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Reducing the risk of spread

Protect your farm from disease

It's vitally important for you to make sure your on-farm biosecurity is up-to-date and protecting your farm.

Take a look at the following topics below:

Buying and selling cattle

  • Buying

    When buying stock, always check the source of cattle and their health history. You can use a DairyNZ pre-purchase checklist.

    Pre-purchase checklist — DairyNZ

    Whenever animals from different farms and groups mix there’s a risk of spreading infection. The following tips will help reduce this risk.

    • Buy and mix from as few sources as possible    
    • Ensure any calves you buy were not fed milk (especially discard milk) from other farms    
    • Deal with a trusted source farm or agent and ask them about:
      • Stock management and trading practices on the source farm
      • The source farm's biosecurity, including boundary fencing and stock quarantine practices
      • All stock movement records being up-to-date and recorded in NAIT
      • Cow and calf health on the farm
      • Only buy cattle that are lifetime traceable in the National Animal Identification and Tracing (NAIT) system
      • When cattle are moved record these movements in NAIT when they happen
      • Ask your transporter if they can transport your cattle without them mixing them with other cattle in holding yards or on the truck
      • Keep any cattle that you buy isolated from your other cattle for at least 7 days. Watch them for signs of M. bovis as noted below:

  • Selling

    If you are selling cattle, be prepared to provide the information above to potential purchasers.


If sending cattle to grazing, protect them from M. bovis by:

  • Preventing nose-to-nose contact with cattle from other sources. Discuss this rule requirement with everyone involved in the care and transport of your cattle.
  • Ask your transporter to avoid mixing your cattle with other cattle in holding yards or on the truck.
  • Make sure all your cattle have NAIT tags in their ears and records are up-to-date.
  • Promptly record all movements in NAIT.
  • If there are cattle from other locations on the grazing property, make sure there’s no opportunity for the different groups to mix.

Managing service bulls

Bulls that have been in contact with infected cows then moved to another herd are a risk for the spread of infection.

To reduce the risk, observe the following precautions during the mating season.

  • Bulls arriving on farm – all ages
    • Bulls should arrive with a NAIT-compliant tag and all movement history details.
    • Ask your vendor or agent about the cattle management and trading practices on the farm of origin. Make sure you let the vendor know your requirements.
    • On arrival, hold bulls separately from the main herd for at least 7 days to assess their health status. Complete procedures such as drenching.

    If you have any concerns about the health of the bulls, contact your vet, before mixing them with the herd.

  • Bulls leaving the farm

    Bulls leaving the farm

    Ensure they are showing no sign of M. bovis. If you are under Active Surveillance, talk to us about best practice.

    If you are under a Notice of Direction or a Restricted Place Notice talk to your Farm Systems Manager

    • If you lease bulls, talk over the options with the owner.
    • R2 bulls to slaughter once mating. They must go directly from your farm to the slaughter premises and not via sale yards or any other intermediate stopping point.
    • R1 bulls may spread infection between dairy farms if they’re used to service multiple cow herds across seasons. When mating finishes on your farm they should go for fattening then be sent to slaughter.
    • If R1 or R2 bulls are being held for further use (such as another mating season) don’t loan or lease them to other farms. Keep them separate from your cow herd and isolated from cattle on other farms.
  • Beef breed bulls

    Beef-breed bulls from a beef property are a lower risk class of stock and M. bovis test results are unlikely to be available. Ask the vendor or agent if the supplying farm deals in cattle from the dairy industry.

    Bulls that have been on a low number of cattle farms, present the lowest risk of introducing infections including M. bovis.

    The best indicator of the level of M. bovis infection risk is the health status of herds that the bulls have been running with, especially levels of pneumonia and lameness.

Managing semen

The Import Health Standard (IHS) regulates semen imports into New Zealand. It recognises semen is a potential pathway for M. bovis. There are controls in place around the husbandry and health status of donor bulls to reduce the risk of introducing the bacteria.

M. bovis can survive freezing. So antibiotics used in the processing of frozen semen may not be completely effective in killing M. bovis.

To reduce the risk of spreading M. bovis via semen, always ask your semen supplier:

  • if they have tested donor bulls for M. bovis
  • what assurance can they provide that their semen is free of M. bovis

Raw milk

  • Sharing milk

    Sharing milk between farms and feeding it to calves is a high-risk activity for the spread of M. bovis. This means you should try to avoid trading raw milk or colostrum if possible.

    Calf milk replacer may be a viable alternative for your farm. Good quality calf milk replacer has a nutritional value comparable to raw milk.

    If you do rely on traded raw milk or colostrum:

    • Minimise the number of farms you source milk or colostrum from
    • Keep records of when and where you source milk or colostrum from and which groups the milk is fed to
    • Avoid feeding milk from cows being treated for mastitis or other illnesses
    • Reduce the risk of M. bovis transmission from fresh milk by pasteurising or acidifying the milk
  • Feeding colostrum to young calves

    During the first 24 hours of life, a calf can absorb antibodies and essential proteins from colostrum that helps protect it against infectious disease.

