ESTIMATION OF VOLUNTARY FEED-INTAKE FROM INSACCO DEGRADATION AND RATEOF PASSAGE OF DM OR NDF

The relation between voluntary feed intake of DM or NDF and fill, calc ulated from in sacco degradation weighted with rate of passage, was te sted in two 3 x 3 Latin square experiments, one with three different r oughages fed alone and one with the same roughages fed together with c oncentrate. Voluntary intake of NDF could be estimated from fill (R2 = 0.82), using the rumen pool size of NDF as an estimate of rumen capac ity. NDF is preferable to DM as NDF is distinct from microbial and end ogenous material. Rumen pool sizes and small intestinal flow of NDF ca n therefore be used directly as estimates of rumen capacity and for ca lculation of rate of passage of undigested feed.