Defatted black soldier fly (Hermetia illucens) larvae meal in diets for juvenile Jian carp (Cyprinus carpio var. Jian): Growth performance, antioxidant enzyme activities, digestive enzyme activities, intestine and hepatopancreas histological structure

A 59-days feeding trial was carried out to estimate the effects of fish meal replacement by defatted black soldier fly larvae meal (DBSFLM) on growth performance, antioxidate enzyme activities, digestive enzyme activities, hepatopancreas and intestinal morphology in Jian carp (Cyprinus carpio var. Jian) juveniles (initial mean body weight, 34.78 g). Five isolipidic (5.29 +/- 0.04%) and isoprotein (40.69 +/- 0.11%) diets were formulated by replacing 0%, 25%, 50%, 75%, 100% fish meal (FM) protein with graded DBSFLM levels of 0%, 2.6%, 5.3%, 7.9% and 10.6%. Each diet was randomly assigned to triplicate groups of 20 fish per aquarium. Fish were fed three times daily to apparent satiation. The results showed that the growth performance and nutrients utilization of fish in five groups were not different (P > 0.05). The hepatopancreas lipid and serum cholesterol content of treated groups was significantly lower than that of the control group (P < 0.05). With increasing dietary DBSFLM level, the activity of the CAT significantly increased. No significant differences in the activity of intestinal protease, lipase and diastase were observed among dietary groups (P > 0.05). The histological examination of intestine showed that when 75% or more FM protein was replaced, apparent pathological changes for example tissue disruption were observed in intestine, and relative gene expression of HSP70 in hepatopancreas significantly increased (P < 0.05). The histological examination of hepatopancreas sections showed less vacimlated with lipid deposits in treatment groups compared with control group. These results suggested that the growth of Jian carp was not affected by dietary DBSFLM, while it boosted antioxidant status of Jian carp by higher CAT activity. However, dietary stress and intestinal histopathological damage was observed when the replacement levels exceeded 75%. The study demonstrates that it is suitable to replace up to 50% of dietary FM protein with DBSFLM.