Or a chicken every couple of days, maybe.
My girl is around 80lbs and my boy is 85 to 90 lbs (had to put him in a diet after he hit 110lbs a few years ago). And the East less than a 1.5 lbs of raw meaty bones and offal per day on average.
They are akita's though and are known for their small to moderate appetites. I think a mastiff is a different kettle of fish. I'd still recommend feeding them raw (puppy primal if you will) though.