The experiment compared the effects of strain and age on egg quality characteristics in ISA Brown, Hisex Brown and Moravia BSL brown-egg laying hens. One hundred and eight ISA Brown hens, forty-five Hisex Brown and forty-five Moravia BSL 20 to 60 weeks old were housed in conventional cages (550 cm 2 per hen). Feed and water were available ad libitum. Eggs were sampled at 21-day intervals, every collecting week 150 eggs per genotype in three age periods, from 20 to 26 weeks, 37 to 43 weeks and 54 to 60 weeks of age. A total of 4,050 eggs were examined. Egg quality characteristics were affected by genotype and age. Egg weight, yolk weight and percentage, Haugh Units increased with the hens' age in all genotypes, but albumen and eggshell percentage decreased, eggshell thickness and strength improved with age. The highest egg weight (65.3 g) and yolk quality (yolk index 45.1%) were found in Moravia BSL at the end of the experiment. In contrast, the best albumen quality (albumen percentage 60.0) values were in Hisex Brown and the eggshell quality measurements (eggshell thickness 0.38 mm) were higher in ISA Brown. -egg layers, strain, ISA Brown, Hisex Brown, Moravia BSL, age, yolk, albumen, shell quality, correlation Brown

Eggshell quality is one of the most significant factors affecting poultry industry; it economically influences egg production and hatchability. Eggshell consists of shell membranes and the true shell that includes mammillary layer, palisade layer, and cuticle. Measurements of eggshell quality include eggshell weight, shell percentage, breaking strength, thickness, and density. Mainly eggshell thickness and strength are affected by the time of egg components passage through the shell gland (uterus), eggshell ultra-structure (deposition of major units), and micro-structure (crystals size and orientation). Shell quality is affected by several internal and external factors. Major factors determining the quality or structure of eggshell are oviposition time, age, genotype, and housing system. Eggshell quality can be improved through optimization of genotype, housing system, and mineral nutrition.

ABSTRACT:The objective of this study was to compare the performance, egg quality, and microbial contamination of egg shells from hens maintained in different housing systems, such as conventional and enriched cages, litter, and aviaries. The housing system significantly (P < 0.001) influenced the performance characteristics. The highest egg production, lowest daily feed consumption, and feed conversion ratio were measured in conventional cages compared to litter and aviaries. Higher egg shell and albumen qualities were observed in conventional cages, whereas hens housed in enriched cages and aviaries laid eggs with a higher yolk index (P < 0.001). The housing system significantly (P < 0.001) influenced the total count of bacteria on the egg surface and the microbial contamination of Enterococcus and Escherichia coli. The lowest values for the total count of bacterial contamination (P < 0.001) were found in eggs from conventional cages (4.05 log colony-forming units (CFU)/egg) and enriched cages (3.98 log CFU/egg). Eggs from aviaries had 5.49 log CFU per egg, and the highest level of contamination was observed in eggs that were laid on litter (6.24 log CFU/egg). The level of the microbial contamination of egg shells from litter and aviaries was by 2 log CFU higher than in eggs from cages. It could be concluded, from the viewpoint of egg safety, a more suitable substitute for conventional cages are enriched cages and aviaries than litter.

ABSTRACT:In an experiment with three strains of Dominant genotype the effect of oviposition on egg quality characteristics was investigated. Laying hens of the Blue strain (group 1), Plymouth Rock (group 2) and their F1 cross (group 3) from 20 to 64 weeks of age were housed on litter (9 birds per m 2 ). The collection time was at 6.00, 10.00 and 14.00 h. Eggs were gathered in a 28-day interval, every two days all produced eggs (720 eggs in total). The time of oviposition was influenced by genotype. The highest number of eggs was collected in the Plymouth Rock strain at 6.00 (53.5%) and the lowest in the Blue strain at 14.00 (11.1%). There were interactions between the time of oviposition and genotype in egg weight. Eggs laid in the morning at 6.00 were significantly heavier (60.5 g, 64.9 g and 62.1 g) in comparison with eggs laid in the afternoon (59.3 g, 62.4 g and 62.7 g). The heaviest eggs were produced by the Plymouth Rock strain. Significant interactions were observed in eggshell weight when the heaviest eggshell was in afternoon eggs (5.6 g, 5.8 and 5.9 g) and F1 genotype. The egg shape index was also affected by the genotype and time of oviposition. Among the albumen quality characteristics only Haugh Units were influenced by genotype and significantly higher numbers were determined in the Plymouth Rock strain (85.0, 85.3 and 84.7). The genotype significantly affected also the yolk index which was the highest in F1 genotype (45.4%, 45.4% and 44.5%).

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