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Weather conditions put cows at risk

Recent rain across much of the North Island, though very welcome for many farmers, has raised the potential of disease among animals.

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Recent rain across much of the North Island, though very welcome for many farmers, has raised the potential of disease among animals.

Facial eczema (FE), if not managed, can be fatal, warns the manager of a national farm consultancy service, and farmers need to be aware of the heightened risks cows (and sheep) face as FE spore counts peak.

"Farmers need to act now, those who are not already getting zinc into their animals are playing Russian Roulette with their animals' lives," says FarmWise Manager Sue Hagenson.

"There is the danger that spore counts will rocket with rain and high humidity, particularly where pastures suffered in the dry. Paddocks with rank feed (a lot of dead grass and dry litter) pose a greater risk to animals, particularly with the current high humidity - which is providing the ideal environment for FE spores.

"To prevent animals contracting clinical or sub-clinical facial eczema farmers need to get zinc into their animals now."

Sue Hagenson says facial eczema is "like exaggerated sunburn," the toxins that cause facial eczema damage an animal's liver and with sufficient toxins in the cow's system, combined with sunlight it is like the animal is photosynthesizing.

"The animal's skin will peel, particularly on the lighter pigmented and exposed areas of its body like the udders, teats or white areas of the coat."

She says a sub-clinical cow can be hard to identify as often there is no obvious sign of symptom or break-out showing, however, sub-clinical cows suffer underlying liver damage and therefore be prone to poor growth, lowered production, ill thrift and when faced with significant stress, decline in health, and in some cases die.

Sue Hagenson says to avoid the devastation caused by facial eczema faced by many farmers last year spore levels must be monitored on farm.

"There is no cure for FE, so prevention is the only protection.

Drench daily

Daily Drenching with zinc oxide assures that each animal is receiving the required dose rate; daily long term dosing is 80 - 90% effective. Points to note; Intervals greater than three days can cause milk fever in some lactating cows. Young and/or dry stock, they can be drenched weekly which is 70 - 80% effective. The less frequent the drenching the less effective it will be.

Spray paddocks with fungicide

Fungicide Spray can reduce the growth of FE spores by approximately 60%. Ensure spore counts are checked before and after spraying to ensure they are below acceptable levels. Pastures will be safe for four to six weeks. Points to note; Spray paddocks when spore counts are low. If spore counts on un-sprayed pasture is +200,000 DO NOT spray as the fungicide will be ineffective. If spores are already present in the paddock(s) allow 5 days after spraying before grazing them.

Treat water

Water Treatment (zinc sulphate) is less effective (provides 70 - 80% protection) however if drenching is not practical adding zinc to your water supply is an option. Points to note; Water treatment is only suitable for long-term treatment. It isn't suitable if stock have access to alternate water sources. Introduce it gradually over five to seven days to allow the stock to get use to it; a drop or 2 of aniseed in the trough can improve the taste.

Rumen Bolus will provide protection in calves between 90 - 250kg liveweight for up to four weeks.

Sue Hagenson said good grazing management is an important tool in the fight against facial eczema.

"Grazing management should focus on minimising the amount of litter left behind in pastures. During danger periods animals should be kept off known hot-spots and over-grazing should be avoided (where this is not possible feeding supplements may be necessary)."

She says any animals with clinical FE need as much shade as possible and should be offered a low protein diet (fed plenty of hay and silage) and have easy access to water, "it may also help to keep dosing affected stock with zinc and B12 supplementation to stimulate the liver.

"It is also important that farmers remember, prolonged zinc can interfere with the animals copper metabolism, so once treatment is finished it is important to check animals' copper and/or selenium deficient."

Sue Hagenson says it is estimated that for every three cows in 100 showing clinical facial eczema, a further 70 may have sub-clinical facial eczema.

Ms Hagenson warns conditions could possibly continue to put animal health at risk for the next six to ten weeks but says district spore counts are available through local vets and from RD1:

"However, the most accurate method of monitoring spore counts is for farmers to count spores on their own farms, as there are often large variations in the spore count between different farms, different paddocks and even different parts of the same paddock and when high spore counts are recorded it is often too late."

Risk levels for spore counts using the faecal method of counting:

Low 300 - 600,000
Moderate 600 - 1,000,000
High > 1,000,000

Risk levels for spore counts using the wash method of counting:

Low risk 0-30,000 spores

Moderate 30,000 -100,000
High risk over 100,000