Functional reserves of the testosterone-synthesizing system in the blood of heifers of different breeds

Abstract

Purpose: Ihe research was conducted to study the functional reserves of the testosterone-synthesizing system of heifers at the 6th month of pregnancy.Materials and methods. The response of the testosterone-synthesizing system of heifers of different breeds to stimulation with chorionic gonadotropin was studied. For the experiment, three breeds of heifers were used (Holstein black-and-white, Simmental and Aberdeen-Angus) and crossbred heifers obtained from crossing the Simmental and Aberdeen-Angus breeds. They were formed into 4 groups of 10 heads in each group by breed and had the same pregnancy period. To assess the functional reserves of the testosterone-synthesizing system, chorionic gonadotropin HCG was injected intramuscularly at a dose of 3-4 thousand m.e. depending on the live weight of the animal at the 6th month of pregnancy. HCG was administered to the heifers three times with an interval of 72 hours. Blood for the determination of testosterone levels was taken before the administration of HCG and 2.12.24, 48 and 72 hours after each administration.Results. It has been established that Aberdeen-Angus breed heifers and crossbred animals that have a higher activity index of the testosterone-synthesizing system have higher functional reserves of the testosterone-synthesizing system in relation to non-heifers of Holstein black-and-white and Simmental breeds. After triple stimulation, the testosterone concentration in black-and-white heifers increased 2.3 times, and in Simmental 2.6 times, in Aberdeen-Angus and crossbreeds 2.9 times.The calculation of the activity index of the testosterone-synthesizing system in black—and—white heifers was 1.3, in the Simmental breed 1.59, Aberdeen-Angus - 1.91, in crossbreeds - 1.92. Conclusion. Thus, the functional loads carried out showed that the higher functional reserves of the testosterone- synthesizing system were possessed by heifers belonging to the Aberdeen-Angus breed and crossbreeds (Aberdeen-Angus x Simmental), which have a higher index of activity of the testosterone-synthesizing system in relation to the heifers of the black-and-white and Simmental breeds.