Effects of dietary defatted black soldier fly (Hermetia illucens) larvae meal substituting fish meal on growth, antioxidative capacity, immunity, intestinal histology and microbiota of juvenile Chinese mitten crab (Eriocheir sinensis)

This study evaluated the effects of replacing dietary fish meal (FM) with defatted black soldier fly ( Hermetia illucens ) larvae meal (DBSFLM) on growth, non-specific immunity, antioxidative capacity, intestinal histology and microbiota of juvenile Chinese mitten crab ( Eriocheir sinensis ). A control diet was designed to contain 200 g/kg FM (Con), then 25 %, 50 %, 75 %, and 100 % of dietary FM was replaced by DBSFLM, referring to DBSFLM25, DBSFLM50, DBSFLM75 and DBSFLM100, respectively. The five isoproteic and isolipidic diets were fed to crab (7.15 ± 0.10 g) for 8 weeks. The results indicated that the final weight, weight gain , feed conversion ratio and survival of DBSFLM25 and DBSFLM50 groups all reached the same level as Con ( P > 0.05). The proper DBSFLM replacement on WG and FCR from broken line model were 49.70 % and 52.90 %, respectively. For immune enzyme activity , ACP , ALP , and LZM activities showed a trend of first increasing and then decreasing, the DBSFLM50 group had the highest activity, and the DBSFLM100 group was significantly lower than the DBSFLM50 group ( P < 0.05). In terms of antioxidant capacity, the T-AOC, T-SOD, GSH-Px activities and MDA content of DBSFLM25 DBSFLM50 and DBSFLM75 groups all shows no significant difference with Con ( P > 0.05), the DBSFLM100 group has the lowest antioxidant enzyme activities and highest MDA content. The intestinal number of folds and folds height in DBSFLM25 and DBSFLM50 groups reached the same level as Con ( P > 0.05). The abundance of intestinal harmful bacteria Vibrio was enhanced with the increase of dietary DBSFLM level ( P < 0.05). In conclusion, the recommended level of replacing FM with DBSFLM was at 50 % (100 g/kg) without negative effect on growth, non-specific immunity, antioxidative capacity, intestinal histology and microbiota of Chinese mitten crab.