Animals tend to be interesting in zombie stories. They are completely ignored by zombies in the Romero classics like Dawn of the Dead. (Remember the dog in the basket?) They are open to be eaten like the horse and the cow in the Walking Dead. And they can even become zombies themselves or at least carriers like the monkeys in 28 Days Later and the dogs in Resident Evil.
There are some who would argue that animals cannot become zombies, and others who would. Frankly that depends on the story teller, but it also depends on the cause of the zombieism. Ask yourself this question: What caused the zombieism in the dog? Was it radiation? Then it’s a radiation zombie. Was it a plague or chemical? Then it’s a chemical zombie. This is why I don’t count animals in their own category of zombie. Zombies are classified according to what caused the reanimation. And regardless of what brought this pooch back, it’s here and it’s dangerous and you have to put it down as quickly as possible.
Dog zombies have appeared in movies from Night of the Creeps, (parasitic zombies) to video games like Biohazard / Resident Evil. The thing with these creatures is that they were generally already scary and dangerous before they turned. Take away the infection and the dogs in Resident Evil are just scary dobermans. That’s it. You can make the whole argument that they are man’s best friend and beloved pet yadda yadda yadda, but when it gets right down to it they are animals and they react on more of an instinctive level than humans already.
The one thing to be certain of is that they are likely to be faster than humans if they are in good condition, once they take damage they are just as likely to keep coming after you until you destroy the brain. One of the dangers in the zombie age is that there are certain to be packs of wild animals out there that are roaming around wild. They might be carriers or they might just not be infected. Either way they could pose just as much of a threat without even being zombies.