SEASONAL VARIABILITY OF HEMATOLOGICAL AND BIOCHEMICAL BLOOD PARAMETERS IN BULLS OF DIFFERENT GENOTYPES

Abstract

Under sharply continental climatic conditions, studying the adaptive mechanisms of young stock cattle is of particular relevance, as hematological and biochemical blood parameters serve as sensitive indicators of the physiological response to seasonal changes in feeding and husbandry. The aim of this research was to assess the seasonal variability of major blood indicators and to compare the adaptive features of young bulls of different genotypes. The study involved purebred Kazakh White-Headed cattle and first-generation crossbreds obtained from mating with Simmental, Limousin, and Auliekol breeds. The methods included determining hematological parameters, serum enzyme activity, mineral composition, vitamin A levels, and protein fractions during the winter and summer periods. The results demonstrated that seasonal factors significantly affected (p<0.05) most parameters: during summer, intensified metabolic activity was observed, reflected in increased transaminase activity, higher albumin concentrations, and elevated total protein levels. Genotype also played an important role: crossbred bulls exhibited greater stability of homeostatic indicators, lower variability in enzymatic activity, and more favorable albumin–globulin ratios. The obtained data highlight the advantages of crossbred young stock in terms of physiological resilience and may be useful for selecting optimal crossbreeding options, as well as improving feeding and husbandry technologies in regions with severe climatic fluctuations.