日本沼虾的蛋氨酸需求量

通过研究饲料中不同蛋氨酸水平对日本沼虾(Macrobrachium nipponense)生长、饲料效率、全虾体组成、肌肉氨基酸组成和肝胰脏消化酶活性的影响,确定了日本沼虾的适宜蛋氨酸需求量。以酪蛋白、明胶、鱼粉、小麦面筋粉和晶体氨基酸为蛋白源配制了6组蛋白质水平为36.07%、能量为18.09 kJ/g的等氮等能的半纯和饲料,各组蛋氨酸实际含量分别为0.38%、0.47%、0.56%、0.64%、0.75%和0.88%。以初始体质量为0.30 g的日本沼虾为试验对象,每组设4个重复,每个重复50尾虾,养殖在规格为0.6 m×0.6 m×0.6 m的网箱中,试验期56 d。结果表明:当饲料中蛋氨酸水平由0.38%升高至0.88%时,日本沼虾的增重率、特定生长率和饲料效率均显著升高(P0.05);饲料蛋氨酸水平为0.64%时,三者均达到最大值;随着饲料中蛋氨酸水平进一步升高,三者均呈下降趋势。当饲料蛋氨酸水平为0.64%时,全虾粗蛋白含量最高,显著高于0.38%组(P0.05)。饲料蛋氨酸水平对全虾的水分、灰分、脂肪和肌肉的氨基酸组成均无显著影响(P0.05)。饲料中蛋氨酸水平显著影响日本沼虾肝胰脏蛋白酶的活性(P0.05),但对脂肪酶和淀粉酶活性均无显著影响(P0.05)。以增重率为评价指标进行一元二次回归分析,得出日本沼虾的蛋氨酸需求量为0.70%,占饲料蛋白的1.94%。

Optimal Dietary Methionine Level of Macrobrachium nipponense

This experiment was conducted to determine the optimal dietary methionine level of Mac- robrachium nipponense, based on the evaluation of growth performance, feed efficiency ratio, body composition, muscle amino acids composition and liver digestive enzyme activities. Six isonitroge- nous （36. 07% crude protein） and isocaloric （18.09 kJ/g gross energy） semi-purified diets were formulated with casein, gelatin, fish meal, wheat glutenand and crystalline amino acid （AA） mix- ture. The measured methionine levels of the experimental diets were 0. 38%, 0.47%, 0. 56%, 0. 64%, 0. 75% and 0. 88%, respectively. Each diet was fed to four groups of 50 Macrobrachium nipponense with an average initial body weight of 0.30 g in floating net cages （ 0. 6 m × 0. 6 m × 0.6 m）.The experim for 56 days. The results indicated that weight gain rate, specific growth rateand feed efficiency ratio increased significantly （ P 〈 0. 05 ） as dietary methionine levels increased from 0. 38% to 0. 88% with their maximum values being attained at 0. 64%, respectively. However, they decreased with further increasing dietary methionine levels. The highest whole-body protein con- tent was observed in Macrobrachium nipponense fed 0.64% dietary methionine. It was significantly （P〈0. 05） higher than that of Macrobrachium nipponense fed 0. 38% dietary methionine （P〈0.05）. No significant difference （P〉0. 05） was found in whole-body moisture, ash and lipid content and muscle AA contents among the treatments. Liver protease activities were significantly （P〈0.05） af- fected by dietary methionine levels, whereas lipase and amylase activities. The second-order regres- sion analysis of WGR against dietary methionine levels indicated that the dietary methionine require- ment of Macrobrachium nipponense was 0. 70% of diet （and 1.94% of diet protein）.