In ruminant digestion, which chamber houses the microbes that ferment fibrous feeds?

• A. Rumen
• B. Abomasum
• C. Omasum
• D. Cecum

Answer: (A)

In ruminants, the main site where fibrous feeds are broken down is the rumen, a large fore-stomach chamber filled with a dense, anaerobic microbial community. Bacteria, protozoa, and fungi ferment cellulose and other structural carbohydrates, turning them into volatile fatty acids that the animal absorbs through the rumen wall for energy. This cooperative digestion of roughage is what makes ruminants able to thrive on high-fiber diets.

The other compartments play different roles. The abomasum is the true stomach with acid and enzymes for protein digestion, the omasum mainly absorbs water and further reduces particle size, and the cecum is a fermentation site more typical of hindgut fermenters rather than the primary site in ruminants.