The proteins fats ,etc. must be digestable...it depends on how much disgestable proteins the dog is getting. Meat, eggs, dairy are digestable proteins....
The Nutro is mostly grains and the proteins are coming from the grains. A food could be mostly made up of feathers, beaks and by-products and contain fractions of grains and still be 27% protein...this means nothing.
The ingredients are the most important thing to look at...because they come by weight. Usually the first 5-6 ingredients tell you what the food is like.
Dogs need to be eating meat...no grains. It's common sense to me that a dog needs meat and will thrive on meat and not grains. Cows do well on grains.
The OP said his dog is very gassy...so the pup is not doing all that well on the food.
Gina