Proximate composition and lipid stability of dourado (Salminus brasilensis, Cuvier, 1817) fillets exposed to different levels of ammonia and oxygen in vivo

High dissolved oxygen exacerbates ammonia toxicity with sex-dependent manner in zebrafish

Ammonia nitrogen is one of the important environmental factors, and causes negative effects for fish health in ecosystem and aquaculture. The toxic effects and mechanisms of ammonia in fish deserve further investigation. In the present study, we exposed female and male zebrafish (Danio rerio) to ammonia (50 mg/L NH₄Cl) with oxygenated (7.5-7.8 mg/L) or non‑oxygenated (3.8-4.5 mg/L) water, to identify the combined effects of dissolved oxygen and ammonia on fish with gender difference. The results showed that oxygenated ammonia exposure increased fish mortality, gill secondary lamellas damage and gill tissue spaces, gene expressions of proinflammatory interleukin 1 beta (il-1β) and apoptotic caspase8 as compared with non‑oxygenated ammonia. Besides, oxygenated ammonia elevated plasma ammonia contents, and decreased the discharge of body ammonia through gills by depressing the enzyme activity of Na⁺/K⁺-ATPase. Notably, when zebrafish were subjected to ammonia stress, more severe mortality, gill damage and tissue inflammatory response were observed in males than females. This is the first study to clarify the gender-dependent impacts of ammonia toxicity, and the adverse effects of oxygenation on ammonia resistance in zebrafish.

Chronic exposure to ammonia induces oxidative stress and enhanced glycolysis in lung of piglets

Ammonia is one of the major environmental pollutants in the pig industry that seriously affects the airway health of pigs. In this study, we aimed to investigate the metabolic profiling changes of piglets' lung tissue after the exposure of 0 ppm (CG), 20 ppm (LG) and 50 ppm (HG) ammonia for 30 days. Compared with the control group, the obvious lung lesions were observed in HG, including interstitial thickening, inflammatory cell infiltration and focal hemorrhage. The significantly increased content of malondialdehyde in HG, combined with the significantly decreased mRNA expression of antioxidase and inflammatory-regulators in exposure groups, implied that ammonia exposure induced oxidative stress and diminished the anti-inflammatory response in lung tissues. Metabolomic analyses of lung tissues revealed 15 significantly altered metabolites among the three groups including multiple amino acids, carbohydrates and lipids. The accumulation of succinic acid, linoleic acid and phosphorylethanolamine and consumption of glucose, quinolinic acid and aspartic acid in ammonia exposure groups, indicated that energy supply from glucose aerobic oxidation was suppressed and the glycolysis and lipolysis were activated in lung tissues induced by chronic ammonia exposure.

Effects of toxic cyanobacteria and ammonia on flesh quality of blunt snout bream (Megalobrama amblycephala)

BACKGROUND

Toxic cyanobacterial blooms result in the production of an organic biomass containing cyanotoxins (e.g. microcystins) and an elevated ammonia concentration in the water environment. The ingestion of toxic cyanobacteria and exposure to ammonia are grave hazards for fish. The present study assessed the effects of dietary toxic cyanobacteria and ammonia exposure on the flesh quality of blunt snout bream (Megalobrama amblycephala).

RESULTS

Dietary toxic cyanobacteria and ammonia exposure had no impact on fish growth performance, fillet proximate composition and drip loss, whereas it significantly decreased fillet total amino acids, total essential amino acids, hardness and gumminess, and increased fillet ultimate pH as well as malondialdehyde content. However, there was no significant interaction between dietary toxic cyanobacteria and ammonia exposure on these parameters. Additionally, dietary toxic cyanobacteria significantly increased fillet initial pH, thaw loss and protein carbonyl content, whereas ammonia exposure did not.

CONCLUSION

The results of the present study indicate that dietary toxic cyanobacteria and ammonia exposure reduced the quality of blunt snout bream fillet. © 2016 Society of Chemical Industry.