Hi Gary, I have fed our dogs raw food for over 13 years now ( which is 80-90% meat and bone with added veg). This is a prepared dog food not DIY but doesn’t contain any grains and all our dogs do just fine on this. Dogs by heritage are not grain eaters and, although they have been domesticated for thousands of years, their teeth, jaws and digestive system have remained those of an animal that mainly eats meat. Many dogs may tolerate a diet with grains but some suffer digestive and other issues as a result of not being able to fully digest this type of food. Cereals have been traditionally added to commercial dog food as they are cheaper than meat and can bulk out the food in order to make more profit from its sale. Dog food sold as ‘grain free’ are not necessarily higher quality as some simply exchange the cereals for legumes such as chick peas or lentils which are vegetable proteins which again is not ideal dog food but may be better tolerated by some dogs than cereals are. The main ingredient of dog food (unless a dog has some unusual allergy or health issue) should be meat with meat or fish as the primary protein source. If grains or legumes are added they should be in really small amounts and not, as in many commercial dog foods, one of the main ingredients.
If your vet stocks only a single brand of dog food, the reason will be that the company producing this brand give them a financial bonus for doing so. The main commercial dog food brands are multi-billion dollar companies who sponsor vet colleges, dog shows, vet surgeries and other pet related businesses in order to boost their sales. Some of these companies nowadays have no background in animal welfare or nutrition at all being multi-national businesses of a wide range of products such as confectionery, cleaning products etc. Colgate-Palmolive who own Hills pet food, Nestle who own Proplan and Purina, and Mars who own Royal Canin (among other brands too) are three of the biggest. Very few vet colleges train their students in nutrition and it is common for nutrition to be a tiny part of their training and linked with the promotion of whichever company sponsors the college so, unless a vet does their own independent research on the subject they are not necessarily best placed to advise on the subject.
If you check out the information on dog food sites such as All About Dog Food you will see not only ratings of individual foods but they have a glossary to explain the meaning and nutritional value of ingredients listed.
If you feel that your puppy is thriving on the food you are giving, check the ingredients and, if you are happy with the nutritional value then there is no need necessarily to change but many dog owners, as you may have seen on the Forum have discovered that their dogs do much better overall health wise on a food free of cereals and, in the case of our dogs, as with some others here, best of all on a raw diet