Effects of fermented mulberry leaves on growth, serum antioxidant capacity, digestive enzyme activities and microbial compositions of the intestine in crucian ( Carassius carassius )

Abstract

Mulberry (Morus alba) leaves are rich in proteins, vitamins and trace elements, which serve as ingredients of feed. However, the application of mulberry leaves is limited by the anti-nutritional factors present in them. In this study, we fermented the mulberry leaves using complex microorganisms containing lactic acid bacteria and yeast and investigated the effects of feed containing 0%, 5%, 10%, 15% and 20% FMLs on growth performance, serum antioxidant capacity, digestive capacity and intestinal microbiota composition in crucian (Carassius carassius). The intestinal microbiota composition was investigated using high-throughput sequencing of 16S rRNA gene. Our results showed that adding 5% FMLs to feed promoted growth performance, serum antioxidant capacity and intestinal digestive enzyme activities of crucian. There was no significant difference between the gut microbiota composition of crucian fed 5% FMLs and the blank control. When added FMLs exceeded 10%, the growth performance, serum antioxidant capacity and intestinal digestive enzyme activities decreased, and the homeostasis of gut microbiota was destroyed. These findings indicated that addition of 5% FMLs not only significantly promoted the growth of crucian, but also improved the antioxidant capacity and digestive capacity.