5Goering , H.K. and P.J. Van Soest. Forage Fiber Analysis (apparatus, reagents, procedures and some applications) [ M]. USDA Agricultural Handbook, 1970,379:20.
6φ rskov E R, McDonald I. The estimation of protein degradability in the rumen incubation measurement weighted according to the rate passage[ J ]. Journal of Agricultural Science, Cambridge, 1979,92 : 499 - 503.
