This site was really detailed and helpful for calculating phosphorus levels, which contributes to kidney problems, while also asserting that high protein is GOOD for a senior dog, as many on this site have also said: http://raingoddess.com/dogfood/phos.html
Unfortunately, the brands listed with low phosphorous also have low protein and are considered by many to be sub-standard foods. I hope one of the experts on this site can give a good rundown on how to feed your senior dog well but also keep their special needs in mind.
