Just because a dog is “senior” doesn’t mean it has these problems. All those problems can potentially happen at any age. I’ve fostered many dogs under 5 (even as young as 1 yr) with joint/eye/digestion/ear issues and have needed hip/knee surgeries and prescription eye and ear drops. A healthy senior can eat regular food (adult, maintenance and all life stages, puppy food). I have a 14 yr old with no active health issues. He is blind and deaf which he was already when I got him last year at 13. He is not on any medications and eats the same foods as all the other foster dogs I have. I use 3.5-4.5 star kibble and top it off with 5 star canned foods which is normally at least 43% protein. He even gets some raw food which I usually make without any plant matter. The dogs get joint supplements and vitamins, antioxidants, supergreen supplements and fish oil. My personal dogs don’t get chemical pesticides which has been linked to some cancers nor do they get unnecessary vaccines. You might want to research “over vaccination”. Try looking up Dogs4dogs dot com, b-naturals dot com, wholedogjournal dot com, dogsnaturallymagazine dot com. These are just a few of the sites pertaining to more “natural” care of dogs. If one of my dogs had late stage kidney disease, at that point I would change the diet, but I wouldn’t change the diet just because they’re a senior in general. Some things possibly connected to cancer is chemical laden commercial kibble, vaccines, the constant application of poisonous pesticides (heartworm and flea/tick meds, fertilizers), even air pollution.
http://dogs4dogs.com/
