[1] Owens V N, Albrecht K A, Hintz R W. Journal of Production Agriculture, 1995 8: 491.
[2] Allen M S, O’Neil K A, Dado R G. In Proc. Tri-State Dairy Nutrition Conf. Indiana, USA, 1992. 21.
[3] Sulc R M, Albrecht K A, Owens V N. Feeding Management, 1999. 167.
[7] Castro P. Regional Office for Europe and Central Asia (REU) Technical Series No.64. 225.
[8] Petisco C, Garcia-Criado B, Garcia-Criado I. Sustainable grassland productivity: Proceedings of the 21st General Meeting of the European Grassland Federation, Badajoz, Spain, 2006. 568.
[9] American Society of Agricultural and Biological Engineers. S358. 2. 1988.
[10] Association of Official Analytical Chemists Kenneth Helrich, Official Methods of Analysis, The Association, U.S. 1990.
[12] Sorensen L K. Journal of Dairy Science, 2004, 87(11): 3826.