Abstract

The salmon industry has reduced fishmeal in aquafeeds with different sources of alternative proteins, including low-cost plant meals. However, high replacement levels cause negative impacts on carnivore salmonids' growth, partly explained by alterations in the inflammatory and antioxidant response. To cope with this situation, we evaluated the effect of a dietary polyphenol supplementation of micro-encapsulated grape pomace extract (MGPE) from wine industry residual by-product in a diet high in soybean meal on growth performance, plasma antioxidant capacity, and gut microbial communities of Oncorhynchus mykiss for 30, 60 and 90 days. For this purpose, we first compared two commercial diets with low and high soybean meal (SBM) content without MGPE, and as expected, the high soybean content diet showed a significant decrease in the antioxidant capacity and the growth performance of the fish. Interestingly, this phenomenon was reverted in fish fed with the high SBM diet supplemented with the MGPE. Complementary, a fish gut microbiome analysis showed a time-dependent drop in microbial richness and diet-dependent changes in the bacterial communities from 60 days of treatment. The data also revealed that a more cooperative gut bacterial community interaction network could be part of the adjustment that explains the recovery of growth and antioxidant capacity in fish fed with the high SBM content diet supplemented with MGPE. These results present the basis for using residual pomace polyphenol extracts from the winemaking process in fish diets to improve the salmon farming industry's sustainability.