[Preliminary results using a combined xylose absorption/hydrogen exhalation test in horses]

In the present study the breath hydrogen (H2) excretion test was combined with the xylose absorption test in 4 normal horses and 9 clinical patients with chronic diarrhea (n = 3) or chronic weight loss without diarrhea (n = 6). All horses underwent a thorough clinical examination. Laboratory evaluations consisted of haematology and serum biochemistry as well as bacteriological and parasitological examination of feces. In addition, serum electrophoresis and abdominocentesis was performed in all the clinical patients. Gastroscopy was carried out in 6 patients and rectal biopsies were obtained from 4 animals. Two animals were euthanized within 4 weeks after the evaluation. The diagnosis of chronic granulomatous enteritis was confirmed in one of them at necropsy, the cause of weight loss in the other remained unexplained. In the remaining animals, specific causes such as management, parasites, chronic infections and diseases of liver, kidneys and heart were excluded, but no specific diagnosis could be obtained. For the combined xylose absorption/H2 excretion test, the animals were starved overnight and given 0.5/kg/bwt xylose as a 10% solution by stomach tube the next morning. Blood samples were collected for plasma xylose analysis at 30 min intervals for 4 hrs, and breath samples were also collected at 30 min intervals for 8 hrs. With the exception of the animal with granulomatous enteritis, the diseased horses showed only slight alterations in either peak concentrations or times to reach peak levels of plasma xylose. None of the healthy animals showed an increase in breath H2 production after xylose administration, whereas five of the diseased animals showed distinct increases of variable heights. In addition, the diseased horses showed higher fasting breath H2 levels (range 7.5-61.5 ppm) than normal horses (range 0-5 ppm). It is concluded that gastrointestinal disorders might be influenced or even induced by a change in intestinal microbial composition, as evidenced by an increased hydrogenic metabolism.