Our last Sheep and Beef Discussion Group was held at Alister Reeves farm and centred around reflecting on the horrendous facial eczema season we all experienced earlier this year. We discussed the latest research, where we are up to with genetics and Ramguard Gold. The session was very well attended with lots of productive discussion and a sociable barbeque. If you are interested in attending future discussion groups, make sure you are on our mail out list for these events.
The following is a summary of the day’s important points.
Facial Eczema FACTS
• P. chartarum is the fungus which causes Facial Eczema; it is widespread throughout the world but not all of these fungi produce the Sporidesmin toxin.
• New Zealand types of fungi seem to almost all produce the toxin, where as in other countries it ranges from 2%-67%.
• How long sporidesmin levels in spores last after sporulation is uncertain.
• Greatest concentration of spores occurs at the base of the sward.
• Germination of the fungus is all year round but sporulation is very seasonal; it is only the spores which cause problems.
• There is no fixed danger period, and it may extend for up to 100 days.
• Onset of cold weather doesn’t mean the end of the danger period; spores will still be there.
• Hills are worse than flats not better.
• Rain does not wash spores away.
Treatment and Prevention
• Remember Facial Eczema is NOT a skin disease; the skin damage is a result of damage to the liver caused by the sporidesmin toxin.
• It is common to have a significant FE problem without animals showing photosensitisation. In cattle it has been shown that it is the 80% of cattle that have no skin lesions, but do have liver damage, that cause the major economic impact.
• Facial Eczema doesn’t just occur on white skin, even black cattle get FE; all animals have a liver!
• Zinc can only help prevent FE. It cannot reverse liver damage already done by sporidesmin.
1 . MONITORING using spore counts is vital to know when to treat. Subscribe to the Gribbles website for weekly spore counts in the area, contact the clinic for more local information, do your own counts, or become one of our monitor farms.
2. AVOIDING The toxin is an important part of FE control; this involves managing pre and post grazing heights, increasing summer survival of grasses, moving animals to safer ryegrass pasture (spore counted), the use of alternative pasture e.g. chicory, clover and plantain and feeding low risk conserved forage or supplements.
3. SUPPRESSING the toxin with fungicide can be a useful way of controlling FE, although it is not always economical or practical on many sheep and beef farms.
4. PROTECTING the animals with Zinc. Zinc works by forming a complex with sporidesmin which prevents the production of free radicals, which cause cell damage. Zinc also inhibits intestinal absorption of Copper which is a catalyst in the reaction.
• Zinc Sulphate in drinking water – this is the least effective method, though widely used, it is now known to not cover animals in high risk periods and should only be used in low risk periods.
• Zinc Oxide by oral drench – less commonly used now due to frequency required etc.
• Zinc Oxide in feed – this is common on dairy farms with high levels of feeding.
• Both Zinc Sulphate and Zinc Oxide need to come from reputable suppliers with certificates of analysis. It can be contaminated with heavy metals and the concentrations can vary.
• Zinc Oxide Boluses – such as Faceguard and Time Capsules; controlled release intra-ruminal boluses are a safe and effective way of administering Zinc and they last four to six weeks and can be repeated.
• Remember Zinc can be toxic if given at too high a dose rate, but can be readily monitored by blood sample.
Copper Supplementation and FE
• Prolonged supplementation with zinc has been associated with low blood and liver copper levels, although it has not been shown to induce clinical copper deficiency.
• Zinc competes with copper for absorption in the gut and possibly at the cellular level.
• Copper supplementation given with or prior to zinc dosing, to counteract this effect, has been shown to reduce the effect of zinc in preventing FE.
• Reduced availability of copper is possibly one of the ways that zinc protects against FE. We know copper is involved in the production of free radicals which cause the liver damage, reducing the copper levels presumably limits this reaction.
• Copper levels should be assessed prior to zinc supplementation and copper should not be given during the FE season.
Genetic Selection For FE Tolerance
One of the most important methods of FE control in sheep, is to genetically select for tolerance. Buying FE tolerant rams is an effective way to help prevent FE on your farm. It is important though to understand how this works to optimise the success of using FE tolerant genetics.
FE tolerance is a highly heritable trait, quantified at 0.42. This means that 42% of a ram’s offspring will carry his ‘tolerant’ genes and, of course 58% of his offspring will not carry his tolerant genes. All his offspring will also carry the ewe’s genes, so any effect in the lambs will always be diluted by 50%, by the maternal genetics. So when first introducing an FE tolerant ram after one season, 42% of his lambs will have half his genetics. This demonstrates why it takes a number of years to lift the overall FE tolerance of the flock. This also reinforces the importance of knowing how long any ram breeder has been testing, and you should always ask your breeder this question.
The Ramguard FE tolerance testing service is a list of SIL ram breeders selecting for FE. However there is a wide variety of sporedesmin dose rates used within the scheme and it is important to know what level the rams are being exposed to. Due to this confusion, the FEGold brand was formed. To join this brand, breeders must fulfil the following criteria:
• Testing with Sporidesmin at 0.60mg/kg
• At least 10 years of testing history
• 10% of sale rams tested for facial eczema tolerance
• All rams used are Ramguard tested
The conclusion of all this information is that no one single prevention or control method is sufficient. In years of overwhelming challenge, such as this last season, even highly tolerant animals can be overcome and in these circumstances giving a Zinc bolus to young or valuable stock is not a failure of the system and will not affect their FE tolerance. It will hopefully keep them alive and productive. Using spore counts on your farm is the best way to know what is going on, and gives you the best indication of when to treat. Although this year was exceptionally bad for FE, all indications are that FE is likely to become worse and more widespread in the face of global warming.