Just be careful with the "odorless" ones as sometimes they are dipped in bleach or irradiated to cut the odor and obviously that's NOT good.
I get mine from bestbullysticks.com. They are from free range cattle and the company is very reputable. Here's the warning on the odorless ones....
Differences Between Bully Sticks | Healthy Dog Blog
(I would assume that Westbrook doesn't get her bullysticks from a supplier that uses bleach or irradiation. This post in no way implies otherwise! I have bought bullysticks from her myself and they were great. I am just warning people to really investigate where they get them and only buy from a reputable company.)