Well Adam... so you had better luck than me with the cats. I also shot at 150 mm, F/2.8 and ISO1600 at that.
Now that you mentioned a snow leopard. I took a shot of one on the same visit to the zoo.
Nikon D90, D80
Nikkor 16-85mm AF-S DX F/3.5-5.6G ED VR, Tamron SP AF 28-75mm F/2.8 XR Di LD Aspherical (IF) macro, Nikkor 50mm F/1.4D, Nikkor 50mm F/1.8D, Nikkor AF-S VR 70-300mm F/4.5-5.6G IF-ED, Sigma 105mm F/2.8 EX DG Macro ||| 2x SB800 | SB600 ||| Manfrotto 190XB