Role of Heredity in Determining Alanine Aminotransferase Levels in Farm Animals

This study focused on estimating the genetic contribution of species affiliation and paternal genotype to serum alanine aminotransferase levels in farm ruminants to identify the inheritance patterns, exploring their potential use as metabolic markers in sire selection programs. Animals of three species at comparable stages of physiological development, kept under conditions typical of each species including the 17–18-month-old Holstein bull calves (n = 29) produced from four bull sires, 4-month-old Romanov ram lambs (n = 31) produced from three ram sires, and Tuva Sarlyk highland 17–18-month-old yaks (n = 25), were used as the models for the investigation. The bulls and sheep were kept under appropriate conditions on the large livestock farms, while the yaks grazed freely in pastures year-round. The sample size was determined in accordance with the 3Rs principle (Replacement, Reduction, and Refinement) of minimizing the use of animals, Directive 2010/63/EU, considering the expected effect size, trait variability, required significance level (α = 0.05), and test power of the test (1-β > 0.80). The ALT levels in all the animals were within the physiological norm, averaging 11.7 ± 0.8 U/L, 17.2 ± 1.0 U/L, and 13.7 ± 1.1 U/L for bulls, sheep, and yaks, respectively. Species affiliation can explain 17% of genetic variability in the enzyme activity. In sheep, the ALT level exceeded that of the levels in cattle and yaks by 46.9% and 24.9%, respectively (p < 0.05). In the Holstein bull calves, the effect of the paternal genotype on the ALT activity accounted for 29% of the variability (p < 0.01). In rams, no similar influence of the sire’s genotype was revealed, which can indicate the species-specific genetic control of the enzyme. The interspecies differences and the paternal genotype influence on the ALT levels in progeny emphasize the roles of heredity and species-specific adaptations in regulating the ALT levels in ruminants, which can be used for health monitoring and improving breeding program.