Dietary Pennisetum sinese Roxb meal reduces lipid accumulation and alleviates enteritis in juvenile grass carp, Ctenopharyngodon idella

Abstract Grass carp (Ctenopharyngodon idella) rarely consume grass-type feedstuffs in the commercial aquaculture industry. In this study, the effects of dietary Pennisetum sinese Roxb meal (PSRM) on the growth, lipid accumulation, and intestinal health of juvenile grass carp were explored. Six practical isonitrogenous (crude protein, 28.61%) and isocaloric (gross energy, 14.69 kJ g–1) diets with increasing PSRM contents (0.0%, 5.0%, 10.0%, 15.0%, 20.0%, and 25.0%; at the expense of soybean meal, wheat meal, and soybean oil) were formulated to feed juvenile grass carp for eight weeks. Fish fed 5–25% PSRM showed significantly increased growth and decreased feed conversion ratios compared with fish fed the control diet; fish that were fed 5% PSRM showed the best growth and feed efficiency. Diets supplemented with 5–25% PSRM significantly reduced lipid accumulation in the hepatocytes of grass carp, as indicated by the suppression of the hepatopancreas index, hepatic crude fat content and lipid droplet distribution, and hepatic triglyceride and free fatty acid (FFA) contents. Dietary PSRM also significantly decreased the lipid content in the adipose tissue by reducing the intraperitoneal fat index (5–25%) and adipocyte size (25%). At the transcript level, dietary PSRM decreased the lipid anabolic capacity and increased the lipid catabolic capacity in both the hepatopancreas and intraperitoneal fat tissues. Dietary PSRM attenuated enteritis-like histological features and reduced the mRNA levels of inflammation-related genes in the midgut of grass carp. Finally, several genes associated with anorexia were significantly upregulated when the dietary PSRM level reached 20%. Collectively, our study shows that diets supplemented with PSRM could improve growth, suppress lipid accumulation in the hepatopancreas and adipose tissue, and improve the intestinal health of juvenile grass carp. We suggest that the supplementation level of PSRM should be 5% for optimal results and should not exceed 20%.