In the doctor's office, obstetricians use ultrasound machines to check on the health of a fetus. On the farm, researchers are using the same device to determine which cattle will produce lean, tasty steaks.

Scientists from the Agricultural Research Service and Iowa State University have found that scanning live cattle with ultrasound can determine their fat and marbling qualities just as well as measurements taken on the carcass. The technology is used most often on Angus cattle, but ultrasound can be used on all breeds.

While researchers have been using ultrasound on farm animals since the 1950s, this was one of the first studies to use it to determine fat content in beef cattle and the first to show how accurate it could be as a predictor.

Ultrasound is a small, non-invasive handheld machine that emits sound waves. These sound waves are turned into images and are displayed on a small monitor so researchers can "see" inside the body. The machine is placed on the animal's back — where rib-eye steaks are located — to see just how lean and muscular the animal is, and to determine marbling, the little pieces of flavor-adding fat in steaks.

While the scanning of each animal may only take a few minutes, the technology will be used primarily by seedstock producers to find ideal cattle for breeding. The researchers at ARS' Roman L. Hruska U.S. Meat Animal Research Center in Clay Center, Neb., and at Iowa State University developed equations to see how accurate the ultrasound is in determining quality beef. They found that ultrasound was just as good at predicting the amount of fat and marbling as traditional methods of studying the carcass.

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