Abstract
Grape seeds (GS) and grape skins (GK) are natural sources of polyphenols with featured antioxidant capacity. An experiment was conducted to investigate the effect of these polyphenol sources in diets formulated to contain the same total extractable grape polyphenol content on growth performance, protein and extractable polyphenol digestibility, plasma and meat α- and γ-tocopherol and thigh meat oxidation in broiler chickens. Five experimental diets were formulated: control, control + vitamin E (200 mg/kg), 30 g/kg GS diet, 110 g/kg GK diet, GS + GK diet (a mixture of 24.4 g/kg GS and 13.1 g/kg GK designed to simulate a reconstituted grape pomace). Feeding chickens with 110 g/kg GK reduced (p < 0.001) daily weight gain, worsened (p < 0.001) feed conversion ratio, increased (p < 0.001) non-extractable polyphenol content in the ileum and in the excreta and decreased (p < 0.05) ileal protein digestibility. Regardless of the grape polyphenol source used, the inclusion of grape byproducts in the diets led to an increase of total extractable polyphenol contents in the ileum (p < 0.01) and the excreta (p < 0.001), which resulted (p < 0.001) in a decrease of extractable polyphenol digestibilities. Alpha- and gamma-tocopherol concentrations increased (p < 0.001) in plasma and in seven-day stored meat in birds fed the diet combining GS and GK with respect to the control group. As it happened with the vitamin E supplementation, feeding the combination of GS and GK also reduced (p < 0.001) the concentration of the lipid peroxidation marker (malondialdehyde) in the stored meat of chickens.
Highlights
IntroductionGrape (Vitis vinifera L.) is one of the largest fruit crops in the world, with an approximate annual production of 77 million tons [1]
Our results showed that the antioxidant potential of dietary grape polyphenols in chickens is affected by the source of grape polyphenols
With the same dietary content of grape extractable polyphenols, the dietary combination of Grape seeds (GS) and grape skin (GK) led to better results than the separate dietary inclusion of these grape byproducts
Summary
Grape (Vitis vinifera L.) is one of the largest fruit crops in the world, with an approximate annual production of 77 million tons [1]. The biggest part of them is destined to the wine production industry. Around 20% of the total weight of grapes used for winemaking results in grape pomace [2], a solid residue left after juice extraction that consists of seeds, skins and stems. Investigations have stressed the importance of byproducts from wine processing as plant materials rich in a wide variety of polyphenols [3,4].
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