MILK PRODUCTIVITY OF COWS DEPENDING ON CALVING SEASON

The study of the calving season of cows is very important from the point of view of animal selection and breeding. The purpose of our research was to investigate the effects of calving season on the milk productivity of cows. The studies were conducted in the separate subdivision "Training and Experimental Farm "Ramzay" of FSBEI HE Penza SAU" on Holsteinized black and white cows. The cows were divided into four groups according to calving season: I - spring, II - summer, III - autumn, IV - winter. As a result of our research, we found that the maximum milk yield in the first and second lactations was observed in cows with autumn calving (6,698 and 7,099 kg, respectively), in the third lactation – in animals with winter calving (7,058 kg) and the minimum milk yield in animals with spring calving period (from 6,435 to 5,766 kg of milk, respectively). At the same time, the maximum mass percentage of fat and protein was determined in cows with summer calving and the minimum – in cows with winter calving. When analyzing the relationship between the number of milking days and milk yield for the entire lactation, the correlation coefficient was 0.82, indicating a fairly strong relationship. When analyzing the relationship between milk yield for 305 days of lactation and milk fat percentage, a negative relationship was observed, ranging from -0.13 to -0.53. The correlation coefficient between the milk yield for 305 days of lactation and the percentage of milk protein shows both positive and negative values and ranges from -0.05 to 0.71. When calculating the correlation coefficient for milk yield for the entire lactation and the amount of milk fat and protein in the milk in all groups studied and for all lactations, a strong positive relationship of 0.99 was found. After studying the calving seasons of the cows in this herd, it is recommended to schedule most of the cows' calvings for autumn and winter calving periods, which can significantly increase milk production per year or milk yield per cow per year in the future.