In order to evaluate the effects of dietary Gracilaria lemaneiformis on growth performance, serum biochemical indices and muscle fatty acid composition of grass carp ( Ctenopharyngodon idellus) , juvenile fish at the average body weight of (15.94±0.10) g were fed six isonitrogenous and isolipid diets containing graded levels of Gracilaria lemaneiformis [ 0 ( control group ) , 1%, 2%, 3%, 4% and 5%, respectively ] for 8 weeks. Each diet fed four water tanks and each tank had 30 fish. The results showed as follows:1) there were no significant differences in weight gain rate ( WGR) , specific growth ratio ( SGR) , survival rate ( SR) and feed efficiency ( FE) of fish fed diets supplemented with different proportions of Gracilaria lemaneiformis ( P>0.05) . 2) Hepato-somatic index ( HSI) of fish in experimental groups was higher than that in control group, and the differences were significant except 5% supplementation group ( P<0.05) . 3) Crude protein content in whole body, liver and muscle was not significantly affected by diets supplemented with different levels of Gracilaria lemaneiformis (P>0.05), however, there were significant differences in the contents of ash and crude lipid in whole body, crude lipid in liver and moisture in muscle ( P<0.05) . 4) Total protein ( TP) , total cholesterol ( TCHO) , triglycerides ( TG) and low density lipoprotein ( LDL) contents in serum in 5% supple-mentation group had the lowest values, and significantly higher than those in control group ( P<0.05) , but no significant differences were found between control group and other experimental groups (P>0.05). 5) Fatty acid composition in muscle of grass carp was affected by diets with different proportions of Gracilaria lemane-iformis. Diets supplemented with different proportions of Gracilaria lemaneiformis could significantly affect the contents of fatty acids except C14∶1, C20∶0 and C20∶2 in muscle ( P<0.05) , and the highest values of poly-unsaturated fatty acids ( PUFA) content and n-3/n-6 PUFA were found in 3% supplementation group. The con-tents of C20∶5 ( EPA) , C22∶5 ( DPA) , C22∶6 ( DHA) and EPA+DHA in muscle in 1%, 2%, 3%, 4% and 5% supplementation groups were significantly higher than those in control group ( P<0.05) . The present results indicate that diets supplemented with a certain proportion of Gracilaria lemaneiformis have no significant effect on the growth of grass carp, but can reduce the blood lipid contents. It can also influence the fatty acid compo-sition in muscle, improve the functional fatty acid contents, such as DHA and EPA, and increase the content of PUFA. The fish fed with 3% Gracilaria lemaneiformis can better increase the functional fatty acid contents was, and the fish fed with 5% Gracilaria lemaneiformis have a relatively better growth performance as well as an obviously lower blood lipid.%为考察饲料中添加龙须菜对草鱼生长性能、血清生化指标及肌肉脂肪酸组成的影响，试验共配制了6种龙须菜添加比例分别为0(对照组)、1%、2%、3%、4%和5%的等氮等脂饲料，投喂平均体重为(15.94±0.10) g的草鱼8周。每种饲料投喂4个水箱(重复)，每箱30尾鱼。结果显示：1)饲料中不同添加比例龙须菜对草鱼的增重率( WGR)、特定生长率( SGR)、存活率( SR)及饲料效率( FE)没有显著影响( P>0.05)。2)各试验组的肝体指数( HSI)均高于对照组，对照组与除5%添加组外的其他试验组的差异均达到显著水平( P<0.05)。3)全鱼、肝脏及肌肉的粗蛋白质含量各组间皆无显著差异( P>0.05)，而饲料中不同添加比例龙须菜对全鱼粗灰分与粗脂肪、肝脏粗脂肪及肌肉水分含量有显著影响(P<0.05)。4)血清总蛋白(TP)、总胆固醇( TCHO)、甘油三酯( TG)以及低密度脂蛋白( LDL)含量以5%添加组最低，显著低于对照组(P<0.05)，其他试验组与对照组没有显著差异(P>0.05)。5)饲料中龙须菜添加比例影响了草鱼肌肉脂肪酸的组成，除C14∶1、C20∶0、C20∶2外，其他肌肉脂肪酸的含量均受到饲料中龙须菜的添加比例的显著影响(P<0.05)，其中肌肉多不饱和脂肪酸(PUFA)含量及n-3/n-6 PUFA均在3%添加组获得最高值。1%、2%、3%、4%和5%添加组肌肉 C20∶5( EPA )、C22∶5( DPA )、C22∶6(DHA)以及EPA+DHA的含量都显著高于对照组(P<0.05)。由此得出，饲料中添加一定比例的龙须菜对草鱼的生长性能没有显著影响，但能降低血脂含量，影响草鱼肌肉脂肪酸的组成，并能提高功能性脂肪酸DHA、EPA及PUFA的含量；饲料中添加3%的龙须菜能更好地增加肌肉功能性脂肪酸含量，而添加5%的龙须菜则草鱼生长相对较好，降低血脂效果更加明显。
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