Replacement of fish meal with defatted silkworm (Bombyx mori L.) pupae meal in diets for Pacific white shrimp (Litopenaeus vannamei)

This study evaluated the effects of replacing fish meal (FM) with defatted silkworm pupae meal (SPM) on growth, diet digestibility, antioxidant capacity, hepatopancreas histology and molting process in Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated to contain 24% FM, then 25, 50, 75 or 100% of FM was substituted with SPM referred to as FM, SPM25, SPM50, SPM75 and SPM100 diets, respectively. Quadruplicate groups (36 shrimp per replicate) of shrimp (0.2 +/- 0.02 g) were fed the test diets to apparent satiation three times daily for eight weeks. No significant difference (P > .05) in growth performance could be found among FM and SPM groups. Apparent digestibility coefficients of dry matter, gross energy and phosphorous were significantly improved by SPM inclusion. Serum antioxidant parameters including total antioxidant capacity and malondialdehyde concentration were beneficially influenced by SMP inclusion. Higher number of B-cells and lower number of E-cells were detected in hepatopancreatic tubules of SPM100 group compared to the other groups. Moreover, total replacement of FM triggered separation of basal membrane and greater interstitial spaces between the hepatopancreatic tubules. Molting time significantly decreased when FM was entirely replaced with SPM. Also, chitin deacetylase activity was enhanced in SPM100 group, but beta-N-Acetyl-D-glucosaminidase activity, and expression of ecdysteroid receptor and retinoid X receptor remained unchanged. To conclude, the entire replacement of FM with SPM did not influence shrimp growth, and its beneficial impacts were found on diet digestibility, antioxidant capacity and molting time. However, the substitution level is recommended to be restricted to 75% as total replacement led to shrinkage of hepatopancreatic cells.