Effects of dietary sodium humate on growth, antioxidant capacity, non-specific immune response, and resistance to Aeromonas hydrophila in genetic improvement of farmed tilapia (GIFT, Oreochromis niloticus)

Abstract

This study was conducted to evaluate the effects of dietary sodium humate (SH) on growth, antioxidant capacity, non-specific immune response and resistance to Aeromonas hydrophila in GIFT tilapia Oreochromis niloticus. Fish were fed diets supplemented with graded levels of SH (0%, 0.1%, 0.2%, 0.4% and 0.6%) for nine weeks. The fish were then challenged by A. hydrophila and their cumulative survival rate was recorded for the next week. Dietary SH inclusion significantly affected daily growth coefficiency (DGC), protein retention (PR), energy retention (ER), midgut antioxidant-related enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase) activities and glutathione content, serum and midgut lysozyme activities, phagocytosis percentage (PP) of head kidney macrophages and post-challenge survival rate. The second order polynomial regression analysis showed that the optimal supplementation level of SH was estimated to be 0.32%, 0.28%, 0.35%, 0.33%, 0.35%, 0.33%, 0.29% and 0.37% for DGC, feed conversion ratio, PR, ER, serum lysozyme activity, midgut lysozyme activity, PP of head kidney macrophages and post-challenge survival rate, respectively. The results suggested that dietary inclusion of 0.28–0.37% SH will contribute to improve the growth and health of GIFT tilapia, indicated that SH can be used as a useful feed additive in the diets of tilapia.