Facial eczema is a common condition that affects cattle, sheep and deer during summer and early autumn. Once confined to East Gippsland, cases are now frequently detected throughout Victoria, Tasmania and New Zealand.
Facial eczema is a common condition that affects cattle, sheep and deer during summer and early autumn. Once confined to East Gippsland, cases are now frequently detected throughout Victoria, Tasmania and New Zealand continues to observe a growing geographical footprint of affected regions.
The initial clinical symptoms observed that are associated with facial eczema are a sudden reduction in milk production within individual cows that is often accompanied with profuse diarrhoea, followed later by the loss of skin on lighter areas of the hide. The condition is particularly prevalent in Holstein cattle, but all breeds can be severely affected. Unfortunately, these external symptoms only occur after the main effect – bile duct damage of the liver – has occurred.
Hepatobiliary (of the liver and bile ducts) damage occurs after exposure to a potent mycotoxin (sporidesmin), which is released in the gut of the animal after it ingests the spores of the fungus, Pithomyces chartarum. This fungus grows on dead and decaying leaf material found at the base of grasses, particularly Perennial ryegrass.
Sporidesmin can cause extensive blockage and damage to the bile ducts of the liver, making the cow unable process chlorophyll which results in photosensitivity, a condition in which the skin becomes very sensitive to sunlight.
The toxin has also been found to affect mammary tissue and the bladder of the affected animal. Typically, these visible signs occur several days after the spores have been ingested and chronic damage has already occurred.
NZ research has shown that only about 10% of the animals affected by sporidesmin display the classical symptoms of skin loss. This means any damage to the liver or negative impact on production, health and fertility often goes unseen. Whilst cows have a natural ability to repair liver tissue, bile duct damage is less responsive meaning that affected animals will present as “hyper-sensitive” with any subsequent exposure.
The best protection is to prevent the damage in the first place by:
If facial eczema is a problem in your herd, monitor the spore levels of your pastures on a weekly basis. The Dairy Australia website contains a set of guidelines about how to take pasture samples and a list of vets who will undertake the spore count for you.
Avoid overgrazing ryegrass pastures during high-risk periods (i.e. summer and autumn, limited pasture availability, high humidity levels and high night-time temperatures). Remember the 10-10-10 rule of thumb, if you have 10 days when the minimum air temperature remains above 10°C and you receive above 10mm of rain, it is time to remain vigilant! Consider providing other fodder options, such as clover, paspalum or fescue pastures, herb and brassica crops, silage or concentrates, during high-risk periods. Limiting exposure to sporidesmin via reduced ryegrass grazing is effectively one of the strongest preventative actions available.
Topping and mulching your pastures may increase the risk of facial eczema outbreaks when left too late, as the residue produced sits around the base of the plant and provides the perfect environment for pithomyces chartarum to proliferate.
Providing an additional source of readily-available zinc in the ration is useful in reducing the risk of sub-clinical and clinical facial eczema. Most rations do not contain sufficient levels of zinc required to form chemical complexes with the toxin to prevent it from causing damage.
Lactating dairy cows require at least 20 mg of elemental zinc per kg of liveweight every day to protect them against facial eczema. This increases to 25mg per kg of liveweight in crisis situations. Ask your nutritional advisor about the amount of zinc oxide required to protect other classes of livestock or other species.
The provision of additional zinc in the ration requires close communication with your nutritional advisor. Any change in the feeding rate must be done under consultation with your advisor to ensure appropriate levels continue to be administered. Serum zinc levels should be monitored during high risk periods, especially when treatment levels of Zinc are offered for more than 90 days. Commence testing four weeks after additional zinc is added to the ration to monitor efficacy, blood serum zinc levels should be in the range of 20-35 umol/L in order to be adequate
Facial eczema should not be confused with forage brassica photosensitivity, which can also cause skin lesions. However, unlike facial eczema, fodder poisoning does not cause hepatobiliary, bladder or mammary tissue damage. Your veterinarian will test blood serum for an enzyme labelled “GGT” to confirm a diagnosis and to best assess the level of hepatobiliary damage that individual cows have been exposed to.
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Further reading: Dairy Australia website. Department of Natural Resources and the Environment Tasmania website.
Publication: “A Review Of Facial Eczema (Pithomycotoxicosis)”, © Copyright Dairy Australia 2011.
