Agreed with you Alan.
>>My confusion is the continued banimine and pen. No signs of colic, no temp so no fever, blood panel was normal so normal what is the vet treating? Not saying you're doing this, but I don't know how many times I ran into someone who tells me the horse just ain't right. When asked what the horse is doing and how they are treating it, it turns out they are trying everything anyone tells them to do. Two days on this drug, switched to this drug, trying this feed, switched to this feed. All they are doing is screwing up the horse more.<<
No point in treating if you don't know what you're treating....
That said, I'd have the vet run a chemistry panel as well as a complete blood profile (CBC) and see if there isn't something that gets picked up there. Another option for the horse is an abdominocentesis (check abdominal fluid) to look for abnormalities.
Middle aged horse, frequent causes of colic there would be sand colic, mesenteric lipomas (fatty growth that can strangulate intestines due to weight), enteroliths (mass of intestinal contents e.g mineralized ball of mucus and/or feed, that is gradually added to over time; can get trapped in various locations of the large intestine), displaced colon etc (pelvic flexure of the large intestine isn't anchored to anything in the horse), large strongylus (S. vulgaris) in the cranial mesenteric artery (loss of blood flow to various parts of the intestine- classic lesion as part of the parasite's life cycle), or various impactions or unknown causes (e.g. horse is opened up in surgery and nothing abnormal can be found). All of the above can cause acute pain or mild, chronic colic. Had a 3 y/o filly in here for surgery last week with a twisted large intestine, mild colic for 2 weeks.
None of the above problems would be fixed with banamine and antibiotics.
Rotating wormers - is not recommended. Use one until it no longer works with some exceptions (e.g. worm for tapeworms yearly or as needed). Recent rep who came through here said the new equine recommendations include doing fecal floats to determine horses who are high shedders, and worm those horses frequently, and horses that are known to be low shedders on an intermittent basis.
I wouldn't assume that because an animal exhibits pain after one wormer, that the contents itself were caustic, painful, etc. It may be that *that* wormer is actually effective against the parasites and they are causing discomfort to the horse during their dying spasms. Not all wormers are equally effective. Saw a 4 month old foal here earlier in the semester that had been wormed with X wormer the month before, they wormed with Y wormer and the foal colicked. At surgery there was a severe ascarid impaction- it had been going on longer than the month between X and Y wormers.