Emma has been involved with FE research that surveyed 106 farms in the North Island, which produced some startling findings.
“One-third of farms had cows with subclinical damage to their livers, which the farmers didn’t know about and two-thirds of farms who gave zinc as a preventative measure were under-dosing.”
Not all animals with FE will show clinical symptoms. It is estimated for every three in 100 cows showing FE, another 70% of the herd might have subclinical FE.
Under-dosing animals by not getting average weights and not checking the delivery system is providing enough zinc are common findings on farms where FE is an issue Cuttance says.
“Farmers really need to be doing regular pasture spore counts at the start of the season and the end of the season when they are going to be making decisions about starting and stopping treatment. This means decisions are informed and based off some data instead of a gut feeling.”
There was a difference between farms and also between individual paddocks, which highlighted the need for accurate testing.
“If spore counts are being done properly to assess the FE risk on your farm, you should be getting a representative sample from a selection of four paddocks across the farm fortnightly or weekly when spore counts start to appear. The sample needs to include grass collected from multiple spots along the diagonal of a paddock and cut just about ground level approximately 1cm.”
There are a variety of ways to dose zinc, from water treatments through to zinc capsules. The more control the cow has over the intake of zinc, the less effective the treatment tends to be, Cuttance says.
Her research showed some of the myths about lime and nitrogen being good for management of FE didn’t have any effect.
“We also looked into different pastures for FE-tolerance. It’s known that chicory and plantain are FE-safe but people tend to sow these with ryegrasses which has been shown to be just as dangerous as ryegrass on its own. Tall fescue has shown promising results with lower spore counts when it is in pure swards.”
Similar research was done in the 1980s, but the current results were worse.
“Although there’s likely other factors involved, it does indicate we aren’t managing it any better. We need to get smarter with what we are doing.”
What is facial eczema?
The fungus Pithomyces chartarum, which grows in the dead litter at the base of pasture, produces a toxin called sporidesmin. When ingested the toxin causes damage to the liver and its bile ducts. Oedema and swelling reduce the number of open bile ducts and fibrous tissue replaces liver cells, reducing the liver’s capacity to get rid of waste product. The waste product of chlorophyll, phylloerythrin, begins to build up in the liver and goes into the blood stream. Phylloerythrin is a photosensitising agent and causes the clinical signs of FE. Zinc binds to the sporidesmin molecule, stabilising it and preventing it from damaging liver and bile duct cells. However, zinc must be at the correct concentration in the blood in order to be effective, (20-30 µmol/L).
