A recent survey found that contrary to most Americans' beliefs, "senior" formula dog foods vary widely in ingredients and have no requirements for what must be included in these formulas for older dogs.

About 1,300 people made up of 92% of dog owners responded to Tufts University's Web-based survey. The majority of respondents, 84.5%, believed that senior dogs need to eat differently than younger dogs. However only 43% of the respondents said they used a senior diet for their older pets and only one-third actually consulted their vet about the diet.

Although professional organizations do mandate requirements for puppy and adult dog food, the Association of American Feed Control Officials and the National Research Council have no such requirements for food marketed for "senior" canines beyond what is required for regular adult dog food, according to Dr. Lisa M. Freeman, co-author of a paper appearing in the latest issue of The International Journal for Applied Research in Veterinary Medicineand professor at the Cummings School of Veterinary Medicine at Tufts University.

Manufacturers "might be increasing protein, decreasing protein or keeping it the same," Freeman said. "That emphasizes to us to look at the individual animal, and not all aging animals need a different diet. It's much, much more important to look at individual dogs."

Respondents tended to assume that senior dog foods were lower in calories, yet this actually varied from 246 to 408 calories a cup. Not all dogs gain weight as they age, some gain weight and some stay the same, Freeman said. Survey respondents also tended to assume that senior diets had less fat, protein and sodium. But, this was also not necessarily the case, with much variation among individual petfood brands, Freeman found.

"The study highlights the diversity among dogs and, consequently, dog food products. Each dog is unique and has distinct needs," said Kurt Gallagher, a spokesman for the Pet Food Institute."Attaining senior status depends on several factors, including the breed and weight of the dog. The differing nutritional needs of dogs are exemplified by the variance in the amount of protein senior dogs should consume."