Effects of dietary polyphenols on mucosal and humoral immune responses, antioxidant defense and growth gene expression in beluga sturgeon (Huso huso)

Tannins are a class of polyphenols, well known for their potent natural antioxidant properties, which have a beneficial effect on the digestive tract and contribute to improving the welfare of terrestrial farmed animals. This study reports the effect of tannins on haematological and non-specific immune parameters, serum enzyme activity and expression of growth genes of juvenile beluga sturgeon (Huso huso). Tannins were extracted from chestnut wood by SILVATEAM and provided in form of powder, under the commercial name of Silvafeed (R) ATX. Triplicate groups of 35 Beluga juveniles each (39.20 +/- 0.63 g) were placed in 9 oval tanks (350 L) and fed with the basal control diet (0% tannins) and the tannin supplemented basal diet (at 0.05 or 0.1%). The trial lasted 6 weeks. The dietary supplementation of 0.1% tannins significantly improved weight parameters and food conversion ratio (FCR) with respect to the control group (P < .05). Dietary tannins had no significant effect on body composition and haematological parameters. Skin and mucus lysozyme and oxidative stress related enzymes activity (CAT, PPO and SOD) significantly increased in the groups fed tannins enriched diets (P < .05). The enzymatic activity of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase did not change between control and tannin fed groups. Finally, the expression of two growths related genes: gh and igf-i was upregulated in the tannin fed groups. Such outcomes indicate that tannins improve growth performance and the general health status of juvenile beluga sturgeon. Thus, our results suggest that tannins administered to juvenile beluga sturgeon may act as growth promoters.