Johne’s: Do you have a problem?
The most likely answer is ’Yes’. You are not alone, as 70% of dairy herds within the UK are suffering from this brutal disease and many don’t even realise.
Johne’s has become more apparent in the UK over the last 20 years, although in reality it has been around for much longer.
It is important the disease is discussed in more detail, and I will explore current research as well as outline a protocol to follow when trying to control Johne’s spread through your herd.
How does the disease work?
Johne’s disease is caused by bacteria which have a very long disease process.
Generally, animals will contract the disease when they are calves as they are most susceptible to new infections when their immune system is weak. After the disease has been contracted the animal may not show any outward signs of infection for years.
Some cows even leave the herd before they show clinical signs, so that farmers could have a Johne’s problem within their herd and not even realise. However it is likely that she will begin to shed the bacteria within the faeces long before she shows clinical symptoms. This is instigated by stress and often calving can be a trigger.
Once the animal begins to shed the bacteria she will develop antibodies, which can be detected through both the blood and the milk. This is the point when the cow is able to infect other animals through both the milk and the faeces.
At the point of calving the susceptible calf is exposed to faeces and colostrum, both of which could help transmit disease. Giving calves colostrum or milk from a Johne’s infected cow is likely to result in them contracting it.
What research has there been on Johne’s in the herd?
Johne’s research is fairly limited, due to the complexity of the disease it can make it quite difficult to do a full research project however some information has been collected.
- In 2010 Collins et.al. observed a significant reduction in Johne’s prevalence on 9 dairy herds, where a blanket Johne’s protocol was implemented. Over the 6 year study every farm had to follow a strict management protocol. This study showed an overall reduction in Johne’s incidence from 11.6% to 5.6%, whilst the reduction in first lactation animals was even greater, reducing from 12% to 3%, proving that an effective management protocol can reduce Johne’s instance.
- In 2012 Espejo et.al. researched into average age of a first positive test for Johne’s. These results showed a mean age of 46.8 months for the first positive test. This puts into perspective the nature of the disease and the slow maturation process that ensues.
- Smith et.al. (2010) did a 2 part study into the effect of Johne’s disease on both culling rates and calving rates. They found that culling rates were significantly increased with Johne’s positive animals within the 6 herds, this is not surprising given the perception of Johne’s positive animals. However the more important finding was a reduction in calving rates as well as a significant increase in calving interval which was increased by an average of 34 days with cows testing positive for Johne’s.
- Raizman et.al. (2009) studied Johne’s from an economic perspective and showed that Johne’s had a significantly negative effect on herd income on a cow by cow basis. They proved that cows suffering from Johne’s at culling had an economic value that was £441 lower than that of a Johne’s negative cow. This was down to production losses suffered over the life of the animal, fertility issues, age at culling and culling value.
It is clear from all of these studies that Johne’s has a major negative impact on the dairy industry both in terms of herd health and economic response. It is crucial that the incidence of Johne’s is reduced.
What is the effect of Johne’s on your herd?
The reality is that on many farms we don’t know the answer.
This is a cause for concern.
The best way to explore this question is for me to ask you the questions.
Johne’s Questionnaire final version which asks a series of questions about your Johne’s control on farm, and along with a scoring system. This scoring system will allow you to see whether you are managing Johne’s effectively or whether you need to form an action plan for control.
What would the action plan be?
Having answered the questionnaire you now have a clear idea of whether you have a problem, and the next step is to tackle the problem .The final plan should involve your vet, but the following protocol will help to reduce the risk of infection.
- Testing – All cows to be tested every three months through a milk test for the first two years. If these tests continue to be clear of Johne’s infected animals, begin to test a relative sample of 30 cows every 3 months to monitor the situation. If these tests show animals to have Johne’s then continue to test all animals every three months until 2 years of clear testing with no positive animals within the herd seen. You should avoid testing within 40 days of TB testing as this can result in false positives
- Marking – Once cows are shown to be positive for Johne’s all cows should be marked so it is clear which animals are Johne’s infected, this can be done through tagging, tail tape or chalk.
- Calving – A separate calving area should be available for all positive cows, as animals are shedding through both the faeces and the milk, the baby calves will be at risk. Positive cows should be separated from the main herd and all calves from these cows should be snatched at birth and moved to a clean calf pen.
- Colostrum – All Johne’s farms should have a bank of refrigerated or frozen colostrum from safe, Johne’s negative animals. This colostrum should then be fed to calves out of cows infected with Johne’s in order to reduce the spread of infection. Pasteurisation will not transform Johne’s positive colostrum into healthy colostrum. All Johnes positive colostrum should be discarded and replaced with some from a healthy cow.
- Calf Rearing – Any dairy calves off Johne’s animals should be isolated and culled as soon as practical, in order to reduce spread of infection and prevent continual Johne’s within the herd. All other dairy calves should be fed on milk replacer as this contains no Johne’s bacteria and will reduce the risk of Johne’s spread through the herd. Under no circumstances should milk from a known Johne’s positive cow be fed, and if feeding whole milk, this milk should be pasteurised as a precaution. It is possible that some Johne’s ‘’negative” cows could begin shedding during the period you are feeding their milk to calves.
- Cow Management – All Johne’s cows should be served to beef semen once aware of the disease, this limits the spread of infection to current dairy offspring and means the disease can be eradicated from the herd at an accelerated rate. Johne’s cows fertility as shown above is compromised as a result of the infection so number of services should be limited in order to avoid losing both time and money on unhealthy animals
- Culling of Johne’s Cows – If Johne’s infection is above 10% within the herd then Johne’s cows should be selected periodically for culling, since the incidence is high it would be difficult to cull all positive animals, however the older infected animals should be culled and the younger ones managed as suggested above. If Johne’s incidence is below 10% farmers should consider culling all Johne’s cow’s dependant on the number of replacements available, and other animals to be culled.
- Explore other options – If Johne’s incidence is particularly high and uncontrollable, farmers should continue to test but consider moving to a flying herd system in order to avoid breeding additional Johne’s infected cattle into the milking herd. Some Johne’s cattle would be bought in but with regular testing this number should slowly become manageable which will mean the herd can move back to rearing their own replacements.
In conclusion it is clear that Johne’s disease has a significant impact on herd performance by the research data that is currently available.
The steps outlined here will allow you to make the necessary changes needed to achieve eradication in accordance with the UK’ Johne’s free’ campaign. It will in the long term, improve herd health as well as herd performance.
Decreasing Johne’s incidence is an effective measure in order to improve efficiency within your dairy herd This will result in increased overall revenue which will prove crucial given the current situation within the dairy industry.
Written by Will Astley – Dairy Technical Specialist