COMPARATIVE ANALYSIS OF THE INFLUENCE OF SEX ON THE RELATIONSHIP OF THYROID HORMONES, AMINOTRANSFERASE ACTIVITY AND PRODUCTIVE QUALITIES IN YOUNG KAZAKH WHITE-HEADED BREED

Abstract

Regulation of metabolic processes in farm animals is one of the key biological factors determining their productive potential. The endocrine system, particularly thyroid hormones (T3, T4), plays a leading role in this process by controlling the direction of energy and protein metabolism. Important indicators of the biochemical status of blood include aminotransferases—aspartate aminotransferase (AST) and alanine aminotransferase (ALT)—which serve as reliable markers of metabolic intensity and orientation. AST participates in energy production by facilitating the entry of amino acids into the tricarboxylic acid cycle, whereas ALT is involved in gluconeogenesis.

The research objective was to comparatively assess the relationship between thyroid hormone levels, aminotransferase activity, and live weight gain in young Kazakh White-Headed cattle (heifers and bull-calves), taking into account sex-related characteristics. The study was conducted at the ages of 8, 15, and 18 months. The results revealed a strong positive correlation (up to r = 0.90) between T3 levels and AST activity in heifers, indicating the key role of T3 in regulating energy metabolism. In bull-calves, anabolic processes predominated, and a decrease in the De Ritis ratio indicated a shift of amino acids toward gluconeogenesis. Overall, growth in heifers was more dependent on endocrine regulation, whereas in bull-calves it was associated with constructive metabolic processes. These findings provide a scientific basis for developing sex-specific feeding strategies.