It is quite common for dogs to gray out around the muzzle and the eyes as they approach old age. Most dogs of any breed do this, and there does not appear to be a specific gene associated with geriatric graying. In a few bloodlines of the Australian shepherd the dogs start losing pigment on the muzzle very early. The pictures below are of Fairoaks Obsidian Jaguar (Jag). As a puppy and a yearling she was a self black with a completely black muzzle. As she entered her second year she started devleoping a distinct "milk mustache". At age 31/2 her muzzle is quite white and the underjaw is also whitening on the mandibles. Her progress will be followed as she depigments over time. Her father Fairoaks Atreyu also had this trait.
This is Jag at 5 months old. She is uniformly raven black like a Labrador, and she has no white muzzle hairs anywhere. Her probable genotype is (A a^t Bb mm S s^i). She has also inherited another color trait but it does not show up just yet.
Here is Jag at age 1 1/2. At this point she has only a few widely dispersed individual white muzzle hairs. Up to age 1 she had none at all. At this point she still looks solid black to the viewer several feet away.
This is Jag at age 3. Her upper muzzle is entirely white and her lower muzzle is also. The skin which stretches across the halves of her mandible are more than 50% white.
She has a lot of individual stray white hairs all over her head, ears, and even a few on the body. She was correctly registered as black, but now she resembles a black bi. In her bloodline both merles and nonmerles can share this trait. The exact mode of inheritance is unknown, but dogs that have this early frosting trait tend to produce it. A deliberate outcross to another bloodline in which it does not occur would help clarify its dominant or recessive status.
© 2004 Lisa McDonald Feedback