Lactobacillus amylovorus alleviates intestinal damage induced by ammonia exposure in yellow catfish (Pelteobagrus fulvidraco): enhanced intestinal barrier function and regulation of intestinal microbiota.

This study aimed to explore whether Lactobacillus amylovorus (LA) mitigates acute ammonia-induced intestinal damage in yellow catfish (Pelteobagrus fulvidraco). A 14-day experiment used 360 healthy fish (initial body weight: 6.26 ± 0.05 g), randomly assigned to 4 groups (3 replicates, 30 fish/replicate): control (CON, 0 mg/L T-AN), ammonia exposure (AM, 125 mg/L T-AN), LA supplementation (LA, 0 mg/L T-AN + LA), and LA + AM (125 mg/L T-AN + LA). LA was sprayed onto commercial feed at 1 × 108 CFU/g. The results showed that the LA + AM had a significantly higher survival rate (78.33 ± 12.58% vs. 40.00 ± 5.00% in AM, P < 0.05), reduced serum/intestinal ammonia levels, alleviated intestinal villi breakage/shedding, and mitigated oxidative stress (lower ROS, MDA; higher SOD, CAT, GSH, T-AOC, P < 0.05). LA regulated inflammation (downregulated il-1β/il-6/il-8/tnf-α/nf-κb mRNA and IL-1/IL-6/p-NF-κB p65 protein; upregulated IL-10 protein, P < 0.05), enhanced intestinal barrier function by upregulating tight/adherens junction (zo-1, claudin-1, occludin) gene/protein (ZO-1, E-cadherin) expression (P < 0.05), and modulated gut microbiota (increased Lactobacillus/Cetobacterium abundance, decreased Plesiomonas/Proteobacteria, elevated α-diversity, P < 0.05). In conclusion, LA protects yellow catfish from ammonia-induced intestinal damage via antioxidant, anti-inflammatory, barrier-enhancing and microbiota-modulating effects, promising as a nutritional strategy to alleviate ammonia stress in intensive aquaculture.