Studies on Sexual Dimorphism in a Cross River Ecotype Local Chicken – Rose Comb (Gallus gallus domesticus)

Sexual dimorphism in the local chicken (Gallus gallus domesticus)-Rose Comb- in Cross River was investigated. Sixty (60) male and female Gallus gallus domesticus chickens were evaluated for the effect of sex on body weight (BW), body length (BL), body girth (BG), thigh length(TL), shank length (SL) and keel length (KL) which were measured fortnightly for twelve (12) weeks. Sexual Size Dimorphism Index (SSDI) and Sexual Dimorphism Index (SDI) were used to confirm relative contribution of each trait to total dimorphism. The values obtained for SSDI and SDI respectively were 1.61 and 61% for BW; 1.26 and 26.52% for TL; 1.23 and 23.81% for SL; 1.22 and 21.50% for BL; 1.18 and 18.20% for BG; 1.17 and 17.94% for KL. To identify the best trait for predicting sex, stepwise discriminate analysis was employed and the Wilk’s Lamda values obtained were BW(0.471); TL(0.452); SL(0.401); BL(0.283); BG(0.272) and KL(0.271). Results showed that there were significant (p<0.05) differences in all measured parameters at week 6 with mean BW, BL, BG, SL, KL and TL of 300.01 and 253.24; 22 and 18.62; 5.20 and 3.98; 4.60 and 3.50; 5.50 and 3.90; 13.10 and 11.20 for both male and female birds respectively. These results indicate that sexual dimorphism is exhibited in all morphometric traits in favor of the male with BW as the highest dimorphic trait. The study also helps for the selection of Gallus gallus domesticus for improvement in meat production and address the problem of sex discrimination during selection for mating before sexual maturity.