The man, whose name was not released, accidentally stepped on the lid to a chute, fell about 40 feet down the chute shaft and became trapped in the silo around 1:30 p.m. at the H.J. Baker & Brothers, Inc. plant on McNeill Road.
His leg got caught in a drilling device, which complicated the rescue, Barber said.
The contractor was up to his waist in dog food because the silo was only about one-quarter to one-third of the way full. He never lost consciousness, but did become dehydrated after several hours in the silo, Barber said.
He was airlifted to WakeMed in Raleigh. The extent of his injuries was not immediately known.
Barber said more than 60 emergency crews were dispatched to the scene to assist with the rescue.
The Occupational Safety and Health Administration is investigating.