生长中期花鲈对L-异亮氨酸需要量的研究

Dietary L-isoleucine requirement of Japanese seabass(Lateolabrax japonicus) in the middle growing stage

本实验旨在研究生长中期花鲈对饲料L-异亮氨酸的需要量。选取初始体质量(159.33±1.20)g的花鲈为实验对象,在基础饲料中梯度添加晶体L-异亮氨酸,配制出异亮氨酸实测含量分别为0.72%、1.11%、1.53%、1.93%、2.31%和2.72%的6种饲料,在海水浮式网箱中进行10周养殖实验。实验结果表明,随饲料中L-异亮氨酸含量的升高,花鲈增重率(WGR)、饲料效率(FE)及蛋白质沉积率(PR)均呈现先上升后下降的趋势,各组间差异显著(P<0.05),且在1.93%L-异亮氨酸饲料组出现最大值,分别为108.55%、0.89、和37.57%。饲料中L-异亮氨酸含量对存活率(SR)、摄食率(FI)、肝体比(HSI)、脏体比(VSI)、肥满度(CF)、体组成和肌肉氨基酸组成均无显著影响(P>0.05)。肝脏谷草转氨酶(GOT)、谷丙转氨酶(GPT)活力随饲料中L-异亮氨酸含量的升高呈现先上升后下降的趋势,各组间差异显著(P<0.05)。饲料中L-异亮氨酸含量对血清甘油三酯(TG)含量有显著影响(P<0.05),在L-异亮氨酸含量为1.93%时达到最大值,显著高于0.72%和1.11%组(P<0.05),但与其他各组差异不显著(P>0.05)。饲料中L-异亮氨酸含量对血清谷草转氨酶(GOT)、谷丙转氨酶(GPT)活力、血清总胆固醇(TC)含量无显著影响(P>0.05)。以增重率(WGR)和蛋白质沉积率(PR)为评价指标,得出生长中期花鲈对饲料中L-异亮氨酸的需求量分别为1.88%和1.84%饲料干重,占饲料蛋白质的4.41%和4.32%。

The present study was conducted to estimate the quantitative requirement of L-isoleucine in Japanese seabass（Lateolabrax japonicus） [initial body weight（159.33 ± 1.20） g ]by feeding six isonitrogenous and isoenergetic practical diets containing graded levels of L-isoleucine 0.72%,1.11%,1.53%,1.93%,2.31% and 2.72%（dry weight）,respectively,named diet 1—diet 6.After a 10-w eek growth trial,results showed that weight gain rate（WGR）,feed efficiency（FE） and protein retention（PR）w ere significantly influenced by the different diets（P 〈 0.05）.The values increased first,and then declined as the dietary L-isoleucine levels increased.The highest values of these three parameters were 108.55%,0.89 and 37.57% in fish fed the diet with 1.93% dry matter of dietary L-isoleucine,respectively.Survival rate（SR）,feed intake（FI）,hepatosomatic index（HSI）,viscerosomatic index（VSI）,condition factor（CF）,body composition and the essential amino acids of muscle were not significantly influenced by dietary L-isoleucine level（P 〉 0.05）.Dietary L-isoleucine significantly affected the activities of glutamic-oxaloacetic transaminase（GOT） and glutamic-pyruvic transaminase（GPT） in livers（P 〈 0.05）.The level of triglicerid（TG） in serum was significantly affected by dietary L-isoleucine levels（P 〈 0.05）.Fish fed the diet with1.93% L-isoleucine had the highest TG value.GOT and GPT activities and total cholesterol（TC） levels in serum were not significantly affected（P 〉 0.05）.In conclusion,appropriate dietary L-isoleucine level can improve the growth of the seabass.On the basis of WGR and PR,using the second-order regression analysis,dietary L-isoleucine requirement of Japanese seabass in the middle grow ing stage were estimated to be1.88% and 1.84% dry diet（4.41% and 4.32% dietary protein）,respectively.