The Department of Agriculture and Food has launched an investigation into the source of the feed given to a six-year-old Cavan cow which developed BSE.
The animal, born in 1998, was identified this week among the six latest cases of Bovine Spongiform Encephalopathy announced.
The animal is now one of three born after Ireland's animal feed controls became fully operational and the investigation is focused on where the animal may have come into contact with contaminated meat and bonemeal.
In theory the cow should not have been exposed to contaminated feed, even though the ban on feeding meat and bonemeal to pigs and poultry was not imposed by the EU until 2000.
This is thought to have been the cause of Ireland's two other "young BSE" cases which were found in Co Limerick in 2002.
It is thought those animals, born in 1999, were fed meat and bonemeal which may have been contaminated by BSE from hoppers that contained feed for pigs and poultry.
The Minister for Agriculture, Mr Walsh, has said the Department is well on its way to eradicating the disease from the State herd as the age profile being found with it are all older animals.
However, both he and his scientific advisers have warned that rogue cases of the disease, i.e., younger animals which should not have been exposed to contaminated food, would appear.
That has been the case in Britain, where the disease was first identified in the early 1980s, and in Northern Ireland, which also had a high level of the disease that hits the central nervous system of the infected cattle.
A Department spokesman said last night it was confident of the controls which are in place, and consumers are protected by the removal from the human food chain of all animal material which could be infected by the disease.