Effects of dietary cysteamine addition to a plant-based diet on growth performance, body composition, hepatosomatic histological structure and metabolism of taurine synthesis in turbot (Scophthalmus maximus L.)

Abstract

This present study was conducted to illustrate the effect of dietary cysteamine on feeding, growth, biochemistry composition, hepatosomatic histological structure and metabolism of taurine synthesis in juvenile turbot (Scophthalmus maximus L.) (2.0 ± 0.01 g) fed high plant protein diets. A fishmeal-based diet (72.5% FM) was designed as the control diet (DietFM). Four isonitrogenous and isolipidic diets consist of 14.0% FM, 23.0% soybean meal and 30.0% wheat gluten meal, which were formulated to substitute FM with 0.0%, 0.05%, 0.1% and 0.15% cysteamine hydrochloride (labeled as DietPP, DietCS-0.05%, DietCS-0.1% and DietCS-0.15% respectively). Fish were stochastically allocated into fifteen 200L tanks and fed twice daily (06:30 and 18:30) to apparent satiation for 9 weeks. Feed intake (FI) in fish-fed DietCS-0.05% was conspicuously higher than that in fish-fed DietPP (p<0.05), and no notable difference was discovered among fish-fed diets with cysteamine inclusion (p>0.05). No conspicuously upward trend was found with the increase of dietary cysteamine in FBW, SGR, WGR, FER, PER, and SR when there was a downward trend in CF, VSI, and HSI (p>0.05). A remarkable increase was discovered from 0.0% to 0.05% cysteamine inclusion in ash content (p<0.05) when no noticeable difference was observed among all the cysteamine inclusion groups in moisture, protein, and lipid content (p>0.05). Only the body taurine content showed a notable increase between fish-fed DietCS-0.05% and fish-fed DPP among the indexes of body taurine, liver taurine, and serum taurine content (p<0.05), whereas no notable difference was observed in hepatosomatic L-cysteine sulfinate decarboxylase (CSD) and cysteamine dioxygenase (CDO) activities among all the cysteamine inclusion groups (p>0.05). The cellular morphology and cell veins in the liver of fish-fed diets with cysteamine inclusion were clearer than those of fish-fed DPP. The results showed that 0.05% cysteamine addition in a high plant protein diet is optimal.