Young black - motley cattle breed growth and development in LLC “Rubin” of Kabansky district of Buryatia

The purpose of research is to study the growth and development of young black-motley breed of different sex and different seasons of calving in the pedigree reproducer of LLC “Rubin”, Kabansky District of the Republic of Buryatia. Previously, such studies were not conducted in the republic. The research material was the results of weighing of 121 bulls and 132 heifers born in 2018. The obtained data were processed biometrically and compared with the breed standard, according to them the absolute, average daily and relative gains were calculated, limits and coefficients of variation in live weight were determined. For heifers, the correlation coefficient between body weight at 10 and 18 months was calculated and an economic analysis of rearing was made. The work shows the high seasonality of calving on the farm. Most of the calves are born in the spring and summer (72 % of calves and 77 % of heifers). Juveniles of the winter calving season (both calves and heifers) surpass in live weight the juveniles of other calving seasons. Heifers and calves of the summer calving season had the lowest live weight indicators. Their greatest lag starts from 6–7 months. This is due to the fact that their puberty will coincide with the most unfavorable season in terms of weather conditions. The way out of this critical period is accompanied by an increase in the coefficient of variation of the live mass, the largest one was in young calves of the summer period: from 8 to 12 in bulls (from 20.5 to 27.8 %), in heifers from 9 to 12 months (18–19 %). Bulls and heifers of all calving seasons are inferior to the standard for the live weight by 10–15 %. But in the herd there are animals superior to the standard. Growing a heifer of standard mass 390 kg in 18 months only by increasing the level of feeding will reduce profitability by 15 %, therefore, the living mass must be increased using the selection methods, in particular using the correlation calculated between the mass of the heifer in 10 and 18 months, equal to 0.40.