Is your dog male? Sometimes male dogs get a hemmoridal problem sorry can't remember what it's called but they do need to get it lanched. I really don't think the cat food has anything to do with your dogs problem. Have no clue how to make your dog unconstipated but just let the dog be when he/she needs to go believe they will go. Is your dog going to the bathroom doing it's business then rubbing it's butt on the ground?
