Pooches, like people, display some outward signs of aging. Graying can be one of those signs, but it's not always one of the first. The appearance of gray hairs varies from breed to breed, and some dogs are more prone to premature graying.
Graying With Age
In general, dogs enter their senior years between the ages of 7 and 10 years of age, according to the ASPCA. Typically, you are likely to see the first signs of graying around the muzzle, particularly in breeds with dark coats or back muzzles. The dog's coat is likely to be less luxuriant than in his youth as he ages. Some breeds with a black mask, such as the Great Dane, may gray prematurely at around 5 years of age.
Doggy genetics affect your pup's tendency to graying. Breeds with a Gg or GG genotype are more likely to have coats that lighten with age. Primarily these are long-haired breeds like the bearded collie, poodles and a variety of terrier breeds.