DefinePK

Abstract

The mechanism of natural selection of the dominant follicle and hormonal regulation of this process in cattle is still insufficiently studied. The purpose of the study was to study the dynamics of the growth of subdominant and dominant follicles in Holstein cows and optimize the technique of scanning the ovaries during the estrus cycle, measuring the parameters of follicle growth, analyzing the results of sonograms and determining the concentration of estradiol in the pre-ovulatory period. To study the growth dynamics of subdominant and dominant follicles, the method of scanning the ovaries of cows during the estrous cycle using PU2200Vet devices and the Mindray Z5 Vet ultrasound scanner equipped with a convex endorectal sensor with a frequency of 5.0-7.0MHz was used. Two or three waves of dominant follicle growth with a duration of 4 to 12 days were detected in the studied animals. The maximum area of dominant follicles ranged from 191.18 to 243.18mm2. It is proved that the growth of dominant follicles in cows during the spontaneous estrous cycle is accompanied by an increase in the subdominant follicle population, per dominant follicle corresponds from 13.66 to 21.0 subdominant follicle. According to the results of the study, the growth rate of dominant follicle was higher compared to the growth of subdominant follicle, the growth rate of dominant follicle was from 0.9 to 4.43mm/day, this indicator for subdominant follicle was from 0.26 to 1.40mm/day. In the pre-ovulatory period, cows have a decrease in the amount of estradiol in the blood serum. The use of Doppler ultrasound scanning of the blood vessels of the corpus luteum allows determining the functional activity of the corpus luteum of the estrous cycle.