This research was conducted to compare the internal markers: indigestible neutral detergent fiber and acid detergent fiber, obtained after 144 h of in vitro (ivNDF, ivADF) and in situ (isNDF, isADF) rumen incubations; and the chromium oxide (Cr2O3) as external marker. The fecal output of dry matter and organic matter and the duodenal flow of crossbred steers, castrated and canulated in the rumen and in the duodenum. The steers were and fed with corn silage or the cassava hulls + citrus pulp, the cassava meal + citrus pulp, and sugar cane + citrus pulp, silages. The animals were adapted to diets during 11 days following 8 days for sampling. The dry matter and the organic matter duodenal flow estimated using the fecal output calculated by the ivADF. It was used a 4x4 Latin Square design with Split-splots. The fecal output results, expressed in live weight percentage, showed that the ivADF (0.88%), isADF (0.85%) and Cr2O3 (0.99 %) supplied biological consistent values and they could be used in spite of the significant differences among them. The internal markers did not show differences among them for the estimation of dry matter duodenal flow with an average of 3.29 kg/day. The chromium oxide overestimated the DM duodenal flow (4.95 kg/day). The organic matter duodenal flow estimates, there were no difference among the markers with an average of 2.73 kg/day.
chromium oxide; indigestible ADF; indigestible NDF; in situ method; in vitro method
