Facial eczema risk higher this season, zinc oxide bolus to be made available

The heightened risk has prompted Dairy Australia to secure an emergency use permit for intra-ruminal zinc oxide boluses to help prevent the condition.

DA will host a webinar on Friday with Dr Andrew Dowling from New Zealand to explain how the boluses can be used by farmers to protect their herd this season.

Facial eczema is a liver disease, often accompanied by photosensitisation, caused by the spores of a pasture fungus that multiply rapidly in warm and humid conditions.

It can have devastating impacts on herd productivity and animal welfare.

Feeding the correct amount of zinc oxide in grain/concentrates at milking can be effective for facial eczema prevention in the milking herd.

However, dry stock, such as heifers, bulls and dry cows, are also at risk of facial eczema.

Dairy farmers are advised to stay informed about facial eczema risk as the high danger period approaches.

As the Bureau of Meteorology is indicating that south-eastern Australia could continue to expect higher than average rainfall this summer, spore numbers are anticipated to rise and so will the risk to cows and dry stock.

Pastures tend to become toxic in summer and autumn when periods of rain or high humidity occur in combination with high night-time minimum temperatures (typically 12 degrees Celsius for 2-3 nights).

Despite recent advances in weather forecasting, use of weather data alone to accurately predict facial eczema danger periods has not been successful in New Zealand or Australia.

DA has discontinued the spore monitoring program and is encouraging farmers to monitor their own spore counts throughout the high danger period.

Instructions for sampling pasture for facial eczema spore counting can be found on the Dairy Australia facial eczema page.

Samples should be refrigerated if not being processed immediately.

Spore counting costs between $20-$50 per sample and can be submitted to any of the following veterinary practices, either in person or by express post.

A dietary intake of elemental zinc of 20 milligrams per kilogram liveweight/day, fed as zinc oxide in grain/concentrates or administered as slow-release zinc oxide boluses, can be effective for facial eczema prevention.

Zinc oxide supplementation is most effective when introduced 2-3 weeks before pastures become toxic.

The concentration of elemental zinc and the level of impurities varies between different zinc oxide feed additives.

Therefore, farmers should ensure a certificate of analysis is provided by the supplier, that it is suitable for use in animal feeds, and the amount of zinc oxide included in each tonne of grain/concentrate or dose is carefully calculated.

Blood testing of cows in 12 herds during the 2019 season indicated that protective levels of zinc in the blood was most reliable when zinc oxide was fed in pelleted form.

More inconsistent results were achieved when zinc was fed via a mineral dispenser or in a powdered form.

If animals are underdosed (e.g. incorrect dose rate, settling out of the supplement, competition between cows) there may be inadequate protection from facial eczema.

Overdosing has also resulted in cases of zinc toxicity.

If using long-acting zinc boluses, animals should be weighed prior to administration and the correct bolus size used.

For more information speak to a nutrition adviser or vet or see Preventing facial eczema in milking cows using zinc oxide in feed.

It is recommended that farmers consider blood testing 10 cows in their herd 30 to 40 days after supplementation of zinc oxide in grain/concentrates starts to check zinc levels are within the required range (blood serum zinc 20-35 mol/L) and adjust their program if required.

Experience in New Zealand indicates that accurate zinc supplementation at preventative levels is likely to be safe for up to 100 days.

After this point, farmers should have blood testing repeated to minimise the risk of toxicity.

A permit to allow supply and emergency use (Permit number - PER90370) of slow-release zinc oxide boluses was granted by the Australian Pesticides and Veterinary Medicines Authority in February 2021.

These boluses, when used correctly, are reported to provide four weeks of protection against facial eczema.

This product will be available through several veterinary clinics during the 2021/2022 Facial Eczema season.

To register for Friday's webinar at 12pm click here.

To find out more, or to purchase zinc oxide boluses, contact Fortis business development manager Nadine Krippner, email nadine.krippner@fortisnz.co.nz or phone + 64 21 494 016.

For any questions, or further information about facial eczema, contact Dr Steph Bullen at stephanie.bullen@dairyaustralia.com.au or p[hone 0417 123 387.

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