Investigation on Functional Reserves of the Testosterone-Synthesizing System in the Blood of 12-Month-Old Heifers in Different Breeds

Abstract

The article presents the data on the functional activity of testosterone-synthesizing system in the 12-month-old black-and-white Holstein, Simmental, Aberdeen-Angus heifers, as well as cross-bred cows (Simmental x Aberdeen-Angus). The study had the following goals set: 1. To compare the data between the experimental groups of heifers of different breeds. 2. To carry out the functional stress tests of the testosterone synthesizing system in experimental heifers at the age of 12 months. 3. To study the functional activity of the testosterone-synthesizing system in experimental heifers of different breeds. 4. To calculate the activity coefficients of the testosterone-synthesizing system in experimental groups of heifers at the age of 12 months. The studies were carried out on black-and-white Holstein, Simmental, and Aberdeen-Angus heifers and their crossbred heifers (Simmental x Aberdeen-Angus). In order to determine the functional reserves of the testosterone synthesizing system, chorionic gonadotropin (CG) was intramuscularly administered at 12 months of age, and the activity of the testosterone synthesizing system was determined. The introduction of chorionic hormone at a dose of 0.5 units/kg causes hyperfunction of the testosterone-synthesizing system. Moreover, the maximum level of testosterone in the blood of heifers at 12 months of age was observed 24 hours after its third administration. The results of the effects of functional stress tests on the testosterone synthesizing system of the heifers indicate that the potential reserves of the testosterone synthesizing system in the Simmental and black-and-white breeds at the age of 6 months are lower than in Aberdeen-Angus and cross-breed animals.