过去一直认为大多数动物（包括水产类）是靠肠吸收氨基酸合成蛋白质时所需要的氮，而事实上，直接吸收一些短肽或较大分子的肽也是非常重要的。肠道吸收氨基酸的运输系统可能因为趋于饱和而限制吸收量，肽在肠道则有另一独立的运输系统，而且吸收速度比氨基酸更快，合成体分子 In the past, it was thought that most animals, including aquatic species, are required for the intestinal absorption of amino acids to synthesize proteins. In fact, it is also very important to directly absorb some short peptides or larger peptides. The intestinal transit amino acid transport system may limit the amount of uptake due to its saturation. Peptides have another independent transport system in the intestine that absorbs faster than amino acids and that synthetic molecules