Protect that wound
As New Zealand’s vineyards gain in age, the risk of them being affected by trunk disease increases.
DairyNZ says fungal spores produced by the fungus Pithomyces chartarum growing on pasture produce a toxin which when ingested by cattle damage the liver and bile ducts.
The damaged liver cannot rid the body of wastes and a breakdown product of chlorophyll builds up in the body causing sensitivity to sunlight, which in turn causes inflammation of the skin.
The first sign of FE is a drop in milk production occurring soon after the intake of toxic spores (subclinical FE). Cows are restless at milking time, seek shade and lick their udder. Another drop in production occurs when physical symptoms (clinical FE) become obvious. Exposed unpigmented or thin skin thickens and peels. Watch white areas, teats, inside the hind legs, and the udder and udder support area.
Not all animals affected with FE show physical symptoms (i.e. clinical FE) though liver damage has occurred. Milk production of animals with subclinical FE can be depressed by up to 50%.
It is estimated for every three in 100 cows showing clinical FE, about 70% of the herd may have subclinical FE.
Badly damaged liver tissue will not regenerate. Chronic wasting and/or death may occur at the time of damage or months later when the animal is under stress, e.g. calving.
The fungus produces spores when grass minimum temperatures are above 12°C for two or three nights and humidity is high (usually January to May). The fungus grows on soft litter at the base of the pasture so hard grazing during danger periods increases the risk of spore intake as does topping which increases the build-up of soft litter.
