Effects of dietary sodium acetate supplementation on growth, intestinal health and ammonia tolerance of largemouth bass (Micropterus salmoides)

Largemouth bass (Micropterus salmoides) is an important freshwater economic fish species. However, with the expansion of farming scale, losses caused by ammonia stress have intensified. This study investigated the effects of dietary sodium acetate supplementation at varying levels on M. salmoides, specifically examining growth performance, serum biochemical indices, digestive enzyme activities, intestinal morphology and structure, immune responses, inflammatory reactions, and ammonia tolerance. The study used M. salmoides an average initial body weight of (7.40 ± 0.06) g which were randomly divided into four groups with three replicates each, and each replicate contained 30 fish. The fish were fed diets containing 0.00% (control group), 0.10%, 0.20%, and 0.40% sodium acetate, respectively. The experiment lasted for 56 days. The results showed that supplementing the diet with sodium acetate significantly enhanced the fish weight gain rate and specific growth rate, reduced the feed conversion rate; and increased intestinal villi length and muscle thickness, promoted the activities of intestinal lipase, pepsin, alkaline phosphatase, Na⁺/K⁺-ATPase, γ-glutamyl transpeptidase and creatine kinase; and increased the contents of total protein, albumin and globulin in serum, and reduced the contents of tumour necrosis factor, interleukin-1 and interleukin-8. After 96 h of ammonia stress, the cumulative mortality of M. salmoides in the sodium acetate groups was significantly lower than that in the control group; the activities of serum lysozyme, total complement, total immunoglobulin, and antibody titers significantly increased; the activities of argininesuccinate synthetase, argininosuccinate lyase, arginase, ornithine transcarboxylase and inducible nitric oxide synthase in liver significantly increased, while the activity of neuronal nitric oxide synthase significantly decreased. The study demonstrated that supplementing the diet with sodium acetate improved the growth performance, intestinal digestive absorption, immune response, and ammonia tolerance of M. salmoides, indicating its potential as a feed additive for M. salmoides and a remedy for ammonia toxicity.