I went to school for 2 years for animal science/pre-vet at NCSU. I dissected all sorts of animals... dogs, cats, horses, goats, pigs, cows, chickens, you name it. Now, herbivores have MULTI CHAMBERED stomachs because of the EXTENSIVE digestive processes that occur as a result of eating so much damn fiber. Forage (hay/grass) is REQUIRED for these animals to function. As mentioned, they also have eyes on the sides of their heads and have the ability to sleep standing as defense mechanisms.
I don't eat forage or graze, and I don't have more than one chamber in my stomach. I eat meat on the daily. If I were an herbivore, I would not crave protein the way I do and my digestive tract would function entirely different. I'm tired of hearing that humans are herbivores... it's so stupid.