Mastiffs aren't large breed puppies they are giant breed puppies and while they do continue to grow the first two years and often through 3 years of age they do not need a puppy food. They need a quality adult or all life stages food. You can add fruits and veggies to his kibble and while they usually don't digest them completely (don't be surprised if you see pieces in his stool) they don't hurt and many dogs like them. You might be confusing raw veggies with raw meat. You shouldn't mix raw meat and kibble in the same meal because they digest at different rates. Almost 8 cups of food at 15 weeks is a lot of food. How is his stool? Can you still feel his ribs? Has he been dewormed recently? And also the food needs to be within the appropriate levels of protein, calcium and phosphorus so that he doesn't grow too fast. I also have a 15 week old EM and granted she was the runt and a slow grower she's now 35 lbs and the bag says to feed her 1.75 cups and I feed her a little more usually since she is so active. In general the better a food is, the less food you have to feed. Good luck with your pup!Hi! I have a 15 week old English Mastiff, Blue, and the last time we visited the vet was 4 weeks ago and he weighed 32 lbs. The vet told me to go ahead and switch him to adult large breed food (we feed him Diamond), is this right?! I'm a little concerned because of what I've been reading about feeding them puppy food until they're 2 years! I worry he's not getting all the nutrients he needs by eating adult food. Should I switch him back to puppy food? Also, he eats 2 1/2 cups 3 times a day which I think is a lot, but he looks an appropriate weight. Is that okay? One more thing, I'm a little confused about how to "substitute" any kind of raw food in with his diet.. Is it okay to give him carrots, broccoli and fruits (he LOVES apples) randomly even though he's on a kibble diet? Thanks a TON for any advice I can get! This is our first large breed puppy so this is all new to me!