My horse was 14 yrs old. I have 5 other Quarter horses also. He was fed free choice grassy hay with twice a day feeding of complete feed 12% pellets 8 lbs total. I was adding warm water to the pellets. He was losing weight is why I started feeding the pellets. He also was on Equioxx(firocoxib) 57mg tablet once a day- Vet prescribed when he showed signs of lameness in one front leg. He never went off feed and never had a fever. He had a barn to go into and a 3 acre lot he had free access to with a waterer in the barnyard and free access to a salt block. I noticed my horse started backing into the wooden fence, the barn wall etc and leaning back against them as if to give him support. Next he started dragging his hind feet. His lameness in the front leg went away. His manure looked fine all during this and he had no trouble urinating. A day later he struggled getting up …we had to help him up to stand. The next two days worsened until he was unable to get himself up to stand. Again no fever and never went off feed. Sadly we had to have the Vet put him down. I wanted to know if any of you had any insight into this. It was very devastating. Vet had no diagnosis to offer.