NORTH GRAFTON, MASS. — Dog owners often assume that pet food for senior dogs is tailored to the nutritional needs of the older pet, possibly offering reduced calories or age-specific nutrients. But results of a new study indicate the nutritional value of food targeted to older dogs can vary widely from brand to brand.

The study, published recently in The International Journal for Applied Research in Veterinary Medicine, was conducted by veterinary nutritionists at the Cummings School of Veterinary Medicine at Tufts University. Tufts researchers surveyed more than 1,300 people online about their dog-food perceptions. Responses were associated with the actual nutritional content of about 40 commercial senior dog foods. The study was led by Dana Hutchinson, DVM, and Lisa Freeman, DVM, PhD.

In one key finding, the majority of respondents (84.5 percent) felt that senior dogs have different nutritional needs from adult dogs.

Another notable finding was that most survey respondents believed that senior dog foods probably consisted of fewer calories. However, calories in the senior foods studied were highly variable, ranging from 246 to 408 calories/cup. Most polled also said that senior dog foods likely contained less fat, protein and sodium. Among the senior dog diets surveyed, these nutrients were not consistent across the board.

Additionally, respondents were not clear whether, when compared to adult dog foods, senior foods would contain more or less phosphorous, limits of which would help dogs with kidney disease. The actual diets had a three-fold difference in phosphorous content.

According to researchers, the study illuminates the importance for owners to be aware that each senior diet is different and may or may not be suited for an individual dog, depending upon his or her body condition and health.