Follicular waves in female cattle

Purpose : to study and summarize data from domestic and foreign authors on the mechanisms of follicular waves in female cattle, the cyclical nature of their manifestation, and the influence of various factors on them.The maturation of follicles within the reproductive cycle in female cattle occurs in waves. Using ultrasound diagnostics and blood sampling for estradiol levels, it was found that in the sexual cycle of cattle, from one to four follicular waves are formed during the estrous cycle. Follicular waves consist of groups of growing follicles with a diameter of ≥ 4 mm, from which the dominant follicle is selected, while the remaining follicles undergo atresia. If the dominant follicle reaches its maximum size (>10 mm) during the wave, ovulation occurs – the cycle becomes two–wave, if it does not reach, then another wave begins, if the follicle reaches its maximum size during it, the cycle becomes three-wave. The frequency of occurrence of follicular waves affects the duration of the sexual cycle – three-wave cycles are longer than two-wave cycles. The use of knowledge about follicular waves is of particular importance for practical purposes, since in the future it will improve the reproduction rates of cattle by improving approaches to selecting the optimal scheme for synchronizing sexual hunting of animals, reducing the cost of insemination and increasing its effectiveness.