Biosecurity on Dairy Farms

Biosecurity on Dairy Farms


Biosecurity risks are inherent to any industry that involves animals and plants. Whether it’s between paddocks, farms, regions and even countries, the risk is never static; and as the world gets smaller and international transport and trade continue to grow a lot can change in an instant. With last year’s outbreak of Mycoplasma bovis in South Canterbury bringing this conversation back into the limelight, it’s more important than ever for farmers to be aware of the risk and do what they can to prevent future outbreaks. 


Mycoplasma bovis (M. bovis) is a bacterial organism that infects cows and can present itself in a number of symptoms depending on the environment or farm it is found on. Overseas, it can be apparent as pneumonia in calves, whereas here it has been linked to swollen joints, lameness and an incurable form of mastitis. M. bovis is unique because it has no cell wall, so while it can be killed easily with UV light or a change in pH it cannot be treated with antibiotics that are designed to target cell walls. 

Although the disease can lead to serious conditions in cattle and be transmitted from cow to cow in a number of ways, it does not infect humans and there is no risk or concern from consuming meat, milk or milk products.

And while the outbreak has been considered extremely unlucky, there is no concrete evidence to suggest that ‘farm zero’ was operating intensely or outside of the norm. There is also no evidence either as to the origin of the outbreak, although early suggestions were imported semen.


Depending on the virus or organism in question, there are a number of ways biosecurity hazards can be transmitted. But in the case of M. bovis, the main risk to cows is other cows while they’re out grazing.

Because the disease is mainly found in the nasal or mucus glands around the nose or inside the throat, they can become infected simply by rubbing noses with other cows as they naturally would. When new calves are born, they can contract M. Bovis from their mother’s milk. And although it’s uncommon, goats can be carriers of the disease without being affected by it.


One of many things that set our farms apart from others across the globe is the fact that M. bovis never used to be present in New Zealand. It’s not uncommon in the Americas, Europe and some parts of Australia, but to maintain productivity and animal welfare the decision has understandably been made to eradicate M. bovis from New Zealand. 

This will take the form of phased eradication over time; where herds identified with the disease will be culled until regular surveillance finds no further evidence. And as this will take a number of years, during the process it is important for all farms to remain vigilant and do what they can to prevent the spread of M. bovis within their own herds. 

Simple changes such as double fencing farm boundary fences to prevent nose to nose rubbing, disinfection stations to clean visitors footwear and/or their vehicles arriving from other farms and close monitoring of the associated symptoms, will all play a part in the long run. And available from DairyNZ, this article on biosecurity and checklist for graziers is a great starting point to help get your operation up to standard.