residues from in situ incubation followed by NDF extraction was similar to the technique described by Ellis et al. (1984) for
preparation of indigestible aNDF (i.e., aNDF remaining after 144 h of in situ incubation). Coefficients of apparent digestion of
dietary components were determined by comparing dietary indigestible aNDF concentration (corrected for that in orts) with
fecal indigestible aNDF concentration as outlined by Cochran et al. (1986). Fecal output (DM basis) was calculated from marker
concentration using the following formula: Fecal output (g/d) = Cr dose (mg/d)/Cr in feces (mg/g feces). The contribution of
pasture to fecal output was estimated after total fecal output was corrected for contribution of the concentrate by subtracting
the indigestible aNDF fraction of concentrate from total fecal output. The indigestible aNDF content of pasture and feces was
used as an internal marker to estimate intake using the following formula: