Yes, some dogs will have more frequent bowel movements on grain free, my dog with environmental allergies does best on Nutrisca salmon and chickpea grain free, but, I have noticed the extra bms, in her case, I don’t consider it an issue.
For my terrier, I mix 1/3rd or 1/2 Dogswell chicken and oatmeal kibble (contains grains) with the Nutrisca kibble (grain free) with good results. Grains are not always a bad thing.
https://www.mspca.org/angell_services/choosing-the-right-diet-for-your-pet/
http://skeptvet.com/Blog/category/nutrition/
I have found the above sites helpful.
