The present study was conducted to evaluate the effects of dietary lipid levels on lipid metabolism, growth performance, antioxidant ability and intestinal morphology of rainbow trout (Oncorhynchus mykiss) under cage culture with flowing water. O. mykiss (average initial body weight 17.64 ± 0.05 g) were fed with six diets (L1, L2, L3, L4, L5 and L6) containing six levels of lipid (10.03 %, 12.97 %, 17.22 %, 20.16 %, 23.19 %, 26.06 %) for 8 weeks. Result showed that weight gain (WG), specific growth rate (SGR) and feed intake (FI) of fish were increased with increasing of dietary lipid levels (P < 0.05). Fish fed D6 diet had higher viscerosomatic index (VSI) and mesenteric fat index (MFI) compared with fish fed other diets. The moisture and crude protein contents in whole body and muscle decreased with increasing of dietary lipid levels, but crude lipid content showed the opposite trend. The hepatic superoxide dismutase (SOD) activity was increased with increasing of dietary lipid levels (P < 0.05), while no significant differences were found in hepatic malondialdehyde (MDA) content (P> 0.05). Correspondingly, the mRNA relative expression of SOD in liver was increased with increasing of dietary lipid levels (P < 0.05). Fish fed the diet (L6) containing 26.06 % lipid level showed the optimal intestinal morphology not only in villus amount and height but also in muscular layer thickness. The lipid metabolism related genes expression such as fatty acid synthetase (FAS), lipoprotein lipase (LPL), were significantly affected by dietary lipid levels (P < 0.05). The mRNA relative expression of FAS was increased from L1 to L4 and then decreased with the increasing of dietary lipid levels. The mRNA expression of LPL in fish fed with L5 and L6 diets were significantly higher than other treatments. These results indicated that the suitable lipid requirement of rainbow trout under cage culture with flowing water was not less than 26.06 %.

本研究旨在评价日粮脂水平对网箱养殖流水养殖虹鳟（Oncorhynchus mykiss）脂质代谢，生长性能，抗氧化能力和肠道形态的影响。给O. mykiss（平均初始体重17.64±0.05 g）喂食六种饮食（L1，L2，L3，L4，L5和L6），这些饮食含有六种脂质（10.03％，12.97％，17.22％，20.16％，23.19 ％，26.06％），持续8周。结果表明，鱼的增重（WG），比生长速率（SGR）和饲料采食量（FI）随着饮食中脂质水平的增加而增加（P<0.05）。与饲喂其他饮食的鱼相比，饲喂D6饮食的鱼的内脏肌指数（VSI）和肠系膜脂肪指数（MFI）高。随着膳食脂质水平的增加，人体和肌肉中的水分和粗蛋白含量下降，但粗脂质含量却呈现相反的趋势。肝中超氧化物歧化酶（SOD）活性随日粮脂质水平的增加而增加（P <0.05），而肝丙二醛（MDA）含量无显着差异（P > 0.05）。相应地，肝脏中SOD的mRNA相对表达随饮食中脂质水平的增加而增加（P<0.05）。饲喂脂含量为26.06％的日粮（L6）的鱼不仅在绒毛数量和高度上而且在肌肉层厚度上都表现出最佳的肠道形态。饮食脂质水平显着影响与脂质代谢相关的基因表达，例如脂肪酸合成酶（FAS），脂蛋白脂肪酶（LPL）（P <0.05）。FAS的mRNA相对表达从L1增加到L4，然后随着饮食脂质水平的增加而降低。L5和L6日粮喂养的鱼中LPL的mRNA表达显着高于其他处理。这些结果表明，在流水中进行网箱养殖的虹鳟的合适脂质需求量不低于26.06％。