If he had two knives Shephard would throw one, but what he's got is a sword and a sharp bit of stone and neither of them is balanced for throwing. The shield would be better for throwing, frankly.

On the other hand, a pig that's trying to gore is a pig that's quartering away from him. That means that a man who's lived most of his life by having a fast hand and eye can dart up to her and thrust the bronze blade between two of the ribs. It won't reach the lungs, not if he wants it back before she turns- but a wound's a wound, especially that close to the spine.