INFLUENCE OF DIFFERENT AGES HEIFERS LIVE WEIGHT ON THE LIFELONG COWS PRODUCTIVITY

Abstract

One of the problems of modern dairy farming is the short period of productive use of cows. This is observed not only in Ukraine, but also in most countries of the world with developed dairy farming. The consequence of a short period of productive use is a decrease in lifelong productivity of cows. The aim of this paper was to study the possibility of influencing the duration of use and lifelong yield of cows by selecting heifers for live weight during their rearing. The study analyzed the lifelong productivity of 1071 cows of the Ukrainian black-spotted dairy breed, starting from their breeding and before leaving the herd. Animals were divided into five groups by living weight at the age of 3, 6, 12 and 15 months using a standard deviation (σ) from the mean value. The number of calving, the duration of productive life, lifelong yield and yield for higher lactation, as well as the average period between calving were determined within the groups. It was found that yield for higher lactation are associated with the weight of heifers during the beginning of pubertal development and the onset of sexual maturity. Animals that had a live weight of + 0.5…1.5 σ at the age of 6 months and more than +1.5 σ at the age of 12 months from the average live weight in the herd were characterized by the highest milk yield. The group of signs of lifelong productivity (number of calving, duration of productive use and lifelong yield) was positively affected by live weight of heifers aged 3, 6, 12 and 15 months, which exceeded the average live weight in the herd by 0.5…1.5 σ. Cows included in these groups outperformed other groups by 0.2…1.4 calving. During the period of use, these cows received 11…32% more milk than the herd average. The research expands the understanding of the influence of heifer breeding on the formation of lifelong productivity of cows and can be used to select livestock and adjust plans for dairy cattle breeding.