Testing herds for M. bovis is complex, which means negative results are a good sign — but not definitive proof that a herd is completely free of the disease.

Simple steps you can take to reduce the risk of spreading Mycoplasma bovis
If you're buying or selling calves or milk over the coming months, here are some simple steps you can take to reduce the risk of spreading Mycoplasma bovis and other diseases.

M. bovis is a bacterial disease that can cause serious illness in calves and adult cattle.

Calves can contract the disease through direct contact with infected cattle, or by consuming milk from infected cows.

Advertisement

Eighty to 90 per cent of infected cattle show no clinical signs, making it nearly impossible to detect a cow with M. bovis by looking at her.

Testing herds for M. bovis is complex, which means negative results are a good sign — but not definitive proof that a herd is completely free of the disease. M. bovis is shed intermittently by infected cattle. Shedding and clinical disease typically occur in times of stress, such as at calving.

That's why it's vital that the sector take every precaution possible to prevent M. bovis from spreading. This includes precautions when buying or selling calves or milk, when it's vital to take biosecurity practices and animal health history into account.

Buying calves:
1. Purchase from as few sources as possible.
2. Deal directly with the source farm or via an agent.
a. Ask about any M. bovis test results available for the farm.
b. Ask about cow and calf health on the farm for the past two seasons, and use the pre-purchase checklist available at dairynz.co.nz/mbovis
3. Purchase only NAIT-registered and tagged calves, and promptly record all movements.
4. Ask your transporter to avoid mixing calves with other cattle in holding yards or on the truck.
5. Keep newly arrived calves isolated for seven days and monitor them for signs of disease.
6. Find a buyer now for your future weaned calves, telling buyers about your efforts to reduce risk of M. bovis exposure.

Feeding milk — on-farm or purchased:
1. Milk that has the lowest risk of containing M. bovis bacteria comes in three forms: calf milk replacer powder, pasteurised milk, or acidified milk.
2. If you're using milk replacer powder, order now to avoid problems with supply.
3. If you're feeding whole milk, consider the following:
a. Discard milk from cows under treatment for illness or mastitis is much more likely to contain M. bovis than milk from healthy cows, so it is strongly recommended that you avoid this.
b. M. bovis is not killed by the addition of potassium sorbate preservative.
c. Yoghurt bacteria will give variable results and should not be relied upon to kill M. bovis.
d. Pasteurisation will kill M. bovis if the machine is maintained and instructions followed.
e. Acidification with citric acid to a pH of five for eight hours or a pH of 4 for an hour will kill M. bovis. Below a pH of 4 the milk becomes progressively unpalatable and calves will drink slowly or refuse to drink altogether. It's best to discuss acidification with your vet.