Fungus threat to dairy cows soars

The facial eczema threat to dairy herds has soared to critical levels in parts of Taranaki this week in perfect growing conditions.

Some monitor sites which had zero counts last week are showing big readings. At Victoria Rd, Oakura, the count rose from 130,000 to 270,000. High counts are being recorded through the region. Pastures may be toxic once spore counts reach above 40,000.

"This is the first big jump in spore counts this season," says Stephen Hopkinson, of Taranaki Veterinary Services. "We would expect to see clinical signs to start showing next week if cows graze that pasture.

"Farmers should be using full dose zinc now because March has been the worst month for FE in the past few years, so we have another month to go and it could well get higher.

"It was pretty bad last year and with this week's warm weather and rain I'm picking it could be worse."

The counts had reached a critical level and the cows had only to graze an affected paddock once to be infected.

"There is not much else they can do but drench with zinc," he said.

"We haven't seen any clinical signs yet in cows on farms we service, but farmers who feed turnips have been noticing skin photo-sensitisation that looks like eczema."

Facial eczema is a disease which causes lowered production and sometimes death from liver damage. 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. Exposed unpigmented or thin skin thickens and peels.

Badly damaged liver tissue will not regenerate. The animal may die when under stress such as calving, but early zinc treatment usually prevents liver damage.

The fungus produces spores when grass minimum temper-atures are above 12 degrees Celcius 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.

- © Fairfax NZ News