A study on growth, histopathology and oxidative stress in Asian sea bass on diets with various loadings of melamine and cyanuric acid adulterants

Effects of melamine (MEL) and its analogue, cyanuric acid (CYA) at various doses on Asian seabass (Lates calcarifer Bloch) are described. Diet 1 (a basal diet without MEL and CYA); diets 2-5 (with MEL and CYA at inclusion levels 2.5, 5, 7.5, 10 g/kg diet, each); diet 6 (with only MEL at 10 g/kg diet); and diet 7 (with CYA alone added at 10 g/kg diet) were examined. It is obvious that those fish that received combined MEL-CYA as follows had low growth and feed conversion ratio (FCR) (P < 0.05): 7.5:7.5, 10:10 or MEL alone diets. Abnormalities were observed in the liver and kidney of fish with combined MEL and CYA supplementation. The renal tubules of fish that were fed with diets 2-5 had golden-brown melamine-cyanurate crystals. Fish given only one type of supplementation did not have such crystals in the kidneys. The highest MEL residue in fillet was detected in the fish that ingested MEL alone (10 g/kg diet). Levels of heat shock protein (Hsp) 70 were elevated in the liver of fish that had ingested MEL/CYA, in combination or alone (diets 2-7) (P < 0.05). There were no significant differences between the treatments (P > 0.05) in the level of Hsp70 in the kidneys of the fish. High dosages of MEL-CYA induced the activities of catalase and glutathione peroxidase in liver and kidneys.