The reported requirements of largemouth bass (LMB, which is native to North America) for dietary protein and lipids varied substantially among previous studies, and this fish fed current formulated diets exhibit poor growth performance and pale liver syndrome. Because amino acids and lipids are known to affect hepatic metabolism and function in mammals, it is imperative to understand the impacts of these dietary macronutrients on the growth and liver morphology of LMB. In this study, we designed six isocaloric diets to determine the effects of different dietary crude protein (CP; 40%, 45%, and 50%; dry matter basis) and lipid levels (7.5% and 10%; dry matter basis) on fat and glycogen deposits, as well as hepatosis in LMB. There were four tanks (12 fish per tank, an average initial weight of 18.4 g/fish) per dietary treatment group and the trial lasted for 8 weeks. Fish were fed to apparent satiation three times daily. Results indicated that LMB fed the 45% or 50% CP diet grew faster (P < 0.05), had less (P < 0.05) glycogen in the liver and smaller (P < 0.05) hepatocyte sizes than fish fed the 40% CP diet, but there was no difference in weight gain or feed efficiency between the 45% and 50% CP diets. The hepatic lipid content did not differ between LMB fed the 40% and 45% CP diets, and the values for these two groups were 29% lower (P < 0.05) than those for LMB fed the 50% CP diet. Compared with the 40% CP group, LMB fed the 45% or 50% CP diet had 8–12% lower content of total minerals, phosphorus, and calcium in the body. Increasing the dietary lipid level from 7.5 to 10% enhanced the weight gains (+ 15%) and feed efficiency (+ 22%), as well as the retention of dietary protein (+ 18%), energy (+ 25%), and phosphorus (+ 7.6%) in the body. No fatty liver occurred in any group of LMB (with hepatic lipid concentrations being < 2%, wet weight basis). Based on these growth, metabolic and histologic data, we recommend dietary CP and lipids levels to be 45% and 10%, respectively, for juvenile LMB.

中文翻译：

---

日粮蛋白质和脂质水平对大嘴鲈（Micropterus salmoides）的生长性能，饲料利用率和肝脏组织学的影响。

在以前的研究中，据报道，大嘴鲈鱼（北美本地产的LMB）对饮食蛋白质和脂质的需求差异很大，并且这种鱼饲喂当前配制的饮食表现出较差的生长性能和苍白肝综合症。因为已知氨基酸和脂质会影响哺乳动物的肝脏代谢和功能，所以必须了解这些饮食中的大量营养素对LMB的生长和肝脏形态的影响。在这项研究中，我们设计了六种等热量饮食，以确定不同饮食粗蛋白（CP； 40％，45％和50％；以干物质为基础）和脂质水平（7.5％和10％；以干物质为基础）的影响。脂肪和糖原的沉积，以及LMB中的肝病。有四个水箱（每个水箱12条鱼，平均初始重量为18）。每个饮食治疗组4克/鱼），试验持续8周。每天将鱼喂饱三顿。结果表明，饲喂45％或50％CP饮食的LMB生长更快（P  <0.05），具有较少（P 在肝脏<0.05）糖原和小（P  <0.05）肝细胞尺寸小于鱼饲喂40％CP饮食，但有体重增加或45％之间的饲料效率没有差别和50％CP饮食。饲喂40％和45％CP的LMB饲喂的LMB之间的肝脂质含量没有差异，两组的值均降低了29％（P <0.05），而饲喂50％CP饲料的LMB则小于0.05。与40％CP组相比，饲喂45％或50％CP饮食的LMB体内总矿物质，磷和钙的含量降低了8-12％。饮食脂质水平从7.5增加到10％可以增加体重增加（+ 15％）和饲料效率（+ 22％），并保留饮食蛋白（+ 18％），能量（+ 25％）和体内的磷（+ 7.6％）。在任何LMB组中均未出现脂肪肝（肝脂质浓度<2％，以湿重计）。根据这些生长，代谢和组织学数据，我们建议青少年LMB的日粮CP和脂质水平分别为45％和10％。