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The aim was to assess the internal and external quality of consumer eggs of egg-laying hens of two selected genotypes depending on their age. All of these hens were kept in enriched cages. There were compared eggs from Hy-Line Brown and ISA Brown hens at the age from 36 to 64 weeks. In total, 3840 eggs from 300 hens were evaluated. Quality of eggs was determined by their technological value. Statistically significant interactions (P = 0.001) between age and genotype were found in all evaluated parameters except for the yolk colour (P = 0.044), whereas there was not found interaction (P = 0.072) between age and genotype in eggshell strength. The significant effect of hens' age was found in all evaluated parameters, with the only exception of the yolk colour. The results showed that the average weight of eggs, eggshell, albumen and yolk increased with the age. Also the eggshell proportion, its colour and yolk index values increased, whereas the egg shape index, eggshell thickness and strength, albumen proportion, Haugh units, the albumen and the yolk index decreased. Statistically significant effect of the genotype was found in all evaluated parameters except for the yolk index. When comparing both genotypes, the eggs from ISA Brown hens had a better quality. The trend of deteriorating egg quality with age was confirmed.
Kraus et al. (Mon,) studied this question.