The second week of July, we changed my Cavalier's food from Science Diet to Eukanuba. He had a hard time with this (diarrhea, mostly) and after about a couple weeks of no improvement, we switched him back to Science Diet. He appeared to be getting much better, as he was energetically eating the full amount of the food and his stools had firmed up--they were still soft, but had form and shape to them. However, in the past three days, he has not wanted to eat and last night he did not eat at all, and his stools have become very runny and just this morning, very mucous-like. The only difference in his diet in the past three days has been that I gave him a "Flossie" chew which is a beef tendon type treat like a pig ear. Besides the problems stated above, he is acting very normal. He is happy, sleeping well, continues to meet us at the door and such, goes on his two walks a day, and plays frisbee. Could this be an effect of the Flossie treat or something more serious?