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The efficiency of xanthophylls in the combined fortification of table eggs

The efficiency of xanthophylls in the combined enrichment of table chicken eggs with ω-3 polyunsaturated fatty acids (PUFAs), vitamin E (VE), selenium (Se), and carotenoids via supplementation of diets for laying hens was studied on 4 groups of cage-housed SP-789 layers (30 birds per group). All groups received a diet containing 2.18% of ω-6 and 1.97% of ω-3 PUFAs, 150 ppm of VE, 0.5 ppm of Se, and 7.5 ppm of total carotenoids; diets for groups 2-4 were additionally supplemented with xanthophylls (10, 14, and 18 ppm of marigold extract “Biofon Yellow”). It was found that the concentrations of ω-6 and ω-3 PUFAs per 100 g of edible parts of the eggs from groups 1-4 were 1093 and 347, 1075 and 393, 1140 and 412, 1298 and 417 mg, respectively. Se amounted to 61.8, 60.9, 62.1, 61.9 μg. Vitamin E was 8.9, 9.51, 9.63, 10.1 mg. Total carotenoids amounted to 176.6; 424.4; 454.2; 701.4 μg. The intensiveness of yolk coloration was 3.8; 6.3; 6.7; 7.0 scores, respectively. The best results were found in group 4.


Introduction
In recent decades functional foodstuffs with beneficial effects on the consumers' health increasingly have drawn the attention of food scientists. These foodstuffs can be enriched with different bioactive substances (BAS): vitamins, trace elements, ω-3 polyunsaturated fatty acids (PUFAs), antioxidants, pro-and prebiotics, etc. [1][2][3][4]. Eggs and poultry meat (which per se are the most cheap and available sources of valuable protein and essential fatty acids) can be functional foodstuffs due to the higher efficiency of the presence of different nutrients and BAS in the diets of poultry in comparison to other diets of food-producing animals [5]. It is known that enrichment of foodstuffs with PUFAs enhances the lipid peroxidation within the foodstuffs during the storage and cooking. This problem could be solved via the concurrent enrichment of these foodstuffs with antioxidants [6] stabilizing the lipids within the foodstuffs, which is beneficial for the consumers' health. An optimal ω-6/ω-3 PUFAs ratio in human diet should be 2-3:1 [7].
Xanthophylls which earlier served for the improvement of egg yolk coloration and consumer attractibility of the eggs are presently also regarded as target BAS in the production of functional eggs [8,9]. Xanthophylls (primarily luthein and zeaxanthin) are the exclusive carotenoids presented in the retina and lens and protecting the eye [10]. These xanthophylls protect photoreceptors and retinal epithelium from the harmful effects of the blue light [11] and decrease the light-induced oxidative stress in the eye tissues [12]. The data on egg morphology ( Table 1) evidenced that at 330 and 360 days of age there were no significant differences between the groups in absolute and relative weights of albumen, yolk, and eggshell, as well as in the albumen/yolk ratio.
The intensity of yolk coloration increased with age of hens and with the increase in dietary concentration of xanthophylls. The highest average color intensity was found in group 4, which was 1.8-fold higher in comparison to control where this parameter was the lowest. The chemical composition of eggs is presented in Table 2. The concentrations of calcium in the eggshell; vitamins A, E, and B2 in yolk; vitamin B2 in albumen at 330 and 360 days of hens' age were similar. The concentration of total carotenoids in yolk increased with the increase in dietary concentration of xanthophylls in groups 2, 3, and 4; maximal concentration was found in group 4, 1.5-3.9-fold higher in comparison to other groups, while minimal concentration was found in control group 1.
The trend was found in higher VE concentration in yolk with the increase in dietary concentration of xanthophylls evidencing certain synergism between these antioxidants.  There were no significant differences between the ages (330 vs. 360 days of age) in the concentrations of ω-6 and ω-3 PUFAs, total carotenoids, VE, and Se in 100 g of edible parts of the eggs. Eggs from groups 2, 3, and 4 had higher average concentrations of total carotenoids (2.4-4.0 times higher in comparison to control group 1) and VE (by 6.9-13.5%); the best results were found in group 4. There were no significant differences between the groups in concentrations of Se, ω-3 PUFAs, and a ω-6/ω-3 ratio.

Conclusions
The results of the trial evidenced the possibility of complex enrichment of table chicken eggs with ω-3 PUFAs, VE, Se, and xanthophylls by supplementation of the hens' diets.
The experimental groups which received wheat-based diet (containing 2.18 of ω-6 and 1.97% of ω-3 PUFAs, 150 ppm of VE, and 0.5 ppm of Se) additionally supplemented with xanthophylls (luthein and zeaxanthin) featured higher productivity, better FCRs, higher concentrations of carotenoids and VE in eggs, better yolk pigmentation in comparison to non-supplemented control without deterioration of egg morphology. The best results were found in group 4 which received 18 ppm of xanthophylls (as 900 ppm of "Biofon Yellow"). Egg production in this group was higher in comparison to control by 4.0%, egg mass output was higher by 4.3%, concentration of total carotenoids per 100 g of edible parts of eggs was 4.0-fold higher, VE was higher by 13.5%, Se -by 0.2%, ω-6 and ω-3 PUFAs -by 18.8 and 20.0%, respectively (at ω-6/ω-3 ratio 3.1:1). FCRs per 10 eggs and per 1 kg of eggs was lower by 3.1 and 2.8%, respectively. The increase in the concentration of total carotenoids in yolk resulted in 1.8-fold higher intensity of yolk coloration improving the market appearance and consumer attractibility of the eggs.