THK and Canine Caviar both offer simple, low fat formulas up to higher protein/higher fat.
Two different types of foods, both great brands.
Jackson won't eat THK - the consistency of it is very weird (IMO) and it's expensive!
Have not tried Canine Caviar yet, but I hear GREAT things about it.
No experience with IBD though. They do have a Special Needs formula. Good luck!