Is all bison grassfed?

A friend asked:

Off the top of your head, do you know if buffalo raising practices are similar to beef?  I ask because I'm unsure if buffalo can be raised with soy/corn feed instead of their natural grass diet.  I also ask because there seems to be no grass-fed label for buffalo.

Farmer's Market Spring

I've been really enjoying the farmer's market lately. Bizarrely enough, some people really want to know what the heck I eat. It's boring to me...but apparently exciting to you?