Feed supplementation with winery by-products improves the physiological status of juvenile Liza aurata during a short-term feeding trial and hypoxic challenge

The search of bioactive compounds obtained from natural sources with beneficial effects in growth and health is an increasing trend in aquaculture. Wine by-products are an excellent source of such compounds, mostly phenolics, with demonstrated antioxidant and immunostimulant activities in vertebrates. The present study evaluated the effects of dietary inclusion (100 g/kg) of two wine by-products (grape pomace and lees) on growth, immune status and metabolism of juvenile golden gray mullet (Liza aurata), as well as the potential protective effect of compounds present in the two by products against induced stress produced by moderate hypoxia. Results evidenced a significant positive effect of grape pomace on feed efficiency, as well as in different indicators of metabolic and immunological status of the fish. Also, a significant negative effect of wine lees on the functional diversity of intestinal microbiota was evidenced. Fish fed on diets containing any of the two by-products evidenced significantly lower levels of cortisol when challenged by hypoxia, this pointing to a protective effect mediated by their contents in phenolic compounds and suggesting an interesting and practical application for these agricultural by-products.