NEW YORK — Butterball apparently has a big fat mystery on its hands: The company says it doesn’t know why some of its turkeys wouldn’t plump up in time for Thanksgiving this year.
Chief executive Rod Brenneman said in an interview that it’s the first time it happened and that the company is investigating what went wrong. Butterball had announced last week that it will have a limited supply of large, fresh turkeys that are 16 pounds or heavier for the holidays.
‘‘It’s a really good question. We don’t have an answer yet,’’ Brenneman said when asked about the cause. But he noted that turkeys are ‘‘biological creatures’’ subject to a variety of factors.
‘‘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.