How Johne’s management cut disease to less than 2% of herd

Consistent efforts to prevent Johne’s disease in a high-yielding Wiltshire dairy herd have resulted in cases falling from a high of 25% (cows identified as Johne’s positive or high risk) to 2%.

Rob Pickford and his vet started noticing clinical signs of Johne’s at Upper Farm, Calne, about 25 years ago.

In 2009, before the National Johne’s Management Plan was developed, they decided to do a whole-herd screen. Since then, they have been improving their approach to Johne’s management and control.

See also: Advice on vaccination protocols for dairy herds

Tom Oxtoby (left) and Rob Pickford © Thoma Washbourne/AHDB

Farm facts 

• Upper Farm, Calne, Wiltshire
• 465ha farmed
• 270-head Holstein and Holstein-Friesian herd, calving in a split block
• Average yield 12,500 litres
• Paddock grazing through summer
• Arable cropping

As well as clinical cases, recovery of animals from other conditions such as left displaced abomasum operations and mastitis was poor, says the farm’s vet of 22 years, Tom Oxtoby, of George Farm Vets.

“We were concerned that there might be a connection between the fact that we were seeing clinical Johne’s cases and having these other problems,” he explains.

“Originally, the only thing we were doing was testing and managing the culls,” says Rob. “Then we started managing [the disease], and that’s when results started coming down.”

He now screens the whole herd quarterly, using individual milk samples that are tested for antibodies, and keeping detailed records of any results that suggest a medium or high risk for Johne’s. Four cows showed as Johne’s positive on the most recent test.

His prevention plan, which he shared at a recent AHDB meeting on tackling Johne’s, includes:

1. Culling On the National Milk Records (NMR) scoring, a figure of more than 30% is positive, and the higher the positivity, the higher the risk of those cows spreading the disease among other animals. Therefore, any animal at Upper Farm that has two scores above 60% or one score over 100% (the maximum score is 290%) is earmarked for culling as soon as possible.
2. Management of high-risk animals High-risk animals are tagged and kept away from the maternity area of non-infected cows.This is to prevent any contamination of the calving area. They are inseminated early in the block and calve in the dry shed.
3. Breeding Johne’s-positive animals not culled are only bred to beef, so no replacement heifers are born to positive mothers.
4. Calves born to Johne’s- positive mothers These are immediately removed from the cow to minimise chance of contact with any infected milk or faeces. They are reared separately from the rest of the calves until weaning.
5. Calf feeding Calves are fed milk powder rather than whole milk. Colostrum is only used from cows recorded as negative at the last Johne’s screen.
6. Hygiene Calves are reared in a separate building and strict hygiene and biosecurity protocols are in place to minimise the risk of transfer of infected muck from the adult herd to the youngstock housing.
7. Protocols All protocols are established following a review of the previous calving. This is done by Rob, Tom and the herd manager, before a discussion with the wider team to get their input on practicality. The protocols are checked and refreshed every six months.
8. Closed herd The aim is to keep a closed herd, through use of artificial insemination. Calving across two blocks gives the option of moving cows from one block to the next if needed. If heifers did have to be purchased, they would be blood tested on arrival.
9. Monitoring For any cows on the high-risk list, their daughters in the herd are monitored and only served to beef semen.

Where to start

“It’s been a long, slow process, but we’ve made very significant progress,” says Tom, attributing the success to Rob and his team’s consistency and attention to detail.

However he says a prevention plan does not have to be comprehensive from the start – a farm with Johne’s or unknown Johne’s status can begin with some simple steps and easy wins.

And testing is the first step. “You can’t do a Johne’s control plan without knowing the status of your cows,” he says. “Bulk testing is very unreliable. You need to do individual cow testing.”

While some testing is better than none at all, whole-herd testing four times a year is best to pick up the infection in the early stages and make management decisions for individual animals.

The first “big-win” management intervention Tom recommends is keeping Johne’s-positive animals away from the calving environment of the rest of the herd.

Not buying any stock from herds with an unknown Johne’s status is also key, he adds.

“There is no downside to improving the Johne’s control of your herd,” says Tom, explaining that the cost-benefit is well established in improving the health, welfare, production and longevity of the herd.

He also stresses that while a prevention plan is already a requirement of some contracts, it is likely to be demanded by more buyers and is important from a public perception point of view.

Perseverance pays

Karen Bond, veterinary adviser at NMR, believes that a “fear factor” puts some farmers off tackling the disease. “They’re worried they’re going to find something awful that they can’t do anything about. [But]

I’ve worked with some farms who are in a really bad place, and we can do things about it,” she says.

The complex nature of the disease can also make it more difficult for farmers to manage, because it will take a few years before the benefits of Johne’s management will be seen.

Sometimes, when they start trying to tackle it, they will see numbers of positive test results go up for the first couple of years. That is because those animals were infected before the management plan was in place.

“When MAP [Mycobacterium avium subspecies paratuberculosis] enters the calf’s body, it hides inside white blood cells and lies dormant for a while,” explains Karen.

This is why there is no point testing youngstock for antibodies.It is not until the cow is put under a level of stress, such as calving or lameness, that the bacteria come out of the blood cells, multiply, and trigger an immune response.

Once the immune system starts attacking the bacteria, it retreats and hides again, which can cause test results to appear negative after a previous positive result (see diagram).

Because false positives are uncommon, she says it is safest to treat any animal cautiously after a positive result to prevent the “one to many” transmission that could occur if one cow infects many calves.

“We’re not going to eradicate Johne’s – it’s just not really feasible – so we’re trying to take it from being a problem, to being a minor inconvenience,” says Karen. The target for that is 1-1.5% prevalence within a herd.