An Auckland man whose dog joined in when he attacked his ex-girlfriend's new partner has been sentenced to five months jail.

William Black has been in custody since June over the attack on Lindsay England.

Judge Roy Wade said Black had gone to his former girlfriend's house in the Auckland suburb of Stanmore Bay and argued with the residents.

At some point Black and England fell to the ground and Black punched England several times.

One of the two dogs Black had with him joined in the attack and only stopped when called off.

England was taken to North Shore Hospital where he was treated for his injuries and blood loss.

Black later breached a protection order by texting his former girlfriend.

He pleaded guilty to the breach of protection order, assault and owning a dog that attacked someone.

He was sentenced to five months prison but as he has already been on remand longer than that, he will be released later today.

An order to destroy the dog was made. 

- © Fairfax NZ News