Surabaya Zoo has a long row of hoofstock enclosures, some of them jammed with big herds. I'm convinced that the zoo uses deer meat to feed the carnivores.
I'm sorry to hear that. I appreciate the zoo's apparent interest in hoofstock because that's my favorite group of mammals, but seeing this many deer in a barren pen is just plain sad. At least they have shade. I hate to go negative, but your hypothesis makes sense in light of the sheer number of animals.