Genetic study of external egg quality traits of native chicken of North of Iran

In the present research, direct and maternal genetic parameters were estimated for external egg quality traits of north of Iran native chickens. Six different animal models with restricted maximum likelihood (REML) method were applied to estimate genetic parameters. External egg quality traits including egg weight (EW), egg shell weight (ESW), egg shell strength (ESS), egg shell thickness (EST), egg shell percent (ESP), egg width (EWD), egg length (EL), egg specific gravity (ESG),egg surface (ES), egg volume (EV) and shell weight per unit of surface area (SWS) were measured on 1540 eggs. The eggswere collected from three different hatchs, in three sequential days from 769 hens. These hens were belonged to the lastgenerations of a pedigreed native chickens that were kept at the Mazandaran chicken Breeding Center of Iran. Estimated direct and maternal heritabilities were based on the best selected models using likelihood ratio test (LRT). Direct heritabilities were 0.331 for ESP, 0.349 for ESG, 0.55 for ES, 0.315 for EWD, 0.314 for EL, 0.147 for ESS, 0.435 for EST,0.526 for ESW, 0.422 for SWS and 0.548 for both EV and EW. The maternal heritabilities were minimum 0.008 for EWD, ESS and maximum 0.013 for EST. Consequently, repeatability values ranged from moderate (0.330, 0.383) for EWD and EL to high (0.716, 0.715, 0.715) for ES, EV and EW, respectively

Keywords:

genetic parameters , egg quality traits , native chicken , REML