If you’ve got the money, the absolute best you can buy is the Nikon D3. I’ve been using the D2X, but will soon be getting a D3. The motor, and downloading capabilities into the camera’s buffer, are what counts, and these two cameras do it well. A fast, large capacity flash memory card helps too. Depending on the kind of wildlife you do will determine which would be the best lenses for you to use. If you’re doing macro, then Nikon has a good line of macro lenses to choose from. If you’re shooting animals you can’t get close to then look into their long telephoto lenses and a very good tripod. If you’re doing set-up shots, then a moderate zoom, like the 18-70mm will work fine, along with at least 4 good Nikon strobes.
Just make sure to shoot everything in RAW for maximum quality.