In the article it is noted that when the age of physiological maturity is reached, most of mares do not go hunting because of genital infantilism. The authors' studies showed that in the group where the repair filly had a systematic communication with the vasectomized stallions at 36 months of age, the reproductive apparatus was well developed, there were no signs of genital infantilism. All mares were found at the age of 36-37 months, and they became foal, at the mares of the control group at the indicated age the sexual cycles did not appear regularly, signs of genital infantilism were noted. The authors note that the vasectomized stallion provides, normal development of the reproductive sexual system of the repair mares, the full formation and manifestation of sexual cycles. The use of vasectomized stallions allows for an early effective prevention of genital infantilism and infertility in repair mares. Dosed communication of fillies with vasectomized colts and sterile coitus during sexual development promoted the physiological development of the genitals and the full manifestation of the sexual cycle.