If you don't already subscribe to "Your Dog" published by Cummings School of Veterinary Medicine at Tufts University, I highly recommend you sign up. It is chock full of wonderful information on pertinent and current research regarding dogs' health, behavior, and every other important aspect of their lives.
In this month's issue there is a great article titled" How to Choose a Food for Your Senior Dog".
As the caretakers for our furry kids, we all want to do what's best for them and as they age, it makes sense that perhaps their dietary needs have changed. So we go into the pet food section of the store and start looking for foods that state they are created especially for canines 8+ or 10+ or Aging Dogs, etc. They usually say they are formulated with the aging dog in mind to keep them young and healthy.
Well, what this article says is that the packaging information is all marketing hype. There has not been enough research done as yet to determine what the essential nutrients are for a dog when he reaches a certain age.
The AAFCO, which is the governing body that sets canine nutrient profiles, has no guidelines yet for senior pets. There is a profile established for puppies and one for pregnant or lactating females, but none for senior canines. With that in mind, what you want to look for on a dog food label is the Statement of Nutritional Adequacy which states that either it has been formulated to AAFCO standards or it has gone through a feeding trial. The latter is much better, but due to the expense of feeding trials, most dog food companies do not go that route.
The bottom line, stay away from the marketing hype! Find or stay with a food that the Statement of Nutritional Adequacy states is appropriate for "maintenance" or "good for all life stages". If it has gone through feeding trials, so much the better, and make sure the manufacturer is reputable.