Whole digesta properties as influenced by feed processing explain variation in gastrointestinal transit times in pigs

Physicochemical properties of diets are believed to play a major role in the regulation of digesta transit in the gastro-intestinal tract. Starch, being the dominant nutrient in pig diets, strongly influences these properties. We studied transport of digesta solids and liquids trough the upper gastro-intestinal tract of 90 pigs in a 3x3 factorial arrangement. Dietary treatments varied in starch source (barley, maize, high-amylose maize) and form (isolated starch, ground cereal, extruded cereal). Mean retention times (MRT) of digesta solids ranged 129-225 min for the stomach and 86-124 min for the small intestine (SI). The MRT of solids consistently exceeded that of liquids in the stomach, but not in the SI. Solid digesta of pigs fed extruded cereals remained 29-75 min shorter in the stomach compared with pigs fed ground cereals (P<0.001). Shear stress of whole digesta positively correlated with solid digesta MRT in the stomach (r=0.33, P