For large breed dogs, if you want to add some freshly chopped vegetables to his food, add it into wet foods where it can be mixed in. That in turn can be added to some kibble if you use it. Chop something like celery leaves, or a bit of lettuce, or carrots, a few slightly smashed blueberries, but don’t add more to his food than one
TBS. It’s enough. Smaller breeds mix 1 TSP. Not all vegetables are good for dogs, so be sure it is acceptable for them.