The dependence of dairy efficiency of cows, heifers of black and white breed on the level of their body weight on the Urals territory

Live weight of cows, heifers has economic, bio-logical significance and is a major sign of breeding dairy cattle. In terms the Ural territory live weight of cows, heifers of black-motley breed in breeding farms with different milk yield level has been poorly studied. The studies have been conducted in a herd of cattle of black-motley breed of breeding farm LLC "Shadrinskoe," Shadrinsk district of Kur-gan region. The objects of the research were heif-ers, cows of black-motley breed. In the study period the animals were kept in the same conditions of feeding and keeping. It was found out that the level of live weight of cows, heifers had a positive effect on milk yield per lactation was 305, 100 days of lactation. Cows with body weight of 551-600 kg of milk yield for 305 days of lactation was 5052 kg, which is more than a live weight of less than 400 kg to 884 kg (21.2 % R≤0,001), and a group of 501-550 kg, 451-500 kg per 561 kg (13.4% R≤0,001), 337 kg (8.1%, p ≤ 0.05), respectively. The milk yield in 100 days of lactation in heifers with a live weight of over 400 kg to 600 kg in groups ranging from 114 kg to 413 kg (p ≤ 0.05, R ≤ 0,001) com-pared with a group of live weight of less than 400 kg. Fat content in milk (3.93 %) and protein (3.26 %) was higher in heifers with a body weight below 400 kg. The difference in fat mass fraction in milk in comparison with other groups was from 0.02 % to 0.13 % and the protein from 0.03 % to 0.05 %. Significant differences in milk fat in groups of cows with a live weight of 501-550 kg, 551-600 kg per 19.0 kg (p ≤ 0.05) and 31.0 kg (R≤0.01), respectively, as well as milk protein in these groups by 17 kg (p ≤ 0.05) and 22 kg (p ≤ 0.05) compared to a group of cows and a live weight of less than 400 kg. Profit from the sale of milk per cow, with a live weight of less than 400 kg was 18 206 r., com-pared with a live weight of 401-500 kg of animal it is lower at 377.59 rubles, compared with a live weight of 501-600 kg difference. The profit was higher at 3140 r. (17.2 %), 3876 r. (21.3 %), re-spectively. The profitability of milk production, de-pending on the level of body weight in the groups ranged from 27.8 % to 30.4 %. In the context of the Urals territory in breeding farms with a yield of 5.000 kg or more, the most desirable body weight, heifers cows of black-motley breed from 451 kg to 600 kg, they had higher milk yield, the amount of milk fat and protein in milk.