I'm a veterinary technician so I'm pretty sure I can help you with that. Lol! The difference between dog food bought in supermarket, petshops and vet. clinics are the ingredients they put in them. Basically the food you're going to buy in supermarket or walmarts are the ''junkfood'' of the animal world. It's cheap because the proteins and meat used are scraps left from the animal (chicken, beef...).
Food that's sold in vet clinics are exclusive to them, you can't find them anywhere else. The reason that it's a little more expensive is that the companies have research centers and a lot of research went behind the food. The also use the best part of the animals to get the proteins from. Don't get fooled if you buy Purina Veterinary Diets just because it says by-products on the bag. The by-products used in this food is actually the best parts of the animals like the liver, bone marrow, intestines.
Petshops sell some good food too. It's not as high quality as vet food but it's still good.
My advice is go for a little more quality food, at least you gonna be sure your puppy gets something good. Also the food sold at vets might be a little more expensive but most of the time the quantities that you need to give to your dog are a little lower to meet the same vitamins/proteins/calories that he needs. If it's a small breed dog, the price difference is low. Most of the time the prices are vets are competitive so go check it out. :)
Hope I helped a little!
Well, IMHO, thats not true at all. You can buy hills in vet, and its actually a poor quality of food for cats, especially the urinary ones. They are so full of grains/fillers and cats dont eat vegies.
You can most certainly buy quality, even the best in your store or online for convenience. For dogs there are so many types, and it depends on the age of the animal what/which you choose. Also the size of the dog.
Some large dogs grow so quickly, you need to get foods with extra calcium, or add it at each feeding.
Read the ingredients, just like you would when choosing your own foods
. Dogs love grains and vegies, they just need to be in the correct percentage. You can make your own dog/cat foods too, which is a lot of fun, for a while.
I did that for years. I had a dobie, a grey, and a chihuahua. I made it once a week, purchased the vit powder online. Its when i was a true vegan, and I turned all dogs/cats to vegans with me. Lol. The cats loved their food, although its very difficult to find non-meat sources for their vits.
Good-luck on your new pup!