Season for zinc as fungi threatens
With warmer weather, grasses and weeds are flourishing. In a short time, fungi will be having a party as well.
The fungus Pithomyces chartarum, which causes facial eczema, produces lots of spores. For cattle, accidentally eating the spores leads to liver damage, subsequent photosensitisation and often horrific skin lesions. By the time 5 per cent of a herd has obvious skin damage, up to 70 per cent of the herd will be liver-damaged and at real risk of developing skin signs.
Spore counting on your farm may help you manage the disease. It will give you an indication of the facial eczema risk on your farm or in specific paddocks.
We advise supplementation with zinc from January to May. It is important to remember that no zinc treatment regime will provide full protection in situations where spore challenge is high. Therefore, careful observation of stock is needed to ensure you intervene at the earliest signs of disease.
Zinc oxide drenching is an option in some dairy herds. It is preferable to drench animals daily, to provide consistent levels of zinc. Over-dosing with zinc can predispose cows to milk fever. Start drenching at half rates and increase slowly for a week or so to reduce the risk of milk fever.
Zinc sulphate added to the animals’ drinking water source is another option. But water uptake of minerals is not guaranteed, even if using an in-line dispenser. Zinc sulphate comes in two forms – monozinc and zinc heptahydrate. The dosage required for monozinc is lower than for zinc heptahydrate; in fact it is almost half. Animals may take time to adapt to the taste of the zinc sulphate in the water so gradually increase to a full dose.