The illegal movement of animals is suspected of being the root cause of the spread of foot-and-mouth disease in the North.
The Stormont executive has called on anyone who knows about the unlawful transportation of livestock to inform the Department of Agriculture immediately.
It is feared that a tiny minority of farmers may have been transporting animals without licence and others may not have reported the symptoms of the virus.
The Ulster Farmers' Union said farmers must be responsible and come forward if they suspect anything or the North will go the same way as Britain.
Four hundred and fifty animals are now dead and waiting to be burnt in Ardboe this evening.
All cattle, sheep and pigs within a one kilometre radius are being killed and in addition, pigs within a three kilometre radius will be slaughtered - an estimated 16,000 in all.
In Co Antrim, forty cattle and 200 sheep have been killed and will be burned on site - with animals at an outfarm belonging to the same farmer being killed today as well.
The Glens of Antrim represent one of the most densely populated common sheep grazing areas in Europe.