EN
The paper compares the chemical composition of milk from Polish Holstein-Friesian Black-And-White (PHF HO) and Montbéliarde (MO) high-yielding cows. The research was based on the results of 36,796 test-day milkings: 25,617 from PHF HO and 11,179 from MO. The analysis included the influence of the successive lactation and its phase, the daily milk yield, the cytological quality of milk, and the season on the content of basic compounds and the fat/protein proportion in milk. The milk from Montbéliarde cows contained significantly more fat (by 0.05%) and protein (by 0.38%) than the milk from the Polish Holstein-Friesian Black-And-White breed. The milk from Montbéliarde cows also had a better proportion of fat to protein (by 0.11). With regard to the fat and protein content, as well as the fat/protein proportion in milk of PHF HO cows, the most important factor was the daily milk yield, whereas the most important determinant of lactose was the level of somatic cells. The factors included in the analysis had less influence on the basic chemical composition of milk from Montbéliarde. The greatest differences in the fat content were related to the daily milk yield, in the protein content to the successive lactation month, in the lactose content to the level of somatic cells, and in the fat/protein proportion to the successive lactation.