Excerpts: To learn the potential production of livestock and livestock products in a given period necessitates the consideration of the available supplies of feed grains and feed concentrates and the supplies that would be required for a specified level of production. To relate feed supplies to livestock production it is necessary to combine all the different species and kinds of livestock and poultry and express the result in units that requires about the same quantity of feed concentrates from year to year. Two devices have been developed in the Department of Agriculture in order to calculate the quantity of grain and concentrates needed in a year for all the livestock in the country, or to find out how much livestock a given quantity of feed will support. Each of these devices has certain advantages and disadvantages.