Sorry, but answers are dependant on the whole picture. Like when she was colicing, how much turnout time was she getting and how much hay (by weight)? Because the change in the incidence of colic may have more to do with the amount of forage she's getting than with the removal of senior feed. And how much water was she drinking before? Has there been a change in the way that water is offered/supplied? Was she in a sandy enclosure?