Effects of different levels of dietary vitamin C on growth performance, digestive enzymes activity and blood stress factors of rainbow trout (Oncorhynchus mykiss) under sub-lethal toxicity of malathion

Document Type : Original Article


Department of Fisheries, Faculty of Natural Resources, Tehran University, Karaj, Iran.


The aim of this study was to investigate the effects of dietary vitamin C (ascorbic acid) on growth performances, digestive enzymes activity and blood stress factors in rainbow trout affected by the toxicity of malathion in water. In this experiment, the fish were subjected to ¼ concentrations of Lc50 96h of malathion for 28 days and during this period, fish were fed with different levels of vitamin C (0, 300, 600 and 900 mg / kg of Feed). At the end of experiment, the results of the study of growth performances showed a significant increase (P<0.05) in weight gain (WG) and specific growth rate (SGR) of fish fed with the highest vitamin level (900 mg/kg diet). Food conversion ratio (FCR) in fish under the aforementioned treatment showed a significant decrease compared to other treatments. In the case of digestive enzymes activity, lipase enzyme activity increased significantly in treatments of 600 and 900 mg/kg vitamin C in diet respectively. However, the activity of other enzymes did not differ significantly in vitamin C different concentrations in the diet (P>0.05). Blood stress indices showed that glucose level was significantly higher in control treatment (0 m/kg) compared to other treatments and blood cortisol levels were significantly lower in the treatment of 900 mg/kg vitamin C in the diet. Finally, the results indicate that vitamin C as an anti-stress agent has been able to reduce stress in fish and improve the metabolic status and consequently the growth performance of rainbow trout.