You veterinarian may want you to add some fiber to your dog's diet to help slim down an overweight canine, help with diabetes or calm diarrhea, constipation or other gastrointestinal woes. Carbohydrate and fiber sources must be cooked to be digestible, according to the Merck Veterinary manual. Uncooked fiber sources can cause diarrhea and gas. While there is no dietary requirement for carbohydrates in a dog's diet, carbs and fiber can provide energy and keep the gastrointestinal tract healthy, according to Merck.
Cook vegetables for your dog. Summer or winter squash, green beans, peas and white or sweet potatoes are all good sources of fiber. Peel potatoes, and don't feed any green or sprouted ones. You can also use low-sodium canned, or frozen, cooked vegetables.
Add a little fruit. Apples and apple sauce, melon, pears, blueberries and cranberries all add fiber and nutrients. As with vegetables, they need to be cooked first. Remove all seeds and pits from fruit, and never feed grapes or raisins. They can be poisonous to some dogs.
Serve your dog a little oatmeal, rice or whole-grain pasta. If your dog already eats a kibbled dry food diet, don't feed much of these; it's already getting a lot of grain. However, if you want to add fiber to a raw or home-cooked diet, grains add both carbohydrates and fiber.
Mix some wheat bran into your dog's food. Bran is very high in fiber, so just use a sprinkle at first. As with any diet change, watch your dog's stool and back off amounts if it starts getting loose stool or flatulence.
Add a small amount of low-sodium chicken or beef broth or meaty canned dog food to fiber sources if you dog is unwilling to eat them.