Quite a few animals chew their food multiple times for more effective digestion - cows for example. Plant fibers are notoriously hard to break down. Horses don’t and if you compare the digestion results, you’ll see a significant difference between horse dung and cow dung.
Besides the ruminants, there are also other animals, the best known being the rabbits, which are not able to reverse the direction of the food to bring it back from the stomach into the mouth, so after a one-way passage of the food through their bodies they must eat it again, to chew it for the second time.
Yeah. Horses are so inefficient at digestion that the largest breeds (such as Clydesdales) would starve to death in huge fields of grass. They can only survive by being fed copious amounts of grain such as oats.
Hmm. Do you have a reference for that? From what I have read, Clydesdales are fine on good pasture (hay in the winter), but they won't be able to do much if any work if they don't get additional feed. They would also likely not be as muscled as a horse with supplemental feed. A clydesdale raised on pasture only might also end up smaller, but they won't starve to death, assuming it is quality pasture.
I'm talking about a large breed raised on grain and then suddenly switched to pasture -- not one raised on pasture its whole life -- as you might see with a retired working animal. They may not literally starve to death, but they will lose a lot of muscle mass and may get sick and die from that, or may struggle to survive the winter.
Given a sample size of my dog, I believe chewing is only necessary for making bland food more delicious. The more yummy the food, the less my dog chews it - thoroughly chewing dry kibble and culminating in literally inhaling something like roast chicken.
Thus, it's because grass and weeds are bland and lacking in tasty fat that bovines and ruminants chew their food for so long and so many times.
Also, it depends if something eats leaves (not very digestible, not very nourishing) vs fruit (very digestible, except the seeds, and highly nourishing).
