Abstract
Trenbolone acetate is a synthetic androgenic growth promoter used in conjunction with other steroidogenic compounds in the majority of beef cattle raised in the United
States. It has been shown to disrupt normal reproductive development in many species. Because trenbolone and its metabolites pass through the urine and feces, aquatic species are likely to be exposed via runoff into water bodies adjacent to feedlots. The red-eared slider turtle (Trachemys scripta) has been used extensively in the past to model the effects of potential endocrine disruptors, like trenbolone, on normal development. It is an ideal model partly because it exhibits temperature-dependent sex determination, a
condition which has been shown to be sensitive to exogenously applied estrogenic or
androgenic compounds. In this study, the effects of low doses oftrenbolone on sex ratios
were examined in turtles incubated at female or male biased temperatures. In addition to
altering expected sex ratios, these first experiments resulted in male and female
hatchlings with grossly hypertrophied phalli. A subsequent set of experiments was
designed to compare the effects of trenbolone against two naturally occurring hormones,
testosterone and 5a-dihydrotestosterone (DHT). DHT is the hormone responsible for
phallus development in mammals and in many other vertebrate species. Trachemys
scripta eggs were treated with identical doses of trenbolone, testosterone, or DHT and
incubated at either a female-producing temperature or one that would normally produced
mixed sex ratios. Trenbolone was shown to be more powerful than DHT or testosterone
in its ability to reverse hatchling sex. It was the only compound to induce hypertrophied
phalli in hatchlings. The benefits of using this compound in beef cattle should be reevaluated and weighed against its capacity to cause developmental abnormalities in
exposed wildlife species.
