红鳍东方鲀幼鱼对饲料中蛋氨酸需求的研究

在半精制饲料中分别添加0、0.30%、0.60%、0.90%、1.20%、1.50%蛋氨酸制成6组等氮等脂饲料,各组蛋氨酸的实际含量分别为0.61%、0.85%、1.10%、1.39%、1.60%、1.84%,对初始体重为(13.83±0.63) g的红鳍东方鲀(Takifugu rubripes)幼鱼在室内流水系统中进行了76 d的喂养实验,探讨其蛋氨酸的需求量。研究表明,当饲料中蛋氨酸水平由0.61%升高至1.60%时,红鳍东方鲀的特定生长率(Specific growth rate,SGR)、饲料效率(Feed efficiency,FE)、蛋白效率比(Protein efficiency ratio, PER)均显著升高(P0.05),且都在1.60%组取得最大值。其中,特定生长率在1.39%、1.60%实验组无显著差异(P0.05),但随着蛋氨酸的进一步升高,特定生长率、饲料效率、蛋白效率比均呈现出下降的趋势;蛋氨酸水平对于蛋白沉积率没有显著影响(P0.05);饲料中蛋氨酸水平对全鱼粗脂肪含量呈现出先升高再降低的趋势,但各组间粗蛋白、水分和粗灰分无显著差异(P0.05);随着蛋氨酸水平升高,肝体比(Hepatosomatic index, HSI)和脏体比(Viscerosomatic index, VSI)呈现先升高再下降,在蛋氨酸含量为1.60%时达到最高,显著高于蛋氨酸0.61%组(P0.05),与其他组无显著差异;血清中甘油三酯、胆汁酸的含量,随着蛋氨酸水平的升高呈现出先升高再降低的趋势,饲料蛋氨酸水平对血清中总胆固醇、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇、总蛋白水平及谷草转氨酶、谷丙转氨酶的活性无显著影响(P0.05)。以特定生长率为评价指标进行一元二次回归曲线分析,得出体重为(13.83～82.47) g的红鳍东方鲀幼鱼的蛋氨酸需求量为1.38%,占饲料蛋白质的2.71%。

Dietary Methionine Requirement of Juvenile Tiger Puffer (Takifugu rubripes)

A 67-days feeding experiment was conducted to investigate the effects different levels on the growth performance and biochemical parameters of tiger puffer [average body weight: (13.83±0.63) g], and to determine the dietary methionine requirement for tiger puffer. There were six experimental isonitrogenous and isolipidic semipurified diets which were formulated with the graded levels of methionine (0.61%, 0.85%, 1.10%, 1.39%, 1.60%, 1.84%, respectively). Each diet was randomly assigned to triplicate groups, and each group contained 30 individuals. Fish were fed fourth daily(07:00, 12:00, 16:00, 20:00) to apparent satiation. The result showed that no significant differences in protein productive value (PPV) were found among dietary treatments (P>0.05). Specific growth rate (SGR), feed conversion ratio(FCR) and protein efficiency ratio (PER) increased with increasing dietary methionine levels from 0.61% to 1.60%(P<0.05), the higest group was observed in methionine levels 1.60% group, and there after showed a declining tendency with increasing dietary methionine levels from1.60% to 1.84%. Hepatosomatic index (HSI) and viscerosomatic index (VSI) of the 1.60% methionine diets was significantly higher than that of 0.61% groups (P<0.05), with further increase from 1.60% to 1.84%, HSI and VSI decreased. The crude lipid contents of whole body were significantly affected by dietary methionine levels (P<0.05), the 1.60% methionine diets was significantly higher than 0.61% groups (P< 0.05), with further increase from 1.60% to 1.84%, crude lipid decreased. while moisture, crude protein and ash showed no significant differences (P>0.05). Dietary methionine levels significantly influenced the contents of triglyceride, bile acid and blood glucose in serum (P<0.05), There were no significant difference in total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, total protein, activity of glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase (P>0.05) in serum. Second-order regression analysis on the basis of SGR indicated that the optimum dietary methionine requirements of tiger puffer were estimated to be 1.38% of diet (2.71% of dietary protein).