Dietary lauric acid improves the protein utilization and muscle growth by promoting intestinal flora and glycolysis in mud crab (Scylla paramamosain)

At present, the rapid development of aquaculture is restricted by the shortage of fishmeal, and it is particularly important to find ways to replace and reduce fishmeal. It is worth exploring whether feed with lower-than-normal protein requirements have adverse effects on the growth of aquatic animals. The aim of the present study was to improve the growth performance of mud crab ( Scylla paramamosain ) by adding lauric acid (LA) and glycerol mono-laurate (GML) to a low protein diet (41.8 % crude protein). Adding 1 g/kg LA or 0.5 g/kg GML to low protein diet can significantly ameliorate the negative effects of low protein diet on mud crabs, and improve the survival and growth performance. In addition, dietary LA or GML supplementation can enhance protein apparent digestibility (ADP), increase protein and amino acid content in muscle, and optimize protein metabolism process. Notably, dietary LA and GML supplementation can activate the glycolytic pathway in muscles and up-regulate the expression of genes related to muscle growth. Moreover, the results of intestinal flora indicated that dietary GML and LA increased the abundance of Rhodobacteraceae, Erysipelotrichaceae, Endozoicomonadaceae and Ruegeria . These flora exhibited a positive correlation with protein digestion, absorption and deposition. In conclusion, the supplementation of LA or GML in low-protein diets can effectively improve growth performance, activate muscle glycolysis pathway, promote muscle development, increase microbial abundance related to protein metabolism, and improve protein apparent digestibility. • Lauric acid and glycerol monolaurate enhanced the utilization rate of protein in the feed for mud crabs. • Low protein diet supplemented with lauric acid and glycerol monolaurate improved intestinal flora of mud crabs. • Lauric acid and glycerol monolaurate promoted muscle growth by activating glycolysis pathway in mud crabs.