I honestly have no idea how horn brush handles are fabricated, but do know that horn is hollow. That being the case, something has to be done to soften, compress and re-harden the horn. Believe that horn can be softened by steaming it but how that is all accomplished, I cannot say. However, if you buy those buffalo horns, I don't think you are going to receive something that you can make a brush handle with. Drinking mug, maybe. Good luck.
The horn you show may have enough at tips for a brush blank but may not.
You can get horn blanks at Masecraft. I was there yesterday morning and they have plenty of large blanks more than adequate for brush handles.
I hadn't thought of it then. I was thinking that mammoth or whatever tusk might be good but this stuff would likely be a lot cheaper. If you can do it, I'd be interested in a quote with Best Badger, but as I'm unemployed, I figure it's unlikely I can do it just now. It's more for future reference.
Thirdeye, how does horn get transformed into something for a brush handle? Or is there enough solid on the pointy end to be used in most cases? Would love to know!