Jun 17

Johnes – taking action

Johnes – taking action
Several milk buyers are now requiring farms to have a johnes control plan in place. This may well be an unwelcome demand when the milk price is where it is, however in the longer term, having some kind of Johnes plan is really important.
There are several reasons for taking action on Johnes:
• Human health – it’s possible that Johnes in cows is linked to Crohnes disease in humans. It’s not proven, but it makes sense for us to make every effort to prevent any potential spread of disease through milk.
• Cow health – Johnes is incurable. Affected cows waste away and eventually die. Before they get to that stage, they often have other health issues such as high cell counts, poor fertility, poor production.
• Farm economics – Johnes can spread un-noticed in a herd. By the time a few cows are clinically affected, there could be lots of animals carrying the disease. The effects of the disease are expensive, and it can take years to get it under control.
So – if you know Johnes is present on your farm, it’s important to have a plan to reduce the spread. If you’ve never had a cow diagnosed with Johnes, it’s equally important to have a plan in place to find out whether it’s there – it often is. You can then nip it in the bud. A herd with an unknown Johnes status is a potential time bomb.
How does Johnes spread?
• An infected cow sheds loads of Johnes bacteria in her muck and milk (much more in muck than in milk).
• If a young calf comes into contact with either, it will probably become infected. (Adult cows are resistant – they won’t pick up an infection from another cow. Only young calves will pick up infection).
• The infected calf will carry the disease, without showing any signs, usually till it’s at least 3 years old. Eventually, it will start to scour and lose condition. Often these animals are just culled as poor performers, without ever knowing that Johnes was the cause.

A common scenario in a herd that doesn’t know it has Johnes is this:
A cow calves, passes muck in the calving pen, and spreads infection to the next 4-5 calves that are born. This goes un-noticed until those calves are in the milking herd and one or two of them start scouring. By this time, they’ve had calves of their own, which are likely to be infected, along with many others.
What should I do about Johnes?
The first step is blood or milk testing to find out whether there’s any johnes in your herd or not. Unfortunately, that’s not as straightforward as it seems. The test won’t detect young animals carrying the disease, until they get older and the disease gets closer to becoming clinical, so repeated tests are needed to find out which cows are affected.

After testing, the measures taken to control Johnes will vary from farm to farm, and will depend on the level of infection.

The main focus of any control plan is to ensure that young calves don’t pick up infection. Calving pens are the main source of infection, so taking measures to prevent calves coming into contact with muck from cows of unknown Johnes status is the key. Milk is also a source of infection, so you need to ensure that any milk fed to calves is not from potential Johnes cows.

Many farms already have a Johnes control plan in place. Every farm is different, so any plan needs to be tailored to an individual farm. Speak to a vet about what the best course of action is for your own farm.

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