"For whatever reason, they just didn't gain quite as well this year," he said.
Like many other turkey producers, Butterball feeds its birds antibiotics to prevent and treat illnesses, which can occur from living in cramped quarters. The use of antibiotics, which also promote growth in livestock, has been the subject of concern that it could lead to antibiotic-resistant germs.
Butterball, a privately held company based in Garner, N.C., declined to say whether it made any changes to its feed formula this year. But the problem seems to have come up rather recently.
For much of the year, Butterball produces turkeys that are frozen and stored until they're ready to be sold for the holidays. But then in October and November, it shifts into production for fresh turkeys. And that's when the company ran into problems with the turkeys not gaining enough weight, Brenneman said.
It hasn't been an issue for some other poultry producers.
"The weather was great, so the turkeys were a little bigger," said Theo Weening, the global meat buyer for Whole Foods Market, which is based in Austin, Texas. The grocer works with smaller suppliers from around the country to sell turkeys that haven't been treated with antibiotics.
Over at meat producer Cargill, spokesman Michael Martin says in an email that the company has never had a problem where its birds didn't put on enough weight to produce an adequate supply of large turkeys.
Mark Kastel, founder of The Cornucopia Institute, a Wisconsin-based group that advocates for organic farming, noted that major poultry producers tightly control production factors, making Butterball's shortage unusual.
"I thought that was very mysterious. I could not think of a rational explanation," Kastel said, suggesting that a change in the feed formula may have been to blame.
Butterball declined to say whether the issue has been resolved or provide details on the extent of its shortage. But Big Y, a supermarket chain based in Springfield, Mass., said in a statement that it had been notified by the company that orders across the country were cut by 50 percent.
Butterball's shortage shouldn't be a problem for most since fresh turkeys only account for about 15 percent of sales, with frozen turkeys accounting for the rest. Butterball also makes only about one out of every five turkeys eaten on Thanksgiving.
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