Mengtong Zheng, Jiteng Wang, Hanying Xu, Tao Han, Laiguo Li
Overall, dietary SCFAs, especially propionate and butyrate, effectively mitigate growth inhibition, hepatic lipotoxicity, and glucose metabolic disorders induced by high-carbohydrate diets, while simultaneously enhancing muscle nutritional value, demonstrating their high potential as functional feed additives in sustainable carnivorous fish aquaculture.
This study evaluated the effects of dietary short-chain fatty acids (SCFAs) on carbohydrate metabolism in largemouth bass fed a high-carbohydrate diet. Juvenile fish (15.33 ± 0.14 g) were fed six isonitrogenous and isolipidic diets for 55 days, containing 10% (C, control), 15% (HC, high carbohydrate), and 20% (EC, extremely high carbohydrate) corn starch and three SCFA-supplemented diets based on the 15% carbohydrate diet level (0.2% sodium acetate (HC + A), propionate (HC + P), butyrate (HC + B)). High-carbohydrate diets significantly reduced growth performance increased hepatic lipid deposition and disrupted glucose homeostasis, with the EC diet inducing pronounced metabolic dysfunction characterized by reduced hepatic glycogen content and impaired insulin regulation. SCFA supplementation (sodium propionate and butyrate) restored weight gain and specific growth rate to C group levels, though no statistically significant difference was observed compared with the HC group. Notably, sodium butyrate significantly improved muscular quality by lowering crude lipid accumulation and increasing beneficial n-3 PUFA and DHA proportions. SCFA supplementation reduced the hepatosomatic index (HSI) and blood glucose levels and enhanced glycolysis, as indicated by increased pyruvate kinase activity and lactic acid levels, while suppressing gluconeogenesis through reductions in pyruvate carboxylase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase activities. These metabolic benefits were associated with the upregulated expression of insulin receptor (ir) genes, rather than increased hormone secretion. Overall, dietary SCFAs, especially propionate and butyrate, effectively mitigate growth inhibition, hepatic lipotoxicity, and glucose metabolic disorders induced by high-carbohydrate diets, while simultaneously enhancing muscle nutritional value, demonstrating their high potential as functional feed additives in sustainable carnivorous fish aquaculture.