The aim of this study was to determine the effect of cattle breed on carcass traits and meat quality of bulls fattened semi-intensively and slaughtered at 18 months of age. The animals were divided into three experimental groups: Group AA -16 Angus bulls, group WK -19 Kazakh White headed bulls, group AK -20 Kazakh Aulie-Ata bulls. All bulls were slaughtered at the end of the fattening period. Angus bulls had the highest (p≤0.05) final body weight (494.9 kg) at 18 months of age. Average daily gain was also highest (p≤0.01 and p≤0.05) in group AA (863 g). Angus bulls were characterized by the highest carcass dressing percentage (56.8%) and the highest fat content (3.4%). Carcass length and thigh circumference were significantly (p≤0.05) higher in AA bulls than in AK bulls. The content of lean meat and fat in the carcass was highest (79.4%, p≤0.05) in AA bulls and lowest in AK bulls. Samples of semitendinosus muscle collected from AA bulls had the highest content of dry matter (24.89%), protein (22.5%) and fat (2.27%, p≤0.05).

Live-animal evaluation of replacement young animals including bull-calves on their own productivity in the breeding of Kazakh White-Headed cattle has of scientific and practical importance. The purpose of the work was a live-animal evaluation of the quality of Kazakh White-Headed bull-calves by their own productivity. Bull-calves of the 3rd group (line of Veteran) in all periods of evaluation on growth can be assigned to the elite-record class. Replacement bull-calves of the 1st group (line of Circled) at all ages for live weight belonged to the elite class. Replacement bull-calves of the 2nd group since 9-month age have been evaluated as a class elite-record. According to the adjusted live weight of replacement bull-calves at the age of 210 and 365 days, the animals of the 3rd group were the best. According to this indicator the bull-calves of the 3rd group at the age of 210 days can be attributed to the 1st class, and at the age of 365 days the elite-record. When evaluating the reproductive capacity of the replacement bull-calves of Kazakh White-Headed breed of different lines the superiority of animals of the 3rd group (line of Veteran) has been found. They have significantly higher scrotum girth than the bull-calves of the 1st group by 7,1 cm or 27,0 % (P ≤ 0,01) and 1,9 cm or 6,0 % (P ≤ 0,05) than the young bulls of the 2nd group. The meat qualities also revealed the superiority of bull-calves of the 3rd group. They had higher indicators for the area of the muscle eye, marbling of meat and a comprehensive assessment of meat qualities. Live-animal evaluation of replacement young animals of beef breeds on their own productivity allows us to quickly increase the number of breeding stock.

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