Abstract
The objective of the study was to evaluate the quality of eggs laid by native breed hens of different ages (33 and 53 weeks of age), with particular consideration of the lysozyme parameters. Eggs were collected from 6 breeds/strains of laying hens under the genetic resources conservation in Poland, i.e. Greenleg Partridge (Z-11), Yellowleg Partridge (Ż-33), Rhode Island Red (R-11), Rhode Island White (A-33), Sussex (S-66) and Leghorn (H-22). The yolks of eggs from older hens had a more favourable, intense colour, but the freshness parameters (albumen height and Haugh units) of these eggs were lower. The albumen of eggs from older hens showed greater content and higher enzymatic activity of lysozyme in both thin and thick albumen. Among the six strains of hens, lysozyme content and enzymatic activity were highest in the egg albumen of strains Ż-33, Z-11 and R-11, and lowest in that of strain H-22. The analysed eggs showed statistically significant correlations between some interior egg quality traits (albumen weight, albumen height, Haugh units, yolk colour) and the discussed enzyme parameters. These traits are influenced by genotype and age of the hens.