Why does my son leave his two dogs in a cage to starve?

I visited my 30 year old son house two days ago and he has to beautiful dogs but I was disgusted at what I saw, his two dogs are so thing and starved to death. I think they will die in starvation if he doesn't feed them, I have talked to him about it and he said that it's none of m business and it's his dogs and he will feed them when he thinks they deserved to be fed. I told him he could go to jail and he just ignored me, what can I do? This is cruelty. II love my son but I seriously think I will throw up if I go over his house to see walking dog skeletons.