How many veterinarians are there in the world?

There are probably a couple dozen different ways you can divide veterinary medicine up. The most common is to differentiate private practice (small animal, large animal, mixed, equine) from industry, research, academia, military, government and other. However, private practice can be divided further into small animal exclusive, small animal predominant, mixed, large animal predominant, large animal exclusive, equine, avian, exotic and the various board-certified specialties. The same is true for non-practice veterinary careers - you can continue to subdivide until you get a fairly homogenous group, but the number of individuals in the group will be pretty small.