中华绒螯蟹幼蟹对苏氨酸需求量的研究

Threonine Requirement of Juvenile Chinese Mitten Crab( Eriocheir sinensis)

通过56d的生长试验确定中华绒螯蟹(Eriocheir sinensis)幼蟹对苏氨酸的需求量。试验设计了6种以酪蛋白、明胶和晶体氨基酸为蛋白质源的等氮等能纯化饲料,通过添加晶体L-苏氨酸,使得饲料中苏氨酸含量分别为饲料干物质的0.86%(对照,无外源苏氨酸)、1.24%、1.61%、2.04%、2.42%、2.81%。选取初始体重为(0.36±0.00)g的中华绒螯蟹幼蟹360只,随机分为6组,每组3个重复,每个重复20只幼蟹。结果表明:随饲料中苏氨酸含量的升高,幼蟹的增重率、特定生长率以及消化酶(胃蛋白酶、胰蛋白酶、脂肪酶和淀粉酶)活力均先升高后降低,在苏氨酸含量为饲料干物质的1.61%时,各项指标均达到最大值,且此时饲料系数最低,蛋白质效率最高,且该组增重率、特定生长率显著高于0.86%、1.24%、2.42%和2.81%组(P<0.05),消化酶活力显著高于其他各组(P<0.05)。饲料中苏氨酸含量对幼蟹的成活率及体成分无显著影响(P>0.05)。幼蟹肝胰腺超氧化物歧化酶、碱性磷酸酶和酸性磷酸酶活力均随饲料中苏氨酸含量的升高呈先升高后降低趋势,并分别在苏氨酸含量为饲料干物质的1.61%、1.61%和2.42%时达到最大值。以增重率为评价指标进行折线回归模型分析,得到中华绒螯蟹幼蟹对饲料中苏氨酸的需求量为饲料干物质的1.59%(饲料蛋白质的3.98%)。

A 56-day growth trial was conducted to determine the threonine requirement of juvenile Chinese mit-ten crab （ Eriocheir sinensis） . Six isonitrogenous and isoenergetic purified diets were formulated using casein, gelatin and crystalline amino acids as protein sources, and the threonine content in those diets was 0.86%（ con-trol, without extra threonine）, 1.24%, 1.61%, 2.04%, 2.42% and 2.81% of dietary dry matter by adding crystalline L-threonine, respectively. A total of 360 juvenile Chinese mitten crab with the initial body weight of （0.36±0.00） g were chosen and randomly distributed into 6 groups with 3 replicates per group and 20 crabs per replicate. The results showed that with the increase of dietary threonine content, the weight gain rate （ WGR） , specific growth rate （ SGR） , and the activities of digestive enzymes （ pepsin, trypsin, lipase and amylase） were firstly increased and then decreased, which reached their peaks in the 1. 61% group, and the WGR and SGR in the 1. 61% group were significantly higher than those in the 0. 86%, 1. 24%, 2. 42% and 2.81% groups （ P〈0.05） and the activities of digestive enzymes in the 1.61% group were significantly higher than those in the other groups （ P〈0.05） . Whereas, the feed conversion ratio （ FCR） reached the lowest value in the 1.61% group, and the protein efficiency ratio （ PER） reached the highest value in the same group. Diet-ary threonine content had no significant effects on survival rate （SR） and body composition （P〉0.05）. The activities of superoxide dismutase （ SOD） , alkaline phosphatase （ AKP） and acid phosphatase （ ACP） in hepa-topancreas were firstly increased and then decreased, which reached their peaks in the 1. 61%, 1. 61% and 2.42% groups, respectively. Using WGR as the evaluation index, dietary threonine requirement of juvenile Chinese mitten crab is estimated to be 1.59% of dietary dry matter （3.98% of dietary protein） by broken-line regress model analysis.