Sexual cycle regulation endocrine mechanisms and folliculogenesis peculiarities in beef cows and heifers in coupling age

The purpose of research is to study the endocrine mechanisms of regulation of folliculogenesis, as well as to develop biotechnical methods to increase the reproduction of the broodstock of cows, the Kazakh white-headed breed and the Hereford breed. The study was carried out on the basis of the Federal State Budgetary Educational Institution of Higher Education Russian State Agrarian University - Moscow Timiryazev Agricultural Academy and FSBEI HVE “Volgograd State Agrarian University” in 2012-2018, as well as in farms of various organizational and legal forms of ownership of the North Kazakhstan and Akmola Regions of the Republic of Kazakhstan and the Volgograd Region of the Russian Federation. It has been established that the sexual cycle in beef cows with one wave of follicle growth is 19 days, in cows with two waves of follicle growth - 21 days, three - 24 days and four waves of growth - 28 days. Subdominant follicles undergo atrisia against the backdrop of low FSH and high progesterone concentrations, after a period of relative stability between 6 and 10 days of the estrous cycle, the dominant follicle reaches a maximum diameter of 13-19 mm on the 6th-7th day of the estrous cycle. The use of the drug surfagon before insemination of cows, its effectiveness was 20.0 %, and in combination with progesterone, i.e. with preliminary gestogenization, the effectiveness was 34.0 %, in the third group, in animals that were injected with surfagon against the background of PMSG, the effect was 66.0 %. Under the use of synthetic prostaglandins in the period from 6 to 18 days of the sexual cycle, the effect is: clatraprostin - 50.0 %, estufalan - 50.0 %, but superfan and estrofan - 46.7 %. The combination of clatraprastin with PMSG gave an effect of 69.4 %, follitropin - 72.2 %, the use of estuphalan with PMSS - 71.4 %, and with follitropin - 70.3 %. The introduction of superfan with GSFA gives an effect of 71.9 %, and with follitropin - 72.9 %.