Here is how I see pet foods, with lower quality food, that as per the discussion is called "crap". The first 5 on the list make the bulk of the food. By products are things that are not used for human consuption, ie hooves, feathers, blood, fat, bones etc. Next we come to the lower quality food, the more that is need to feed for tha animals to absorb nutrients, but because of high fat content in these food dogs tend to get over weight if fed more or under weight if feed less.
Now our pets may be pooping to what seems normal, but with the higher quality food, the body absorbs more, so there is less to come out. And even if we think that our pets are doing great, live long lives, seem perfectly health etc, they can benifit greatly from a healthier diet.
My dog grew up on Iams for the first almost 3 yrs of his life. He became fat, so I put him on a weight maintence Iams, that didn't help either but just moderate weight loss, also my other dog on Iams also, I couldn't keep weight on her. Then I discovered holistic foods, and transfered them over to Solid Gold Hund-N-Flocken. Reggie went from way over weight to between 70-72lbs, Lili put weight on that she needed and maintained a good weight. They were more active because they had the need energy from their foods. They did not become completely wiped out from exercise, but were a healthy tired and were back to normal the next day instead of taking 2 days to recover from just going to the dog park.
Another HUGE thing I noticed is that once I took them off of the "crap" food, they did have smaller poops, and also, I discovered that if they got "crap" treats that contained corn or another filler, they had poop that was very grainy like they ate sand, because they're body just pushed it out.
Now Jazzysmom, you talk about your nieces dog passing because of "poor aging", this doesn't do with the food and IMO only that you are comparing the dogs problems to what was fed. From your description it sounds more like genetics, breeding etc.
Like I said earlier that very many peoples dogs do well on said "crap food" and live to longer lives. But they say an "average" life span for most dogs are 8-12 or so yrs, and I say average. But with healthier diets and proper exercise dogs that are fed holsitic foods live much longer than their "average" numbers. My father has huskies for sledding, most are retired now, and those that are retired are all in their high teens. A husky's average age is 10-12, and they have two right now that are 16 and still going very strong. They had to put one down last week due to old age of 18, her back legs went out on her.