the effect of a successive lactation and its stages on the yield and composition of milk in Jersey and Polish Holstein-Friesian (PHF) cows. Investigations were conducted from 1999-2005 on 117 Jersey and 408 PHF cows, kept in the same barn. Higher contents of butterfat (+1.79%), protein (+0.71%), solids (+1.95%) and urea (+7.5 mg/1) were found in the milk of Jersey cows. In turn, PHF cows were characterized by higher milk yields (+5.2 kg/day) and 4%FCM (+1.1 kg/day), as well as a higher somatic cell count (SCC) in milk (+43 thousand/ml). It was found that with age Jersey cows were more persistent in milk production than PHF cows. Contents of butterfat, protein and solids in milk increased in Jersey cows up to the third lactation, and they remained constant thereafter. Contents of butterfat and protein in the milk of PHF cows did not change with age, while that of solids decreased. The butterfat content in milk in both breeds increased at successive stages of lactation. The protein content in milk increased at individual stages of lactation in Jersey cows, while in PHIT cows it decreased and the contents of solids in milk increased with the course of lactation in both breeds. Milk urea concentration was closer to its metabolic optimum in Jersey cows. SCC increased with age and along with the course of lactation in both breeds, although changes affected by these factors were much smaller in Jersey cows than in PHIT cows.