Effect of exogenous estrogen treatment on gonadal morphology, morphometry and estrogen receptor alpha mRNA expression in gonads of male chickens (Gallus domesticus)

The current study was designed to investigate the post-hatching ERα expression in left gonads of male chickens along with gonadal morphology when the exogenous estradiol supply is continuous, assuming the gonadal ERα is the limiting factor to maintain the feminizing effects of the male to female sex reversal trials in chickens. Shaver brown chicken eggs were incubated with two in-ovo injections (0.1mg/egg) of estradiol cypionate.

Males hatched from treatment eggs were raised with (T2) and without (T1) weekly post-hatching injection of 0.1mg/chick estradiol cypionate intra muscularly. At 1, 4 and 8 weeks of age morphology and ERα mRNA expression of gonads were determined. ERα expression increased significantly with age (P<0.0001) in all groups and differed significantly among treatments (P<0.0001) where the highest expression observed at T2 followed by T1. However the interaction effect was insignificant (P=0.1203). All treated chicks showed left gonad similar to control female. However, T1 chicks showed a poorly developed right gonad while T2 showed a prominent right gonad which was similar to C male gonads. In conclution, the exogenous estrogen supply causes an increase in ERα expression in male left gonads with age in a diminishing pattern along with morphological and morphometric changes of gonads.