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 nondigesti ble, nonabsorbable marker, such as chromic oxide (Cr2O3), must be incl uded in the diet because simple T-cannulae do not divert chyme complet ely. This study was conducted to evaluate the excretion pattern of Cr2 O3 in cannulated dogs because the kinetics of Cr2O3 has not been previ ously investigated in this nonruminant species. Chromic oxide was adde d to four diets fed to eight cannulated mixed-breed dogs in a Latin-sq uare design. The four diets contained reciprocal proportions of protei n from texturized vegetable protein (0% to 57%) and from beef(100% to 43%), so protein and carbohydrate digestibility varied among diets. Al l 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 less than or equal to .0 3). Recovery was not different among diet groups. Ileal DM digestibili ty was approximately 2 percentage units lower on d 1 (P <.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 collectio n. Spot sampling may therefore result in inaccurate estimates of nutri ent digestibility. In conclusion, Cr2O3 may be used as a marker to mea sure digestibility in dogs with simple T-cannulae, but total collectio ns should be attempted for greater accuracy.