Abstract: [Objective] To assess the effects of human chorionic gonadotropin （hCG） on follicular development, ovulation rate, pregnancy rate and serum reproductive hormone level in jenny.[Method] A total of 60 jennies with dominant follicle diameters of 30-35 mm （n=30） and larger than 35 mm （n=30） were selected. For either of the two jenny herds with different dominant follicle diameters, a 500 IU/head hCG treatment group （n=10）, a 1 000 IU/head hCG treatment group （n=10）, and a control group （n=10） without hCG treatment, were set respectively. The experimental jennies received hCG treatment by intramuscular injection. B-ultrasound examination were carried out every 24 h to observe the follicular development status, and the follicle diameters were determined. The heads of ovulated jennies were recorded, and the ovulation rate was calculated. Artificial insemination was performed. Pregnant examination was carried out on 18^th day after insemination. The heads of pregnant jennies were recorded, and the pregnancy rate was calculated. The serum levels of estradiol （E₂） and progesterone （PROG） were measured at 0, 24, 48 and 72 h after hCG treatment. [Result] In both of the jenny herds, the follicle diameters were increased with the elevation of hCG dosage; for the jennies with dominant follicle diameters larger than 35 mm, the two treatment groups ovulated within 24 h after receiving intramuscular injection of hCG, while no ovulation was observed in the control group; in both of the jenny herds, the ovulated heads and ovulation rate of the treatment groups were increased compared with their corresponding control groups at 48 h after hCG treatment; for the jennies with dominant follicle diameters larger than 35 mm, the ovulation rate reached up to 100% at 72 h after 1 000 IU/head hCG treatment; in both of the jenny herds, the conception rates of the hCG treated jennies were higher than those of the controls, and showed an increasing trend with the elevation of hCG dosage. For the jennies with dominant follicle diameters larger than 35 mm, the pregnancy rate reached up to 50% at 72 h after 1 000 IU/head hCG treatment. In both of the jenny herds, the serum E₂ levels were largely increased at 24 h after 1 000 IU/head hCG treatment compared with that at 0 h, and the serum PROG levels also exhibited an overall increasement during 0 to 72 h. [Conclusion] Intramuscular injection of hCG improves the ovulation rate, pregnancy rate and serum levels of E₂ and PROG of jenny, and the dosage of 1 000 IU/head has better efficacy.

Key words: jenny, human chorionic gonadotropin, dominant follicle, ovulation