Rearing system, utility type and age of hens as factors modifying the hydrolytic activity of lysozyme

The aim of study was to analyse the impact of the utility type, age and rearing system of hens on egg quality traits and the enzymatic activity of egg albumen lysozyme (LA). The research material consisted of eggs from two genotypes of hens: Hy-Line Brown laying hens and Ross 308 parental stock (meat-type). Laying-type hens were reared in two systems (60 eggs/system): intensive (litter, balanced feed) and extensive (open runs, on-farm fodder). The second variable was the age of hens from the parent stock (29, 33, 41, 53 and 70 wks; 60 eggs/age). Selected quality traits of eggs (egg weight, albumen weight and its proportion in the egg, albumen height, and Haugh unit) were measured, as well as albumen lysozyme activity. The rearing system significantly modified egg weight, albumen weight, and thick albumen height, but did not affect LA. LA also did not depend on the utility type of birds; however, it decreased after 33 weeks of age. The enzymatic activity of lysozyme was highly negatively correlated with the age of hens, and positively with albumen height and Haugh unit.