OBJECTIVE To characterize the expression of monocarboxylate transporters (MCTs) 1 and 4 and the ancillary protein CD147 in the intestinal tract of healthy equids and determine the cellular location of CD147 in the intestinal epithelium. ANIMALS 12 healthy horses and ponies slaughtered for meat production or euthanized for reasons unrelated to gastrointestinal tract disease. PROCEDURES The entire gastrointestinal tract was removed from each equid within 45 minutes after slaughter or euthanasia. Tissue samples were obtained from the antimesenteric side of the duodenum, jejunum, ileum, middle part of the cecum, sternal flexure of the ventral colon, pelvic flexure, sternal flexure of the dorsal colon, and descending colon (small colon). Expressions of MCT1, MCT4, and the ancillary protein CD147 were examined in tissue samples from each of the 8 intestinal locations by means of quantitative PCR assay, immunoblotting, and immunohistochemical analyses. RESULTS Expression of MCT1 was most abundant in the cecum and colonic sites, whereas expression of MCT4 was predominantly in the proximal section of the intestine (small intestinal sites and cecum). Immunohistochemical analysis revealed that MCT1 and CD147 were present in the membranes of enterocytes (in crypts and villi). CONCLUSIONS AND CLINICAL RELEVANCE The anatomic distribution of MCT1 and MCT4 in the equine intestinal tract determined in this study together with the previous knowledge of the sites of substrate absorption indicated that MCT1 might predominantly contribute to the uptake of short-chain fatty acids in the large intestine and MCT4 might predominantly contribute to the uptake of lactate in the small intestine.

Objective: To determine the effects of raw meat–based diets with and without inulin or yeast cell-wall (YCW) extract on macronutrient digestibility, blood cell counts, serum metabolite concentrations, and fecal fermentative end-product concentrations in healthy adult dogs. Animals: 6 healthy adult spayed female dogs (mean ± SD age, 5.5 ± 0.5 years; mean body weight, 8.5 ± 0.5 kg). Procedures: Dogs were fed each of the following 6 diets for 21 days, the order of which was randomly assigned in a Latin square design: beef control, beef and 1.4% inulin, beef and 1.4% YCW extract, chicken control, chicken and 1.4% inulin, and chicken and 1.4% YCW extract. Each diet trial consisted of a phase for diet adaptation (days 0 to 14) and a phase for measurement of urine and fecal output and content (days 15 to 20). On day 21, food was withheld for blood sample collection. Afterward, the next diet trial began immediately. Results: All dogs maintained desirable fecal quality characteristics and produced low fecal volume. All diets were highly digestible (protein digestibility > 88%; fat digestibility > 97%). Differences in fermentative end-product concentrations among all diets were minor, but a significant increase in fecal short-chain fatty acid concentrations was evident when dogs were fed beef-based diets with inulin and YCW extract. Fecal spermine concentrations were higher with diets containing inulin and YCW extract than with control diets. Blood cell counts and serum metabolite values were within reference limits after each trial. All diets resulted in maintenance of nitrogen balance. Conclusions and Clinical Relevance: Results suggested the raw meat–based diets evaluated were highly digestible in dogs. The increase in fecal short-chain fatty acid concentrations achieved when inulin and YCW extract were included may be beneficial to canine health.