You'd have to be careful about doing this in the US, because I understand that, unfortunately, a lot of cow dung is contaminated with Grazon and other herbicide

You'd have to be careful about doing this in the US, because I understand that, unfortunately, a lot of cow dung is contaminated with Grazon and other herbicides. People will get cow dung to fertilize their gardens, and accidentally sterilize them instead. Granted, given that it passes through the cow's digestive tract it'd probably pass through yours too, but I still wouldn't want to ingest large quantities of herbicide. This is all tragic and stupid, obviously. What could be a fertilizer is turned into a toxin.