Effects of enzymatic hydrolysis chicken by‐product in high plant‐based protein diet on growth performance, digestive capacity, antioxidant capacity and non‐specific immunity of juvenile turbot ( Scophthalmus maximus L.)

Abstract

A 60-day feeding trial was conducted to investigate the effect of enzymatic hydrolysis chicken by-product (EHC) supplementation in high plant protein diets on growth performance, digestive capacity, antioxidant capacity and non-specific immunity of juvenile turbot (Scophthalmus maximus L.). The diet with 620 g/kg fish meal (FM) was used as the positive control group (FM group), while the diet with 372 g/kg FM and 256 g/kg degossypolled cottonseed protein were used as the negative control group (0 g/kg EHC group). Based on the negative control diet, grade levels of EHC (10, 20, 30 and 40 g/kg) were added, respectively. Results showed that fish fed with a high plant protein diet showed significantly lower growth performance, digestive capacity, antioxidant capacity and non-specific immunity than those of the positive control. The supplementation of 20 g/kg EHC significantly increased growth performance of fish as compared to the negative control. Furthermore, the digestive capacity of turbot fed the diet with 20 g/kg EHC was significantly improved by increasing activities of trypsin, pepsin and lipase and the expression of peptide transporter 1 (pept1). The antioxidant capacity and non-specific immunity of fish fed the diet with 20, 30 and 40 g/kg EHC were significantly improved by increasing activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (T-AOC), lysozyme (LZM) and acid phosphatase (ACP) in serum, decreasing the expression of interleukin-1β (il-1β) and tumour necrosis factor-α (tnf-α) and increasing the expression of transforming growth factor-β (tgf-β). In conclusion, the adverse effect of high plant protein diet on growth performance of turbot could be improved with the supplementation of 20 g/kg EHC, which could be due to the positive effect of EHC on digestive capacity, antioxidant capacity and non-specific immunity of juvenile turbot.