Cannot add much more to Pinkfest..detailed post extraordinary, so well written
But I do add Slipper elm to my horses or dogs diet if they have some bowel problems and also some bran....It helped the "ferals" when they first arrived as they had all sort of issues.
Slow bowel movements, reduced motility, can be due to genetics too. But often it can be caused by previous issues with constipation. It has made to bowel slower, smoother and larger.....
We feed Oats and bran (RAW) with our meals (dogs) for those sort of problems.
It cannot always be sorted and sometimes it is something the dogs or humans live with forever, same as some have irritable bowel and super fast action. Just make sure there is plenty of fiber for the dog. One of the reasons pumpkin/sweet potato often works so well is it fiber content. White rice is not really good. if you do use rice use brown. I like RAW oats better.
In the human world we do give longer then 8 hours for the pellets to move on...some even 24 hours. As long as they do travel through, you will be able to manage. As long as something (poop) passes regularly and is of a good consistency you should be able to manage. You can joint the poop watcher Club, its free.