yeast is cheap. you should be able to go to your local mill and get some. I would start with 5 or 10 pounds that will last you awhile. sometimes it is already in your feed if you buy premix. when we add to feed we use a handful at each feeding.
they say it is like probios(if thats how you spell it?)It just gets every thing working better,But that's all I know about it so if anyone could educate us...
Yeast will help w/ the rumen bugs. My thoughts is that it's probably already in your bagged feed. I personally wouldn't add anymore to a feeding program.