> You can buy brewer's yeast at any one of the food co-ops or (at a higher
> price) from Bread and Circus.
 
Animal feed grade can be had in 50 pound bags through feed mills that make
cattle and hog feed.  Price is about 50c US/lb or so for the good stuff.
some has a lot of meal and growth medium in it and is not fit for bees.
Read the analysis and compare.
 
I think a BEE-L search may find my comments on yeast nutrient content
analysis some time back, but if not, email me and I'll get the docs out
and post what the good stuff should have in it.
 
Allen