Barnes D M, Calvert C C, Klasing K C
Department of Animal Sciences, University of California, Davis 95616, USA.
J Nutr. 1995 Oct;125(10):2623-30. doi: 10.1093/jn/125.10.2623.
The effect of supplementing a methionine-deficient, isolated soy protein diet (0.5% total sulfur amino acids) with 0.2% D,L-methionine (DL-MET) or a molar equivalent of D,L-2-hydroxy-4-(methylthio) butanoic acid (DL-HMB) was assessed in chicks over an 8-d feeding study. Chicks consumed DL-HMB diet ad libitum (HIGH) or were restricted to the level consumed ad libitum by chicks fed the basal diet. The DL-MET diet was fed at the same two levels as the DL-HMB diet. Supplementing with either methionine source resulted in significantly greater growth rate, efficiency of feed conversion, and accretion and synthesis of protein in the gastrocnemius and pectoralis muscles. These increases were greater for chicks consuming feed ad libitum as compared with feed-restricted chicks and were not affected by methionine source. Rate of muscle protein degradation appeared to increase with supplementation of either methionine source, but only when feed intake was permitted to increase. The relative in vivo conversion of DL-HMB vs. D-MET to L-MET was similar in all groups as indicated by pool sizes of methionine, tRNA(met), and tRNA(cys), and rates of protein accretion and synthesis. These data demonstrate that dietary DL-HMB and DL-MET are used with similar efficacy to support skeletal muscle protein accretion and rates of protein synthesis when feed intake is equalized.
在一项为期8天的饲养研究中，评估了在蛋氨酸缺乏的分离大豆蛋白日粮（总含硫氨基酸0.5%）中添加0.2% D,L-蛋氨酸（DL-MET）或摩尔当量的D,L-2-羟基-4-（甲硫基）丁酸（DL-HMB）对雏鸡的影响。雏鸡自由采食DL-HMB日粮（高采食组），或限制采食至基础日粮组雏鸡自由采食的水平。DL-MET日粮的饲喂水平与DL-HMB日粮相同，设两个水平。添加任何一种蛋氨酸来源均能显著提高雏鸡的生长速度、饲料转化率以及腓肠肌和胸肌中蛋白质的沉积和合成。与采食受限的雏鸡相比，自由采食的雏鸡上述指标的增加幅度更大，且不受蛋氨酸来源的影响。肌肉蛋白降解率似乎随着任何一种蛋氨酸来源的添加而增加，但仅在采食量允许增加时出现。蛋氨酸、tRNA(met)和tRNA(cys)的库大小以及蛋白质沉积和合成速率表明，所有组中DL-HMB与D-MET在体内向L-MET的相对转化率相似。这些数据表明，当采食量相当时，日粮中的DL-HMB和DL-MET在支持骨骼肌蛋白沉积和蛋白质合成速率方面具有相似的功效。
