The country's largest bull testing centre has been rocked following confirmation of an IBR outbreak at the facility last week.
Some 47 of the National Cattle Breeding Centre's (NCBC) top bulls are now awaiting slaughter, including SOK and KOZ, the two top-ranked dairy bulls in the ICBF's spring 2011 sire list.
NCBC is fearful that more of 18 remaining bulls will test positive before the end of the week in what has been described by management as their "worst nightmare come true".
Staff at the NCBC headquarters at Enfield, Co Meath, were said to be shocked following news of the outbreak. The breeding firm suffered from previous outbreak of IBR at their young bull unit just over a year ago.
However, NCBC can take some consolation from the fact that a number of new young bulls with EBIs of up to €240 have been shielded from the disease by virtue of their location on a separate unit.
Developments in genomic testing will accelerate the introduction of this next generation of bulls over the next 12 months.
In addition to huge loss of their best bulls, the stud also faces dumping 100,000 doses of semen, valued at more than €1m.
"We will be discarding all the semen collected in the period after our last clear test as a precautionary measure," confirmed NCBC's chief executive, Bernard Eivers.
However, he said he was confident that the centre would still have enough previously collected semen to cover demand for the coming spring AI season.
"If we need more, we can tap into our alliance with other semen centres around the world," Mr Eivers pointed out.
The bulls that have already been confirmed as positive for the disease include the top dairy sires SOK, KOZ, FLT, HRJ, UPH, GVV, NFT, IRP and GMZ.
Some of the country's top beef bulls have also been hit, including the Charolais bulls CF85 and KIB, Limousin sires FL25 and CVV, Angus bull FIW and Hereford sire AGI.
Investigations by the Department of Agriculture's virology unit are on-going to establish the source of the outbreak, with attention focusing on the possibility that some of the bulls may have had a latent form of IBR when they first arrived at the stud.
Strict biosecurity protocols, such as compulsory showering for staff before entry to the sheds, have been standard practice for years at NCBC. Initial tests indicate that the disease became established at the Enfield unit during the last week in January. There were no visitors to the centre during this period.
This latest disease outbreak will raise more questions about the lack of an IBR eradication programme in Ireland, similar to those already under way in Germany, France and Italy.
Most Scandinavian countries are already IBR free. In contrast, it is estimated that 80pc of Irish dairy herds are infected with the virus which causes pneumonia-type symptoms and compromises productivity.
Disease outbreaks in elite bull testing centres on the continent are rare in comparison to the track record here.
A statement from NCBC said that the current GeneIreland programme, which is operated in conjunction with ICBF, was unaffected and that the centre was forging ahead with plans to genotype up to 1,000 bulls in 2011.