Saturday, December 9, 2023

Debunking FE myths and managing the disease

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Misinformation and fantastical tales abound about facial eczema but one vet says farmers need to get past these and manage the disease.
Only a handful of cases of facial eczema in cows will show visible signs of the disease.
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This article first appeared in our sister publication, Dairy Farmer.

Farm veterinarian and researcher Emma Cuttance has heard every tall tale imaginable when it comes to facial eczema (FE) prevention.

One  of her favourite stories is that FE-infected cows die during calving time because they have lived off their unborn calf’s liver, she told farmers at a Smaller Milk and Supply Herds (SMASH) field day at Eureka in Waikato.

The calf then gets born and the cow does not have a liver to live off.

“That’s one of the wonderful myths that’s come out.”

It had taken people 70 years to realise that FE was a fungus, she said.

“From here to now, there’s been an amazing amount of bullshit that’s come out about facial eczema.”

Other falsehoods include that rain or cold weather reduces FE-causing spores, or that mushrooms growing in paddocks are a sign it is time to get a spore count done.

Cuttance said her ultimate favourite is that farmers do not need to spore count “because you can watch the white butterflies. They tell you everything you need to know if FE is a problem. 

“As an industry, you guys have heard all of this crap and somehow we have to be able to manage this disease properly,” she said.

All of this misinformation makes it harder for farmers to treat when it was found. The key to managing FE using information directly specific to the farm in question. 

There are three key areas for managing FE – understanding the disease, dealing with the fungus and knowing how to prevent it.

“This disease is all about the liver,” she said.

“You’re not going to see it. You’ll have it, I guarantee it, but you won’t see it.”

Farmers cannot tell by looking at their cows if they are infected or not, and studies in 2014 and 2022 showed one third of farms in New Zealand have cattle with significant liver damage.

“Most of the time farmers wouldn’t have any clue whatsoever.”

This impacts the cow’s performance because the liver is the body’s powerhouse, including its waste disposal unit. If this is compromised, the cow cannot get rid of toxins in its body.

For the cow, it drops its milk production, not by a little but by an enormous amount. It is also an animal welfare issue, and farmers can manage it to make it better and prevent clinical cases.

Farmers need to consider what conditions are like at pasture level for the fungus that causes FE. It thrives in humid weather with temperatures around 24degC.

The fungus’s spores move with air currents and water films, and will shift if someone walks through an infected pasture.

“They have found spores 6m high in the air,” she said.

Breeding is playing an increasingly important role in FE prevention because at some future stage regulators may start paying closer scrutiny to zinc usage on farms.

“No one’s said it yet, but it’s going to happen I’m absolutely certain of it,”  Cuttance said.

The best way to recognise and avoid the toxin causing FE is through spore counting – and farmers need to understand its limitations so they can use the method the best way they can.

The counts are extremely variable with samples taken from neighbouring farms nothing alike. 

“Your farm is totally different because the micro environment for that spore is totally different to someone else’s farm.”

They also vary between paddocks on the same farm and between grasses within each paddock, which affects the spore count results even more.

Most importantly, farmers should manage their risk based only on the spore counts from their own farm. 

Regional or district counts should only ever be used as a guide. When those counts start climbing,  samples should be taken from their own farm. Making decisions based on someone else’s spore counts is extremely risky.

The samples need to be from the same paddocks every week until the farmer’s management programme starts.

Using crops such as plantain, chicory or other types of supplementary feed in the cow’s diet is another method of avoiding FE as spores tend not to grow on these species.

Zinc is the most common suppression tool used to reduce FE risk. However, for it to work, large concentrations are required. In a 2013 study where animals were blood tested, it was found that only 40% of farmers were using zinc in sufficient quantities to impact the toxin that causes FE. 

A second test last year using bulk milk samples showed that 81% of farmers did not have enough zinc.

“Zinc absolutely works but you have got to have enough to make a difference,” Cuttance said.

Often the dosage is not calculated right because not enough farmers weigh their cattle.

Adding zinc to water is common but problematic because of the amount of variability in what cows drink, the potential for water leaks – and the fact that it makes the water taste awful.

Zinc can also be added to feed. This, too, has issues around mixing and consumption variation among the cows. 

Capsules are increasingly popular but should only be administered after spore counts are completed and show that spore numbers are above the risk threshold.

One of the best ways to ensure the correct dosage for each cow is drenching because it allows the farmer to control the dosage. 

Key to a proper FE management plan is getting enough information to see if what is being done is working.

A farm properly managing FE gets spore counts from their own farm, has a management plan, monitors that plan, adjusts it if necessary and retains this plan until the spore counts are lowered.

The moment that farmers start guessing spore count numbers or zinc dosages is the moment their plan falls over, Cuttance said.

Around 88% of farmers believe their FE management plan is effective, according to a 2022 survey. Cuttance believes this is so high because farmers only see a handful of cases where the visible signs of the disease are seen. 

“If you find yourself saying, ‘This season’s going pretty good because I’ve only got two cows with eczema’, that’s when you need to check yourself and say, ‘Holy crap I’ve probably got 100.’

“That’s the mind change we need to have.”

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