3NRC. Nutrient Requirements of Beef Cattle (7th Rew Ed) [M]. Washingington DC : National Academy Press, 1996.
4Erasmus L J, Botha P M. Amino acid profile and intestinal digestibility in dairy cows of rumen-undegradable protein from various feedstuffs [J]. J Dairy Sci, 1994, 77: 541-551.
5Hvelplund T M, Weisberg, R, et ol. Estimation of the true digestibility dietary protein in the small intestine of ruminants by the mobile bag technique[J]. Acta Agric Scand Sect Anim Sci, 1992, 42: 34.