Effect of Moringa oleifera Leaf Meal Supplementation on Growth Performance, Morphological Indexes, Antioxidant Status and Resistance to Streptococcus agalactiae of Nile Tilapia (Oreochromis niloticus)

An 8-week feeding trial was conducted to evaluate the effect of Moringa oleifera leaf meal (MOLM) on growth performance, antioxidant status and morphological indexes in Nile tilapia (Oreochromis niloticus). Resistance to Streptococcus agalactiae was also assessed based on a 192h challenge experiment after feeding trial. Fish (initial mean weight 4.05 +/- 0.05g) were held in 21 tanks (volume 300L, 30 fish/tank), with triplicate treatment groups being fed to apparent satiation three times each day on practical diets adding different levels of MOLM (0, 0.1, 0.5, 2, 5, 10 and 20%). Sampling procedure was performed after 24h of fasting. Growth metrics showed no significant differences among groups. Whole-body lipid content, viscerosomatic index and intraperitoneal fat ratio were decreased as dietary MOLM levels increasing. Total superoxide dismutase (T-SOD) and reduced glutathione content (GSH) were significantly influenced by MOLM. Moreover, the lowest cumulative mortality rate (CMR) after challenge experiment was noted in 10% group. Based on CMR and quadratic regression analysis of liver GSH content, it was concluded that dietary MOLM levels of 8.15-10.00% may be beneficial for enhancing resistance to S. agalactiae infection. Our results suggest that the maximum additive amount of MOLM reached 20% under the condition of the present study.