Many veterinarians know that dogs of different ages have different dietary requirements. A new study provides another piece of evidence that supports the idea of age-based diets in dogs.

A team of researchers from the University of Illinois has analyzed for the first time the gene expression profiles of colonic mucosa in dogs as a function of age and diet. The objective of the study was to compare the colonic mucosal gene expression in healthy young adult dogs with that of senior dogs that were fed two types of diet: animal-protein based and plant-protein based.

The study found that "the colonic mucosa of senior dogs had increased expression of genes associated with cell proliferation, inflammation, stress response, and cellular metabolism, whereas the expression of genes associated with apoptosis and defensive mechanisms were decreased in senior vs. young adult dogs. No consistent diet-induced alterations in gene expression existed in both age groups, with the effects of diet being more pronounced in senior dogs than in young adult dogs."

Essentially the older dogs had more genetic changes in their colons than the younger dogs. Not a revelation in and of itself, but it is a good "proof of concept," said Ernie Ward, DVM, chief-of-staff of Seaside Animal Care in Calabash, N.C.

Ward pointed out two important findings in the study.

The study says that even in healthy older dogs, "observations indicate that the aged colon appears to have an increased risk of inflammation and a decreased functionality of cellular defensive mechanisms."

"That is another call to action to vets," Ward said. "Lots of things in the GI tract are changing as the dog ages. This is saying there are changes at the genetic and cellular level. It just gives us more scientific evidence to the importance of life stage diets and nutrition."

The other significant finding was that the older dogs benefited most from a "restricted feeding method."

According to the study, "a restricted feeding method, to maintain body weight, was used for senior dogs in this experiment, which may have attenuated some of the effects of age on gene expression associated with colonic metabolism, as caloric restriction generally decreases overall metabolic rate."

So feeding an older dog enough calories to maintain a healthy weight may actually prevent some of the genetic problems.

"If you feed your dogs too much, they are more likely to create some of these gene expressions," Ward said. "This is one more bit of ammunition vets should have when making dietary recommendations to clients."

The study "Gene expression profiles of colonic mucosa in healthy young adult and senior dogs" was published in the online journal, PLoS One.

AAHA Nutritional Assessment Guidelines for Dogs and Cats