Evaluation of external markers to estimate fecal excretion, intake, and digestibility in dairy cows

The objective of this study was to compare the use of an external marker titanium dioxide (TiO2) as an alternative to chromic oxide (Cr2O3) in dairy cows. Four dairy cows were allocated in individual pens and fed concentrate supplement and Pennisetum purpureum cv. Cameroon cut daily. Fecal excretion, forage and total dry matter (DM) intakes, and digestibility were measured and estimated with TiO2 and Cr2O3. Chromic oxide overestimated and TiO2 tended to overestimate fecal excretion compared with total fecal collection. Forage and total DM intakes were overestimated by Cr2O3. The apparent DM digestibility was underestimated by Cr2O3 and TiO2. The organic matter (OM) digestibility was underestimated by both markers. There were greater mean bias, mean squared prediction error, and root of the mean squared prediction errors for all parameters estimated with Cr2O3. In conclusion, estimates using TiO2 were more precise and accurate indicating that it can replace Cr2O3 as an external marker for grazing dairy cows. © 2014, Springer Science+Business Media Dordrecht.