George's lawyer, Gaye Gray, said his actions were cruel but "not premeditated".
She said he was extremely remorseful for his actions and did not pursue bail because he thought it inappropriate to do so.
George had also written a letter of apology to the 6-month-old dog, which he had looked on as family.
"That may seem quite unusual, but that dog was his friend."
Ms Gray said George's criminal history included possession of an offensive weapon, assault and threatening behaviour, but his pattern of offending had been broken by his relationship with a local woman.
Judge Rosemary Riddell said George's life had been dysfunctional and punctuated by alcohol and substance abuse.
She said he had a high risk of reoffending and had tried to shift the blame to his neighbours who called the police.
Imposing the jail term, Judge Riddell told George his attack was "cowardly and brutal on a poor, defenceless animal".
"This should deter you from doing this again but it should also deter others."
Outside court, George's partner of 15 years, Lisa Waka, said she did not excuse what he had done. "The sentence is what it is ... It can't be helped."
Ms Waka said she and George had relationship difficulties "like any other couple".
"But we could have sorted it out if he didn't go stupid."
She said their two children, aged 11 and 14, had been subjected to bullying since their father was arrested four months ago. Other children called their dad a murderer.
Te Kuiti SPCA president Sandra Squire said the sentence was pleasing.
"I think that this is the longest sentence handed down for this type of offence, a lifetime ban, and we couldn't have asked for more.
"I think it is a very clear message that has been sent.
"I think the defence's argument was very poor and the magistrate took that into consideration and formed a very good opinion of the facts."
Ms Squire's colleague, SPCA inspector Michell Sanders, said George's defence that he reacted after the dog bit him was no excuse.
"Dogs don't bite unless there is a reason."
