Even quiet, docile dogs can turn into killers, especially if they join other dogs in a pack, according Minister of State for Housing and Urban Renewal Damien English.
Dog owners must be mindful that with ownership comes responsibility, owners must ensure their dog doesn't get the chance to attack sheep, he said.
Minister English was speaking at his father's family farm in Bohermeen, Co. Meath, ahead of the busy lambing season.
"Owning a dog means that you have to feed, house and care for your pet, but you must also remember that you have to keep them under control at all times.
Never let your dog out unsupervised, especially at night.
"From growing up on a farm, and especially from the time around lambing season I fully understand that dog attacks can cause serious injury and can kill sheep.
"They also have a very negative impact, both financially and emotionally, on the farmers involved and on their families," he said.
The number of dog attacks on sheep and lambs over the last number of years is unacceptable and they are avoidable, the Fine Gael TD said.
"Dog Wardens and the Garda Síochána are doing what they can, but they cannot be in every part of the country at all times. The solution rests with dog owners.
"Whether you live in or near the countryside or visit it for recreational purposes, I ask that you be on guard the whole time.
Do not give your dog the opportunity to attack sheep and cause distress and pain to both sheep flocks and their owners.
Minister English pointed out that, under the Control of Dogs Acts, it is the responsibility of dog owners to ensure that they are in control of their dogs at all times.
Attacks on sheep can result in economic losses to the farmer, for which the dog owner can be held liable under the Act.
Flocks particularly vulnerable in Spring
Some 2.5m lambs will be born on farms all over Ireland this spring, with sheep flocks being particularly vulnerable to dog attacks at this critical time, especially during the night, Minister English added.
In addition, the presence of dogs, even on a lead, can alarm sheep prior to lambing and can have a detrimental effect on them as well as their lambs, the Meath West TD said.
The Minister reminded owners of the duty to ensure that their dog is not responsible for injury to sheep or for the stress and financial loss to sheep owners and their families.
Some sheep, even if they do survive, never recover fully from a dog attack and can suffer ongoing health problems, including reproduction problems and nervousness.
"While it is recognised that the vast majority of dog owners are responsible, a momentary lapse in concentration can have disastrous consequences.
"Dog owners need to be particularly vigilant at this time of year and care should be taken to ensure all dogs are secure at all times,” the Minister said.