Kati-Kati High school student joins fight against Facial Eczema on farms
Pippa Grierson, is currently a student at KatiKati college in her last year of school. For the past four years she has been researching the effect that Agricultural Lime has on killing toxic Facial Eczema spores, both in the short and long term. Below she explains her research into the ongoing issues of Facial Eczema and the interesting results her investigation has uncovered.
The Biology of Facial Eczema
Facial Eczema is caused by animals ingesting toxic spores from the fungus Pithomyces chartarum that grows in the dead litter layer of pasture. When climatic conditions are favourable (warm and humid), the fungus produces large numbers of these spores, which contain a toxin called sporidesmin. Sporidesmin causes severe and irreversible liver damage, and the liver damage is the underlying cause of the symptoms displayed in the animal. The symptoms you see in the affected animal are -
1. Liver damage - stock will be generally unwell, go off their food and lose weight. Dairy cows will show a drop in milk production, while sheep can show a reduction in wool production. Reproductive losses can be severe and deaths from sudden liver failure are common. Serious long-term health problems can occur in animals that have recovered from liver damage.
2. Classic Facial Eczema (photosensitivity) - this is the most obvious sign of the disease and often only a few animals with liver damage show classic facial eczema. As a result of liver damage, the animal’s skin can become overly sensitive to sunlight, a process called “photosensitisation”. This results in severe sunburn, mostly on the head and face and exposed areas of the body. Animals will be restless, seek shade and scratch or rub at their face and shake their head, their ears will tend to droop and the eyes may close as the face swells. Over the next few weeks, the burnt skin becomes thickened and leathery, and will eventually peel off. Because there is really no effective treatment for facial eczema, once an animal has facial eczema the emphasis is on prevention.
I first started this project as a school science fair, with the idea suggested to me by my father who had noticed a difference in spore counts between the limed and un-limed paddocks on his home farm in Otorohanga whilst growing up.
Lime reduces spores counts in trial. From my research I have found that in the short term, weekly or fortnightly sampling and spore counting showed that Ag. Lime applied at 2.5 t/ha reduced the numbers of facial eczema spores within 7 days from 110,000 to 5,000 spores/g and maintained spore numbers below the danger level of 50,000 spores/g . In the long term 2008 spore counts on plots last treated with Ag. Lime in 2007 averaged a count of 15 714spores/g leaf, 2006 averaged a count of 39 286spores/g leaf and 2005 average count of 58 571spores/g leaf, considerably below the 2008 control plot which had counts ranging from 75 000 to 230 000, with a mean of 148 571 spores/g.
A significant decrease in spore counts can be seen in as little as seven days from applying
The results show that once applied the Ag. Lime decreased the spore counts within 7 days of application and in the long term kept spores down for three years. Even though the Ag. Lime con¬centration had decreased over the four years , the number of spores had just reached the crucial 50 000 spore count, which is the danger level.
This backs up my theory that over time the residual effect of the Ag. Lime decreases, so from a farming perspective I would recommend a re-application of Ag. Lime at 2.5T/ha in the fourth year, or tactical use by sectioning the farm into thirds and applying Ag. Lime annually to a different third of the farm.
The short term and long term results show a repeating trend of 2005, in the 2006, 2007 and 2008 trial plots. Also by repetitions of trials have shown that the Ag. Lime still has an effective short term effect upon the spore counts even in years with extremely high spore counts such as 230 000 spores/g. So as a prevention method for facial eczema, my trials have proven Ag. Lime as a very effective, and well worth use by farmers.