The present study was conducted to investigate the protein requirement of grouper Epinephelus coioides at grow‐out stage (initial weight of 102.8 ± 1.02 g). Six iso‐lipidic diets were formulated using white fish meal and casein as protein sources with graded levels of protein (350, 400, 450, 500, 550 and 600 g/kg). Grouper was hand‐fed twice daily to apparent satiation in triplicates for 8 weeks. The results showed that lack of protein will lead to the declined of weight gain and specific growth rate and suitable protein not only improved growth, but also reduced feed coefficient rate. In addition, high‐protein level diet significantly decreased the morphological index of grouper. For the body proximate composition analysis, the high‐protein diets (500, 550, 600 g/kg) significantly increased the protein contents in the whole body and muscle which was contrary to as observed for the lipid content. High‐protein diets significantly improved the total protein levels of plasma which were contrast to as observed in triglyceride contents. Moreso, the cholesterol content was observed to be significantly decreased after high‐protein diet supplementation. The intestinal protease activity was observed to increase significantly with increasing protein supplementation whereas a decreasing trend was observed for the lipase and amylase activity with the highest going for the groups fed diets containing 350 g/kg protein as compared to the others. The liver alkaline phosphatase, superoxide dismutase and lysozyme activity increased with increasing protein level which later decreased. On the other hand, the acid phosphatase activity showed a significant downward trend. Based on SGR, the broken‐line regression analysis showed that the optimum dietary protein level and digestible protein level of the grouper Epinephelus coioides at grow‐out stage were 466.65 and 395.79 g/kg, respectively.

中文翻译：

---

石斑鱼石斑鱼成鱼期的蛋白质需求

本研究旨在调查石斑鱼石斑鱼的蛋白质需求量在成长期（初始体重102.8±1.02 g）。使用白色鱼粉和酪蛋白作为蛋白质来源，按蛋白质的分级水平（350、400、450、500、550和600 g / kg）配制六种等脂饮食。每天两次给石斑鱼喂食，一式三份，以使其饱食，持续8周。结果表明，缺乏蛋白质会导致增重和比生长率下降，而合适的蛋白质不仅会促进生长，还会降低饲料系数。此外，高蛋白饮食会明显降低石斑鱼的形态指标。对于人体的临近成分分析，高蛋白饮食（500、550、600 g / kg）显着增加了全身和肌肉中的蛋白质含量，这与脂质含量所观察到的相反。高蛋白饮食显着改善了血浆总蛋白水平，这与甘油三酸酯含量观察到的相反。此外，补充高蛋白饮食后，胆固醇含量明显降低。观察到肠道蛋白酶活性随蛋白质添加量的增加而显着增加，而脂肪酶和淀粉酶活性则呈下降趋势，而含350 g / kg蛋白质日粮组的脂肪酶和淀粉酶活性最高。肝碱性磷酸酶，超氧化物歧化酶和溶菌酶活性随蛋白质水平的升高而增加，随后降低。另一方面，酸性磷酸酶活性显示出明显的下降趋势。基于SGR，斜带石斑鱼在养成阶段分别为466.65和395.79克/千克。