    Pasteurisation and acidification can destroy some of these antibodies and proteins. So there are benefits to feeding unpasteurised or non-acidified colostrum to calves under 24 hours old. However, you should take extra care to ensure the colostrum is not infected with M. bovis.

    Pasteurised or acidified colostrum and milk is suitable for feeding to calves over one day old.

  • Milk treatment advice


    Pasteurisation will destroy M. bovis bacteria if done correctly.

    ∙ The recommended treatment is 60°C for 60 minutes.

    ∙ Refer to manufacturer specifications for operating the pasteuriser.

    Acidification with citric acid

    To kill M. bovis by acidifying milk, it needs to be at a pH of 4.5 for at least 8 hours.

    ∙ Citric acid is available online and from farm merchant stores.

    ∙ Use cool (10°C to 24°C) or cold (less than 10°C) milk to minimise coagulation or clot formation.

    ∙ Always add acid to milk, not milk to acid.

    ∙ Acidification works best when adding citric acid to fresh milk.

    ∙ It's important to accurately measure the weight of citric acid and volume of milk. Use a rate of:

    • 5g citric acid per litre of whole milk
    • 550g per 100 litres of whole milk, and
    • 5kg per 1000 litres of whole milk.

    ∙ Sprinkle the acid on top of the milk while the milk is being agitated.

    ∙ At pH 4.5, milk separates, but with gentle mixing goes back into a homogenous solution.

    ∙ Do not acidify below pH 4 as this will result in:

    • thickened milk
    • risk of complete coagulation, and
    • calves not drinking the milk.

    ∙ Gentle mixing of the milk twice a week is the recommended method. Continuous or vigorous mixing causes coagulation.

    ∙ For systems that pipe milk, the milk may coagulate in pipes or tubes with blockage of lines and nipples. This can result in the feeding of whey to calves if the casein coagulates.

    Testing pH

     ∙ Test the pH of milk half an hour after adding citric acid to the milk.

    ∙ Test again just before feeding the milk to calves.

    ∙ Use pH test strips. You can buy these online and from farm merchant stores.

    ∙ It can be difficult to keep an electronic pH meter clean and calibrated when working with milk. If using one, make sure you clean and calibrate it regularly.

Calf days, cattle shows and events

Organisers of calf days and other events where cattle are present should take extra biosecurity steps to avoid the spread of M. bovis.

Bringing animals from different herds together does pose a relatively low risk of disease spread. But with good measures in place and precautions, any risks can be minimised and events like these can still go ahead.

You can find our calf club and event resources below.

 What can exhibitors do?

Do not transport animals on properties under any suspicion of exposure to M. bovis to shows and events.

Do not take animals showing clinical signs of any disease to shows, as per normal biosecurity practice.

∙ Make sure you tag your cattle with a NAIT-compliant tag registered to your property.

∙ Keep your NAIT  (National Animal Identification and Tracing) movements up-to-date and accurate. Record movements to and from the event.

NAIT — information on animal identification and tracing

Stock movements

  • Tracking off-farm movements

    NAIT (National Animal Identification and Tracing) is New Zealand's cattle and deer tracing system. Complying with it is law.

    It's critical that you keep up-to-date and accurate NAIT records. This will help us track cattle movements and locate any that could be of interest to the eradication Programme.

    It’s also a useful tool for managing your own on-farm biosecurity. It provides a life history of brought-in animals.

  • Tracking on-farm movements

    As well as recording farm-to-farm cattle movements in NAIT, it’s useful to keep good records of on-farm animal movements.

    Make a map of your farm and keep detailed records of livestock movements around it. This helps you document the potential for contact between different groups of cattle on the farm.

    NAIT — information on tracking cattle movements

  • Adverse weather

    During adverse weather like floods, animals may end up on someone else’s property.

    If your animals end up on a farm that is under movement controls, MPI will assess the risk of M. bovis spread. We will decide whether the animals need to remain where they are or if we can release them.

    MPI will review these situations on a case-by-case basis.

    Talk to us if you’re affected by adverse weather and have concerns about the welfare of your animals.


  • Rural contractors

    Create designated “clean” areas on your farm, where bobby calf and slink pick-ups and other public movements can take place. For example, use the tanker track or house driveway.

    Make sure these areas are well separated from areas of the farm where you keep stock.

  • Farm visitors

    Make available for any visitors:

    • a foot bath with disinfectant and a scrubbing brush to clean boots, and
    • clean hot water and soap for washing hands and any equipment that is taken on and off the farm.

    Note: any common agricultural disinfectant will be effective. Be sure to remove all organic matter before disinfecting.

Protect your farm from disease

Farmer tip

Carry on feeding your cattle silage or baleage as normal. It’s also okay to sell it to other farmers. This is because silage or baleage is extremely unlikely to spread M. bovis. The ensiling process creates an acidic environment (approx. pH 4.5) which M. bovis bacteria can not easily survive.

Managing the risk of M. bovis [YouTube video from Dairy NZ]

Biosecurity WOF - a DairyNZ resource developed with farmers, for farmers. We recommend that you ask your veterinarian to help you work through this check list.