D G Kennedy1, Renger F. Witkamp2, J. D. G. McEvoy2, Julia Currie2, Andrew Cannavan2, W. John Blanchflower2, Christopher T. Elliot2
1Department of Agriculture for Northern Ireland, Stormont, Belfast, UK.
2Department of Agriculture for Northern Ireland , Veterinary Sciences Division , Stormont, Belfast, BT4 3SD, UK