Burroughs W, Nelson D K, Mertens D R
J Dairy Sci. 1975 Apr;58(4):611-9. doi: 10.3168/jds.S0022-0302(75)84617-0.
Metabolizable protein and selected metabolizable amino acid requirements for lactating cows were described, and tentative values were established for differnt yields of milk.A new expression"urea fermentation potential of feeds," describes urea use in lactation rations for partial satisfaction of protein and amino acid requirements. Tentative urea fermentation values were established for the more common cattle feedstuffs. Four lactation rations were formulated with different fermentation values to illustrate the variable feeding value of urea in satisfying amino acid requirements at different yields of lactation. Urea had the highest feeding value in lower-protein rations when fed to cows with medium to low yields of milk.Conversely, urea, by the metabolizable protein system, had little or no feeding value in lactation rations having more than about12% protein on a dry matter basis or in rations supporting lactations in excess of 25 to 30 kg of milk per cow per day.
描述了泌乳奶牛的可代谢蛋白质和选定的可代谢氨基酸需求，并针对不同产奶量确定了暂定数值。一个新的表述“饲料的尿素发酵潜力”描述了泌乳日粮中尿素用于部分满足蛋白质和氨基酸需求的情况。为更常见的牛饲料确定了暂定的尿素发酵值。配制了四种具有不同发酵值的泌乳日粮，以说明在不同泌乳量下尿素在满足氨基酸需求方面的可变饲喂价值。当喂给中低产奶量的奶牛时，尿素在低蛋白日粮中的饲喂价值最高。相反，根据可代谢蛋白质系统，在干物质基础上蛋白质含量超过约12%的泌乳日粮中，或在支持每头奶牛每天产奶量超过25至30千克的日粮中，尿素几乎没有饲喂价值。
