Productive longevity of the Black-and-White breed of cows in relation to age and live weight at the first insemination
In recent years, the duration of the economic use of cows in dairy cattle breeding has noticeably decreased, which causes great economic damage to the dairy cattle breeding industry and complicates selection. In this regard, it is relevant to study the factors affecting the productive longevity of cows and the development of measures aimed at solving the problem. The purpose of the research: to determine the optimal age and live weight of heifers at the first insemination, which will increase the productive longevity of black-and-white cows. Scientific research was carried out in the JSC «Uspenskoe» of the Tyumen region. Subject: black-and-white cows that left the herd at the end of one or more lactations (n= 243). The cows were divided into groups: I - first insemination at the age of 13-14 months, II - 15-16 months, III - 17-18 months and IV - 19 months and older. Studies have established that cows in group III had the greatest duration of productive life - 1208.2 days, and cows in group IV did not differ from cows that were inseminated at 14 months and earlier with a live weight of 362 kg on average. In terms of the number of completed lactations, cows of groups II and III exceeded group I with a difference of 0.66 (P> 0.95) and 0.73 lactations (P> 0.95), respectively. Cows of group II differed in terms of life-long milk yield, amount of milk per day of productive life, they had an advantage over cows of group I in the amount of 6531.5 kg (P> 0.99) and 1.84 kg (P> 0.99) milk respectively. Among the four groups, cows of group II were able to maximize their productive potential, this fact is confirmed by milk yield for the highest lactation - 7969 kg of milk, which is especially noticeable against the background of cows of group I with a milk yield of 7116 kg. Thus, the research results demonstrate that the best indicators of productive longevity are distinguished by cows that were inseminated at the age of 15-16 months with an average live weight of 372 kg.