Final answer:
The polygastric digestive system in ruminants, with its multiple stomach chambers, aids in digesting roughage by leveraging microbial action to break down cellulose and strong muscle contractions for mechanical digestion.
Step-by-step explanation:
The polygastric digestive system aids in digesting roughage primarily by having multiple stomach chambers. These specialized chambers each play a role in the microbial digestion of plant material, which is difficult to digest due to the presence of cellulose. Cellulose is a complex carbohydrate that animals cannot break down with their enzymes. However, microorganisms within the stomach chambers of ruminant animals produce the enzyme cellulase, which can break down cellulose. As the food moves through the multiple chambers, stronger smooth muscle contractions help to mechanically break down the plant material, and the microbial action helps to chemically digest it. This allows ruminant animals to extract nutrients from plant-based foods more efficiently than monogastric animals can.