Nematodirus forecast tool puts focus on targeted treatment

Sheep farmers are being urged to avoid blanket worming and instead combine a revamped nematodirus hatching forecast with on-farm risk assessment to protect their lambs.

Independent sheep consultant Lesley Stubbings told a recent Sustainable Control of Parasites in Sheep webinar that the forecast tool has been updated to help farmers make better treatment decisions.

The online nematodirus hatching forecast tool, based on 140 weather stations, now flags “hatching imminent”, “hatching in progress” and “post hatch”.

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Farmers, vets and advisers can select their nearest or most representative weather station and use the coloured symbol warning system to quickly check the level of risk.

The forecast also provides guidance on management actions and treatment options.

It provides a clear indication of when the weather situation has gone past peak hatching by using a different shaped symbol – additional features farmers can use to make targeted treatment decisions.  

“What the forecast is doing is telling us whether or not nematodirus is hatching at peak rates, and if we’re putting those at-risk animals in the place where they may suffer from nematodirosis,” said Ms Stubbings.

She added that nematodirosis can strike very quickly, particularly if there has been a cold spell followed by a very rapid warm-up.

“Then we get these mass hatches. Suddenly on pasture, there is a real crescendo of infected larvae that lambs can pick up,” she said.

Risk assessment

To help reduce the use of parasiticides and blanket treatment, farmers are encouraged to assess lambs and grazing risk in combination with the forecast.

“What we’re really trying to concentrate on this time is to target those groups that need it. Get the right time and the right animals,” she said.

“First and foremost, is the field actually contaminated? Are the lambs six to 12 weeks of age? Are there any other concurrent issues you’ve got, such as coccidiosis?”

Treatment decision

Growing scrutiny of parasiticides in the environment has sharpened the focus on targeted treatments.

“We are very aware that whenever we’re using parasiticides, there is going to be an exposure to the environment and fauna.

“But if we use this mantra of ‘as much as necessary, as little as possible’, that applies not just to exposure of the parasites, but exposure of the environment.

“Using those principles is allowing us to take some pressure off there as well.”

Before deciding on a treatment, farmers are also advised to consider elevation and field aspect, which can shift hatch timing by days.