为了探讨饲料蛋白质和碳水化合物对斜带石斑鱼的互作效应,实验采用3×3因子设计,配制蛋白质水平(P)为38%、45%和52%,淀粉水平(S)为10%、20%和30%的9种实验饲料,分别饲喂斜带石斑鱼56 d.结果显示,38%粗蛋白与10%淀粉饲料组(38P/10S饲料组)增重率显著低于其他各组,52P/10S组增重率最高,但与45P/20S、45P/30S、52P/20S组差异不显著.增加饲料蛋白质或淀粉水平显著增加饲料效率、鱼体蛋白质与脂肪含量及肝糖原肝脂含量,而降低摄食率和鱼体水分含量.增加饲料蛋白质水平降低蛋白质效率,但增加淀粉水平却增加蛋白质效率及肝体比与脏体比.饲料蛋白质水平和淀粉水平对鱼体灰分含量无明显影响.肝中肝酯酶、脂蛋白酯酶、脂肪酸合成酶、谷丙转氨酶和谷草转氨酶活性均随蛋白质或淀粉水平的升高呈显著上升趋势.增加饲料蛋白质水平显著降低肝中葡萄糖-6-磷酸酶活性,而增加肝中苹果酸酶活性,但对肝中葡萄糖激酶、丙酮酸激酶、磷酸果糖激酶、磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸脱氢酶活性没有明显影响.增加饲料淀粉水平显著增加肝中葡萄糖激酶、丙酮酸激酶、磷酸果糖激酶、葡萄糖-6-磷酸脱氢酶和苹果酸酶活性,但显著降低磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸酶活性.上述结果显示,斜带石斑鱼的生长和肝脏代谢明显受饲料蛋白质和淀粉水平的影响,其中,糖代谢酶活性受淀粉水平的影响较大,而受饲料蛋白质水平的影响较小,斜带石斑鱼生长适宜的饲料蛋白质和淀粉水平分别为45%和20%.%A 3×3 factorial experiment was designed to determine the interactive effects of dietary protein and starch levels on growth performance of grouper (Epinephelus coioides). Nine diets were formulated to contain three levels of crude protein (P) (38%, 45% and 52%) and three levels of starch (S) (10%, 20% and 30%). Fish were fed the diets twice daily over a 56-day study period. Fish fed 38% crude protein and 10% starch diet (38P/10S diet) had significantly lower weight gain rate than those fed other diets, and fish receiving 52P/10S diet achieved highest weight gain rate among the test diets, but comparable to fish receiving diets 45P/20S, 45P/30S and 52P/20S. Increasing dietary crude protein and starch levels led to increased feed efficiency, whole-body protein and lipid liver glycogen content and liver lipid contents, and reduced daily feeding rate and whole-body moisture content. Increasing dietary protein level decreased protein efficiency ratio, but increasing dietary starch level increased hepatosomatic index, protein efficiency ratio and viscerasomatic index. Dietary protein and starch levels did not affect whole-body ash content. Hepatic lipase, lipoprotein lipase, fatty acid synthetase, glutamic-oxalacetic and glutamic-pyruvic transaminase activities increased with the increase in dietary protein or starch level. Increasing dietary protein level resulted in lowered liver glucose-6-phosphatase activity, and elevated liver malic enzyme activity, but did not affect liver activities of glucokinase, pyruvate kinase, phosphofructokinase, phosphoenolpyruvate carboxykinase and glucose-6-phosphate dehydrogenase. Increasing dietary starch level led to increased liver activities of glucokinase, pyruvate kinase, phosphofructokinase, glucose-6-phosphate dehydrogenase and malic enzyme, but reduced activities of phosphoenolpyruvate carboxylase kinase and glucose-6-phosphatase. These results indicate that the growth and liver metabolism of grouper were affected by both dietary protein and starch levels, in which the enzyme activity related to glucose metabolism responds to dietary starch level more sensitively than dietary protein level. The diet containing 45% protein and 20% starch is suitable for the optimal growth of this fish species.
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