Corn oil. Its a little easier on their systems than other oils. It takes maybe a table spoon for a lab size dog, and maybe two for a dane. Less for a smaller dog. Pour it over their food, or a little can of wet food. If that dose doesnt work double it the next day. it wont take long for it to work!
Canned pumpkin works great if you can get your dog to eat it! Especially with a little corn oil on it.
bonus? Corn oil really gives their coat a nice sheen, and will add bulk to a skinny dog if given daily.
Pumpkin is chock full o goodness. You can tell by its bright color that its going to be going to be good for you. Not only is pumpkin loaded with vitamin A and antioxidant carotenoids, particularly alpha and beta-carotenes, its a good source of vitamins C, K, and E, and lots of minerals, including magnesium, potassium, and iron.
Half a cup of canned pumpkin has 6.5 grams of effective carbohydrate and 3.5 grams of fiber.
The seeds are also worth latching on to. Pumpkin seeds, also called pepitas, are loaded with minerals, seem to have an anti-inflammatory effect, and may even help protect against prostate cancer and osteoporosis. A quarter cup has about 5 grams of effective carb and 1.5 grams of fiber.
Pumpkin is also excellent for diabetics and pre-diabetics; it helps generate healing in the pancreas.