The influence of prepubertal partial sinistral ovariectomy on the subsequent reproductive function of domestic hens (Gallus domesticus )

Each of 20 White Leghorn hens of 13 to 14 weeks were subjected to partial sinistral ovariectomy and sham-operations. In half of the hens from each group, the percentage of egg production and clutch size were noted until 50 weeks of age. The growing pattern of normal ovarian follicles was also recorded at 26 weeks of age in a rest half ofthe hens in the two groups. The percentage of egg production and the mean and variance of clutch size did not differ significantly (P / 0.05) between the partially ovariectomized and sham-operated groups. The growing yellow follicles (>8 mm) in the rapidly developing phase in these two groups did not vary, although the smaller follicles (4 to 8 mm in diameter) remained significantly (P / 0.01) more in the shamoperated control group than in the partially ovariectomized group. This observation indicates that smaller follicles (4 to 8 mm) developed in the larger (>8 mm) follicles more efficiently in partially ovariectomized hens than in the sham-operated (control) hens. In a second experiment, one group of hens had all the yellow follicles (>8 mm) removed, while a second group of hens was left untreated. On the 3rd and 6th day post treatment, the hens were examined for the presence of ovarian follicles. No significant (P / 0.05) difference in the growing pattern of subsequent follicles (2 to 4 or 4 to 8 mm) was detected due to treatment. These data demonstrate that the mechanisms that regulate follicular growth and atresia are adjust to maintain normal ovulation following partial ovariectomy.