Investigation of effect of variouslevels of Lactobacillus acidophilus on serum oxidative stress response and biochemical parameters of rainbow trout (Oncorhynchus mykiss) exposed to lead in diet

Application of functional ingredients like probiotics could be effective in promotiong of aquatic animals performance. The aim of this study was to investigate the effect of various levels of probiotic bacterium Lactobacillus acidophilus on some serum biochemical and antioxidant factors of rainbow trout (Oncorhynchus mykiss) following dietary lead poisoning. 375 trout fish were randomly divided into five groups in three replications. Groups 1, 2 and 3 were respectively fed with diets containing 5 × 106, 5 × 107 and 5 × 108 CFU / g probiotic bacteria from beginning to end of the experiment. Group 4 (control) was fed witha diet free of probiotic and lead. Group 5 was fed with probiotic-free diet for 45 days and then with a diet containing 500 μg / kg lead nitrate (for 21 days) to end of the experiment similar to probiotic-consuming treatments. Bleeding of fish was done on days 0, 45, 52, 59 and 66. The results showed that levels of glucose, phosphorus,ALP and SOD were significantly higher and cholesterol and triglyceride levels were significantly lower (p <0.05)in group 2 compared to control group after 45 days probiotic consumption. After lead exposure, LDH values on day 59 and ALP values in all days were significantly lower in group 2 compared to group 5 (p <0.05). Also, catalase and SOD levels were significantly higher in group 2 than group 5 on day 66 (p <0.05). The results of this study revealed that Lactobacillus acidophilus,as a probiotic,can be effective in improving the blood serum indices of trout before and after lead exposure. Also, level of 5 × 107 CFU / g of probiotic had a better effect on the serum parameters.