I'm pretty sure the answer is GUM but with another name like POLYMERYS or something like that.
The teachers hates that the students chew gum
The cow likes to masticate grass (gum is a Synonym of masticate)
The hard one is the monkey. There is a tree called the Mountain Grey Gum also known as the Monkey Gum. The Eucalyptus cypellocarpa. I suppose its name has something to do with the monkeys eating it.
Also found this
"Nevertheless, gum comprises an important part of monkeys’ diet. Wild monkeys collect the gum from the acacias, which precipitate the product. In fact, monkeys depend on the gum in order to fully utilize their digestive system."