Eggshell and Bone Quality in Two Different Genetic Groups of Aged Layer.

Abstract

The present study was conducted on two aged commercial laying breeder strains (Hy-Line Brown and Hy-Line W-36) to evaluate genetic differences of eggshell and bone quality (at 71 and 72 wks of breeders’ age, respectively). In addition, mortality rate, egg production performance (Beginning from 60 to 70 weeks of layer breeders' age), internal organs and reproductive measurements (at 72 wks of breeders’ age) were also determined. Brown layer breeder strain at the end of laying cycle had significantly higher mortality rate compared to the white one. White layer breeder hens had significantly higher percentages of hen-day and hen-housed egg production (59.91 and 45.82%, respectively) compared to the brown one (55.27 and 35.27%, respectively). Brown Hy-Line layer breeder strain had better eggshell quality (wet or dry shell weight, shell percentage, shell thickness and eggshell breaking strength) than W-36 Hy-Line layer breeder strain. While, no significant difference was detected between the two layer breeder strains for egg weight or egg shape index. No significant differences between breeder strains for shank length, relative liver weight and abdominal fat percentage were detected. The white layer breeder strain had significantly higher relative oviduct weight (4.54%) compared to the brown one (3.23%). Brown layer breeder strain recorded higher humerus width (8.25mm) in comparison with the white one (7.90mm). Tibia bone weight of brown layer breeder strain had significantly heavier by 22.87% as compared to the white strain. Also, the brown breeder strain recorded higher tibia width, thickness and strength in comparison with the white one. Tibia bone strength of brown layer breeder strain had greater by 33% than that of the W-36 layer breeder strain. A positive correlation coefficients were detected between humerus bone strength and both eggshell thickness and strength in brown and white strains.