What is the best food to feed my English Mastiff puppy?

I have been doing a lot of research on what to feed my english mastiff puppy. I am hoping for suggestions from others with mastiffs or giant breeds. I want to feed him a really good quality food at a somewhat reasonable price. Also, I have heard that they only need puppy food until they are 4 months, is this true? I would really appreciate some advice on this issue! Thanks!