A Kentucky man convicted of scalping his ex-girlfriend told the judge "I don't need a lecture" as he was handed a 21-year prison sentence.

Zachary Gross, 31, was convicted of ordering his pit bull dog to attack his then-girlfriend Marilyn Stanley, with both the animal and Gross taking part in ripping her scalp from her head.

Despite a surgeon testifying in court that the injuries on Stanley's head matched those caused by a sharp knife, Gross told the court his dog, and not he, was responsible for the attack.

"For her injuries — I feel horrible for what happened. I don't feel responsible. I maintain my innocence," Gross told the judge in comments carried by The Kentucky Enquirer.

"It is what it is. I'm not asking for your mercy. Just give me the 20. I don't need a lecture."

His ex-girlfriend suffered permanent nerve damage from the attack, and has had six surgeries to repair her head, although her hair will never re-grow.

Stanley said the attack had taken places because Gross had become annoyed with something she had posted on Facebook. According to the prosecution, Gross told her: "You're bald now. Who's going to want you now?"

When the terrified Stanley refused to drop a knife she had picked up in self-defence, Gross ordered his dog to attack her – with the animal tearing off part of her head along with part of her ear, and Gross also knifing her head, Boone County Sheriff's spokesperson Tom Scheben told Fox News.

Gross then drove her home to her mother's house, where she arrived with some of her scalp in a plastic bag.

The dog has been ordered to be put down, while Gross was given a 20-year sentence for the attack and a further year for violation of probation, also linked to the attack case.