Routine worming of every ewe in the run-up to lambing is unnecessary in animals that maintain good body condition.
Independent sheep consultant and SCOPS representative Lesley Stubbings says it’s ewes under nutritional stress that need managing for worms around lambing.
“The key is identifying and targeting these ewes, rather than blanket treating everything before lambing,” said Ms Stubbings.
“Traditionally, we have used the number of lambs a ewe carries as the main indicator of this stress that can lead to the increase in worm egg output. However, an EIP study in Wales identified it is the ewes under most nutritional stress, as indicated by the loss in body condition, that have a weakened immune response and shed the highest number of worm eggs in their dung,” she said.
Which ewes to target
Therefore, ewes losing body condition should be targeted. “A significant loss (>0.5 units) in body condition score around lambing is suggested as the most meaningful and practical way to indicate which ewes to treat.
“In well-fed flocks, this means the numbers treated are normally very low, but it also allows us to take account of the variation between years or mobs of sheep,” she said.
This year, poor, very wet weather conditions, variable forage quality and some farms caught in Bluetongue control zones may mean some ewes face nutritional challenges, increasing the risk of producing and shedding worm eggs.
Ms Stubbings urges farmers to measure body condition before lambing, for example, at scanning and again when ewes are receiving their clostridial boosters to monitor which ewes are losing condition and to target treatment accordingly.
“By targeting the peri-parturient rise (also known as spring rise) and reducing egg counts that occur in some ewes around lambing, we can help reduce the source of pasture contamination for lambs,” she said.
Fit, healthy adult ewes use their immunity to minimise the number of worms establishing in their guts and the number of eggs these worms produce.
However, in the run-up to lambing, ewes divert their nutritional resources to the growing lamb, which can comprise their own immunity and let the worms residing in their gut produce more eggs. The ewes under the most nutritional stress will have the most comprised immunity, hence the increased worm egg output.
Responsible wormer use
Using a long-acting moxidectin 2 percent wormer in ewes, such as CYDECTIN 2 percent, can reduce egg output over an extended period, reducing pasture contamination. However, it must be used responsibly to delay the development of resistance, warns Zoetis vet Patricia van Veen.
“It can be difficult, for all sorts of reasons, to move away from a farm’s routine, like worming all ewes around lambing. By setting yourself the small challenge to not treat the best 1 out of 10 ewes according to their body condition, you are starting that journey.
“It’s essential if farmers consider using CYDECTIN 2 percent, they work with their animal health advisor to ensure it is used correctly. That way you can confidently move your flock to strategically worming only those likely to produce the most pasture contamination.
