The effects of substituting fish meal with soy protein concentrate on growth performance, antioxidant capacity and intestinal histology in juvenile golden crucian carp, Cyprinus carpio × Carassius auratus

Abstract

This study was to evaluate the effects of substituting fish meal (FM) with soy protein concentrate (SPC) on growth, non-specific immune function, antioxidant capacity and intestinal histology in juvenile golden crucian carp, Cyprinus carpio × Carassius auratus. Six isonitrogenous (40 % crude protein) and isolipidic (8 % crude lipid) diets were formulated with SPC to replace 0 % (FM control; SPC0), 20 % (SPC20), 40 % (SPC40), 60 % (SPC60), 80 % (SPC80) and 100 % (SPC100) of FM. Groups of golden crucian carp (initial weight 2.45 ± 0.01 g) fed each diets were cultured in triplicate 100-L tanks (50 fish per tank), and the fish were fed three times a day (07:00, 12:00 and 17:00) to apparent satiation for 8 weeks. Results showed that the growth performance and feed efficiency were significantly decreased when dietary FM was completely replaced by SPC compared with control group. However, no significant differences were found on feed intake (FI) and survival rate (SR) among all groups. Compared with the control group, offering SPC100 diets significantly reduced the crude lipid and crude protein contents of the whole-body and muscle. Similarly, the protease activities of the proximal intestine, mid intestine and distal intestine showed a similar trend, and the SPC100 group was significantly decreased than the SPC0 and SPC20 groups. Typical characteristics of distal intestinal damage are shown in the SPC100 group, including the atrophy of mucosal fold, widening of lamina propria and separation of epithelial mucosa from the lamina propria. The activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in liver decreased with increasing dietary SPC levels. Additionally, replacing 80 % and 100 % of dietary FM with SPC will reduce the antioxidant capacity and non-specific immune function of golden crucian carp. These results indicate that under the reported conditions SPC may be included in the diet up to 393.4 g/kg as a substitute for FM, replacing about 80 % of FM in the diet of juvenile golden crucian carp.