Effect of dietary multi-stimulants blend supplementation on performance, digestive enzymes, and antioxidants biomarkers of common carp, Cyprinus carpio L. and its resistance to ammonia toxicity

With the expansion of the fish farming, functions of growth-stimulants including protective and antioxidative agents should be examined for their potential benefits to the farmed fish. Generally, a single feed supplement was used to enhance fish growth but the use of multi-stimulants blend is rarely evaluated. It is hypothesized that fish diets enriching with multi-stimulants blend would improve fish performance and reduce stress response better than a mono-stimulant. Therefore, an eight-week feeding trial was conducted to determine the effect of dietary supplementation of Aquamax pellet blend (AMP; a mixture of Bacillus amyloliquefaciens, sodium butyrate, zinc methionine, and digestive enzymes) on growth performance, body composition, digestive enzymes, and antioxidant status of common carp, Cyprinus carpio L. Fish were fed on diets enriched with 0.0, 0.5, 1.0, 2.5, and 5.0 g AMP/kg diet. After the feeding trial, fish were exposed to 0.5 ppm of unionized ammonia for 6 h and fish mortality was observed. Fish growth and feed intake enhanced significantly with rising AMP levels from 0.5 up to 2.5 g/kg diet after which fish growth dismissed. Comparing with the control diet, intestinal amylase, lipase, and protease as well as activities of superoxide dismutase, catalase, and glutathione peroxidase significantly rised, while lipid peroxidation, measured as malondialdehyde, significantly decreased with AMP supple-mentation up to 1.0-5.0 g/kg diet. In addition, it is noticed that the AMP supplementation improved fish re-sistance against ambient ammonia stress where the mortality of the control fish was significantly higher (65%) than those fed AMP-enriched diets (25-35%). The regression analysis in the present investigation showed that the optimum dietary level of AMP supplementation was found to be 2.5 g/kg diet.