A static model of developed water use for U.S. cattle production was constructed on a spreadsheet. Water use included that consumed directly by various classes of animals, water applied for irrigation of crops that are consumed by the cattle, water applied to irrigated pasture, and water used to process animals at marketing. Government statistics were consulted for numbers of cattle and crop production. The most recent statistics available for numbers of cattle and crops in individual states were used. On January 1, 1992, a total of 33.8 million beef cows and 5.7 million replacement heifers were in U.S. breeding herds, 12 million animals were on feed, and approximately 28 million animals were fed annually. Thus, the U.S. beef cattle herd produced 6.9 billion kg of boneless beef. Beef cattle directly consumed 760 billion L of water per year. Feedlot cattle were fed various grain and roughage sources corresponding to the regions in which they were fed. Feeds produced in a state were preferentially used by cattle in that state with that state's efficiency; any additional feedstuffs required used water at the national efficiency. Irrigation of crop feedstuffs for beef cattle required 12,991 billion L of water. Irrigated pasture for beef cattle production required an additional 11,243 billion L of water. Carcass processing required 79 billion L of water. The model estimates 3,682 L of developed water per kilogram of boneless meat for beef cattle production in the United States. The model was most sensitive to the dressing percentage and percentage of boneless yield in carcasses of feedlot cattle (62 and 66.7, respectively). A 10% change in either of these parameters resulted in a corresponding 8.6% change in the water required for beef production. A 10% increase in the number of animals on feed resulted in a decrease in the amount of water per kilogram of boneless beef by 5.2%. Changes in irrigated pasture management would also be an effective means of decreasing the water requirement. The water requirement of 3,682 L/kg of boneless beef is much lower than previously suggested.
