Gored by antelope.
Simon Hawker, 30, was trying to remove a piece of wood caught up in the nyala's 2ft horns.
But the antelope took fright, butted the keeper and skewered a deep wound in his left thigh, which needed stitches.
Curator Peter Bircher of Marwell Zoo, Winchester, Hants, said: "The wound looked very nasty but the animal just walked away."
The nyala, from Africa, grows up to 4ft tall and weighs nearly 20 stone.
It is only the second time in 30 years that a Marwell keeper has been attacked.