It comes down to are you happy with the ingredients and is your dog happy. When it comes to cost with dogs of this size it shouldn't be an option because a 5lb bag at $24 lasts two months, my wine for one bottle is around the same....
If you are pleased with the reaction and the stool is good and the dogs health is good then that should be enough.
I do suggest staying away from corn wheat soy and anything with a lot of meal like ingredients. |