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为了掌握虹鳟鱼饲料中蛋氨酸的利用情况,我们进行了一个喂养实验。准备了5种实验饲料。1号饲料,是一种基本饲料,以含50％的酪蛋白作为唯一的蛋白源。2号—4号饲料,分别依次在基本饲料中加入0.5％,1.0％,和1.5％的L—蛋氨酸而制成。5号饲料,以含50％的蛋清蛋白作为蛋白源。喂养加入蛋氨酸饲料的鱼,在其肝部和肌肉中积累了大量的蛋氨酸。与此相对的是,肝中的牛胆碱含量只受喂养实验的轻微影响。通过加入蛋氨酸至1.0％,提高了鱼蛋白质净利用率(NPU)。然而如果加入的蛋氨酸量达到1.5％时,鱼的NPU值反而低于1.0％时的水平。该实验结果表明:虹鳟鱼通过一个转硫作用将蛋氨酸转变成半胱氨酸的能力是有限的,当以含大量蛋氨酸饲料喂鱼时,蛋氨酸不能充分利用。
In order to grasp the use of methionine in rainbow trout feeds, we conducted a feeding experiment. Prepared five kinds of experimental feed. Feed # 1 is a basic feed containing 50% casein as the sole source of protein. 2 - 4 feed, respectively, followed by adding 0.5% basic feed, 1.0%, and 1.5% of L-methionine and made. 5 feed, with 50% egg white protein as a protein source. Feeding methionine-fed fish accumulates a large amount of methionine in its liver and muscle. In contrast, the content of hog choline in the liver is only slightly affected by the feeding experiment. Increasing fish protein net utilization (NPU) by adding methionine to 1.0%. However, if the amount of methionine added reached 1.5%, the NPU of the fish would instead be less than 1.0%. The results of this experiment show that rainbow trout have a limited capacity to convert methionine to cysteine via a trans-sulfur effect and that methionine can not be fully utilized when feeding fish containing large amounts of methionine.