Nutritional Regulation of Protein Synthesis in Ruminants

动物体内的稳态是通过蛋白质、碳水化合物和脂质代谢的协调来维持的。因此，为了提高反刍动物的生产效率，弄清蛋白质合成与其他营养物质代谢之间的关系至关重要。本试验测定了能量摄入和能量来源对血糖代谢和氨基酸、蛋白质合成的影响及其相互关系。本研究选用成熟山羊。饲喂黄花干草块、玉米粉和豆粕作为基础饲粮。在本研究中，我们进行了三个实验。它们分别是(1)淀粉补充；(2)非蛋白质摄入；(3)碳水化合物来源。对每个实验进行了[U-^<13>C]葡萄糖、[^2H_5]苯丙氨酸和[^2H_2]酪氨酸的同位素稀释方法，并测定了周转率。蛋白质合成速率由苯丙氨酸的周转率和氧化为酪氨酸的速率估算。血液中苯丙氨酸、酪氨酸、葡萄糖和蛋白质合成的周转率随能量摄入的增加而增加。碳水化合物来源对其影响不大。由此可见，山羊蛋白质的合成和营养物质的代谢受能量摄入的影响，而不受能量来源的影响。

Homeotasis of animals is maintained by coordination of protein, carbohydrate and lipid metabolism. For the efficient production of ruminants, therefore, it is important to clarify the relationship between protein synthesis and other nutrient metabolism. In this experiment, the effects of intake and source of energy on metabolism of blood glucose and amino acid, protein synthesis and their relationship were measured. Mature goats were used in this study. They were fed aflalfa hay cubes, ground corn and soybean meal as a basal diet. In this study, three experiments were conducted. They were (1) starch supplementation, (2) non-protein intake and (3) source of carbohydrate. For each experiment, the isotope dilution methods of [U-^<13>C]glucose, [^2H_5]phenylalanine and [^2H_2]tyrosine were conducted and the turnover rates were determined. Protein synthsis rate was estimated from turnover rate of phenylalanine and its oxidation rate to tyrosine. Turnover rates of blood phenylalanine, tyrosine and glucose and protein synthesis increased with increasing energy intake. They were influenced little by source of carbohydrate. Therefore, it was suggested that in goats protein synthesis and nutrient metabolism are influenced by energy intake but not by source of energy.