Taurine can play a positive role in growth, liver health and resistance to Aeromonas hydrophila of yellow catfish Pelteobagrus fulvidraco exposed to ammonia stress for a long time

Abstract

Ammonia is an important environmental pollutant that is toxic to most aquatic animals, and nutrient manipulation is an effective regulatory pathway. To assess the influence of taurine supplementation on growth, liver detoxification and anti-bacterial infection of yellow catfish subjected to ammonia exposure for a long time, three experiment diets with different taurine levels (0.50, 1.00, and 2.00 %) were formulated and fed to fish (7.28 ± 0.05) g under three ammonia levels (0.00, 25.00 and 50.00 mg/L total ammonia nitrogen) for 56 days. The results showed that hepatic glycogen and whole-body protein contents were reduced, suggesting that energy deficiency caused by ammonia poisoning plays an important role in growth inhibition; elevated serum alanine aminotransferase and aspartate aminotransferase levels suggest liver injury, which may be caused by oxidative stress (decreased activities of superoxide dismutase and catalase, and expressions of SOD and CAT) and inflammation (increased contents of tumor necrosis factor α, interleukin 1 and interleukin 8, and expressions of TNF α, IL 1 and IL8), analysis of tissue sections further confirmed this finding. Furthermore, after injection with Aeromonas hydrophila, cumulative mortality increased proportionally with the rise in ammonia levels, the observed decrease in serum complements C3, C4, immunoglobulin M, and antibody titer contents emerged as a crucial factor contributing to the decreased disease resistance. The exogenous taurine was found to alleviate the negative impact of the above-mentioned ammonia poisoning. This study provides valuable insights into the mechanism of ammonia-induced aquatic toxicology in fish.