There were no external injuries except for two small wounds on a front paw and the back of the neck.
X-rays showed no additional signs of trauma, he said.
"This is potentially a serious offence. If we catch the culprit and it is found to be a wilful act of cruelty the offender could be liable for a penalty of up to $100,000 or five years imprisonment."
Mr Dawson said the SPCA was looking for the owner of the cat who would be devastated by the news.
"The case is very unusual and worrying. We are looking to the public for any information that could aid in our investigation."
The cat was a black and white, domestic, medium-haired and neutered male.
Anyone with information that could assist in the investigation or help locate the cat's owner is asked to call them on 0800 INSPECTOR.