Estimating Farm Animals' Feed Efficiency

Agricultural Research Service scientists have discovered new formulas to determine the amount of feed required to maintain life--called basal metabolism--in farm animals. In recently published articles in the Journal of Animal Science, the researchers argue that in ewes, factors other than weight, such as age, breed and nutritional history, need to be taken into consideration when predicting basal metabolism. The discovery should lead to more efficient use of feed and may save producers money.

Livestock use the feed they receive to support their basal metabolism, to maintain their current weight and to grow. Changes in any of these can change how efficiently feed is used for production. Metabolic rates decrease as animals grow older.

Efficiency of feed use is important because feed accounts for about 60 percent of the total production cost of cattle and sheep. ARS animal scientist Harvey C. Freetly, along with agricultural engineers John A. Nienaber and Tami M. Brown-Brandl, are conducting studies to help farmers develop low-cost feeding strategies, focusing on how much feed is actually needed and how feed is used by animals.

Their research, conducted at ARS’ Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb., shows that the breed of an animal affects how fast its metabolism decreases as it ages. Since it is not practical to create separate feed requirements for each breed of sheep, these scientists have proposed that breed differences in basal metabolism can be accounted for by describing the maturity of the animal rather than its age. Studies are being extended to determine if similar relationships occur in cattle.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.