Hormones: here's the beef: environmental concerns reemerge over steroids given to livestock - animal excretions release synthetic hormones into environment - Statistical Data Included

Science News, Jan 5, 2002 by Janet Raloff

For now, he cautions, plenty of unanswered questions remain about whether and how much livestock wastes contribute to pharmaceutical pollution in U.S. waters (SN: 4/1/00, p. 213).

Indeed, notes Rigshospitalet endocrinologist Niels Skakkabaek, an organizer of the Copenhagen meeting, when it comes to the environmental fate of livestock steroids, "the most frightening thing is that we still know so little."

The Financial Lure of Hormones

Each year, U.S. farmers send 30 million head of cattle to feedlots. This is where animals get beefed up on high-protein chow. To enhance the animals' production of muscle--that is, meat--livestock producers treat 80 percent of all feedlot cattle with steroid hormones.

Some cows get steroids in their feed. Others receive one or more hormones via a controlled-release implant in their ears. Economically, these hormones offer a bonanza.

It costs farmers about $1 to $3 per head to treat their livestock with either procedure, notes animal scientist Michael J. Fields of the University of Florida in Gainesville. Treatment increases animals' growth by 20 percent, so each cow in a feedlot typically gains 3 pounds per day, he says. Moreover, for each pound that it gains, it consumes 15 percent less feed than an untreated animal does.

"This feed efficiency works out to a cost savings of about $40 per head--so you get more protein at a cheaper cost," Fields says.

The Center for Veterinary Medicine at the Food and Drug Administration has approved the use of these hormones because they tend to leave only small concentrations--ones believed to be harmless--in meat. However, the regulators haven't considered what effects the hormones might have after being excreted into the environment. --J.R.