The corn mash by product left over from the ethanol process is an excellent cattle feed. It is a good protein source, as they only take energy out for the production of ethanol. I fed some last spring to my cows that had calved, as it had been a cold hard winter and I wanted to flush the cows before we started breeding. I have never seen a set of cows gain so much weight in such short order.... and their milk production greatly increased to a point where I wondered if I was going to have scour problems in the calves. There are oftentimes feedlots close to ethanol plants so that they can use the by products. A 10,000 head feedlot located about 30 miles from the ethanol plant in my home town uses as much of the byproduct as they can in their rations. Another 50,000 head lot here has it's own ethanol plant and these two ventures compliment each other very well.
For many years we fed the stillage produced from a local distillery. It was usually 70-80 % corn and the balance was rye or wheat. We fed it year round and we could run 100 cows on a pasture that normally had a carrying capacity of 25-30 head. This pasture has about 1 mile of creek wandering through it, and in the 4 years we fed stillage, I never saw a cow drink at the creek. The cows would walk a mile to drink the stillage rather than drink at the creek along the way. It was great for AI breeding, as I fed it in the morning and evening, and I could simply cut out the cows in heat when they came to the stillage trough and AI them 12 hours later. We used to AI close to 200 cows and heifers in those days, and the conception rates were great. Another bonus for feeding this product is that you can get 2-4 extra calves from some of your best older cows. They stay in great shape, and can survive very well drinking stillage rather than having to only roughage for grass for their nutrition.
I would suggest that you pay attention to the cost of this product. I find that they sometimes price it too high but if they are having a hard time moving all of the byproduct, you can sometimes strike a good deal with them for longer term use.