饲料蛋氨酸水平对异育银鲫幼鱼生长性能影响的研究

Effects of Dietary Methionine Levels on the Growth Performance of Juvenile Gibel Carp (Carassius auratus gibelio)

  • 摘要: 研究通过8周的生长实验, 研究饲料中不同蛋氨酸水平对异育银鲫(Carassius auratus gibelio)幼鱼生长性能、体成分、氨基酸沉积率的影响。实验以鱼粉、豌豆浓缩蛋白、喷雾干燥血球粉为蛋白源, 设计低蛋氨酸(0.57%)实用基础饲料, 并在此基础上分别添加0、0.08%、0.16%、0.24%、0.32%、0.40%的DL-蛋氨酸配成蛋氨酸含量分别为0.57%、0.64%、0.74%、0.81%、0.88%、0.95%(干物质基础, 实测值)的6种等氮等能(粗蛋白质: 37.22%, 总能: 17.61 MJ/kg)的配合饲料。选取初始体重为2.60 g的异育银鲫幼鱼为实验对象, 每个处理3个重复, 每个重复50尾鱼, 养殖系统为室内循环水养殖系统, 每天表观饱食投喂4次。结果显示在饲料中补充DL-蛋氨酸会显著提高异育银鲫幼鱼的特定生长率和蛋白质沉积率(P0.05), 表明异育银鲫可有效利用外源DL-蛋氨酸。各处理组实验鱼肥满度、肝体比、脏体比差异不显著(P0.05), 不同蛋氨酸水平对全鱼水分、粗脂肪、能量没有产生显著影响(P0.05), 补充DL-蛋氨酸显著提高鱼体的粗蛋白质含量, 灰分含量显著降低(P0.05)。随着饲料中蛋氨酸水平的提高, 全鱼蛋氨酸沉积率显著降低, 之后再升高(P 0.05)。补充DL-蛋氨酸可以有效促进其他必需氨基酸在鱼体内的沉积。在饲料中胱氨酸水平为0.42%时, 通过折线模型回归分析, 以蛋氨酸沉积率得到的异育银鲫幼鱼蛋氨酸需求量为占饲料干物质的0.89%, 即占饲料蛋白的2.17%。

     

    Abstract: Methionine is usually the first limiting amino acid in many fish diets, especially those containing high levels of plant protein sources, such as soybean meal, peanut meal, and cottonseed meal. In the present study, an 8-week growth trial was conducted to evaluate the effects of dietary methionine (Met) levels on growth performance, nutrients retentions of gibel carp (Carassius auratus gibelio) with the initial weight of 2.60 g based on practical diets. Six isonitrogenous (crude protein content 37.22%) and isoenergetic (gross energy 17.61KJ/kg) diets were formulated with different levels of DL-methionine, i.e., 0, 0.08%, 0.16%, 0.24%, 0.32%, 0.40%. The determined Met levels were 0.57%, 0.64%, 0.74%, 0.81%, 0.88% and 0.95% and then defined as DLM0 (basal diet), DLM1, DLM2, DLM3, DLM4, and DLM5, respectively. Fifty fish were batch weighted and put into each tank and each treatment had triplicate tanks. All the experimental fish were stocked in a flow-through system, fed four times a day (9:00, 12:00, 15:00, 18:00). The water temperature fluctuated from 26 to 28C and dissolved oxygen was maintained at ~7.0 mg/L. The results indicated that specific growth rate (SGR) and protein productive value (PPV) significantly increased with the DL-Methionine supplemented diets (P0.05), indicating that gibel carp could utilize crystallized DL-Met. Maximum final body weight (FBW, 11.15 g), highest specific growth rate (2.60%/d), and protein productive value (37.02%) were observed in fish fed with diet containing methionine at 0.951% level (DLM5). There were no significantly differences on morphometric parameters and whole body nutrients compositions except crude protein and ash (P0.05). Whole body crude protein of fish fed with Met supplemented diets were higher than that of the control group, while ash content of the control group was significantly lower than those of all other groups (P0.05). The methionine productive value (MPV) was reduced with increasing levels of methionine up to 0.876% of diet (DLM4) (P0.05), and then increased in the DLM5 group. While other essential amino acid productive values increased with the higher methionine levels in diets, a third-order polynomial regression analysis of specific growth rate indicated that the growth performance of juvenile gibel carp might be improved if the methionine levels enhanced subsequently. Broken-line model of MPV indicated that optimum Met level in the diet of juvenile gibel carp was 0.89% of diet (dry matter basis), or 2.17% in terms of dietary protein with cystine level at 0.42%.

     

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