The grand champion goat from this year's Colorado State Fair has been disqualified after testing positive for an unapproved feed additive.
Margaret Weinroth, who raised Theodore the goat, will not receive its $5,500 (£3,500) sale price and is barred from future livestock events at the fair.
A second goat raised by the Weinroth family also tested positive for the additive, ractopamine.
They denied any wrongdoing and said their feed may have been tampered with.
Tests carried out on Theodore's urine revealed traces of ractopamine, a muscle growth additive approved by the federal government for use by swine but not goats.
Teenager Margaret Weinroth is an animal science student at Colorado State University.
She has a track record of rearing prize-winning goats, with another of her animals claiming top honours at the National Western Stock show in 2010, the Pueblo Chieftain newspaper reported.
Susan Weinroth, Margaret's mother, told reporters the family's animals have always tested clean and that the family was shocked.
The feed for both goats had been "moved and dumped and tampered with" during the fair, she said.
Theodore and a goat raised by Margaret's younger brother both became sick after eating the feed, Ms Weinroth said.
"I can't say if it was sabotage. All I can say is what happened," she said.
Chris Wiseman, general manager of the Colorado State Fair, which ran in August and September, told the Associated Press that Ms Weinroth had told him about the feed incident.
While the sale money would still be lost, Mr Wiseman said the ban on participating in future events would be lifted if officials find someone else did place the food additive in the goat's feed.