Salter D N, Montgomery A I, Hudson A, Quelch D B, Elliott R J
AFRC Institute for Grassland and Animal Production, Shinfield Research Station, Reading, Berks.
Br J Nutr. 1990 May;63(3):503-13. doi: 10.1079/bjn19900137.
The influence on protein accretion and whole-body protein turnover of changing dietary protein quality while maintaining constant energy intake was studied by varying the degree of lysine supplementation of a lysine-deficient barley-based diet given to growing pigs. Measurements of nitrogen metabolism and whole-body protein turnover, using both classical and 15N end-product methods following a single dose of [15N]glycine, were made in 49-kg male pigs given diets containing 109 g lysine-deficient protein/kg supplemented to make them (1) 'deficient', (2) 'adequate' and (3) 'in excess' with respect to lysine. The 15N dose and protein intake values used to calculate amino N flux from the cumulative urinary excretion of 15N in urea and ammonia were corrected respectively for apparent digestibilities of [15N]glycine and total N determined in a separate experiment in pigs fitted with simple ileal cannulas. N retention and biological value were significantly increased by lysine supplementation of the deficient diet to the 'adequate' level, but were not further increased by the higher level of supplementation. Rates of growth paralleled these changes. The poorer biological value of the unsupplemented diet 1 was shown also in a significantly higher excretion of urea N compared with diets 2 and 3. N digestibility was not markedly influenced by the level of lysine supplementation. Both whole-body protein synthesis and degradation increased markedly on 'adequate' supplementation of the diet with lysine, but did not increase further with an excess of lysine. It is concluded that the increase in protein accretion rate observed on supplementation of the diet with lysine was due to a greater increase in the rate of protein synthesis than of degradation, rather than a decrease in degradation rate.
通过改变给予生长猪的以赖氨酸缺乏的大麦为基础的日粮中赖氨酸的添加程度，研究了在保持能量摄入量恒定的情况下，日粮蛋白质质量变化对蛋白质沉积和全身蛋白质周转的影响。对体重49千克的雄性猪饲喂含109克/千克赖氨酸缺乏蛋白质的日粮，并补充赖氨酸使其达到（1）“缺乏”、（2）“充足”和（3）“过量”水平，采用经典方法和单剂量[15N]甘氨酸后15N终产物法测定氮代谢和全身蛋白质周转。用于根据尿素和氨中15N的累积尿排泄量计算氨基氮通量的15N剂量和蛋白质摄入量值，分别针对在装有简单回肠插管的猪中进行的另一项实验中测定的[15N]甘氨酸和总氮的表观消化率进行了校正。将缺乏日粮补充赖氨酸至“充足”水平可显著提高氮保留和生物学价值，但更高水平的补充并未使其进一步提高。生长速率与这些变化平行。与日粮2和3相比，未补充日粮1的生物学价值较差还表现为尿素氮排泄量显著更高。赖氨酸添加水平对氮消化率没有明显影响。日粮赖氨酸“充足”补充时，全身蛋白质合成和降解均显著增加，但赖氨酸过量时并未进一步增加。得出的结论是，日粮补充赖氨酸后观察到的蛋白质沉积率增加是由于蛋白质合成速率的增加幅度大于降解速率，而不是降解速率的降低。
