Salty and Thunder, my two eldest dogs, are on a protein restricted diet. The protein content of the food they are allowed to eat cannot be over 18 percent. It is near impossible to find a senior food out there that meets this requirement. I have found 3, Wellness which they hate, Blue Buffalo which they hate more and Bil-Jac which they seem to love. They have been eating it now for a couple of months and seem to still like it and it doesn't seem to be affecting them adversely in anyway. Problem of course is that now both Max and Scout who do not need to eat a senior protein restricted diet seem to prefer Salty and Thunders food over their own and have refused to eat the Fromm's adult gold they had been eating perfectly well for the last year or so.
So last time I went to buy the Bil-Jac senior I picked up an adult bag for Max and Scout. They love the food, have stopped raiding Salty and Thunders dishes and had no problems with the quick transition to a new food. My concern is that I have always heard bad things about the food and to be quite honest I don't think Scout is doing as well on this food as she was on the Fromms. Her coat is no longer soft and fluffy and she is shedding like a SOB.
I personally don't like Bil-Jac. They use by-products, corn, and BHA/BHT. I would keep looking for a different food. My dogs are on the Fromm Gold as well and do WONDERFUL on it. Maybe re-visit the Wellness idea. They will eat it if they get hungry enough =)
Another option may be a low protein, home prepared diet.