The dairy cow, like other ruminants, has four compartments in its stomach. The first compartment, the rumen, partially degrades feedstuffs by anaerobic microbial fermentation processes. The fourth compartment, or abomasum, corresponds to the single stomach of nonruminants, where final degradation of ingested material takes place.

The author acknowledges the Maddox Dairy (RuAnn), Riverdale, California, for supplying animals, feed, and facilities, and Udi Sosnick and Richard Borba for assistance in completing the experiment.