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

Abstract

Our objective was to examine differences in marker excretion patterns between Cr 2O 3 and TiO 2 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 Cr 2O 3 and 2.5 g TiO 2. 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 TiO 2 and Cr 2O 3 concentrations exhibited a diurnal pattern after feeding in all three experiments, but there were no marker × time interactions. Although fecal concentrations of TiO 2 were higher than Cr 2O 3 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 TiO 2 behaves similarly to Cr 2O 3 within the gastrointestinal tract, and thus is an acceptable alternative to Cr 2O 3 for use in site and extent of digestion studies with ruminants.