My 23 yr old arabian gelding has been very lethargic. He only ate half his dinner, and keeps laying down. He does not thrash or bite his sides like he is colicking, but just lays flat on his side, or upright, for about 15 min, gets up and walks or trots around, and lays back down after being up for about 15 min. He drank plenty of water. I am not sure that he is colicking. He has had diarrhea for a few days now and in the past month I have noticed he takes a while to pee. Do I need to keep him on his feet? When I tried that, he hung his head and was so miserable. Walking a few times around the barnyard increases his breathing.