Abstract
Since the rejection of fecal odor by cattle causes the formation of dung patch in pastures, it is necessary to investigate the changes in the volatiles from feed in the digestive tracts and clarify the characteristic volatiles from feces. In this study three different diets: Italian ryegrass haylage, lucerne hay cube, and lucerne hay cube and formula feed were fed to two steers and the headspace volatiles from the feeds, rumen and duodenum juices, and feces were adsorbed on Tenax-GC and identified using a GC and a GC-MS. In the rumen some volatile compounds found in the feed decreased or disappeared while new volatiles appeared. The characteristic volatiles commonly found in the rumen were methyl ethyl ketone, phenol, p-cresol, indole and skatole. The profiles of voltiles of gastrointestinal juices were affected by the pH values. The VFAs (volatile fatty acids) could not be detected in the headspace volatiles of rumen juices at the original pH ranging 6.70 to 7.90, but after making the juice strongly acidic (pH 2.0), the VFAs could be detected. The production of volatiles in the digestive tracts were also influenced by the diets fed to the steers. The feeding of lucerne hay cube and formula feed, which has plenty of water soluble carbohydrates and protein, produced more volatiles in the digestive tracts than Italian ryegrass haylage and tended to increase the production of sulfur containing volatiles. Methyl ethyl ketone, phenol, p-cresol, indole and skatole were the characteristic volatiles from feces compared with the volatiles from feed and some portions of these compounds seemed to have been already produced in the rumen.
