Compartmentalization of Intestinal Tract
To study the chemical, enzymatic, and microbial actions in different compartments of the intestinal tract, the tract can be compartmentalized using a multiple cannulation approach. By inserting intestinal cannulas in various places in the small intestine, the disappearance of nutrients in the GI tract may be compartmentalized. In a simple model, a cannula is inserted into the duodenum and into the ileum. Pigs are fed experimental diets and samples of fecal materials, ileal digesta, and duodenal digesta are collected. An inert marker is included in the diet, and the apparent digestibility of nutrients is then calculated in each sample using equation [4] above. The disappearance of nutrients in the stomach, in the small intestine, and in the large intestine, respectively, may subsequently be estimated. If additional cannulas are inserted in the hindgut, digestibility values and microbial fermentation in different compartments of the large intestine may also be studied. 
In the Stein Monogastric Nutrition Laboratory at the University of Illinois, multiple cannulation has been used to study the digestibility of dry matter, nitrogen, and phosphorus in each section of the GI-tract. Likewise, the metabolism of exogenous enzymes and the breakdown of phytic acid in the digestive tract have also been studied in animals that were equipped with duodenal and ileal cannulas.
