How do ruminants digest tough grasses and other plant foods?

Ruminants, which belong to the order Artiodactyla, have evolved a specialized digestive system to process tough plant materials like grass, as their bodies cannot produce the enzymes necessary to break down cellulose.12

The process relies on a multichambered stomach and symbiotic microorganisms:12

• Fermentation: Ingested food enters the rumen, where it is softened and subjected to bacterial fermentation. These microorganisms break down cellulose into acetic acid and other short-chain fatty acids, which the animal absorbs for energy.12
• Rumination: Ruminants store food quickly and later regurgitate it as cud. By chewing the cud, they further break down the plant fibers and mix them with ruminal fluid, facilitating more efficient digestion.12
• Final Digestion: The re-chewed material passes through the remaining stomach chambers—the reticulum, omasum, and abomasum—where further digestion occurs.1

This process also allows ruminants to synthesize essential microbial protein and vitamins, reducing their dietary dependence on external sources.2