Comparison of chemical composition of eggs from laying hens housed in different production facilities

Anotace: Eggs as a part of human diet dates to the prehistoric period. After the domestication of Gallus species, Gallus gallus domesticus and their eggs spread across the globe. Eggs proved to be one of the best and affordable sources of nutritionally important components in human diet, such as proteins, vitamins, lipids and some dietary significant elements. Progress in egg production methods, in European union, is recently mostly focused on the improvements in the field of welfare of laying hens, which is part of the plan set by European union council directive 1999/74/EC. Nowadays there are 4 main egg production systems divided by the way of keeping laying hens – Enriched cage, Free range, Barn and Organic. The aim of this study was to evaluate the impact of different hens housing systems on elemental (Ca, K, Mg, Na, P, Ca, K, Zn), total protein and lipid composition of whole eggs, yolk and albumen. Elemental analysis was performed by ICP-OES, total lipid content by Kjehldahl method and total lipids by Soxhlet extraction. Differences in whole egg were found in 8 from 9 tested parameters – K, Mg, Ba, Fe, P, Zn, total lipids and proteins. Assessment of the differences were done by ANOVA and Tukey`s test. Production systems were also successfully differentiated by principal component analysis. It was found that eggs from alternative production systems did not exhibit higher nutritional value than eggs from conventional cage facilities. In the case of total protein, conventional eggs contained highest average amount. It was also evident, that impact on chemical composition is difficult to assign to production system in general, which was confirmed by alternative studies from this field, which in many cases considerably differs.