Digestion of cereals in the equine gastrointestinal tract measured by the mobile bag technique on caecally cannulated horses

The mobile bags procedure was used to measure the disappearance of starch and proteins in the precaecal as well as in the total intestinal tract of four caecally cannulated horses. Experimental grains were oats, barley and maize, each in four different forms: ground, pelleted, extruded and micronized. The horses had 16 to 20 mobile nylon bags containing one of the experimental cereals intubated through a nasogastric tube together with the morning meal. Some of the bags were captured with a magnet through the caecal cannula and analysed for contents of starch and protein. The remaining bags were captured from the faeces and underwent the same analysis, and the digestibilities in the different parts of the gastrointestinal (GI) tract were calculated. Oats had a high degree of starch digestibility (0.949 precaecally and 0.990 totally), considerably higher (P<0.05) than barley (0.705 precaecally and 0.960 totally) and maize (0.663 precaecally and 0.910 totally). However, oats had a higher precaecal digestibility of protein (P<0.10), but a lower total tract digestibility than the other grains (P<0.01). The high-temperature treated cereals (extruded and micronized) had a higher total tract digestibility of protein than the untreated cereals (P<0.01). The pelleted and micronized cereals had the highest precaecal digestibility of protein. Differences in digestibility should be considered when formulating rations for the athletic horse.