9Orskov E R, Mcdonald L. The estimation of protein degradability in the rumen incubation measurents weights according to the rate of passage[J]. Journal of Agricultural Science. 1979.92:799-803.
10Van Keuren RW et al. Study of nylon bag technique for in vivo estimation of forage digestibilily[J].Animal Sci., 1962,21:340-345.