The use of chromic oxide as a marker for measuring small intestinal digestibility in cannulated dogs.

Small intestinal digestibility can be measured by comparing feed with effluent collected from an ileal T-cannula. Nevertheless, a nondigestible, nonabsorbable marker, such as chromic oxide (Cr2O3), must be included in the diet because simple T-cannulae do not divert chyme completely. This study was conducted to evaluate the excretion pattern of Cr2O3 in cannulated dogs because the kinetics of Cr2O3 has not been previously investigated in this nonruminant species. Chromic oxide was added to four diets fed to eight cannulated mixed-breed dogs in a Latin-square design. The four diets contained reciprocal proportions of protein from texturized vegetable protein (0% to 57%) and from beef (100% to 43%), so protein and carbohydrate digestibility varied among diets. All feces were collected during wk 2 and all ileal effluent during wk 3 of each diet period. Ileal recovery of Cr2O3 was almost complete (94%) and was greater than fecal recovery (87%) (P < or = .03). Recovery was not different among diet groups. Ileal DM digestibility was approximately 2 percentage units lower on d 1 (P < or = .007) than on d 2 to 4. Nevertheless, ileal DM digestibility varied little on these subsequent days so single-day collections should be accurate. Chromic oxide concentration in chyme varied widely during each collection but increased at the start and declined towards the end of each collection. Spot sampling may therefore result in inaccurate estimates of nutrient digestibility. In conclusion, Cr2O3 may be used as a marker to measure digestibility in dogs with simple T-cannulae, but total collections should be attempted for greater accuracy.