What age cows are you feeding and what condition are they in? If they are running age cows then hay should be fine, we keep on grass hay that averages 12% protein until they calve, as they calve we sort them off into a separate pasture and feed them alfalfa that averages 18% protein. Depending on what grazing is available makes up a difference in how many pounds we feed if it's open and not to cold we start out around 22 pounds if it's snow covered and cold maybe as much as 28 pounds. After they calve we feed between 30 to 35 pounds of alfalfa. You can get by with grass and put protein tubs out for supplement if your hay does not have the protein content.
First calf heifers might get a little different ration as they are still growing and also growing the calf, like wise older cows may need different feeds for them to maintain their condition and raise a high quality calf. I am sure there is a nutritionist in your area that can analyze your feeds that are available to you and give you some good recommendations.