Dietary sodium propionate optimizes intestinal microbiota and promotes growth performance, lipid metabolism and ammonia tolerance in yellow catfish (Pelteobagrus fulvidraco)

This study investigated the effects of sodium propionate (SP) on intestinal microbiota and liver lipid metabolism in yellow catfish (<i>Pelteobagrus fulvidraco</i>). A control diet containing 42% crude protein was formulated, and experimental diets were created by supplementing 0.00%, 0.25%, 0.50%, 1.00%, and 2.00% SP. A total of 600 juvenile yellow catfish (averaging 3.20 ± 0.10 g) were randomly allocated into five dietary treatment groups (SP0 to SP4), with each group consisting of three replicate tanks (<i>n</i> = 3) and 40 fish per tank. The fish were fed their respective diets for 42 d. Results demonstrated that supplementation with 1.0% SP significantly improved weight gain rate (<i>P</i> < 0.001) and specific growth rate (<i>P</i> < 0.001), while reducing the feed conversion ratio (<i>P</i> = 0.002). Furthermore, 1.0% SP significantly enhanced intestinal pepsin (<i>P</i> < 0.001), amylase (<i>P</i> < 0.001), and lipase activity (<i>P</i> < 0.001), and significantly enhanced serum total antioxidant capacity (<i>P</i> = 0.006), superoxide dismutase (<i>P</i> < 0.001), and catalase activity (<i>P</i> = 0.044). 16S rRNA sequencing and quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that 1.0% SP supplementation significantly increased the relative abundance and copies of the beneficial bacteria <i>Cetobacterium</i> (<i>P</i> < 0.001). Liver lipid metabolism analysis showed that 1.0% SP significantly decreased liver total triglycerides (<i>P</i> = 0.027) and total cholesterol levels (<i>P</i> = 0.004). Moreover, 1.0% SP significantly upregulated the expression of genes associated with liver fatty acid oxidation, including peroxisome proliferator-activated receptor alpha (<i>pparα</i>) (<i>P</i> < 0.001), carnitine palmitoyltransferase (<i>cpt</i>) (<i>P</i> < 0.001), adipose triglyceride lipase (<i>atgl</i>) (<i>P</i> < 0.001), acyl-coenzyme a oxidase (<i>aco</i>) (<i>P</i> = 0.028), and hormone-sensitive lipase (<i>hsl</i>) (<i>P</i> < 0.001), while downregulating the expression of genes involved in fatty acid synthesis, such as fatty acid synthase (<i>fas</i>) (<i>P</i> < 0.001) and acetyl-coa carboxylase (<i>acc</i>) (<i>P</i> < 0.001). Histological analysis via hematoxylin-eosin staining revealed that SP supplementation significantly reduced liver steatosis and hepatocyte vacuolation. In conclusion, SP supplementation promotes fatty acid oxidation via the PPARα/ACO pathway, thereby reducing liver lipid accumulation. Additionally, SP supplementation significantly increased the survival rate of yellow catfish under acute ammonia stress (<i>P</i> < 0.001). These findings suggest that SP has potential as an environmentally-friendly dietary supplement to improve growth performance and physiological health, enhance liver lipid metabolism, and modulate the intestinal microbiota in yellow catfish.