Growth Performance and Immune Response of Snakehead, Channa striata (Bloch 1793) Fed Soy Diets with Supplementation of Mannan Oligosaccharides

This study evaluated the effectiveness of mannan oligosaccharides (MO) supplementation in fish meal (FM), soybean meal (SBM) and soy protein concentrate (SPC) formulated feeds for snakehead, Channa striata (Bloch 1793) in a two-way factorial experiment. Factors were diet (FM, 40% FM replacement by SBM, and 40% FM replacement by SPC) and MO supplementation (0%, 0.2%, or 0.4% MO). Growth was significantly affected (p 0.05) by diet and MO supplementation, as well as their interaction. Feed conversion ratio, protein efficiency ratio and survival were significantly affected (p 0.05) by diet, but only survival was significantly affected (p 0.05) by MO supplementation, and interactions were insignificant (p 0.05). Red blood cell counts were not significantly affected (p 0.05) by diet, MO supplementation, or the interaction, but white blood cell counts were significantly affected (p 0.05) by diet and MO supplementation, not the interaction. Immunoglobulin (Ig) levels were significantly increased (p 0.05) by MO supplementation and the MO x diet interaction, but diet did not affect Ig levels (p 0.05). Following a 15-d bacterial challenge with Aeromonas hydrophila, lysozyme levels were significantly increased (p 0.05) by MO supplementation and the MO x diet interaction, but not by the diets themselves. Cumulative mortality did not differ among fish fed different diets (p 0.05). Our results suggest that MO supplementation may improve diet performance in snakehead culture, although full-scale commercial trials should be conducted to confirm this.