Facial eczema is a condition caused by the spores of a fungus commonly found living on ryegrass. Hot and humid weather triggers the fungus to ramp up spore production, so spore numbers can explode given the right conditions. The most obvious sign of the disease is sunburn in ruminant animals, which is where the somewhat misleading name ‘facial eczema’ has come from. The sun damaged faces and udders of affected animals are however just an indicator of a more sinister chain of events happening in the animal:
- When spores are consumed by animals grazing the pasture, they release a potent mycotoxin into the gastrointestinal tract.
- This toxin is then absorbed into the bloodstream and is directed to the liver for detoxification.
- The liver becomes overwhelmed with the toxin and liver damage results (in particular, we see bile duct thickening and blockages).
- A damaged liver is unable to effectively process chlorophyll (found in grass) so a breakdown product of chlorophyll spills over into the blood and it is the elevated levels of this breakdown product circulating in the blood that causes sensitivity to the sun.
As you can see it is a complicated domino effect – so by the time you physically see the problem, such as photosensitivity, the animals are already suffering with liver damage.
If you live in an area of New Zealand that is affected by facial eczema due to climatic conditions (most of the North Island and the top of the South) it is worth keeping your eye on local spore levels. This data is often given out free of charge by vet clinics. District averages are helpful for understanding facial eczema risk but spore counts can be different across a farm at any one time, let alone from farm to farm, so you may want to do some spore counts on your property.
There are some ways to prevent the spores causing liver damage:
- Take animals off pasture that has
a high spore count – although
this is often not the most
- Fungicides can help to reduce the spore count by hitting the fungus before it produces spores and can be targeted at the worst paddocks.
- Feeding high levels of zinc
Zinc forms a complex with the toxin which inhibits its ability to cause damage in the liver. Zinc can be delivered to stock via water, boluses or bulk NRM compound feed and blends formulated with a high zinc level specifically for preventing facial eczema. For people with less stock, NRM’s MultiFeed Nuts + Zinc in 20kg bags is a great option for aiding in the prevention of facial eczema in cattle and sheep. Just make sure you follow the feeding rates on the bag as it is important to dose the right among of zinc per kilogram of body weight to ensure adequate coverage.
It is also best to start delivering the zinc a few weeks before spores reach dangerous levels so talk to your vet and try to pre-empt the danger period. Feeding high amounts of zinc for extended periods of time can cause toxicity, so ensure that you do not
feed high levels of zinc for longer than
a 100-day period.
For further information, contact your local Nutritional Specialist or the friendly team at your local Farmlands store.
Article supplied by Stacey Cosnett, NRM Nutritionist.