Edward Orlando, assistant professor of biology at St. Mary's College of Maryland (SMCM), was the leading author in the study that included researchers from five U.S. institutions. The scientists examined minnows in three streams that flow into Nebraska's Elkhorn River. Their findings showed "significant alterations in the reproductive biology" of fish immediately downstream from a large Nebraska cattle feedlot.

The scientists said they do not know whether the damage was caused by natural hormones in cattle or by synthetic ones administered to the animals. Their report states that the findings "clearly demonstrate" that effluent from feedlots is hormonally active, whether it is natural or synthetic. About 30 million head of cattle are raised in U.S. feedlots each year, and nearly all are implanted with growth-promoting synthetic hormones.

Orlando said the scientists took their samples from a site directly connected to a retention pond at the base of a large feedlot. Several spots along the river contained hormones, indicating that "this [result] is not due to one farm in one location." Orlando added that laboratory tests from the study showed that the feed-lot effluent-receiving site contained a complex and potent mix of androgens (male sex hormones), and estrogens (female hormones).

According to the study, published in the online version of the scientific journal Environmental Health Perspectives, the male fish had one-third less testosterone and their testes were about half as big as those of unexposed fish upstream. The female fish had about 20 percent less estrogen and 45 percent more testosterone than females from the uncontaminated stream.

The scientists caution that further investigation of livestock farms is "urgently needed if we are t
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Contact: Marc Apter
mlapter@smcm.edu
240-895-4381
St. Mary's College of Maryland
18-Dec-2003