Hard questions were raised, some with no answers.

Farmers questioned the Ministry for Primary Industries (MPI) and industry representatives about disease testing and biosecurity issues at a Mycoplasma bovis meeting in Winton last month.

One question raised was how some farmers would sell young stock, such as bobby calves, because putting calves together at stockyards could spread the disease.

Beef + Lamb New Zealand policy and advocacy general manager Dave Harrison said if farm systems involved saleyards and bringing in more calves, then farmers needed to decide whether or not that was a risk they were willing to take.

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''Saleyards are going to be a risk area,'' he said.

''The risk needs to be managed and you should do whatever you can to protect your farm business.''

Other questions raised included how accurate the bulk milk testing was and the plan going forward with this.

MPI senior policy adviser Emil Murphy said after calving, bulk milk testing would start again.

How many rounds of milk testing was still to be confirmed, he said.

The accuracy of the bulk milk tests was very high, as the disease appeared in the milk.

''The problem with the PCR tests is if the cows aren't shedding at the time,'' Mr Murphy said.

Another question from the floor was about where Mycoplasma bovis could have come from, as it had been confirmed it was not the Australian strain here in New Zealand.

MPI response director Geoff Gwyn said they did not know the country where it had come from, but MPI had narrowed it down to two continents - North America or Europe.

''The challenge we face around identifying the exact point of origin is what we rely on ... it's about them [other countries] putting their DNA strains in to some form of library.''

There was a very limited supply of strains documented, he said.

MPI had not given up on finding out how the disease had entered New Zealand or where from, and investigations were continuing.

Southern Rural Life