Changes in milk productivity indicators by lactation

Relevance . Modern dairy cattle of the Middle Urals are distinguished by their large mass. These are large animals with a high genetic potential of 10-12 thousand kg or more of milk per lactation. It is of interest to assess the further possibility of increasing the breeding value of Holstein breed animals, including productive longevity. The aim of the work is to study the variability of milk productivity indicators of cows-daughters of different breeding bulls depending on the age in lactation. Methods . The research was conducted in the conditions of a typical agricultural enterprise for the production of milk — a breeding reproducer for the breeding of Holstein cattle. The object of the research is cows-daughters from breeding bulls Altaesquaye, Campman, Charman and Emen. The material and data for comparison were the database of the IAC “SELEX — Dairy Cattle”, the results of our own research. Milk yield for 305 days of lactation by lactation, MJ and MDB in milk by lactation were taken into account. Results . As a result of the research, it was found that the milk yields of cows-daughters of different bulls-producers vary differently depending on age. Thus, the milk yield of Altaesquaie bull cows had the highest rates during the second lactation, and then stabilized with fluctuations in one direction or another by 350–700 kg with a constant decrease (starting from the 5th lactation). The same changes were noted in the daughters of bull Charman. The daughters of the Campman bull increased milk yield to age-appropriate lactation, and then decreased with fluctuations in lactation. The daughters of bull Emen have been found to have increased milk yields up to and including the 5th lactation. The same changes were found for MJ and MDB in milk, which is confirmed by fluctuations in the coefficient of variability depending on age.