BLOOMINGTON, Ind. — A hormone used to promote growth in beef cattle remains in the environment longer than previously thought, according to the co-author of a study on the compound.
The hormone – trenbolone acetate (TBA) – is a highly potent synthetic equivalent of testosterone, said Adam Ward, an assistant professor in the Indiana University Bloomington School of Public and Environmental Affairs. He authored the study along with faculty from the University of Iowa and the University of Washington, Tacoma/Seattle.
Beef producers implant the hormone into the ears of their animals to promote weight gain. A majority of U.S. beef cattle are treated with TBA or one of five other growth hormones not included in the IU study, Ward said.
While in the animal’s body, TBA undergoes a series of chemical reactions, he stated. By the time the hormone is excreted in manure it has metabolized into 17-alpha-trenbolone, a compound chemically similar to TBA. The compound may cause harm to aquatic life if it works its way into a waterway, Ward explained.
Conventional wisdom had been that sunlight would cause 17-alpha-trenbolone to go away in stream water when exposed to the sunlight, Ward noted. A 2013 study found the previous thinking wasn’t accurate.
"The study found that ‘17’ can come back in the dark," he explained. "It also found that sunlight causes it to cycle between different forms. It doesn’t mean it’s gone. In the sunlight, it’s still behaving like a testosterone.
"It may be less potent, but it’s not harmless. It creates a slightly different risk."
Ward and his co-authors sought to determine how long 17-alpha-trenbolone might remain in the environment and what the potential risks might be. Their study found concentrations of the compound may be 35 percent higher in streams than anticipated. Because those compounds remain in streams longer than originally thought, biological exposure was 50 percent higher than expected, he said.
The compound may harm fish through lower reproduction rates or by causing a sex reversal, Ward said. "It’s a pretty potent hormone," he stated. "Very low concentrations can have large impacts on the aquatic ecosystem."
The IU study was done using computer models, Ward said, adding the next step is research in the field. "We need to get out and take measurements," he explained. "We don’t have a lot of faith in previous studies. We have to figure out the best way to sample for this in the environment."
The National Cattlemen’s Beef Assoc. referred a call regarding the study to Merck & Co., which manufactures a product – Revalor – containing TBA. Attempts to reach company officials to comment for this article were unsuccessful.
Field studies done at Purdue University did find a similar reversion with TBA, though the compound was found in small amounts, said Linda S. Lee, a professor and associate department head in the Department of Agronomy.
"Yes, I think it happens and it may explain some anomalies (found in fish)," she said. "But I question the relative impact and significance to aquatic health. There are so many things going on in waterways, such as pesticides. It’s hard to say if any changes in fish might be due to (TBA)."
For Lee, "the jury is still out" on the cost-effectiveness of TBA as a growth promoter.
The implants are used for quick weight gain but producers will keep their animals off the implants longer than recommended in order to achieve tenderness and flavor, she said. The implants tend to lower both in beef cattle, she added.
Ward hopes those in the beef industry understand the study isn’t intended to point fingers but, rather, to inform.
"Everyone agreed the risk was minimal, but now we know differently," he said. "We want to stress that nothing should suggest that producers have done anything wrong, and nothing suggests the pharmaceutical industry has done anything wrong. We just don’t know as much about this compound as we originally thought."
It may be necessary for the federal government to revisit how it regulates tens of thousands of compounds used annually, he said.
As for producers using the hormone, Ward said they should voice their concerns to suppliers of TBA and similar compounds.
"I should emphasize I’ve never known a single farmer or single producer out to do the environment harm and I don’t think anyone is," he said. "The point is not to pick on the industry but to use this as an example."
