Assessing Differences in the Quality Properties and Ultrastructure of Eggshell as Affected by Chicken Strain and Flock Age During Incubation Period

Three hundred hatching eggs from two layer breeder flocks (Hy-Line Brown and hy-Line W-36; 150 each) were obtained at three different periods of laying cycle (early, middle and late stages). The hatching eggs were randomly taken to assess the impact of chicken strain, age, and hatching time on some eggshell measurements and structures. Results indicate that egg weight, shell percentage and shell thickness were significantly affected by strain, breeder age, and incubation time. Increasing rate of calcium absorption and utilization by the embryos during the embryonic stage clearly reflects the decrease occurred in eggshell strength. The differences of eggshell breaking strength during incubation time periods were 0.41 and 0.55 kg/cm2, the differences due to the incubation time may be due to the higher demand for calcium utilization in the late incubation period (18 days), observed on the10th day of incubation. Brown eggs recorded significant higher calcium percentage in eggshell compared to the white ones. The brown breeder hens recorded significant higher total pores per egg compared to the white egg. Concerning eggshell ultrastructure, total thickness of the brown eggshell was significantly higher than those of the white eggshell by about 3.7%. All parameters, except for total thickness, were significantly affected by the interaction between strain and breeder age. Finally, we conclude that some traits including egg weight, shell percentage, shell thickness, calcium percentages in eggshell, and total pores per egg were significantly affected by strain, breeder age, and incubation time. Eggshell ultrastructure of brown egg was better compared to the white ones.(AU)

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

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.(AU)

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

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.