Depends on what you mean with "usable". The whole horn is hollow with porous bone inside. The actual "horn" is not more than about 5mm thick and a bit prone to cracking in concentric circles. It's difficult to get straight sections out of it but can be straightened to some extent by first boiling and then clamping till it's dry. Unfortunately you will also find that it will try and straighten itself again in due time.
Have a pair of kudu horns in the garage that was a present from friends in the Karoo. It is difficult to get usable pieces from, but really worth it. I love the colour. And the best I could get was only 3mm thick.
