Rearing system, utility type and hens’ age as a factor modifying lysozyme's hydrolytic activity

<b>The aim of study was to analyze 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 material consisted of 120 eggs from two genotypes of hens: Hy-Line Brown and parent stock of Ross 308. Laying-type hens were reared divided into 2 systems: intensive (litter, balanced feed) and extensive (open runs, farm fodders). The second source of material was hens age (29, 33, 41, 53 and 70 wks) of the parent stock.. Stocks were differentiated in terms of the hens age (29, 33, 41, 53 and 70 wks). Eggs quality traits and LA were evaluated. The LA of was higher in eggs from laying than from broiler breeder hens. It decreased with the hens’ age and increased with albumen mass, it was also positively correlated with albumen height and Haugh's units. The rearing system considerably modified mass of egg and albumen and the dense albumen height, but does not affect the LA.

Selected Physical and Chemical Characteristics of Eggs Laid by Hens Fed Diets with Different Levels of Hybrid Rye

The aim of the study was to evaluate the effect of different levels of dietary hybrid rye on eggs laid by Isa Brown laying hens and their quality, such as physical parameters, nutritional value (basic chemical composition, cholesterol content, fatty acid profile) as well as safety (microbiological purity). A total of 72 Isa Brown hens aged 26 weeks were allocated to 3 groups fed with 0%, 15% and 25% levels of hybrid rye in their diet up to week 50. At week 50, 72 eggs per group were collected for analysis. The 25% rye level had no significant effect on most of the examined physical parameters; however, a tendency to heavier eggs in this group was noted. An increased rye level resulted in lighter yolks with a lowered share of redness and yellowness compared to those obtained from hens fed a control diet. The administration of 25% of rye in the diet influenced the basic chemical composition of the yolks by increasing the water content and reducing the fat content, but with no significant effect on the contents of ash, chlorides and cholesterol. The sum of saturated fatty acids in yolks decreased along with the increase in dietary rye level while the sum of mono- and polyunsaturated fatty acids increased. Moreover, a lowered ratio of ω-6: ω-3 fatty acids was found with dietary rye level increases.