GENETIC RESPONSE OF BODY WEIGHT, SECONDARY SEXUAL CHARACTERS AND HATCHABILITY OF GIMMIZAH CHICKENS SELECTED FOR BREAST CIRCUMFERENCE

Abstract

This experiment was conducted to study the effect of long term selection for breast circumference (BC) of Gimmizah (GM) chickens on some body measurements of males at 12, 25 and 45 weeks of age such as body weight (BW), BC, shank length (SL), and secondary sexual characters as comb length (CL) and wattle length (WL), besides fertility with hatchability and their genetic parameters. Two hundred and twenty GM hens with twenty males were randomly chosen and considered as base population (G0). Chicks produced from G0 were selected for BC at 12-wk of age and selected through additional five generations. The results revealed that selection for BC significantly increased BW at 12-wk of age for selected line compared to control one among 4 and 5 th generations. Comb length for selected lines had significantly increased compared to control lines for CL12 in G4 and G5. Wattle lengths for selected lines were increased (p˂0.05) in the last three generations compared to the rest ones among all the experimental ages. There were a significant improvement of fertility and hatchability of fertile eggs percentages among the subsequent selected generations. Most of heritability ( estimates for CL and WL were considered high and ranged between 0.50 and 0.78. Low estimates of were recorded for which ranged between 0.02 to 0.14 and for hatchability of fertile eggs between 0.02 and 0.05. Furthermore, CL represented high genetic correlation with fertility among the bird's ages and generations. In conclusion, body circumference could be used as selection tool for improving body weight and secondary sexual characters without detrimental effect on fertility, besides suggesting other body measurements as shank, comb and wattle lengths could be included in selection index.