If we cannot eradicate Mycoplasma bovis, New Zealand's sharemilking structure is in jeopardy, VetSouth managing director Mark Bryan says.

''If we don't eradicate, I can't see how the sharemilking structure will survive.''

Dr Bryan spoke to farmers in Winton last week about how the disease was tracking in the region.

Sharemilking was a unique part of New Zealand's dairy industry and Mycoplasma bovis was a threat to it. ''It's what's allowed people to work through the industry,'' Dr Bryan said.

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As most sharemilkers owned their animals, if a herd was found to have Mycoplasma bovis, financially the sharemilkers were not in a good position.

''Overnight your asset is worthless,'' Dr Bryan said.

There were 25 infected properties in Southland and Otago in total, 17 of which were active.

''I think it's very eradicable,'' Dr Bryan said.

The spring bulk milk testing, which was due to start soon, would confirm how things were, he said.

''I'd suspect we'd find some more positive farms.'' If that number was something like 200-300, it would change the situation, he said. One of the issues being dealt with was why some animals were showing clinical signs and others were not, he said.

''We've pushed MPI to find out why some have clinical signs and some don't,'' Dr Bryan said.

In the beef sector, the issue was much more complex, as the testing was very difficult, he said.

Overall, farmers needed to keep it in context, and the chances of getting Mycoplasma bovis were very very slim.

The vast majority of risk was around animal movement and buying in waste milk, Dr Bryan said.

There was still risk of a spread through boundary fences and other vectors, but they were minor. Service bulls were another risk area, but all of these risks were manageable.

If farmers were to remove the animal movement and waste milk risks, then they would become the only risk, he said.

Dr Bryan encouraged farmers to complete a risk assessment. VetSouth had developed a model for dairy farms, which was available, he said.

NICOLE.SHARP@alliedpress.co.nz

Southern Rural Life