Growth performance and gut response of broiler chickens fed diets supplemented with a grape pomace extract

During the last decade, interest in dietary supplementation in animal feeding with extracts originating from wine by-products has grown, mainly due to the antioxidant properties and the potential immune response stimulation in animals of the polyphenolic compounds they contain. Therefore, this study aimed to evaluate how the dietary supplementation with polyphenols from grape pomace (0 mg/kg, 250 mg/kg, 500 mg/kg, and 1000 mg/kg) affected growth performance of 560 female Ross broiler chickens from hatching to 41 d of age, and jejunum gut morphology at different ages (12, 23, and 34 d). The dietary supplementation with 1000 mg/kg grape pomace polyphenols resulted in significantly lower body weight (P <0.01) and daily weight gain (P<0.01) compared to the control diet and the diets with 250 and 500 mg/kg polyphenols. The addition of grape pomace extract did not affect feed intake at a significant level (P >0.05), even though it was numerically the lowest in chickens fed the highest supplementation level (86.8 g/d, 87.1 g/d, 88.5 g/d and 85.1 g/d in pens fed diets at 0 mg/kg, 250 mg/kg, 500 mg/kg, and 1000 mg/kg). On the other hand, the supplementation with 500 mg/kg and 1000 mg/kg polyphenols significantly increased feed conversion ratio (P <0.01) compared to the control diet or the diet with 250 mg/kg. Regarding gut morphological analysis, jejunum villi height was higher (P <0.01) in chickens fed the diet containing 500 mg/kg polyphenols compared to the ones fed the other diets. Additionally, villi height significantly increased over time (P <0.01), and significant interactions between age and diet were recorded showing that differences among dietary treatments increased over time (P <0.01). In conclusion, a different response was observed depending on the dietary supplementation level of polyphenols which has been associated by other authors to the effects on feed intake level and the immune response (stimulating or suppressive effects). In detail, in the present study, no effect of the lowest dose was recorded; villi height increased when chickens were fed the intermediate dose (500 mg/kg) while growth performance was depressed with the highest inclusion level (1000 mg/kg). Funding: The research grant of M. Boskovic Cabrol is supported by the DEMyo project (No 101063055) funded by the European Commission under the HORIZONMSCA-2021-PF-01 call.