Urea is used as a cheap source of non-protein nitrogen (converted by rumen micro-flora into protein) - may add to concentrate ration at rate of 1-3%是什么意思_Urea is used as a cheap source of non-protein nitrogen (converted by rumen micro-flora into protein) - may add to concentrate ration at rate of 1-3%在线翻译_英语_读音_用法_例句