The effects of symbiotic Biomin Imbo supplementation on the antioxidant activities, digestive enzymes and microbial flora of grey mullet, Mugil cephalus intestine

In recent years, the use of dietary supplements, especially synbiotics, in the diet of farmed fish has been considered due to its beneficial effects on fish health. In this study, the effects of different levels of symbiotic Biomin Imbo were examined on the antioxidant activities, digestive and bacterial flora in the intestine of Mugil cephalus. One hundred and twenty grey mullet with a mean weight of 3.92 ± 0.43 g were reared in 60-liter aquaria for 60 days (10 fish in each aquarium) and the treatments were fed with diet containing symbiotic supplement at different levels including 0.5 (T_0.5) , 1 (T₁), 1.5 g (T_1.5) synbiotic per kg of feed, while control contained no supplementation. Feeding was carried out manually. At the end of the experiment, the fish intestine was removed and antioxidant enzyme activities including superoxide dismutase, glutathione peroxidase and glutathione S-transferase as well as digestive enzyme levels including lipase, amylase, alkaline phosphatase, protease, pepsin, chymotrypsin along with microbial flora were assayed. According to the results, superoxide dismutase activity at T₁ and T_1.5 and glutathione S-transferase and glutathione reductase at T₁ were significantly increased compared to the control (p<0.05), whereas glutathione peroxidase activity did not exhibit any significant difference (p>0.05). The high levels of synbiotic displayed significant effects on all the digestive enzyme activities except for alkaline phosphatase and lipase (p<0.05). Total number of viable and lactic acid bacteria in T₁ and T_1.5 significantly increased compared to the control, while the number of coliforms in these treatments was significantly decreased (p<0.05). The findings of the present study exhibited that the diet containing 1 g synbiotic per kg of feed can be used as a suitable dietary supplement for grey mullet.