I have a mixed breed (Pom-a-poo) that needs his done regularly. It does run through some breeds more than others (small to med poodles come to mind). Out of all of the dogs I’ve had, only one has needed this done regularly.
If we don’t have them expressed they can rupture, which is absolutely not for the faint of heart. It is a smell like none other. I could do this procedure at home, but prefer to have either my vet or my groomer do it. Not only because of the odor, but also because my dog does not like me back there.
We’ll have to have a vet weigh in on this to know “why” some dogs are more susceptible. I know from my vets, that once a dog has the need to be expressed, they will most likely always require the service. As far as I know, it’s the same as with some humans being more inclined to hemmoroids over another…it seems once an issue like that begins, it tends to be a continuing issue.
As for the food question, our dogs are fed a grain-free diet. We do allow for bits of treats/foods that have grains, but those are few and far between.