Dietary fructooligosaccharide can mitigate the negative effects of immunity on Chinese mitten crab fed a high level of plant protein diet

Abstract An 8-week feeding trial was carried out under controlled condition to evaluate the effect of dietary fructooligosaccharide (FOS) on growth performance, whole body composition, antioxidant status and immunity of crabs fed high levels of plant protein diets. Thus, six experimental diets were formulated (designated as F 0 P 50 , F 0 P 60 , F 0 P 70 , F 0.2 P 50 , F 0.2 P 60 and F 0.2 P 70 ), which contain two FOS levels (0 or 0.2%) and three plant protein levels (50, 60, or 70%) according to a 2 × 3 factorial design. The results showed that weight gain increased significantly as dietary plant protein level decreased from 70% to 50%. At 50% plant protein level, the addition of 0.2% FOS can significantly elevate weight gain (WG) ( P 0.2 P 50 and F 0.2 P 60 diet. Crabs fed F 0.2 P 50 diet showed significantly higher crude protein content ( P P  > 0.05). Catalase (CAT) activity in crabs fed F 0.2 P 50 increased significantly ( P 0 P 60 , F 0 P 70 , F 0.2 P 60 and F 0.2 P 70 , but malondialdehyde (MDA) concentrations decreased significantly ( P P propo ) was significantly ( P myd88 ). The mRNA expressions of mitochondrial manganese superoxide dismutase ( mtmnsod ), lipopolysaccharide-induced TNF-α factor ( litaf ) and toll like receptors (tlrs) were significantly affected ( P cytmnsod ) mRNA expressions in F 0.2 P 50 and F 0.2 P 60 groups were significantly higher than those in F 0 P 70 and F 0.2 P 70 groups. The results in this study indicated that supplementation with 0.2% FOS can enhance growth performance in crabs fed lower plant protein diets and as well improve immunity in those fed with higher plant protein diets.