异育银鲫幼鱼对饲料中赖氨酸的利用及需要量研究

THE UTILIZATION AND REQUIREMENT OF DIETARY LYSINE FOR JUVENILE GIBEL CARP

以添加晶体氨基酸的半精制饲料饲喂异育银鲫幼鱼,通过69d的生长实验来确定其赖氨酸需要量。饲料以白鱼粉为主要蛋白源,饲料中的总赖氨酸含量分别为1.82%、2.32%、2.82%、3.32%3、.82%、4.32%和4.82%7个水平。实验在室内循环水养殖系统中进行,每种饲料随机3个重复。实验结果表明,异育银鲫能够利用饲料中的晶体赖氨酸、蛋氨酸。在投喂后3h,其血浆中的游离赖氨酸、蛋氨酸含量最高。当饲料中赖氨酸含量为3.32%时,异育银鲫的终末尾均重、特定生长率和鱼空壳占体重的百分比最高,肝体指数最低。当饲料中赖氨酸含量为3.82%时,异育银鲫的干物质表观消化率显著高于其他组(P<0.05)。赖氨酸含量为2.32%的饲料组,蛋白表观消化率最高,其能量表观消化率显著低于其他饲料组(P<0.05)。肝脏谷氨酸草酰乙酸转氨酶(AST)活性以4.82%组最高,谷氨酸丙酮酸转氨酶(ALT)活性以1.82%和4.82%组最高,3.32%组最低,各饲料组间差异不显著(P>0.05)。血红蛋白含量以赖氨酸含量为2.82%的饲料组最高,4.82%组最低;随着饲料中赖氨酸含量的升高,异育银鲫红细胞数下降,血清脲氮含量升高,且血清脲氮含量具有组间显著性差异(P<0.05)。根据折线法,由异育银鲫的特定生长率同饲料中赖氨酸水平的相关性得出其赖氨酸需要量为3.27%,占饲料蛋白的8.52%。

Two experiments were conducted to investigate the utilization of crystal amino acids and the dietary requirement of lysine for juvenile gibel carp （ Carassius auratus gibelio ）. Two kinds of formulated diets supplemented with crystal lysine or methionine were fed to fish and blood were sampled and plasma free amino acids .content were determined. A 69-day growth trial was conducted to determine the quantitative dietary lysine requirement using diets containing white fish meal as the main source of protein, supplemented with crystalline amino acids. Seven isonitrogenous and isocaloric diets containing graded levels of lysine （1.82, 2.32, 2.82, 3.32, 3.82, 4.32 and 4.82g/100g, dry diet）were formulated. Fish were randomly stocked in triplicate groups in 56-1 indoor flow-through tanks. The fish were fed to apparent satiation during the experiment. The results showed that juvenile gibel carp is able to absorb dietary crystalline lysine and methionine, the highest content of free lysine and free methionine in plasma were observed at 3h after feeding. The highest specific growth rate（ SGR）, final body weight and carcass weight/body weight（CW/BW） were observed at 3.32% dietary lysine, while hepatosomatic index（HSl） was lowest. The apparent digestibility coefficients of dry matter was significantly affected by dietary lysine contents, and the highest value was observed at 3.82% group （ P 〈 0.05）. The apparent digestibility coefficients of gross energy was also significantly affected by dietary lysine concentrations, and the highest was observed at 2.32% group （ P 〈 0.05）. The apparent digestibility coefficients of crude protein were not significant between the groups （ P 〉 0.05 ） . The activity of liver glutamic-oxalacetic transaminase（AST） and the glutamic-pyruvic transaminase（ALT） was not significantly affected by dietary lysine. AST and ALT was highest at 4.82% group. Haemoglobin was highest at 2.82% group, and lowest at 4.82% group. With the increase in dietary lysine, the content of serum urea increased significantly （ P 〈 0.05） while the number of red blood cell decreased. The optimal dietary lysine requirement for maximum growth of Carassius auratus gibelio was 3.27 % of dry matter or 8.52 % of protein based on broken-line regression.