Efficacy of vitamin E with or without probiotic, astaxanthin or rosemary extract on growth performance, survival, haematological parameters, antioxidant activity and liver enzymes in rainbow trout (Oncorhynchus mykiss)

Growth and health status of rainbow trout (Oncorhynchus mykiss) (170.46 +/- 1.16 g) fed diets containing 50 mg kg(-1) vitamin E (control), 250 mg kg(-1) vitamin E, 500 mg kg(-1) probiotic (Bacillus lichiniformis + Bacillus subtilis each at 10(8) cfu g(-1)), 50 mg kg(-1) astaxanthin and 500 mg kg(-1) rosemary (Rosmarinus officinalis) extract were assessed for 4 months. No significant differences were seen in growth performance among treatments and between treatments and control (p > 0.05). The highest values of protein and lipid efficiency ratios were observed in 250 mg vitamin E, astaxanthin and rosemary trails. Probiotic trail demonstrated lower activity of liver superoxide dismutase (p < 0.05), while rosemary trail was superior (p < 0.05). Vitamin E trail exhibited an improvement in liver glutathione peroxidase compared to other treatments (p < 0.05), while catalase activity was insignificant among the treatments. Total leucocytes, neutrophil, red blood cells and haemoglobulin were insignificantly higher in fish fed probiotic and rosemary than other treatments. The lowest and the highest levels of activity of alanine aminotransferase in fish liver were measured in fish fed diets astaxanthin and control fish, respectively (p < 0.05), while no difference was seen in aspartate aminotransferase (p > 0.05). Fish fed with bacilli probiotic and rosemary extract resulted in higher survival rates compared to other treatments. Overall, these data exhibited that application of diets containing 50 mg vitamin E plus each rosemary extract (50 mg kg(-1)) or bacilli probiotic (500 mg kg(-1)) could be effective in maintaining health status of rainbow trout.