Genetic and Phenotypic Trend and Inbreeding Effects for Sexual and Egg Production Traits of Iraqi Local Chickens

Abstract

A study was conducted to estimate genetic and phenotypic trend and inbreeding effect on a sexual and egg production trait in Iraqi brown local chickens. Data on 2234 hens raised in poultry research stations from successive 6 generations of selection for high egg production during the first 24 weeks of production were used. Data of age at sexual maturity (ASM), body weight at sexual maturity (BWSM), first egg weight (FEWT), egg weight (EW), egg number (EN), and egg mass (EM) were recorded individually. The univariate animal models under Average Information Restricted Maximum Likelihood (AI-REML) of Wombat package were applied to estimate the heritability, BLUP-breeding value and inbreeding rate. The heritability estimates based on individual animal model was 0.39±0.05, 0.42±0.05, 0.17±0.04, 0.68±0.04, 0.40±0.05 and 0.40±0.05 for the traits mentioned above respectively. Average breeding values across generation tend to be positive in productive traits but it was negative in ASM, BWSM and FEW. The overall predicted genetic gains, after 6 generations of selection, estimated by the regression coefficients of the breeding value on generation number were equal to -0.010, 0.029, 0.033, -0.397, -1.514, and -41.541, for ASM, BWSM, FEWT, EW, EN and EM, respectively. In conclusion, the moderate to high heritability estimated for egg production traits suggested that these traits could be improved through selection. The effect of the inbreeding rate negatively on some traits and positively on other traits suggested that both traits could not be improved simultaneously using additive selection. The inconsistency between phenotypic and genetic trends suggests that genetic progress was not achieved in a higher magnitude.