Hi Lauren-
You will want to email Protein for Pets and request a nutrient analysis of the formula in question. Then you will want to use the numbers given for the calcium and phosphorus into this tool: /best-dog-foods/best-large-breed-puppy-food/
If the ca/phos ratio falls between 1.1:1 and 1.5:1 and the ca/calorie ratio does not exceed 3g/1000kcals, the food is safe to feed your giant breed.
However, the only formulas I see on the link you gave are adult maintenance formulas, which is not recommended for large/giant breed puppies.
