A Levittown man pleaded guilty Friday to beating his 11-year-old German shepherd with a shovel and causing injuries so extensive that the dog had to be euthanized, attorneys said.

Michael Gallagher, 57, admitted that he put a zip tie around the neck of his dog, Bella, District Attorney Madeline Singas said.

Gallagher then put her in a black plastic bag and beat the dog with a metal shovel, in what the prosecutor called an act of “depravity.”

Gallagher pleaded guilty in County Court in Mineola to a felony charge of aggravated cruelty to animals, Singas and defense attorney Lawrence Carra of Mineola said.

Singas said she would urge a maximum prison term of 2 years when Gallagher is sentenced Nov. 20.

Carra and an aide to Singas said Acting Justice Teresa Corrigan indicated she will impose a sentence of 4 months in the county jail, followed by five years’ probation.

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Gallagher has agreed not to own or control any animals for 20 years, his attorney said.

Singas said that the beating last Dec. 23 did not kill the dog. Witnesses realized that Bella was still alive after seeing her head move slightly, the prosecutor said.

When Gallagher’s wife arrived home, she cut the zip tie from the dog’s neck and rushed her to an animal hospital, Singas said.

The veterinarian determined that the injuries, which included blood and tissue coming out of her head, were fatal, and euthanized the dog to prevent any further pain and suffering, Singas said.

“My office takes crimes against animals extremely seriously because we know those who abuse animals often harm people, too,” Singas said in a statement.

“The depravity shown by this defendant toward an innocent and defenseless dog is sickening, and I am grateful to our animal crimes prosecutors for holding him accountable,” she said.