Routine worming of in-lamb ewes unnecessary

Routine pre-lambing worming of all ewes is not only unnecessary, it also wastes time and money. And even when drenches are alternated it’s a practice that could trigger triple resistance to anthelmintics and end a farm’s ability to run sheep, according to Cumbria vet Mat Colston.

He says with more than 80% of the ewe flock now showing resistance to white drenches, farmers should consider only dosing ewes whose body condition pre-lambing suggests treatment with anthelmintics would be advantageous.

“Providing ewes have been on a correct in-lamb diet and are carrying the correct amount of body condition, flock owners should try a new regime and not dose a portion of their sheep. A good example would be single bearing ewes that shouldn’t be under any physical stress when they’ve been properly managed,” he says.

But, not dosing ewes pre-lambing can also be applied to fit, twin-bearing ewes, adds Mr Colston. “I would however urge anyone wanting to introduce a new approach to worming to discuss this with their vet and introduce a plan that best suits their own flock.”

Basing his advice on the findings of the National Sheep Association’s SCOPS research (Sustainable Control of Parasites in Sheep), he says selective pre-lambing worming will not lead to lambs being more at risk from ingesting worm eggs from pasture.

“Sheep producers worry untreated ewes will carry high worm burdens, but adult ewes rarely suffer from worms. I’m not advocating never worming ewes and at pre-tupping time ewes should again be checked for body condition score and a faecal worm egg count taken. It may be necessary at that time of year to dose those in poor body condition with a high worm burden. But there’s no need to dose all adult sheep routinely.”

However, in nine cases out of 10 farmers are using wormers when there’s no need to. This is not only wasting time and money but it’s also contributing to the increasing problem of anthelmintic resistance, stresses Mr Colston. He says no worming should ever be undertaken without first assessing the worm burden through egg counts.

“Worming will always be part of responsible sheep management but those who are routinely worming because they feel it’s a fail-safe are underestimating the huge problems they face in the future through anthelmintic resistance. Anyone buying ewes and lambs this spring must quarantine them to avoid infecting pasture with resistant worm eggs and creating big problems for their own sheep.”

CASE STUDY Whinfell Park, Penrith

About 800 single-bearing ewes at Whinfell Park, Penrith won’t receive their traditional pre-lambing worming this spring as the flock evaluates research which questions the need to routinely dose in-lamb ewes.

The flock, part of the beef and sheep enterprise of Cumbria farmers Messrs Jenkinson, numbers in excess of 3250 ewes in total comprising North of England Mules and Texel x Mules. All ewes are normally dosed once a year at about two weeks before lambing which starts on 1 March.

“It’s a system we’ve been happy with but our general worming policy has been under scrutiny for sometime and for the last four years lambs have only been wormed when we found high faecal eggs counts,” says Whinfell Park shepherd Alan Law.

Vet Matt Colston of Frame, Swift and Partners, Penrith suggested stopping the routine worming of all ewes based on on-going research into the use of anthelmintics.

Not worming ewes routinely will result in considerable saving on cost and on labour, says Whinfell Park farm manager Iain Scott: “The vet advice is concentrating more on the need to dose when necessary to avoid a build-up of resistance.”

Faecal samples from lambs are collected from fields in early April and continue every three or four weeks throughout the summer. Only when this sampling indicates a high worm burden are lambs dosed. About 10-12 samples are taken from a field carrying about 150 lambs.

Before taking worm egg counts, Mr Laws reckoned half the time they were dosing lambs that didn’t need it. “Now we’re selling more lambs that have never seen a drench. We’re strict about worming and never worm lambs without sampling the muck first. This new approach has also made a huge difference to the labour needs required to routinely worm up to 6000 lambs every three weeks.”