Any animal that is prone and cannot get up is in real trouble.. especially a male as pee-ing is an issue. The only thing I can tell you is that the longer he is down, the less likely he will be to get up. This does not mean he will never get up.. but every 12 hours down decreases the likelihood.
Keep getting fluids in him. The Vet should have taken a blood sample to make sure the Ca/P ratio was ok along with checking a lot of other things. So many things could be wrong.....
There is something about the outside of a horse that is good for the inside of a man. ~Winston Churchill
) Dinosaur Horse Trainer