Animals – Facial eczema prevention

The current warm, wet conditions are ideal for fungi growth on pasture grasses, some of which have toxic effects on grazing animals. Farmers and lifestyle block farmers with ruminants (cattle, sheep and goats) or camelids (llamas and alpacas) should be monitoring for the facial eczema causing spores of the fungus Pithomyces chartarum. I recommend dung sampling animals to assess levels of spores being eaten (the fungal toxins are absorbed and the spores then pass out in the dung). Pasture sampling can also be used to assess the level of pasture contamination. Under a microscope, the fungal spores resemble pineapple shaped hand-grenades which is a good metaphor for the effects the spores produce in the liver of animals, where the toxin sporodesmin is concentrated in bile. The toxic sporodesmin destroys bile ducts, damaging surrounding liver tissue, which in extreme cases causes liver failure and death. The secondary effects of this liver damage mean that chlorophyll from the green grasses can not be excreted completely and the ensuing high levels become photodynamic under the skin causing burning, especially in white areas of cattle and around the face and ears on sheep. This latter effect gives the disease its facial eczema name.

The fungus grows on dead leaf material around the base of pasture plants. Animals which graze pasture often eat specific areas, especially with high clover plant populations, right down to the ground, thereby also eating the dead leaf material as a component along with the tasty clover plants. So it is a misconception that light grazing pasture (animals only need to eat the top of the plants to obtain a good meal) will prevent the animals eating the toxic spores.

Commercial sheep farmers in the Rodney region purchase or genetically select animals which can withstand higher levels of the toxic spores. Selection of rams with facial eczema tolerance is good advice and while improved tolerance is achieved in a single generation, up to six generations is required to increase the gene frequency in a flock to a level where significant facial eczema tolerance is achieved.

To get a facial eczema tolerant flock quickly, buy in stock with good tolerance levels and continue to use rams with high facial eczema tolerance. Increasing levels of zinc in ruminants’ diets has been found to aid protection from facial eczema damage and most commercial farms use this option for facial eczema prevention. Zinc can be used in several forms including boluses which are inserted orally, zinc oxide which is added to feed daily, and zinc sulphate which can be added to drinking water. Ruminants and camelids in Northland benefit from facial eczema prevention in the autumn.