Usually a colic that leads into the next day is not a good sign. I have limited experience with minis themselves, but have years of experience with retired older horses. Some Ive lost to colic, one in particular, my favorite mare of all time, I still miss her to this day, that just about ripped my heart out for good. She had gotten an impaction stuck behind her pelvis, the vet couldnt get it around the bone with manipulation, very sad scary day, no time for surgery (probably wouldnt have anyways because its an outrages cost), euthinized an hour later. I believe from the minimal info ive read about minis and colic is that the vet cannot safety do a rectal exam...is this true? Yet I have read they are better candidates for ultrasounds as they are easier to read on a mini. I always call the vet if colic hasnt subsided within a few hours of administering banamine and walking, no use in waiting, only prolonging the inevidable and leaving the mare in pain. Thats my experience though. To each there own. Good luck! thoughts are with you and your mare...colic is such a scary and heartbreaking thing to go through.