The Staffy diet plan will need to include animal proteins and healthy carbs, vitamins and minerals, and omega fatty acids--nutrients every dog needs to maintain its health in the long term. This means the best dog food for Staffies is premium dry kibble, as it contains balanced portions of the above-listed ingredients.
Staffordshire Bull Terrier food portions: adults will need about 2½ cups of dry food per day, divided into two meals. (And since the breed is prone to bloat--an often-fatal condition that occurs when a dog's stomach fills with air when it "wolfs" its food--allow one hour between exercise and feeding, and vice versa.) Staffy puppies need a bit less: depending on age, about 1¾ cups per day, divided into three meals (not two) until the age of six months.
For more info, here's a Staffy puppy feeding guide:
Dog AgeDog WeightFood TypeAmountFrequency2 Months10 lbsDry (Puppy formula)0.25 cups3x/day3 Months15 lbsDry0.4 cups3x/day6 Months25 lbsDry0.6 cups3x/day9 Months30 lbsDry* (Puppy/Adult)1 cup2x/day12 Months+35 lbsDry (Adult formula)1.25 cups2x/day*--Around this time, transition to adult food by mixing in adult formula with the puppy formula, in slowly increasing amounts with each meal, for one week.
Try if possible to stick to the above-listed portions. If constantly overfed (and under-exercised), these dogs will easily become overweight--and a fat Staffy dog will have numerous health problems and a potentially shortened lifespan. You can help control your Staffy's weight by having consistent feeding and exercise schedules, by not feeding the dog table scraps, and by not leaving food in the dog's bowl all the time.
If you're worried your Staffy is overweight, try this simple test: run a hand along the dog's side, and if you can't feel any ribs, it's diet time--which means less food and more exercise!