Effect of alpha-lipoic acid on growth, body composition and activity of some antioxidant enzymes in muscle, liver and intestine of rainbow trout (Oncorhynchus mykiss)

The aim of the present study was to evaluate alpha lipoic acid (ALA) supplementation as an antioxidant source. In this experiment, rainbow trout with average weight of 22.16 ± 0.02 g were studied in four treatments with three replications for eight weeks. Experimental diets included control (non-supplemented commercial diet), 500 mg/ kg ALA, 1000mg/ kg ALA and diets containing 1500 mg/ kg ALA. After eight weeks, growth parameters, fish muscle composition, levels of glutathione-S-transferase (GST), glutathione (GSH) and catalase (CAT) activity were measured in muscle, liver and intestine. The results of growth factors showed that percentage of weight gain, length increase and specific growth rate were significantly (p<0.05) different between treatments and highest in 500 and 1000 mg/ kg ALA. Results of rainbow trout carcass fed with ALA showed a significant difference in protein and dry matter (p<0.05), and treatment containing 1500 ALA concentration showed the highest carcass protein and dry matter. In addition, the effect of different concentrations of alpha lipoic acid on the activity of GST, GSH and CAT enzymes in muscle, liver and intestinal tissues was significant (p<0.05). In muscle, CAT increased with increasing ALA concentration. Also, the highest and lowest amounts of GSH and GST were observed at 1000 and control concentrations, respectively. In the intestinal and liver tissues, the activity of GSH, GST and CAT enzymes was higher in treatments containing ALA. Considering the results of growth, increase of carcass protein and improvement of antioxidant enzymes activity by ALA, it is recommended to use this supplement at a concentration of 1000 mg/ kg.