GLUCOSE ABSORPTION

Indications for performing this test: The Oral Glucose Tolerance Test (OGTT), a carbohydrate absorption test, is indicated in any disease in which a horse shows signs of having malabsorption, such as dull coat, chronic diarrhea, chronic weight loss, etc. This test allows assessment of the absorptive capacity of the small intestine, but it must be noted that the amount of glucose found in the plasma will vary not only in relation to the amount that is absorbed, but also with the quantity and concentration of the glucose given, the age of the animal, the animal's diet, and the length of time the animal has been fasted. In addition, a flattened curve may be indicative of small intestinal bacterial overgrowth or food allergies, not malabsorption. Still, it is generally useful and will detect disorders that are fairly diffuse in the small intestine, or that affect entrance into or movement through the small intestine.

A horse showing signs compatible with a malabsorptive disorder.

The Procedure: After being fasted for 18-24 hours, the horse is given 0.5 to 1 g/kg of 10% glucose solution via a nasogastric tube. Later, blood samples are collected into sodium fluoride tubes at intervals of thirty minutes beginning at time zero (when the glucose is administered) and ending at 240 minutes after administration. More recently it has been reported that samples can be obtained only at time zero and at 120 minutes, thus minimizing time constraints, and still yield diagnostic results.