Check with your vet, but I might want to get the stools firmed up a bit before making a food change, then gradually introduce the new food over a few days as the article suggests.
http://cvsecvet.com/Specialties/MedicalResource/53 Excerpt below
Feeding A Bland Diet
DIET: When offering food, please offer small meatballs of a bland diet if tolerated. There are various bland prescription diets such as Hill’s I/D or Royal Canin GI Low Fat you may try. Please ask for a written prescription to have them filled. A home cooked bland diet is any combination of the below carbohydrate and protein source, and should be in small frequent meals 3-4 times daily for 3-5 days. If this is tolerated and stool becomes formed, then switch to twice daily feedings and then slowly transition back to normal diet over the following 3-5 days by mixing the two.
1) A mixture of a carbohydrate from the following list and a protein from the following list:
Carbohydrate Proteins
Boiled white rice Boiled drained lean hamburger
Boiled potatoes Low fat cottage cheese
Boiled plain pasta Boiled chicken (no bones or skin)
2) Feeding Instructions: Mix one carbohydrate with one protein at a ratio of 3/4 carbohydrates and 1/4 proteins. Feed approximately one cup of cooked carbohydrate and four ounces of protein per 20 pounds of body weight daily.
