I have the same issue with one of my pups. From day one, he's been a food inhaler. He's now 9 months. I put a tablespoon of plain, fat-free yogurt in with his kibble (just enough to lightly coat the food) and that slows him down. The yogurt makes the kibble stick to the bottom and sides of the bowl so he has to work a little harder at getting the food out of the bowl and into his vacuum cleaner of a mouth
I should note that he doesn't chew his food, either. Before I began adding yogurt to his meals, he'd eat so fast that the food would come back up within five minutes of him eating and it would look exactly like it did in the bowl (only wet). Not a single morsel had been chewed. From a health perspective, I don't think inhaling food is something to be too concerned about (they're still getting the nutritional benefits of the food), but it may cause problems down the road in terms of dental health since chewing helps remove plaque and tartar from the teeth. I brush my guys' teeth and provide them with plenty of bones to chew on which, in Sarge's case (he's my food inhaler), is really important since he does have a tendency to inhale.
Hope this helps. Good luck with your pup
