Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist — Cattle producers in many areas of Oklahoma have been fortunate this summer to receive timely rains. Many big round bales of hay have been stored for winter feeding. Meeting the supplemental protein needs for the cows and replacement heifers consuming that forage must be done properly and economically. Protein is a vital nutrient for the ruminant because protein is necessary for the multiplication of, and the feed digestion by the microbes in the rumen. The microbial population in the rumen of cows is largely responsible for digesting cellulose in standing or harvested forages.