Question: vegan potting soil?

Hi. I grow wheat grass for my rabbits and rats (it is a wonderful, heathy treat for them), but I cannot find animal-free potting soil at any garden centers here in Colorado. Am I just not looking in the right place? Is there a widely / generally available animal-free potting soil? The last mix I had contained poultry manure. Yuk! Any help would be appreciated.
(By: Dorothy)