Well, I guess I'll be putting a call into the vet tomorrow morning. Just got back from a trip to find my mule is not eating his grain. He is, however, eating his hay. Attitude is good... he was the first to greet me at the gate and follow me around. Just doesn't want his 4 ounces of oats. The horses were happy with their oats so I don't thinks its a "bad bag" of grain. Although it is dark out, a quick spin around the paddock with a flashlight revealed at least one pile of runny manure.
Any guesses to his ailment? I'll go out a few times tonight to make sure he's not going into colic.
I should add that the occassional loose stool is not new to him. Besides the regular worming, I've done a five day panacur purge and a double equimax worming and they didn't clear up the loose stool. He gets it about once a month (for the past three years). Your suggestions are appreciated!