传统营养学主要是把氨基酸作为合成蛋白质的前体去研究蛋白质和氨基酸的需要量。近年来，人们对氨基酸在物质代谢和免疫功能调控中所起的作用越来越感兴趣，并提出了功能性氨基酸的概念。功能性氨基酸是指除了合成蛋白质外还具有其他特殊功能的氨基酸，其不仅对动物的正常生长及维持是必需的，而且对多种生物活性物质的合成也是必需的。例如精氨酸能提高受孕率，促进胚胎发生，增加血流量，增强抗氧化活性，促进蛋白质合成、免疫细胞增殖和肠道发育，最终提高动物繁殖性能及胚胎和新生动物的生长与健康。因此，在日粮中添加功能性氨基酸可大大提高猪的营养状况和生产性能。

        Much attention has been traditionally paid to the role of amino acids in protein synthesis and their requirements in animal nutrition. Recently, there is growing interest in regulatory roles of amino acids in nutrient metabolism and immune responses. They are called functional amino acids which are necessary not only to animal growth and maintenance requirement, but also to the synthesis of bioactive molecules. Remarkably, arginine can enhance conception rates, embryogenesis, blood flow, antioxidant activity, protein synthesis, immune cell proliferation, and intestinal development, thereby improve fertility, fetal and postnatal growth, and neonatal health. Therefore, large scale availability of feed grade functional amino acids holds great promise for enhancing the efficiency of nutrient utilization in pigs.