in some brands you will have to contact the company.
The problem is also in "where do the calories come from" as well as 'where does the protein come from" Also "where does the calcium come from"
Many brands get the protein/calories/calcium from different vegetables. This is practically useless to dogs. For example, in a cheap dog food the main source of calories and protein is actually corn - dogs can't digest it. That is why you feed so much of it - the dogs need a huge amount to get the same calories as a meat source. Even with meat, some dogs don't do well on certain proteins. Some times it isn't the proteins but the prep process. In some cases, a certain brand may be too rich. So a food with a lower % of calcium might put more calcium in a dog's body because of the source.
For example, Taste of the Wild is a great food. Highly recommended and highly rated. One of my dogs did great on it. The other, chronic diarrhea. Same with Blue Buffalo. Even though he didn't have the runs, he just didn't do as well on it as you would expect.
The main problem with vets is that they don't get any training in nutrition. What they do get is largely sponsored (and taught!) by Purina and Hills Science Diet. Both are actually some of the lowest ranked foods in the world. On paper, they have good calories, good % of protein, etc. But most of it is in a form that dogs can't digest or absorb.
