Features of Growth and Development in Heifers of Holstein and Black-and-White Breeds

: The study of the characteristics of the growth and development of farm animals is of interest in breeding, as it will help to improve animal breeds, as well as serve for the organization of fast and economically rational raising of productive livestock. The research aims to study the characteristics of growth and development and indicators of reproduction of the Holstein and Black-and-White breeds. For research, three groups of 10-day-old heifers were formed. Body weight was considered by individual weighing at birth, at 3, 6, 9, 12, 15 and 18 months. The reproductive indices of heifers were studied according to the data of the log of inseminations and calving of cows: The age at the first insemination, the age at fertilization and the number of inseminations per 1 fruitful insemination were considered. The conducted studies led to a conclusion that the Holstein heifers had an advantage in live weight over the Black-and-White heifers at the age of 6 months by 19.5 kg and 15.5 kg (P≤0.001), at 12 months of age by 18.4 kg (P≤0.01) and 19.2 kg, at 18 months by 28.0 kg and 25.3 kg (P≤0.01), respectively and exceeded them in growth intensity during the entire study period. The Holstein animals matured faster and were inseminated 43.2-45.8 days earlier than the Black-and-White animals that were inseminated at 511 days. Profits from raising the Holstein heifers were higher by $48.79-54.79.