The DSPCA's on-call inspector was phoned by a garda in the Dun Laoghaire Rathdown area of Dublin reporting an incident.
A PIG was beheaded with an axe in a South Dublin garden. Gardai and the DSPCA were called to the house on December 22 after neighbours heard the animal's distressed squeals.
On arrival, the DSPCA Chief Inspector Liam Kinsella was greeted by the "horrific sight" of a large pig that had been slaughtered in the back garden of the detached house.
"Reports indicate the animal was in extreme distress and pain for a prolonged period of time," he said.
A team of gardai were already on the scene and an axe was embedded in a block of wood near by.
It is understood that a number of people have been questioned by gardai and that charges are expected to follow.
"It had its ear tag removed while still alive, making it untraceable," Chief Inspector Liam Kinsella said.
"Reports indicate that that the animal was in extreme distress and pain for a prolonged period of time," he said.
Mr Kinsella added: "Slaughter of animals for human consumption should only be carried out in registered premises and not in a residential back garden."
Investigations are continuing by gardai and the DSPCA as to the origin of the animal.
At the scene, blood from the pig could be clearly seen flowing along the ground and the head had been severed.
The carcass was lying on a makeshift table, and there were joints from the animal clearly intended for consumption.
A garda spokesman said that its investigations are ongoing and a court appearance is expected in the coming weeks.
Following the incident, CEO Brian Gillen said the DSPCA would welcome the "speedy introduction of the Animal Health and Welfare Bill which is currently before the Dail".
It is the third case involving the slaughter of animals in back gardens the DSPCA has had to deal with in the past few months.