Final answer:
Herbivores digest cellulose with the help of bacteria in the rumen, a part of their stomach, which secretes cellulase to break down the tough plant fibers into usable glucose monomers.
Step-by-step explanation:
Once an herbivore swallows plant material, the food travels to a section of its stomach known as the rumen. The rumen is filled with bacteria and sometimes protists that aid in the digestion of cellulose, which is abundant in plant material. These microorganisms secrete the enzyme cellulase, which breaks down the β 1-4 linkages in cellulose, transforming it into glucose monomers that the animal can use as an energy source.
The digestive system of herbivores such as cows, buffalos, and horses contains multiple chambers with the first one, the rumen, playing a key role in digesting tough plant fibers. This compartmentalization allows for microorganisms to ferment the ingested plant material, enabling the herbivore to obtain nutrients that would otherwise be inaccessible due to the absence of cellulase in their own digestive enzymes.