The lenokBrachymystax lenok (Pallas) is one of the most important salmonid fish in northeast China. To date, no information on the optimal dietary protein and lipid levels of this species has been reported. A 10-week feeding trial with four dietary protein levels (40%, 45%, 50% and 55% crude protein) and two dietary lipid levels (8% and 16% crude lipid) was conducted to assess the dietary protein and lipid levels for the growth and of amino acids of juvenile lenok. The results showed that weight gain (WG), specific growth rate (SGR), con-dition factor (CF) and hepatosomatic index (HSI) were significantly affected by dietary protein and lipid levels (P<0.05), and there were also significant interactions between these two factors (P<0.05). WG, SGR, CF and HIS rose with increasing dietary protein levels at each lipid level, and decreased after that. The growth of fish fed the high-lipid level diet was significantly higher (P<0.05) than that of fish fed the low-lipid level diet at 40% and 45% protein diet, whereas these values showed an opposite trend at 50% and 55% protein diet. Fish fed diets with low protein levels had the lowest survival levels of all groups. The lipid content of muscle increased significantly with increasing lipid levels (P<0.05), while moisture, crude protein and ash content were not affected by dietary lipid level. The protein content of muscle increased significantly with increasing protein levels (P<0.05), while lipid and ash content were not affected by dietary protein level. The lipid content of fish fed high-lipid level diets was significantly higher than that of fish fed lower-lipid level diets at each protein level. The protein content of fish fed diets 55P/8L and 55P/16L was significantly higher than that of fish fed in other groups. Seventeen amino acids were found in the muscle of fish. The percentages of total amino acids and the ratios of essential amino acids: total amino acids showed no significant difference among the treatments (P>0.05). The content of the different amino acids was stable and the constitutional rate of the EAAs met Food and Agriculture Organization and World Health Organization standards. The results indicated that the optimum protein and lipid levels for the lenok were 50% and 8%, respectively; and the optimum protein: energy ratio for this species was 29.36 g/MJ.%本研究旨在探讨不同蛋白质和脂肪水平对细鳞鲑(Brachymystax lenok)幼鱼生长、体成分以及肌肉氨基酸含量的影响。采用蛋白质水平为40%、45%、50%和55%，脂肪水平为8%和16%，共8组实验饲料。在水温为(16±0.2)℃的循环流水水族箱系统内进行为期10周的养殖试验。采用常规生化分析方法对该鱼肌肉营养学组成及含量进行测定分析。研究结果表明，不同蛋白和脂肪水平对细鳞鲑幼鱼增重率、特定生长率、肥满度和肝体比等均有显著影响(P<0.05)。随着蛋白水平增加，增重率、特定生长率、肥满度和肝体比率先升高后降低，其肌肉粗蛋白含量也随之显著升高(P<0.05)，而对粗脂肪和粗灰分不存在显著影响；随着脂肪水平增加，其肌肉粗脂肪含量也随之显著提高(P<0.05)，而对水分、粗蛋白和灰分含量不存在显著影响。肌肉中共测定出17种氨基酸(除色氨酸)，不同蛋白和脂肪水平对氨基酸总量(WTAA)和必需氨基酸的构成比例(WEAA/WTAA)不存在显著影响。综合生长性能与氨基酸模式的实验结果，本研究认为细鳞鲑幼鱼最适蛋白质和脂肪水平分别为50%和8%，适宜蛋能比为29.36 g/MJ。
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