Differential development of sex-related characters of chickens from the GSP and PNP/DO inbred lines after left ovariectomy.

To elucidate strain differences in the sex reversal of genetic females to phenotypic males, GSP and PNP/DO females were left ovariectomized (ovx) between one to three days after hatching, and the degree of masculinization based on sex-related characters, histological analysis of the right gonad and hormone assay were assessed at one year of age. The GSP and PNP/DO inbred lines were both derived from the Fayoumi breed and are only differentiated based on the red blood cell antigen type carried by each inbred line. Combs and wattles were found to be significantly bigger (P<0.05) in the GSP ovx compared with the PNP/DO ovx chickens, although male plumage patterns were more pronounced in the PNP/DO ovx. Spurs were observed both in the GSP and PNP/DO ovx chickens with no significant difference (P>0.05) in length compared with the respective male controls, and body weight was not significantly different (P>0.05) compared with the female controls. The weight of the right gonad was significantly heavier (P<0.05) in the GSP ovx than in the PNP/DO ovx. Positive correlations were found in the sex-related characters as well as the plasma testosterone level and right gonad weight in both the GSP and PNP/DO ovx chickens, but not in the spur length, which showed a negative correlation in the PNP/DO ovx chickens. Histological analysis revealed that the right gonads of the PNP/DO ovx chickens were morphologically developed compared with the GSP ovx chickens, which showed more advance stages of spermatogenesis. It could be inferred that PNP/DO females that exhibit a hereditary persistent right oviduct are more responsive to the masculinizing effect of ovariectomy compared with GSP females, suggesting that genetic background may have a possible contribution to the degree of masculinization and subsequent development of sex related characters.