Anotace:
Selection in meat cattle herds requires caution due to the manifestation of inbred depression in traits that affect the economics of this livestock industry. This paper analyses the productivity of inbred and outbred bull calves of the Ukrainian meat cattle breed and justifies methods of pair selection in purebred herds with natural pairing. In bull calves, the growth of animals and traits of their meat productivity after slaughter were considered. Inbreeding was determined based on their pedigree. Inbred animals tended to have a growth rate of 10.2% from birth to 8 months of age. Afterwards, their average daily gain in live weight decreases sharply compared to outbred peers, who grow faster over a more extended period. From 8 to 18 months of age, it is probably (p >0.95) higher by 27.3% compared to inbred animals. Inbred bull calves have higher variability (Cv,%) in average daily gains. This indicates different adaptations to the environment during the suckling period and after weaning. Outbred animals tend to gain 2.3% of body weight at 12 months, 4.7 at 15 months, and 10.3% at 18 months. Its variability with age decreases by 7.4 points in inbred bull calves and 0.4 points in outbred ones, from 8 to 18 months. The inbred animals spent 29.5% more feed per kg of gain (p >0.95) than the outbred ones. Inbred bull calves vs outbred ones at 15 and 18 months of age tend to improve the expression of meat forms by 1.3 and 2.7%. They are relatively shorter and have a more rounded barrel. As a result, they have a shorter period of rapid growth. With the small size of the Ukrainian meat cattle population, one of the most important problems is reducing genetic variation in beef productivity traits and manifesting inbred depression in them. In purebred commercial herds, the mating of close animals should be avoided. To do this, an "order" for bulls should be made, and pairs should be selected without using inbreeding at different grades. Thus, outbred bull calves will reach live weight more quickly, spending less feed per growth unit, and have better basic slaughter traits.