Dynamics of milk productivity of cows of Black-and-White breed by lactations

Abstract

The age of cow use is of big importance for the practice of dairy farming, since earlier culling of cows leads to a lack of milk, and later culling leads to the decrease in genetic progress. The purpose of the researches was to determine the dynamics of milk productivity of cows of Black-and-White breed by lactations. The researches have been carried out in the OJSC Breeding Farm “Oktyabrsky” in the Ferzikovsky district in the Kaluga region, where cattle of Black-and-White breed are bred. The object of researches was the breeding stock of Black-and-White cattle that had been lactating for five lactations. It has been found that the increase in milk yield occurred from I to IV lactation. For example, first-calf heifers had 6154,9 kg of milk yield and were statistically significantly inferior to cows of II lactation by 242,8 kg (P < 0,001) or by 3,9 %. The superiority of cows of III lactation over first-calf heifers in milk yield was 466,2 kg (P < 0,001) or 7,6 %. The maximum differences in milk yield between first-calf heifers and cows IV lactation were 704,8 kg (P < 0,001) or 11,5 %. Cows of V lactation also significantly outperformed of fi rst-calf heifers in milk yield by 381,6 kg (P < 0,01) or 6,2 %, but their milk yield was lower than that of cows during III and IV lactation. It has been revealed in the course of research that cows of all the studied lactations were characterized by sufficiently high milk productivity for cattle of Black-and-White breed. There was the increase in milk yield with the age of animals. The increase in milk yields dynamically occurs till IV lactation, and then their decrease is observed.