以初始体重（8.25±0.37） g的草鱼幼鱼为试验对象，分别采用异亮氨酸（isoleucine，Ile)水平为0.77 %、1.07 %、1.37 %、1.67 %、1.97 %和2.27 % 6组等氮(粗蛋白35.25 %)半纯化日粮对草鱼进行了72 d生长试验，研究其日粮异亮氨酸需要量。结果表明：（1）日粮Ile水平为1.67 %时，草鱼增重率、特定生长率和蛋白质效率最高，饲料系数最低；鱼体空壳率和肥满度达到最大值，内脏指数最小；草鱼体水分、体脂最低，体蛋白、灰分最高；肌肉水分最低,粗蛋白最高。而各水平之间肌肉粗脂肪无显著差异(P> 0.05)；日粮Ile水平为1.67 %时，草鱼肌肉Ile含量和肌肉氨基酸总量最高。（2）随日粮Ile水平增加，肌肉RNA/DNA呈先升后降趋势，Ile 1.67 %水平组最高；而肝脏谷氨酸脱氢酶却呈先降后升趋势，Ile 1.67 %水平组最低。血氨在Ile 0.77 % ~ 1.67 %水平组之间处于稳定状态，高于1.67 %水平后呈上升趋势。血清白蛋白受日粮Ile水平的影响不显著（P> 0.05）。（3）随日粮Ile水平增加，血清甘油三酯和胆固醇均呈先降后升趋势，且在Ile 1.67%水平组，两项指标均为最低值，显著低于其他水平组（P< 0.05）。根据增重率、特定生长率、饲料系数和蛋白质效率与日粮Ile水平的二次曲线关系，确定草鱼幼鱼日粮(粗蛋白35.25 %) Ile适宜需要量范围为1.41 %～1.49 %(日粮基础)或4.0 %～4.23 %(日粮蛋白基础)。

540 grass carps ［initial body weight （8.25±0.37） g ］ were randomly divided into 6 treatments (90 for each treatment, 30 for each replicate) to investigate the nutritional physiological effects of dietary isoleucine on grass carp by feeding with six graded levels of crystalline isoleucine (0.77 g, 1.07 g, 1.37 g, 1.67 g, 1.97 g and 2.27 g per 100 g dry diet) which have the same isonitrogenous diets (35.25 % protein) with caseingelatincorn gluten mealcrystalline amino acid mixtures as protein source supplemented. Amino acid pattern in diet is to simulate the amino acid pattern found in the whole body protein of grass carp except for isoleucine. Each diet was randomly assigned to triplicate groups of 30 juvenile grass carp in freshwater floating net cages (1.0 m ×1.0 m ×1.0 m). After a 72day feeding trail, the results showed that: When the dietary isoleucine level was 1.67 % level, weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) got the maximum and feed conversion rate (FCR) got the minimum (P<0.05); deinternal organ ratio (DOR) and condition factor (CF) got the maximum, viserosomatic index (VIS) got the minimum; moisture and crude lipid of body were minimum, protein and ash content of it were the maximum(P<0.05); Moisture of muscle was minimum, protein were the maximum(P<0.05), but the difference of crude lipid was not significant(P<0.05). When the dietary isoleucine reached 1.67 % level, both the content of isoleucine and total amino acids in the muscle were maximum. The RNA/DNA of muscle rose first and then went down, when the dietary isoleucine reached 1.67 % level, RNA/DNA of muscle were the maximum, and the difference was significant(P<0.05). Glutamate hydrogenase activity of liver went down first and then raise, when the dietary isoleucine reached 1.67 % level, glutamate dehydrogenase activity was the lowest, and the difference was significant(P<0.05). When the content of isoleucine went up, the blood ammonia was leveling off at the beginning, when the dietary isoleucine reached 1.67% level, the blood ammonia rose. The difference of the albumin in the serum was not significant(P<0.05). TG and CHO went down first and then rose, when the dietary isoleucine level was 1.67 % level, TG and CHO were the lowest, and the difference was significant among groups(P<0.05). The conic analysis of WG, SGR, FE and PER against dietary isoleucine level indicated that optimal dietary isoleucine requirement for juvenile grass carp was 1.46 %,1.49 %,1.45 %and 1.41 % of the diet (corresponding to 4.14 %, 4.23 %, 4.11 % and 4.0 % of dietary protein on a dry weight basis). So the range of optimal dietary isoleucine requirement for juvenile grass carp was 1.41%-1.49%(dietary base) or 4.0 %-4.23 %(protein base).

国家“十一五”科技支撑计划(2006BAD03B03)