Alterations in non-specific immune responses, antioxidant capacities and expression levels of immunity genes in Labeo rohita fed with graded level of carbohydrates

A 45-day feeding trial was conducted to study the effect of feeding graded level of gelatinized starch (GS) on stress parameters, growth and immunity of Labeo rohita. Fish were fed with four semi-purified diets containing 30% crude protein with graded level of gelatinized starch, 30% (T₁), 35% (T₂), 40% (T₃) and 45% (T₄). The results exhibited higher weight gain % (WG), specific growth rate (SGR) and protein efficiency ratio (PER) in 45% GS fed group (T₄) with significantly (p < 0.05) lowest feed conversion ratio (FCR). The blood NBT and serum complement 3 (C3), serum protein, albumin and globulin contents were increased with the increase in GS level in the diet. The SOD, catalase, alanine transaminase (ALT) and aspartate transaminase (AST) in liver increased significantly (p > 0.05) with the increasing level of GS in the diet. In addition, the high carbohydrate level (CHO) 40% and 45% significantly upregulated the mRNA level of immune related genes like Nuclear Factor Kappa B (NFkB) and Interleukin (IL8) in both liver and kidney. Furthermore, highest percentage of survival was found in T₄ group after challenged with Aeromonas hydrophila followed by T₃ group. The results of the present study suggest that Labeo rohita fingerlings can utilize the high digestible carbohydrate upto 45% without affecting growth and immunity.