Facial eczema is the clinical indicator of a disease of the liver, which is caused by ingestion of the toxic mycotoxin sporidesmin, produced by the fungus Pithomyces Chartarum, which is found in ryegrass-dominant pastures.
The cow grazes and ingests the toxin. Hot and humid weather creates an environment for spores to multiply rapidly.
The spores affect the bile ducts in the liver and cause damage to the liver, bladder, face, ears, vulva and mammary glands.
In animals where the infection is obvious, the skin reddens, then becomes crusty and dark. Eventually the skin peels off, leaving large raw areas susceptible to infections and flystrike. Affected animals may collapse in severe pain.
Unfortunately, animals can also be affected without showing significant outward symptoms of infection.
According to research from ProDairy, up to 80 per cent of affected animals show no clinical signs of toxicity. But their milk production, general health and reproductivity diminishes.
Gippsland’s Herd Solutions vet Chelsea Hair said the current weather conditions were ideal for a rapid increase in facial eczema incidences.
“The fungus loves hot, humid weather conditions,” Dr Hair said.
“A lot of dairy farmers know they should talk to their feed nutritionist about how to supplement their cows’ feed with zinc before the onset of these sort of conditions.”
When the bile duct and liver damage occurs, cows are obviously affected with photosensitivity, sunburn that looks like scaling of the skin.
“A common indication is scaling of the unpigmented skin, like the nose and udders are affected,” Dr Hair said.
“And white cows are obviously more severely affected, because they have huge amounts of unpigmented skin.
“But it’s more the stuff you can’t see that you need to worry about, too.
“Because it affects bile ducts, you’re going to get chronic scarring of those bile ducts.”
There are also risks with feeding zinc supplements, which is why it should be in consultation with a feed nutritionist.
“You should only feed zinc for 100 days before you get toxicity effects,” Dr Hair said.
“There’s a risk from giving the cows too much zinc.
“There’s a bit of a lag from when you start putting zinc into the feed before it becomes protective.
“But it’s better to start putting it in now than not do it at all.”
Facial eczema is painful for the cow, and a significant animal welfare problem.
Skin lesions typically occur two weeks after first ingestion of the spores and lead to death, reduced weight gain and poor reproductive performance.
Nutritionists with Reids Stockfeeds have noted outbreaks of facial eczema in all dairy regions of Victoria and coastal areas of Australia.
Dairy farmers are recommended to avoid, if possible, close grazing of pasture, avoid putting cows into paddocks that have been cut for hay or late-topped, consider growing summer crops and alternate grazing between native and improved pastures if feasible.
Pasture spore counts can be proactively monitored, allowing for early intervention.
There is more information about facial eczema on the Dairy Australia website.
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