Changes in egg production rate induced by progesterone injection in broiler breeder hens

A polycystic ovarian follicle (PCCF) syndrome associated with high baseline concentrations of progesterone (P-4) without preovulatory luteinizing hormone (LH) surges has been reported in turkey hens. The PCOF syndrome could be induced in turkey hens by injecting P4 (0.33 mg/kg per d) daily early in the reproductive period for 10 to 12 d and then waiting 3 wk for the syndrome to develop. It was hypothesized that an arrest in laying associated with the PCOF syndrome could be induced by daily injection of P-4 in restricted-fed broiler breeder hens. Hens were divided into 5 treatment groups and were injected subcutaneously daily with P-4 in canola oil at dosages of 0, 0.17, 0.33, 0.5, and 1.5 mg/kg per d for 13 d, at 14 wk of egg production when they were 41 wk of ace. Blood samples were collected on d 7 and 13 immediately, before P4 injection. Oviductal and ovarian morphologies were measured at necropsy I d after the last P-4 injection. Egg production rate was reduced by injection Of P-4 at dosages < 0.17 mg/kg per d. At dosages of 0.5 and 1.5 mg/kg per d, ovarian hierarchical follicles had regressed. None of the broiler breeder hens had the PCOF syndrome at necropsy, but a high incidence of hens holding hard-shelled uterine eggs for several days was observed. Concentrations of LH decreased with P-4 injection at >0.17 mg/kg per d, and P-4 concentrations were increased with P-4 injection at >0.5 mg/kg per d. Estradiol-17beta (E-2) concentrations were decreased at all P-4 dosages. It was concluded that egg production rate was reduced by daily injection Of P-4 at dosages >0.17 mg/kg per d, and egg production ceased and ovarian follicles and the oviduct regressed at dosages >0.50 mg/kg per d. The PCOF syndrome, however, was not induced in restrictedfed broiler breeder hens by P-4 injection.