Medicine
The veterinarian concluded that the cheetah needs to take medicine in order to avoid catching a bad case of ammonia. This could really be a matter of life or death and something had to be done. But when the only problem was the officials at the zoo could not get the cheetah to eat anything, it refused all food and water.
When animals get sick they can act differently, sometimes they behave with hostility towards people or they become very shy. They don’t usually want to eat or drink anything and just want to be left alone. This cheetah was no different than the rest and this could become a problem.