The Animal Health Board says it may be difficult to track down the source of a recent outbreak of of bovine tuberculosis in four Taranaki dairy herds.
The board's southern North Island regional co-ordinator, Terry Hynes, says the infected herds are going through calving at the moment and TB testing will resume once that is over.
He says the only herd movements at present are bobby calves which are sent straight to the works.
Mr Hynes says DNA typing will be carried out from the cattle which are destroyed and it is possible this could lead to the source of the infection, as each area has a different strain of TB.
In Northland, where one cow in a large herd near Kaitaia was infected with bovine TB in July, movement of animals is also restricted and testing is on hold until after calving finishes sometime next month.