Effects of replacing fish meal with defatted black soldier fly (Hermetia illucens) larvae meal on growth performance, nutrient retention, serum biochemical parameters and digestive enzymes activity of juvenile Pelteobagrus fulvidraco

A 56-d feeding trial with 480 yellow catfish (Pelteobagrus fulvidraco) juveniles (1.67±0.01) g initial body weight was carried out to estimate the effect of replacing fish meal with defatted black soldier fly larvae meal (DBSFLM) on growth performance, nutrient retention, serum biochemical parameters and digestive enzymes activity of juvenile P. fulvidraco. Fish were randomly allocated into four isolipidic and isoprotein dietary treatments which were formulated by replacing 0 (T0), 20% (T20), 40% (T40) and 60% (T60) of fish meal (FM) protein with DBSFLM. Each treatment was randomly assigned to triplicate groups of 40 fish per aquarium. Fish were fed twice daily to apparent satiation. With increasing content of DBSFLM, the final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) of yellow catfish increased first and then decreased. Growth performance of FBW, WGR and SGR in T20 were highest and higher than T60, whereas the feed conversion rate was the lowest. The feed intake in T20 and T60 was higher than that in control and T40 groups. With the increasing content of DBSFLM, the intraperitoneal fat index (IFI) was declining, T60 group was lower than control, and ash, calcium retention declining with T40 and T60 groups lower than control.There was no difference of condition factor, viscera index, hepatosomatic index, intestine index and gastric index among treatments. Nutrient retention such as protein,lipid and phosphorus, moisture, crude protein, lipid and ash in whole body were not affected by dietary treatments. Compared with control, the serum cholesterol and triglyceride were reduced and the high density/low density lipoprotein cholesterol increased in T20, T40 and T60 groups and pepsase and intestinal trypsin increased in T40 group. Results suggested that the growth performance and body composition of yellow catfish juveniles were not affected by dietary DBSFLM and the optimal alternative ratio was 20%, which was better than control. The replacement of fish meal with DBSFLM may reduce IFI, serum triglyceride, cholesterol and ash, calcium retention and increase protease activity.