Man jailed for operating on dog with knife

A botched attempt at home surgery with a kitchen knife left Nippy the cattle dog with a 15-centimetre open wound and forced the RSPCA to put him down.

Now his owner, 45-year-old Adelaide man Michael Toft, has been jailed for a month in what an RSPCA inspector says is one of the worst cases of animal cruelty she's ever seen.

"The actual wound itself was quite horrific. It was clearly infected and it was very large," the inspector, who did not want to be named, told AAP.

"The dog was breathing quite rapidly and was in a deal of distress and couldn't walk. I actually had to carry it to the car."

Toft cut a cancer out of the 18-year-old cattle dog's shoulder in June 2014 and was jailed on Wednesday after pleading guilty to one count of ill treatment of an animal in the Port Adelaide Magistrates Court.

The case came to light after the RSPCA was tipped off by email.

"There's no doubt that the dog would have died a slow, painful death if it wasn't reported and we hadn't stepped in," the inspector said.

She said Toft was "matter of fact" when spoken to after the surgery, telling her he could not afford a vet.

"He was eerily calm and he admitted everything. He showed me the video he had taken on his phone of the dog prior and then of the dog after surgery."

"He told me that he believed that when a vet saw his work, the vet would be quite impressed."

As well as the jail sentence, Toft was banned from owning any animals in the future.