Steer Bloating up

Have had problems with a steer bloating up on me the last few days. Have not changed his ration at all. Last weekend I got hay that had more alfalfa than they were used to. After he bloated up the first time I pulled the hay from them thinking that was it and have since used some plain grass hay. Was a little better for a day but still bloated some. Have noticed that he will still eat grain and such. I do turn them out in an acre or so lot that has some grass and weeds, mainly weeds thanks to the dry weather. Could there be something out there?? Fair is this week for us. Not sure what I need to do or what i'm doing wrong, but knew there were some people smarter than me here that would have some ideas. Thanks!

Would Bet the ph in the gut got out out of wack,  try baking soda in the feed,  tide detergent works good but it just keeps him down.have seen an ulcer cause it but that is way down the list.  If your feed is a custom mix, may have had hog feed in the batch before yours. Simplify the feed a bit,  more roughage, less of the additives,  see what happens. 
There are times you just get a bloater,  learn to deal with it.

Is your fair the end point for your calf? If so probably the simplest thing to do would be to either put out a bloat block or get the granulated bloat guard and put it in the feed. Don't overreact and get to changing things up too much, but you do need to watch things carefully. Two TBS of baking soda per head per day mixed in his feed may do it for you, but bicarbonate may already be in his diet, if so it probably won't help. Good luck, Cab.