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The quality of egg shell and bone properties of hen are important for hen welfare, consumers, and producers. Parameters of the genetic selection have both desirable and undesirable effects among themselves. Until recently, it has been stated that the concept of shell quality is not only about breaking strength, thickness, and weight of shell, but also microscopic properties of the shell. In this study, the effect of index selection including age and weight at sexual maturity, number of eggs and egg weight on eggshell structures, hatching results, and hybrid performance was determined. Ninety Barred Rock 1 (BAR-1) and ninety Rhode Island Red 1 (RIR-1) hens and twenty RIR-1 cocks (46 weeks old) were used. BAR-1 and RIR-1 were classified according to the breeder index value as low and high. Egg quality characteristics, embryo development and hatching results were examined in eggs obtained from these lines. In the hybrid eggs with high breeder index, the thickness of the palisade layer, breaking strength, ash, and Ca level of the shell were lower and cone similarity and egg weight were higher than that with low breeder index. The breaking strength of the egg shell had a significantly positive correlation with the palisade layer thickness of the shell. In addition, the tibia weight of the high breeder index group was lower than that of the low breeder index group. Differences in femur and tibia weights in hybrids with low and high breeder index increased with age. A negative correlation was observed between hatchability and the thickness of the palisade layer. Further studies are needed to determine which selection programs positively affect the thickness of the palisade layer, the Ca level and the breaking strength of the shell, the number of broken eggs, and the tibia weight in layer hybrids.

The quality of egg shell and bone properties of hen are important for hen welfare, consumers, and producers. Parameters of the genetic selection have both desirable and undesirable effects among themselves. Until recently, it has been stated that the concept of shell quality is not only about breaking strength, thickness, and weight of shell, but also microscopic properties of the shell. In this study, the effect of index selection including age and weight at sexual maturity, number of eggs and egg weight on eggshell structures, hatching results, and hybrid performance was determined. Ninety Barred Rock 1 (BAR-1) and ninety Rhode Island Red 1 (RIR-1) hens and twenty RIR-1 cocks (46 weeks old) were used. BAR-1 and RIR-1 were classified according to the breeder index value as low and high. Egg quality characteristics, embryo development and hatching results were examined in eggs obtained from these lines. In the hybrid eggs with high breeder index, the thickness of the palisade layer, breaking strength, ash, and Ca level of the shell were lower and cone similarity and egg weight were higher than that with low breeder index. The breaking strength of the egg shell had a significantly positive correlation with the palisade layer thickness of the shell. In addition, the tibia weight of the high breeder index group was lower than that of the low breeder index group. Differences in femur and tibia weights in hybrids with low and high breeder index increased with age. A negative correlation was observed between hatchability and the thickness of the palisade layer. Further studies are needed to determine which selection programs positively affect the thickness of the palisade layer, the Ca level and the breaking strength of the shell, the number of broken eggs, and the tibia weight in layer hybrids.