Page 196 - Natural Antioxidants, Applications in Foods of Animal Origin

Natural Antioxidants in Poultry Products 175
VetBooks.ir diets of broilers. Vit. E was reported to improve phagocytic ability of the

immune system in broilers (Konjufca et al., 2004). It has also been reported
that under heat stress condition dietary vit. E supplementation improved the
immune response of broilers. Even supplementation of vit. E decreased the
production of fishy color because of fishmeal oil in diet and warmed over
color in refrigerated cooked meat and raw frozen meat (Niu et al., 2009).
The stability of the meat has been correlated with the tissue concentration
of α-tocopherol. For poultry, levels of 7 µg/kg α-tocopherol in muscle are
recommended to prolong the keeping quality of meat. The supplemented
tissues were more stable in cold store. Feeding of vitamin supplemented
diets (10–20 ppm) showed significantly lower levels of thiobarbituric acid
reactive substances (TBARS) in the meat measured after 5 and 10 days of
storage (Lohakare et al., 2005).
The effects of vit. E in ducks are different. The effect of feeding of
α-tocopheryle acetate at different levels to day old white Pekin ducklings
revealed significantly increased concentrations of vit. E in breast, thigh,
liver, and heart tissues in dose dependant manner. Supplementation though
enhances oxidative stability, was more effective for thigh muscle than breast.
α-tocopherol, which easily gets deposited in the egg yolk, is used as
antioxidant in animal nutrition (Galobart et al., 2001). But, other existing
substances in yolks may also prohibit oxidation, as selenium or carotenoids
(Yaroshenko et al., 2004). Antioxidants are deposited in yolks according to
dietary levels. Enriching egg yolks with α-tocopherol or carotenoids can
be done in a wide range and does not affect egg quality, except that with
increasing levels of carotenoids intensity of yolk color increases. While
supplementing carotenoids to diets, it has to be considered that yellow and
red pigments should be added in ratios given by the manufacturer to avoid
off-colors (Galobart et al., 2001). The artificial carotenoids (canthaxanthin)
usually supplemented to the layer’s diet cover more than 90% of total carot-
enoids in the egg. Enriching eggs with selenium is more complicated as high
levels of selenium in the food are toxic for humans. Nevertheless, it is easy to
enrich eggs with 35 μg Se which amounts to 50% of the recommended daily
intake (RDI) for humans (Yaroshenko et al., 2004). No negative impacts of
antioxidants on any egg quality criteria are known.
Although, the eggs provide considerable amounts of vit. E and sele-
nium, but, enriching eggs with n-3 PUFA will result in a higher liability of
eggs to oxidation and to off-colors (Tserveni-Gousi et al., 2004). Off-colors
may further occur by the use of fish oil as a dietary source. Therefore, for
the production of omega-3 enriched eggs only high quality fish oil should
be used and distinct amounts of antioxidants (α- tocopherol) should be