This is Jax. Jax is a service dog in training with Paws and Stripes. (He got into a little bit of birthday cake.) If you're interested in learning more about Paws and Stripes or helping to support them, go to www.pawsandstripes.org or https://www.facebook.com/pawsandstripes501c.
FYI, it's not a muzzle, it's a "Halti" or "Gentle Leader". It keeps them from pulling against their neck.