We eliminated all soy from our animals diet a few years ago due to the fact that they are a GMO crop. Also, I don't think soy is by any means a natural food for any animal. The fact that you have to roast them before feeding tells me it isn't something that animals should be consuming. I have been using yellow peas (which are widely grown in Canada) as a replacement. They are a bit lower in protein, but digestibility is easier, and they don't need roasted prior to feeding.
I will be feeding it to a dairy cow as the title references.