The key to worm control and grazing management

Efficient parasite control and good grazing management go hand in hand, according to independent sheep consultant Lesley Stubbings. “It is essential producers get grass management right for optimal animal performance,” she says. “There’s a danger grazing management can be counter productive to parasite control, but the fact is, when stock are provided with high-quality feed, they are more able to cope with a parasite challenge.”


And to achieve this, grass should be grazed at 4-6cm. “At this level, grass quality is at its highest – the key is to maintain it at this height by matching stocking density with grass levels and measure dry matter production on a regular basis.”

Nutrition and health also have a huge influence on how an animal copes with a worm challenge, so it is paramount farmers make the most out of grass.

Grazing at the correct height also influences parasite burdens, with shorter swards increasing parasite concentration. “Most larvae are in the first 3cm of the sward – above 4cm and the concentration drops rapidly – so going in at this height has as much to do with parasite control as producing good quality feed.”

And producers with the luxury of having both cattle and sheep on farm, should use the balance of stock to their advantage.


“By grazing pasture with cattle one year and sheep the next, you can reduce the parasite burden for the following season,” she says.

“Assess where the risk is on your farm and graze cattle accordingly. For example, fields where ewes and lambs were grazed this season should be prioritised for cattle.” In this way, you can prevent nematodirus risk.

Weaning can also act as an excellent parasite management tool, says Ms Stubbings.

“Mid-season is when parasites are at their highest. This is when lambs can be moved to low risk pastures, such as silage or hay fields and sheep and cattle swards can be swapped.”


Targeted worm treatment at weaning is also key to preventing the build up of worm resistance in the flock, she says.

“Do not treat all stock at weaning – use egg counts to assess risk in the flock and when counts are low, there is no need to drench.”

But when moving sheep onto low-risk pastures, it may be worth targeting treatment to the smallest animals, as these could potentially be worm carriers, says Ms Stubbings.

The key is to minimise the number of resistant worms on pastures, stresses Simon Harris (job title?), Novartis.

“There is a role for using a wormer when stock first come onto farm. SCOPS recommends using a quarantine dose of monepantel (orange wormer) – a new family of wormers with no resistance – for maximum control.”


Introducing Chicory into the sward is also another way of reducing parasite risk, explains Ms Stubbings.

“Chicory included in a rye grass, clover mix can provide an excellent nutritional base.” The structure of the plant also makes it difficult for worms to climb up – reducing the chance of ingestion, while the plant itself is thought to have anthelmintic properties.

And there is some evidence to suggest the high level of nutrition provided by Chicory means even when stock are exposed to high egg counts they are more able to cope with the challenge.

Case study: Rotational grazing sheep and cattle

Rotational grazing cattle and sheep has been part of a strategy by Cornwall farmer Steven Thorn, to prevent unnecessary use of wormers.

“We regularly worm early lambs, but once weaned, we only worm in response to faecal egg counts – we don’t want to use wormers when it’s not necessary and this is where rotational grazing stock comes into play.”

Ground is grazed by cattle one year and then with sheep the next year, with the aim to cut down sheep parastites.

Grazing in such a way was influenced by a reduction in the grazing platform at Lower West Panson, St Giles on the Heath.

“We were grazing extensively, with 800 sheep and 200 mostly Limousin cattle on 243ha (600 acres), but following renting out a proportion of ground, grazing land was reduced and stocking density increased.

“Rotationally grazing stock was a means of minimising the risk of increased parasite numbers by resting fields.”

BOX For more information on resistance management visit the worming demonstration areas at 11:00 and 14:00, where observers will be shown how to get to grips with resistance. A seminar on “resistance management, getting it right” will also take place in the seminar marquee at 10:00.

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