尿素氮的再循环利用对于维持反刍动物体内氮的营养代谢具有重要意义。尤其当日粮氮摄入不足时，反刍动物会更加依赖再循环的尿素氮。本文阐述了内源尿素氮对于反刍动物氮代谢的重要性，研究反刍动物尿素氮代谢的方法、影响尿素氮代谢的因素以及调控反刍动物尿素氮循环代谢的机制等，并对当前调控反刍动物尿素氮循环代谢机制的研究热点尿素转运蛋白进行了简析。

As ruminants, recycling utilization of urea nitrogen has significant meaning for maintaining normal metabolism of nitrogen; especially under the condition of insufficient intake of nitrogen, ruminants depend more on the recycling urea nitrogen. The article elucidated the significance of endogenous urea nitrogen for ruminant nitrogen metabolism, the research methods of ruminant urea nitrogen metabolism, the influence factors of urea nitrogen metabolism and the mechanism of regulating urea nitrogen recycling metabolism in ruminants and described the urea transporter which tended to be concerned by researchers recently as a potential mechanism on regulating recycling metabolism.［Chinese Journal of Animal Nutrition, ２００9，２1（5）:609-616］