Age dynamics of growth of replacement heifers depending on origin from sire

Abstract

For insemination of the breeding stock of dairy cattle the semen of sires of both domestic and foreign breeding is used. Due to the fact that the issues of herd reproduction have become one of the most important factors of progress in dairy cattle breeding, the rearing of replacement young animals is given great importance. The purpose of the research was to study the age dynamics of the growth of replacement heifers depending on origin from sire. It was found that the diff erence in live weight at calving between heifers from diff erent sires was insignifi cant and amounted to 1,4 kg or 4,7 %. The heifers from the sire Sayan had the highest live weight at the age of 18 months – 425,3 kg, the heifers from the sires Cassio and Mers were slightly inferior to them by 3,6 and 5,3 kg. According to the rearing periods the heifers grew unevenly. The uneven growth of heifers from diff erent sires, although it had a common pattern, but diff ered by groups. So, from 6 to 12 months of age, there was a decrease in absolute gain in all groups, but in the next period (12–15 months), there were features in the change in absolute gains. So, in heifers from the sire Das, the absolute gain remained at the same level, and in heifers from the sires Sayan, De-Su, Touareg, Cassio, it continued to decline, while in heifers from the sires Gavano, Marrs and Bentley it is increased. On average, over the entire rearing period, it ranged from 21,0 to 22,0 kg per month. Thus, the system of rearing of replacement heifers on the farm allows us to get good results. The age of the fi rst insemination of heifers, depending on the origin of the sires ranges from 14,0 to 15,9 months with eff ective insemination at the age of 14,8–16,9 months, which suggests the use of early terms of the fi rst insemination of heifers. The live weight of heifers at the fi rst insemination meets the requirements for cattle of Black-and-White breed, regardless of their origin from sire.