Opinion: Remember farm biosecurity when moving or buying stock this autumn

There are many stock movements in the late autumn and early winter period. Photo / Mark Mitchell

OPINION

As the risks of Mycoplasma bovis in the North Island have lessened and the Indonesian outbreak of foot and mouth disease is no longer a news item, it is easy to become more relaxed about the disease risk bringing outside animals on-farm.

There are many stock movements in late autumn and early winter, so it’s well worth considering the risks of bringing infection or disease onto the farm.

Farm biosecurity can be defined as reducing the risk of introducing disease or infection.

It can also be widened to include weeds and pests. Good biosecurity principles to consider are:

1. Isolating and observing incoming animals before allowing contact with other animals already on the farm.
2. Have good animal health programmes in place to minimise the spread of disease in your herd. This can be good mastitis prevention programmes and vaccination. Contact your vet if there are unusual outbreaks of disease.
3. Prompt disposal of any dead animals.
4. Introduced products can be a potential risk and source of infection.
5. People visiting the farm, their vehicles and equipment can spread disease. Provide good washing and cleaning facilities for visiting contractors. Ensure that these are well maintained.
6. Inspect and regularly maintain good boundary fences.
7. Stock movements – When buying stock or moving stock from one property to another site, it is vitally important to check the disease status of these animals.

Diseases or infections to consider include:

Bovine Viral Diarrhea (BVD) – blood test all purchased animals and check they are BVD virus negative. Check the recent history of BVD in the herd and the recent Bulk milk BVD test history. It’s also essential all bulls purchased or leased are checked to be negative for BVD virus and are also fully vaccinated for BVD. Regular bulk milk BVD testing is excellent biosecurity screening and is cheap insurance that can prevent an expensive BVD outbreak in the herd. BVD virus can also be transmitted from infected stock on a neighbouring property over the fence, so double fencing on boundary fences is important.

Johne’s disease – many herds have a low incidence of this condition. Clinically affected animals scour, lose weight and may develop “bottle-jaw”. Johne’s disease can be a difficult disease to diagnose before the onset of clinical signs. It is possible to herd test for Johnes’s disease and this can form part of a good disease control plan. The herd test will not detect all animals that go on to develop clinical signs.

Staph aureus mastitis is an infectious form of mastitis transmitted from cow to cow by the milking process. Some strains of staph aureus are resistant to penicillin and these can be more difficult to control on-farm. There is a bulk milk test, called the dairy antibiogram, that detects and monitors antibiotic resistance in mastitis bacteria on a dairy farm.

Leptospirosis – check there has been a regular annual vaccination history for all animals on-farm.

Salmonella – this can be a risk when buying young calves from sale yards. New pathogenic serotypes of salmonella can also be carried onto the farm through bought in animals of all ages.

Theileria: It is recommended not to buy or bring in pregnant heifers and cows from tick-free areas into areas such as Waikato, where the disease is already widespread or endemic.

Keep Nait records up to date at all times. These animal movement records are vital in any major disease outbreak to find infected animals and their farms of origin.

The DairyNZ website has some excellent Biosecurity tools and resources for dairy farmers.

• Neil Macpherson is a veterinarian at Vetora