I mainly use a Nikon 200 f/2 VR II or a Zeiss 100 f2 Makro Planar. Camera is a Nikon D800E or Nikon D3. Wouldn't mind a Nikon 400 f/2.8 but they're about $14,000 and I wouldn't get enough use out of it nowadays.
Good luck with your new lens; 400mm is a great focal length for most wildlife.