According to the sixth edition of the Nutrient Requirements of Beef Cattle, the amount of protein required in the diet for pregnant beef cows in their last trimester of pregnancy varies based on the cow size and weight. Large-framed cows require more protein each day than a smaller, more moderate-framed cow. For instance, a 1,400-pound cow will require 25 pounds of dry matter each day and 1.9 pounds of actual protein each day. Compare this to a 1,000-pound cow that requires 20 pounds of dry matter each day and 1.6 pounds of protein each day. To determine the pounds of protein you are feeding your cows, a nutrient analysis of the forage you are feeding is required. Once you know the percent protein in the forage, you can determine the actual pounds of protein that the cows are receiving. If you are feeding 25 pounds of grass hay each day and the protein content is 8 percent, simply multiply 25 times 0.08 to determine the pounds of protein received: 25 x 0.08 = 2 pounds of protein. If the protein level is below the required level, a protein supplement will have to be added to the ration.