canine digestion and diet

Question
I have a mutt that looks like a dingo and she's truly omnivorous. I haven't found a fruit or vegetable that she doesn't like (except maybe lettuce). She constantly "grazes" on grass without the usually canine response of throwing up. She pulls off and eats the berries of our cotoneaster bushes. She eats the concord grapes off our vine (which scared me given that I've learned grapes can result in kidney failure but she eats them with apparent impunity), and crab apples that have dropped to the ground. Given that these supplements mirror the diet of coyotes and other wild carnivores, it really doesn't surprise me. However, her digestive system is very sensitive and her stool is almost always very soft. I've tried several different brands of high-quality dry food with different meat bases and even tried grainless versions (the latter which resulted in lots of nasty farts), none of which helped firm her stool. We've also tried probiotics and live-culture yogurt and still have not seen improvement. Lately, she's developed really horrendous smelling farts (and she's been on the same dry food now for months). I thought it might be the grapes but they've been gone for over a week. About a month ago, we switched from giving her fish oil tablets to sprinkling flax seed meal over her food to help keep her coat looking great but we're now wondering if she's become intolerant to the flaxseed meal which is resulting in farting. Two questions, then. How can we improve the overall health of her digestive system and hopefully firm up her stool? What might be causing her farts?

Answer
I don't think you have any chance of firming up her stools as long as she is foraging this, that, and everything else.  In general, well formed stools are usually a sign of a good diet.  Are what she is producing a problem cleaning up?  For guide and other service dogs, ease of clean up is a huge issue.  For a dog that usually eliminates in its own backyard, even cow pies aren't that much of a problem to clean up.  Maybe quit fighting it.  

As for the gas attacks.  If you are feeding a quality chow, you don't need to add flax seed meal or anything else.  Why flax seed?  Corn oil has over 3 times as much of the linoleic acid dogs need as linseed.  Most fish oils have very little if any.  I would cut out the flax seed and see how she does.  If her coat isn't good, try Iams or Pro Plan.  Many dogs thrive on them.