Effects of partial substitution of enzymatic hydrolysate of poultry by-product meal for fishmeal on the growth performance, hepatic health, antioxidant capacity, and immunity of juvenile largemouth bass (Micropterus salmoides)

Abstract

A 95-day experiment was conducted to evaluate the feasibility of partially substituting fishmeal with enzymatic hydrolysate of poultry by-product meal (EHPB) as feed for juvenile largemouth bass (Micropterus salmoides). Five diets (EHPB0, EHPB3, EHPB6, EHPB9, and EHPB12) of fishmeal were 45% (0% EHPB, the control group), 41% (3.1% EHPB), 37% (6.2% EHPB), 33% (9.3% EHPB), and 29% (12.4% EHPB), respectively. The initial mean weigh of largemouth bass was 22.35 ± 0.08 g. There were no significant differences in growth performance among all EHPB groups compared with the control (P > 0.05). The growth performance of EHPB3 was significantly better than that of EHPB12 (P 0.05). Hepatic glutathione (GSH) content and glutathione peroxidase (GPx) activity were highest for the control (EHPB0). The hepatic superoxide dismutase (SOD) and catalase (CAT) activity levels were significantly lower for all treatments than the control except for EHPB3 (P < 0.05). Keap1 in the Nrf2 pathway was significantly upregulated and cat was significantly downregulated under all treatments compared with the control except for EHPB3 (P < 0.05). Jnk1/2, nf-κb, il-8/10, tnf-α, and traf2 were significantly upregulated under EHPB6 relative to the control (P < 0.05). The diet containing 29% basal fishmeal (12.4% EHPB) did not affect the growth performance of juvenile largemouth bass. However, the optimal levels of the genes related to antioxidant performance and immune function were attained under 3.1% EHPB (41% fishmeal).

Keywords

• Enzymatic hydrolysate of poultry by-product
• Growth performance
• Hepatic health
• Largemouth bass