I like the choice of black and white for this. Though the sharp focus on the grasses tend to draw my eye away from the lioness' face a bit, I really like the shot.
There is no point whatsoever to make this picture B&W. It actually seems like it would have been much better in colours. It looses the depth and the clarity.
If you had to make it B&W you should have at least take the contrast up. Without it it's too blend.