Growth promotants help stimulate growth in cattle by increasing the efficiency in which nutrients in feed are converted to lean tissue. When administered to animals in very small doses, certain products supplement hormone production and improve growth rates by allowing the animal to produce more muscle and less fat.
Five of the six growth-promoting products used in the United States are manufactured in the form of implants, about the size of the lead from a regular pencil. They are administered under the skin of the animal's ear. The sixth promotant is mixed with feed and administered orally.
Approximately 90 percent of the fed cattle in the United States are implanted with growth promotants. In larger feedlots, the rate approaches 100 percent.
The estrogen level in a 3-ounce serving of beef from an implanted steer is about 1.9 nanograms (a nanogram equals one billionth of a gram); the level in the same size portion of beef from a non-implanted steer is 1.3 nanograms. By comparison, a non-pregnant woman produces 480,000 nanograms of estrogen daily.
The increased efficiency that implants offer saves U.S. families hundreds of dollars each year by lowering the cost of retail beef by 20 to 30 cents per pound. Without growth-promoting hormones, the supply of beef would be smaller and the average retail price of beef would increase by 10 to 15 percent. Growth promotants help reduce the total cost of beef production by $50 to $80 per animal.
