He told dairy farmers at the Northland Agricultural Research Farm field day a $50 a head difference in price caused farmers to buy South Island stock rather than those produced locally.
And the one high-risk farm identified by the Ministry for Primary Industries in the Dargaville area had received stock not only from Canterbury but also from a Mycoplasma bovis infected farm.
That happened after the Dargaville farmer was assured by a stock agent the animals were from Waikato.
About 3000 farms are now considered at risk of having the disease but because of the difficulty of determining whether stock are carriers it is likely quite a few of the farms now on watch by MPI would eventually be found to be clear, he said.
“There is a high amount of false positive and false negative tests.”
Mud and manure on boots are a low risk of spreading the disease.
“But milk and mucus is a bigger risk so cow -to-cow spread is important. The bacteria does not survive for long periods outside the cow.”
Overseas there had not been the same animal health problems seen on the South Canterbury farm where M bovis was first identified.
“There were joint infections and around 200 cases of mastitis when the cows were dry,” Lowe said.
Testing was difficult on live animals as the disease stayed dormant in the tonsils, with a swab needing to be taken to test for the disease’s presence. Stock culled from properties where the disease is present is being tested after the animals were slaughtered.
“But there’s a huge amount not carrying it,” he said.
A problem that will have to be addressed before mating for spring calving, done around October , is making sure bulls going on to farms to be used once AI is finished are clear of the disease.
“There’s talk about a tonsil swab of those bulls but that’s going to be a risk.”
