The effects of fish meal replacement with ultra-micro ground mixed plant proteins (uPP) in practical diet on growth, gut and liver health of common carp ( Cyprinus carpio )

Plant proteins are widely used for fish meal replacement in aquafeeds, but anti-nutritional factors in plant protein reduce fish growth performance and impair fish health. The present work aimed to study the effects of improving fish meal replacement percentage with ultra-micro ground mixed plant proteins (uPP) on growth, gut and liver health of common carp. Carps were fed with a practical basal diet with partial fish meal replacement by plant proteins or the basal diet supplemented with 2.5 % or 5% uPP for 16-week. Results indicated that uPP addition did not affect growth and survival of common carp at a supplementation level up to 5% (p 0.05). However, 5% uPP up-regulated the intestinal expression of inflammation related genes (p < 0.05) and reduced HIF-1 alpha expression (p < 0.05). Moreover, dietary 5% uPP increased serum ALT (p = 0.06) and AST level (p < 0.05) and up-regulated liver expressions of inflammation related genes (p < 0.05). The Simpson diversity index of gut microbiota was lower in 5% uPP group compared to control (p < 0.05). The relative abundance of Fusobacteria and Cetobacterium was lower (p < 0.05), while Proteobacteria including Shewanella and Citrobacter was higher in the 5% uPP group compared to control (p < 0.05). In contrast, 2.5 % uPP did not increase inflammatory and injury parameters in fish intestine and liver, but rather improved the expression of occludin and defensin in the intestine compared with control (p < 0.05). Moreover, no significant differences were found in gut microbiota between 2.5 % uPP group and control. Together, our study suggests that low-level uPP addition can be adopted to further improve fish meal replacement, while dietary 5% uPP impairs gut and liver health of common carp and negatively affects intestinal microbiota.

Automated summary

The study suggests that low-level uPP addition can enhance fish meal replacement, while 5% uPP in the diet has negative effects on gut and liver health of common carp and disrupts intestinal microbiota.