The aim of this research was to evaluate selection studies towards increasing eggshell colour intensity and homogeneity, without reducing egg production of brown-egg-laying hens at the Poultry Research Institute of Ankara, Turkey. This study was based on data obtained from 1342 pedigree Barred Rock-1 (BAR-1), 1158 pedigree Rhode Island Red-1 (RIR-1) and 611 hybrid (RIR-1 x BAR-1 or ATAK-S) brown laying hens, where eggshell colour and egg production performances were determined. Hens were selected for dark, uniform shells and egg production performance, as paternal and maternal lines from RIR-1 and BAR-1 base populations. Colour coordinates; L* (brightness), a* (red/green scale), b* (yellow/blue scale) and eggshell colour index (SCI) were determined. The values of L*, b* and a* were significantly changed during the study. The estimated heritabilities for BAR-1 hens of egg weight (EW), L*, a*, b* and SCI were as follows: 0.62, 0.64, 0.62, 0.55 and 0.32; The RIR-1 hen values were as follows: 0.51, 0.74, 0.64, 0.22 and 0.39, respectively. It was concluded that the performance of parents and hybrids was better than that of the base populations, with respect to the characteristics studied.ARTICLE HISTORY

No abstract

This study examines the effect of grandparent, parent, and hybrid brown chickens, selected from 3 generations of pure lines, on hybrid egg-laying performance. The study was conducted at the Poultry Research Station of Ankara. In the first stage, 4 grandparent lines were derived from 2 pure line base populations. Grandparent lines included 2 male lines (low body weight and high egg weight) and 2 female lines (low body weight and high egg production). In the second stage, grandparent male and female lines were reciprocally crossed to produce 4 parent lines. In the third stage, male and female parental lines were crossed to produce 4 hybrid lines. The average age at first egg of grandparents, parents, and hybrids was 147.

The study was carried out to identify some production traits of the pure Barred Rock 1 (BR1) line and rapid × slow feathering line crosses derived from the BR1 pure line, in addition to F1 crosses of all these dam lines with Rhode Island Red 1 sire line. The BR1 line previously used a brown layer dam line for barred/non-barred day-old chick auto-sexing and synthetic slow and rapid wing feathering lines. Parent lines showed significant differences in sexual maturity and egg production (P < 0.01) and early embryonic mortality (P < 0.05). However, there was no significant difference in weight at sexual maturity, average egg weight, hatchability of fertile eggs, hatchability of total eggs set, and middle and late embryonic mortalities. A significant difference was found among F1 crosses with respect to weight at sexual maturity (P < 0.05), but no significant difference (P > 0.05) could be determined for age at sexual maturity and egg production. Overall, rapid feathering hens had better production traits than slow feathering hens. The dual crossbred parent lines exhibited almost the same level of egg production traits compared with the pure line.

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.