No abstract

In the last few years, interest in the supplementation of selenium (Se) to animal feed has increased. The results of various studies have shown that eggs with defined selenium content may be used as a new potential source of this scarce element in human nutrition. The selenium content in eggs after dietary supplementation in organic form is about 22-27 µg/egg. This amount represents up to 40-50% of the Recommended Dietary Allowance, which is 55 µg of Se for the adult human. Additionally, due to its antioxidant properties, selenium contributes to the oxidation stability of fat and protein in the eggs of laying hens fed a selenium-supplemented diet. Therefore, selenium addition can affect certain properties of eggs and improve their shelf life. The results of investigations into the physico-chemical properties of different forms of Se have proven that dietary supplementation in the organic form shows higher biological availability than inorganic selenium.

The aim of the present study was to assess the effects of selenium feed supplements on the functional properties of eggs. The hens in experimental groups were fed diets supplemented with 0.2 mg/kg selenium from sodium selenite (Group 1), selenium-enriched yeast (Group 2), synthetic L-selenomethionine (Group 3), or hydroxy analog of selenomethionine (Group 4). The Control Group (Group C) was fed with basal feed without supplementation. The highest values of albumen gel firmness were shown in Group C eggs; differences with all experimental groups were significant (p \ 0.001 to p = 0.009). It was ascertained that albumen gel firmness correlated with albumen pH (r s = 0.490; p \ 0.001), which was highest in eggs from non-supplemented hens. Group 1 eggs and Group C eggs showed lower albumen foaming capacity (p \ 0.001) compared to eggs from other groups. Both albumen foaming capacity and albumen foam stability were higher in Group 2 eggs than in Group C eggs (p \ 0.001). The highest yolk foaming capacity was found in Group 2 eggs (p \ 0.001). Sponge cakes baked with Group C eggs had a smaller volume than those baked with eggs from Group 2 (p = 0.005), Group 3 (p = 0.004) and Group 4 (p = 0.024). The results of the study confirmed that selenium added to the laying hen feed significantly affected the monitored functional properties of both albumen and yolk. The most distinctive effect of selenium was shown in eggs from the group supplemented with selenium-enriched yeast, for which the results of albumen foam capacity and stability and yolk foaming capacity were the best.

The aim of this study was to assess the effects of four types of selenium (Se) feed supplements on the indicators of the oxidative stability of egg yolk. A total of 1,740 Bovans Brown laying hens were divided into 4 experimental and 1 control group. The diets fed to the experimental groups were supplemented with 0.2 mg/kg of Se, provided as sodium selenite, Se-enriched yeast, synthetic L-selenomethionine and hydroxy-analogue of selenomethionine. The highest concentrations of MDA, an indicator of secondary lipid oxidation, were confirmed in the Control Group eggs (P < 0.001). Egg yolks from the Control Group were found to have the highest lightness (P = 0.032), the lowest colour chroma and the lowest proportions of the red and yellow colours (P < 0.001). The highest vitelline membrane strength was measured in eggs from groups fed diets supplemented with organic Se (P < 0.001). No significant differences were found between groups in the total fatty acid content, the content of saturated and unsaturated fatty acids or the n-6/n-3 fatty acid ratios. Our study confirmed the effect of Se feed supplements on the concentration of MDA and the colour indicators of egg yolk and on the vitelline membrane strength.