We took the oil out of Pie's evening feed last evening, and voila! no digestive pain whatsoever, despite having his Banamine reduced to one dose in the morning. And today, when the vet came to do a blood draw to recheck his liver/bile situation (poor Pie's becoming quite the pincushion), she commented on how bright, alert and interactive he was - in fact at this point I'd say he looks great.
And there are more clues . . . Those of you who've been reading for a while may (very vaguely) remember that Pie had what (in hindsight) was an identical digestive attack after p.m. feeding on January 31. We blamed that on him being misfed another horse's dinner, and that horse was getting different feed. But we were all perplexed at how acute his symptoms were considering the very small amount - one cup - of different feed he'd been given. Here's the clue - the wrong food was a high-fat feed (Ultimate Finish) that Fritz was receiving to help him gain weight. There's the fat again - that's what caused the problem even though the amount was small. Then Pie had another attack on February 8, and none that we've noticed between then and last week, although there was the mysterious tying up episode on May 11 - I'm still not sure what that was all about - he was in severe pain and sweating profusely. That may or may not be unrelated.
So, looking back, it's clear that he's had this liver/bile duct problem all along, but we didn't know because he was able to tolerate fat in his diet - he's been getting cocosoya oil all along - unless it was too much - the winter episode where he was fed extra fat - or if his system was somehow otherwise disturbed, as with the recent vaccinations. The pain he's experienced seems to be because the fats aren't being broken down properly by bile in his small intestine, and end up undigested in the caecum - hence the pain and large amounts of gas, and his feeling somewhat better once the gas passes through.
Or at least that's the theory at this point. We'll see what the bloodwork shows and then go from there, but if we can at least make him comfortable again by removing the extra fat from his diet, that will be progress.