Application of
biological activities of grape polyphenols in poultry nutrition

The biological
effects of polyphenols have been extensively studied in vitro and in vivio in
animal models (Yu and Ahmedna, 2013). However, data from poultry is still very
limited. When applied to poultry nutrition, they offer promising possibilities
as tools for improving certain aspects of meat quality, antioxidant status, immunity and for modifying intestinal


Antioxidant activity

activity is the most notable bioactivity of phenolic compounds from GP (Xia et
al. 2010; Georgiev et al. 2014). In vitro and in vivo studies have
shown that flavonoids present in wine by-products behave like free radical
scavengers by acting as powerful antioxidants and metal chelators. This
inhibits formation of the superoxide ion and indirectly inhibits
redox-sensitive transcription factors and pro-oxidant enzymes (Puiggros et
al. 2005). They also activate antioxidant enzymes, reduce ?-tocopherol
radicals (tocopheroxyls), inhibit oxidases and increase levels of uric acid and
substances of  low molecular weight. The
antioxidative properties of polyphenols result mainly from their ability to
donate hydrogen from hydroxyl groups positioned along the aromatic ring in
order to terminate the free-radical oxidation of lipids and other  biomolecules (Foti et al. 1994). Among
the phenolics, monomeric forms are less potent as hydrogen-donating radical scavengers
than polymeric phenols (Fiueroa-Espinoza and Villeneuve, 2005).

           Hajati et al.
(2015) reported that grape
seed extract (GSE) supplementation (150, 300, 450 mg/kg) reduced blood levels of total TG, LDL-C and increased
HDL-C in broilers. The
mechanism by which dietary GP supplements affect the concentrations of plasma
lipids is not fully understood. However, herbs and herbal products are known to
induce hypocholesterolemic effects by reducing the activity of
3-hydroxy-3-methylglutaryl-CoA reductase (HMGCoA reductase), the rate-limiting
enzyme in cholesterol synthesis (Hong et al. 2012).Seven et al.
(2008) reported that feeding plant extracts rich in phenolic compounds resulted
in an increase in blood GSH-Px activity of chronic heat-exposed broiler
chickens. The malondialdehyde (MDA) compound is an end product of the oxidative
degradation of lipids and is an indicator of oxidative stress (Del Rio et al.,

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