Abstract
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.
Highlights
Table eggs are a valuable component of the daily human diet, and they include readily available protein, vitamins, and a variety of trace elements (Anton et al, 2006)
The study material consisted of eggs collected from 6 breeds/strains of laying hens included in the conservation programme 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)
Except for the shape index, albumen height and Haugh units, all the egg quality traits were at the same time influenced by genotype and age
Summary
Table eggs are a valuable component of the daily human diet, and they include readily available protein, vitamins, and a variety of trace elements (Anton et al, 2006). After analysing the results of many international studies, it was hypothesized that in this large population of hens under conservation in Poland, not selected for many years, interior egg quality traits are highly related to the level of valuable lysozyme. This enzyme is one of the most valuable natural substances, which likely has a greater potential than has been identified, and hen’s egg albumen is the only source from which it can be obtained on a commercial scale. The study will answer which of the studied strains of native hens lays eggs with the highest lysozyme content and determine the effect of layer age on this egg quality trait
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