Cattle Growth Hormones in Waterways Could Be Causing Gender Distortion in Fish
Normal human development is guided by a precise sequence of hormonal processes. Disrupting hormone levels during critical periods of development can lead to detrimental developmental consequences. Evidence of this potential has recently been observed in development of fish in waterways contaminated by runoff from commercial cattle feedlots. Most of the approximately 12 million cattle raised in the United States are given hormones and steroids to promote growth. Runoff from these feedlots where these animals are kept has carried these hormones and steroids into waterways, where sexual development abnormalities have been observed in the native fish. University of Florida endocrinologist Lou Guillette discovered native female fathead minnows downstream of several feedlots with male characteristics and male fish with abnormally small testes and almost feminized heads. Other researchers have also reported that fathead minnows appear to be particularly sensitive to trenbolone acetate, a potent form of the male hormone testosterone.

Most focus on hormones from the commercial meat industry has centered around the effects of these substances on those eating them. These new findings highlight the developmental risks from abnormal hormonal levels as well as bringing to light an additional environmental impact of the commercial meat industry.