Defatted black soldier fly (Hermetia illucens) larvae meal can replace soybean meal in juvenile grass carp (Ctenopharyngodon idellus) diets

Abstract

In order to study the effects of replacement of soybean meal (SM) with defatted black soldier fly larvae meal (BSFLM) in grass carp production practice, juvenile grass carps with initial body weight of (10.10 ± 0.28) g were selected for subsequent tests. Five isolipidic (49.1–50.3 g kg−1) and isonitrogen (321.4–327.8 g kg-1) experimental diets were formulated by replacing 0 % (SM), 25% (BSFLM25), 50% (BSFLM50), 75% (BSFLM75) and 100% (BSFLM100) of SM with BSFLM, respectively. After 56 days of feeding, the changes of growth performance, body composition, serum biochemical indexes, antioxidant capacity, digestive enzyme activity, intestinal and liver tissue structure, and intestinal microbiota of grass carp were detected. The results showed that there were no significant differences in growth, feed efficiency and muscle proximate compositions among the treatment groups. The BSFLM100 group had significantly higher TG content than the other groups. Catalase activity was significantly increased in BSFLM25 and BSFLM50 groups compared with that in the SM group. The activities of amylase and lipase in BSFLM50, BSFLM75, and BSFLM100 groups were lower than the control group. Compared with the SM group, the intestinal villi length and the thickness of the intestinal wall of BSFLM75 and BSFLM100 groups were decreased. Gut microbiota analysis showed no significant changes in the operational taxonomic unit (OTU) diversity and richness indices among treatments. However, the abundance of Aeromonas and Shewanella decreased significantly after substitution with BSFLM. These results show that there was no negative effect on growth performance and improved the antioxidant capacity of grass carp when dietary SM complete replacement by BSFLM. However, when the replacement level exceeds 50 %, intestinal histomorphology may be damaged.