What's up with the way a donkey sounds?

My friend has donkeys and when they make this sound can be several reasons. Hers do this when its feeding time, mating, or trying to get the others attention or danger is near. The noisiest was the stud donkey. Boy are they loud and its neat to hear them yeehaw...LOL

Perhaps it's ill or has parasites or feels lonely (animals do have feelings, in my experience with them). Has the donkey repeated this behavior or was it a one time off? Obviously, something upset it.

Donkeys bray at feeding time when something scares them or excites them.

I'm thinkin lonely. they do that in situations when they are hurt, hungry, want attention, disturbed, feel threatened, etc.