Excretion patterns of titanium dioxide and chromic oxide in duodenal digesta and feces of ewes

Our objective was to examine differences in marker excretion patterns between Cr2O3 and TiO2 in mature ewes fed diets varying in level of forage. Three experiments were conducted using an all forage diet, a 50% forage diet, and a 25% forage diet. In all three experiments, ewes were dosed intraruminally twice daily at feeding with gelatin boluses containing 2.5 g Cr2O3 and 2.5 g TiO2. Following 7 days of adaptation to markers, fecal grab samples were collected at 6-h intervals for 6 days, representing every 1-h interval in a theoretical 24-h clock. On days 14–16 of each experiment, spot samples of duodenal digesta were collected at times representing 0, 2, 4, 6, 8, and 10 h after the morning feeding. Duodenal TiO2 and Cr2O3 concentrations exhibited a diurnal pattern after feeding in all three experiments, but there were no marker×time interactions. Although fecal concentrations of TiO2 were higher than Cr2O3 in all three experiments, there were no significant marker×time interactions observed. The lack of significant marker×time interactions resulted in little effect of sample collection frequency on mean concentrations of either marker, and as such, the frequency with which either duodenal or fecal samples are collected may be reduced in animals dosed twice daily without markedly affecting mean marker concentrations. Although estimates of digesta flow may differ between markers, the patterns of marker excretion observed suggest that TiO2 behaves similarly to Cr2O3 within the gastrointestinal tract, and thus is an acceptable alternative to Cr2O3 for use in site and extent of digestion studies with ruminants. © 2005 Elsevier B.V. All rights reserved