We have a duroc barrow that last night decided not to eat. We had him out and worked him as usual. When he went into his pen he started throwing up. Did it 4 or 5 times then went and laid down. When we fed him he had no interest in it. Thought he would be over it this morning but when we fed he sucked some of the water off the top the laid back down. This is not like him, he weighs 140 lbs and has never had a problem eating. We have not changed anything. I guess it could be an ulcer? How long can they go without before I should be concerned? My theroy is he will eat when he gets hungry and I need to hold him some but don't want to do it like this. Any suggestions?