BY- Dr Stephanie Bullen
Maffra Veterinary Centre
Facial eczema (FE) can have substantial impacts on the productivity, health and welfare of dairy cattle as seen in outbreaks across Gippsland between January and April 2011.
FE occurs as a result of ingestion of the sporidesmin toxin, produced by the fungus Pithomyces chartarum which grows mainly on rye grasses. The spores are absorbed across the gastrointestinal tract and cause damage to the liver, bladder and mammary gland.
Despite its name, FE is not a skin disease. Photosensitisation of the skin occurs secondary to liver and bile duct blockage, typically two weeks after ingestion. Therefore in outbreak situations, the majority of affected animals may have little or no obvious skin lesions and it is liver damage that causes the greatest economic impact.
Cows affected by FE may have initial transient diarrhoea followed by a sudden drop in milk production. This is followed by skin irritation, restlessness, shade seeking, weight loss, large sheets of skin sloughing and occasionally blood-stained urine and jaundice.
Weather conditions favorable for the growth of P. chartarum occur in late summer and autumn (generally January – May) when periods of rain or high humidity occur with high night-time minimum temperatures.
In response to the major 2011 outbreaks of FE, Dairy Australia initiated a program to measure pasture fungal spore counts on 24 sentinel farms across Gippsland.
Spore counting begins in January each year and a general alert to farmers is issued if spore counts rise to dangerous levels. In such situations, farmers are strongly advised to consider monitoring their own spore counts and start feeding zinc oxide supplements to their herd.
Spore counting services are currently offered by the West Gippsland Veterinary Centre, Tarwin Veterinary Group, Yarram Veterinary Centre and the Maffra Veterinary Centre. These clinics will be able to provide additional information on the method for collecting pasture samples for spore counting.
Farmers can find more information and keep track of local pasture spore counts at the Dairy Australia facial eczema pasture spore monitoring page at www.dairyaustralia.com.au/facialeczema
There are various control and prevention strategies for facial eczema. In Australia, the inclusion of zinc oxide in feed is the most widespread prevention strategy.
Zinc works by forming a complex with sporidesmin which limits its ability to cause oxidative damage. The desired dietary intake of elemental zinc is 20mg/kg live weight/day and should start two to three weeks before pastures become toxic.
However, an important risk with this strategy is the potential for zinc toxicity because the amount of zinc required to prevent FE is close to the level that is likely to cause toxic effects.
Therefore, it is imperative that the correct procedures are followed and farmers work closely with their stock feed suppliers, vet and nutrition advisor to ensure their preventative programs are effective and safe.