Effects of dietary glycinin on the growth performance, immunity, hepatopancreas and intestinal health of juvenile Rhynchocypris lagowskii Dybowski

This study was to evaluate the effects of glycinin on the growth, digestion, immune function, antioxidant capacity, and hepatopancreas and intestinal morphology of juvenile Rhynchocypris lagowskii Dybowski (R. lagowskii Dybowski). Graded levels (0, 10, 20, 40 and 80 g/kg) of isolated glycinin were added to the basal diets to formulate five experimental diets containing 0.0, 7.6, 15.5, 30.8 and 60.4 g/kg immunologically active glycinin, respectively. Five diets were used to feed R. lagowskii Dybowski for 8 weeks. Results showed that the weight gain rate and specific growth rate of fish were significantly reduced by dietary 40-80 g/kg glycinin (P < 0.05), and dietary 80 g/kg glycinin significantly reduced the feeding rate, protein efficiency rate and feed efficiency rate (P < 0.05). Protease activity of hepatopancreas and intestine, and whole-body crude protein content were significantly reduced by dietary 40-80 g/kg glycinin (P < 0.05). In serum, dietary 40-80 g/kg glycinin significantly reduced lysozyme and alkaline phosphatase activities, and complement 3 and immunoglobulin M contents (P < 0.05); while significantly increased the diamine oxidase activity, D-lactic acid and endothelin-1 concentration (P < 0.05). In mid intestine, distal intestine and hepatopancreas, dietary 40-80 g/kg glycinin significantly upregulated interleukin-1 beta and tumour necrosis factor-alpha mRNA levels (P < 0.05), and down-regulated transforming growth factor-beta and interleukin-10 mRNA levels (P < 0.05); dietary 40-80 g/kg glycinin significantly reduced catalase, glutathione peroxidase and total superoxide dismutase activities (P < 0.05), and increased malondialdehyde content (P < 0.05). Furthermore, dietary 40-80 g/kg glycinin destroyed the morphological structure of intestine, including atrophy and breakage of mucosal fold. Similarly, typical characteristics of hepatopancreas damage were observed when 40-80 g/kg glycinin was added, including increased the lipid vacuoles, and the nucleus shifted, dissolved and disappeared. Concluded, dietary 40-80 g/kg glycinin induced inflammation and oxidative damage, weakened immune and digestive functions, and ultimately inhibited the growth of R. lagowskii Dybowski

Automated summary

The study evaluated the effects of glycinin on juvenile Rhynchocypris lagowskii Dybowski, showing that high concentrations of glycinin can reduce growth performance, digestive enzyme activity, immune function, and antioxidant capacity, while damaging the morphology of the hepatopancreas and intestine.