Probation officials said Monday that Rodell Vereen, 51, was let out of prison March 1.
Vereen must complete two years of probation or he will have to finish the five-year sentence he received in November 2009 after pleading guilty to buggery and trespassing. The Sun-News of Myrtle Beach first reported Vereen's release.
Vereen was arrested after the owner of the horse staked out her stable and caught Vereen sneaking inside. She held him at gunpoint until police arrived.
The owner said she spent several nights in the barn after catching Vereen having sex with the animal on surveillance tapes. She feared he had returned because her horse was acting strange and getting infections again. She also noticed dirt and hay piled up near the horse's stall in Longs, about 20 miles northeast of Myrtle Beach.
Vereen was caught having sex with the same horse in late 2007 and was on probation from that incident when he was arrested a second time, authorities said.
The owner of the horse didn't immediately return a message from The Associated Press on Monday, but her husband said she knew Vereen was out of prison and she was scared he would come back to their stables.
A phone number for Vereen couldn't be found. Before he pleaded guilty, he told Myrtle Beach television station WMBF-TV he was sorry if he hurt the horse or anyone else. He said he wasn't taking his medicine for schizophrenia when he went to the stables and promised to keep taking his medicine when he got out of prison.
Vereen also must continue to register as a sex offender.
Information from: The Sun News.