Five hoggets and eight lambs were killed on the farm of Patrick and Noel Woulfe in Dunganville, Ardagh, Co Limerick.
The Limerick farmers happened upon two dogs attacking their sheep on Thursday morning 28 April.
Among the lambs attacked, four were killed and four had to be put down.
The hoggets were taken to the knackery.
Patrick Woulfe, Noel's son, believes the dogs involved were Alsatians.
"We came down to the field and they were at it. The father went out to the owner and told him.
"We had eight hoggets killed last October as well," he said.
The dogs were put down by the vet, according to Woulfe.
Limerick IFA county chair Seán Lavery said that people may assume they have a friendly dog but when dogs get into a pack they will kill.
"I'm not sure anyone has been fined the €2,500 yet.
"It would be a good enough fine if there was adequate enforcement around it," he said.
He added how critical the role of the dog warden is in these cases.
"Some are more concerned about dog littering and management of dogs on beaches and in parks than in the countryside," Lavery added.
Woulfe's sheep were Mayo mules.
"Gardaí are investigating an incident that occurred in Ardagh, Co Limerick, in which a number of sheep were attacked on 28 April 2022," a spokesperson said.