Abstract
The present study was conducted on pair aged commercial laying breeder strains (Hy-Line Brown and Hy-Line W-36) to evaluate genetic differences of eggshell and bone quality. In addition, egg production performance, mortality rate, internal organs and reproductive measurements were determined. Correlation coefficients among some eggshell and bone traits were calculated. White layer breeder hens had significantly higher percentages of hen-day and hen-housed egg production compared to the brown one. Brown Hy-Line layer breeder strain had better eggshell quality compared to W-36 Hy-Line layer breeder strain. The white layer breeder strain had a significantly higher relative oviduct weight compared to the brown one. Brown layer breeder strain recorded the higher humerus width in comparison with the white one. Tibia bone weight of brown layer breeder strain was significantly heavier by 22.87% as compared to the white strain. Moreover, the brown breeder strain recorded the higher figure of tibia width, thickness, and strength. In conclusion, at the end of the laying cycle, brown Hy-Line layer breeder strain exhibited better eggshell quality, body weight and tibia bone quality than those of W-36 breeder strain. Positive correlation coefficients were detected between humerus bone strength and both eggshell thickness and strength in brown and white strains.