Abstract
The aim of this study was to determine the relationship between behavioral reactivity and fattening performance in bull calves of different genotypes reared under dry-steppe conditions in western Kazakhstan. The research included four groups of young cattle: purebred Kazakh White-Headed animals and crossbreds obtained from Kazakh White-Headed cows inseminated with Simmental (beef type), Limousin, and Auliekol sires. Observations were conducted from birth to 18 months of age, taking into account changes in body weight, average daily gain, feed intake, and behavioral structure during both the winter and summer periods. It was established that crossbred bull calves exceeded purebreds in birth weight by 2.0–5.1 kg (p < 0.001) and by 12.9–40.2 kg at 18 months of age. The Simmental × Kazakh White-Headed genotype resulted in the greatest average daily gain (858 g) and the most efficient feed utilization (7.49 feed units per kilogram of weight gain). Behavioral analysis revealed that crossbred bull calves spent significantly less time on locomotor activity than purebred animals did, which corresponded to reduced nonproductive energy expenditure and increased weight gain. A calm behavior type was identified as a factor enhancing fattening efficiency. Simmental × Kazakh White-Headed crossbreds proved to be the most economically advantageous for beef cattle production under dry-steppe conditions.