Judgment was handed down in the Melmoth Magistrate's Court on Tuesday, said the NSPCA.
Ntombela and one of his bodyguards, Shabalala, were found guilty of the act.
Ntombela was found guilty and sentenced to a fine of R4,000 or six months' imprisonment, half of which was suspended for five years.
His bodyguard was found guilty and sentenced to a fine of R2,000 or six months' imprisonment, which was suspended for five years.
The NSPCA's Meg Wilson said they were satisfied with the conviction, but not the sentence.
"Unfortunately sentences do not seem anywhere near adequate for the suffering that the dog endured, but two men, one of which holds a high political position, now have a criminal record.
"A strong message has been sent – no one is above the law and animals need to be treated with the greatest compassion," Wilson said.