Johne's disease can devastate a dairy herd, as it is virtually impossible to eradicate the bacterial disease once it enters the farm.

With no cure available, previous studies have suggested that the disease can cost approximately 1% of gross milk revenue, which is the equivalent of losing more than €30/cow in a year.

Johne's is caused by paratuberculosis, a subspecies of Mycobacterium avium, which is related to infectious organism that causes tuberculosis (TB).

The disease causes the infected cows to 'waste away' as they suffer through chronic diarrhoea, weight loss, and infertility.

With the suspected cases of bluetongue in Northern Ireland, and the usual bovine TB currently at the forefront of dairy farmers minds, it is easy to forget about Johne's.

Ideally farmers should consider joining the Irish Johne's Control Programme for support in keeping the infection out.

Some animals can release large amounts of the contagious paratuberculosis bacteria in their faeces despite appearing healthy and showing negative results for the disease in their bloods.

As the disease silently spreads, the herd will be impacted through;

Reduced milk production;
Premature culling leading to increased cost of unnecessary stock replacement;
Lower value cull animals;
Increased levels of lameness;
Lower feed conversion efficiencies leading to increased feed costs;
Negative effects on herd fertility;
Higher cell counts;
Increased veterinary costs and associated increase in antimicrobial usage.

Reducing the risk of Johne's

If calves are being contract reared, or if you have animals on an outfarm, the risk of contamination is far higher, which will then spread when the animals return to the home block, so ensuring high standards of biosecurity are in place with contract rearers is essential.

The same principal goes for animals who are attending shows or marts, or animals bought externally.

Another major risk is for farmers importing slurry or manure, as there is a risk of the slurry containing the bacteria, which will inevitably infect your paddocks when spread.

Bacteria can also enter the farm from dung on the vehicles and equipment of visitors or contractors.

Effective biosecurity is the best way to keep Johne's off the farm, as it can take years for the first symptoms to show after first infection, leaving time for the disease to spread within the herd.

Despite not being 100% accurate, blood tests are the best method of picking up early stages of Johne's disease, therefore farmers should be ideally testing annually.

'Closed herds' have the best chance of not bringing the disease in, so farmers should reduce the number of bought-in animals, or source animals from low-risk herds that have shown negative blood test results for several years.

The disease can also spread through water. Your herd should be drinking from the mains if possible.

However, many farms use private sources, such as wells. When supplying animals with this water, it should be tested regularly for paratuberculosis.

Farms should also fence off stagnant water sources, such as ponds, as these are perfect grounds for this organism to live in.