ISSUE FOCUS FEED & ADDITIVE MAGAZINE September 2024 39 antioxidants. Certain vitamins (E, C or A), carotenoids and selenium are commonly used antioxidants in feed. However, for various reasons (incl. cost-effectiveness and toxicity) they are not the most ideal type to fully prevent an increased negative impact of cellular oxidation on the aging animal. Distinct classes of polyphenols, originating from specific botanical sources, however, have proven to be powerful and versatile antioxidant solutions. Of course, not all polyphenolic types are as suitable or efficient in mitigating the stress level in the bird. For polyphenols to be truly impactful antioxidants within the body, they require particular characteristics. Firstly, they should have a moderate chain length or molecular weight to guarantee a sufficient gut absorption (i.e. for exerting a systemic effect). Secondly, an adequate water solubility is of utmost importance to also provide intra-cellular protection of key biological structures. Moreover, a low redox potential is a crucial chemical property also for polyphenols to easily neutralize free radicals. It refers to the tendency to donate an electron to different oxidizing agents. Multiple polyphenols show a lower reduction potential and thus higher antioxidant activity than Vit. E, and some specific types even outperform Vit. C. This property also enables polyphenols to regenerate antioxidative vitamins and carotenoid pigments when these are in their used form. Overall, selected polyphenols should dispose of multiple antioxidant mechanisms such as a: 1. broad-spectrum neutralization of different radical types (i.e. scavenging power), 2. significant recycling of oxidized in vivo antioxidants (i.e. regenerating power), 3. active stimulation of the endogenous antioxidant system (i.e. upregulating power) Dietary polyphenols of such specific nature will prevent oxidative damage to a significant level in breeders. This includes reducing inflammation of the intestinal epithelium to safeguard nutrient absorption and a sufficient barrier against invading pathogens. After gut absorption, they will also help minimize inflammatory processes within the radical-challenged reproductive tract. As such, these polyphenols secure rooster semen quality as well as ovarian follicle quality in the breeder hen for a successful egg fertilisation. But also during the subsequent egg incubation, accumulated polyphenols in ovo help improve the antioxidant status of hatching eggs, thereby supporting optimal embryo growth. Because they effectively recycle and spare Vit. E as potent in vivo antioxidants, such polyphenols also help preserve a high level of transferred Vit. E from the maternal diet to the yolk sac (which is retracted into the embryo's abdominal cavity by the time of hatching). This built up reserve is of high nutritional importance as newborn chicks
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