克氏原螯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28.25%、能量为16.07 kJ/g的等氮等能的半纯合饲料, 各组蛋氨酸实际含量分别为0.39%、0.53%、0.71%、0.86%、0.98%和1.13%。以初始体质量为(9.80±0.15) g的克氏原螯虾(Proambarus clakii)为试验对象, 每组设4个重复, 每个重复12尾虾。养殖试验于室外网箱(规格为60 cm×60 cm×60 cm)中进行, 饲养周期为56 d。结果表明, 当饲料中蛋氨酸水平由0.39%升高至1.13%时, 克氏原鳌虾的增重率、特定生长率和饲料效率均显著升高(P<0.05)。当蛋氨酸水平为0.86%时, 三者均达到最大值。当蛋氨酸水平进一步升高时, 三者均呈下降趋势。试验各组的成活率为83.33%~91.67%, 但无显著差异(P>0.05)。当蛋氨酸水平为0.86%时, 全虾粗蛋白含量最高, 其显著高于0.39%组(P<0.05)。日粮蛋氨酸水平对全虾的水分、灰分和脂肪含量以及肝胰脏组成和肌肉氨基酸组成均无显著影响(P>0.05)。肌肉粗脂肪含量以蛋氨酸水平0.98%组最低, 其显著低于0.39%组(P<0.05)。饲料中蛋氨酸水平显著影响肠道蛋白酶的活性(P<0.05), 但对脂肪酶和淀粉酶活性均无显著影响(P>0.05)。以增重率为评价指标进行一元二次回归分析, 得出克氏原螯虾的适宜蛋氨酸需求量为0.94%, 占饲料蛋白质的3.36%。本研究通过分析饲料中不同蛋氨酸水平对克氏原螯虾生长、饲料利用、虾体组成、肌肉氨基酸组成和消化酶活性的影响, 确定克氏原螯虾的适宜蛋氨酸需求量, 以期为其人工配合饲料的研制提供基础数据和理论依据。

Optimal dietary methionine requirement of red swamp crayfish (Proc­am­barus clarkii)

We conducted this experiment to determine the optimal dietary methionine requirement of red swamp crayfish (Procambarus clarkii), as was based on the evaluation of growth performance, feed utilization, body composition, muscle amino acids composition and digestive enzyme activities. Six isonitrogenous (28.25% crude protein) and isocaloric (16.07 kJ/g gross energy) diets were formulated with the protein sources originated from casein, gelatin, fish meal, wheat glutenand and crystalline amino acid (AA) mixture. The measured methionine levels of the experimental diets were 0.39%, 0.53%, 0.71%, 0.86%, 0.98%, and 1.13%, respectively. The dietary AA pattern, except for methionine, was applied to the muscle AA pattern of this apecies. Each diet was fed to four groups of 12 crayfish with an average initial body weight of (9.80±0.15) g in floating net cages (60 cm × 60 cm × 60 cm). Crayfish was fed three times daily for 56 d. The results indicated that weight gain rate, specific growth rate and feed efficiency ratio all increased significantly (P<0.05) as dietary methionine levels increased from 0.39% to 1.13% with their maximum values all being attained 0.86%, respectively. However, they all decreased with further increasing dietary methionine levels. Survival rate ranged from 83.33% to 91.67%, and showed no significant difference (P>0.05) among all the dietary treatments. The highest whole-body protein content was observed in crayfish fed 0.86% dietary methionine. It was significantly (P<0.05) higher than that of crayfish fed 0.39% dietary methionine, but showed little difference (P>0.05) with that of the other treatments. No significant difference (P>0.05) was found in whole-body moisture, ash and lipid content and liver composition and muscle AA contents among all the treatments. The muscle lipid content of crayfish fed 0.98% dietary methionine was significantly (P<0.05) lower than that of crayfish fed 0.39% dietary methionine, but showed little difference (P>0.05) with that of the other treatments. Intestinal protease activities were significantly (P<0.05) affected by dietary methionine levels, whereas the opposite was true for lipase and amylase activities. The second-order regression analysis of WGR against dietary methionine levels indicated that the optimal dietary methionine requirement of red swamp crayfish was 0.94% of diet (and 3.36% of diet protein).