Estimation of voluntary feed intake from in sacco degradation and rate of passage of DM or NDF

Abstract

The relation between voluntary feed intake of DM or NDF and fill, calculated from in sacco degradation weighted with rate of passage, was tested in two × 3 Latin square experiments, one with three different roughages fed alone and one with the same roughages fed together with concentrate. Voluntary intake of NDF could be estimated from fill ( R 2 = 0.82), using the rumen pool size of NDF as an estimate of rumen capacity. NDF is preferable to DM as NDF is distinct from microbial and endogenous material. Rumen pool sizes and small intestinal flow of NDF can therefore be used directly as estimates of rumen capacity and for calculation of rate of passage of undigested feed.