Effective worm control in sheep should not rely on anthelmintics alone and instead needs a integrated approach, according to experts and farmers in a sustainable parasite control press briefing.
While anthelmintics remain an important part of effective worm control in sheep, an approach that incorporates other factors including nutrition and achieving optimum body condition through the year, a strict weaning policy and appropriate grazing strategies should be used to help reduce the level of challenge by parasites and reliance on anthelmintics.
Where anthelmintics are administered, this should be done as accurately as possible using a targeted approach.
These were some of the messages from a recent Sustainable Control of Parasites in Sheep (SCOPS) press briefing.
With lambing underway or approaching for the majority of flocks, some of the ways a targeted approach might be adopted were discussed, including avoidance of routine drenching of adult ewes.
Farmers treating ewes to manage the ‘spring rise’ were advised that fit, well fed ewes should be left untreated, in light of new research.
Although it was previously thought that ewes carrying higher litter sizes were more likely to shed eggs, more recent evidence points to body condition score (BCS) and degree of nutritional strain the ewe is under as more likely determinants.
SCOPS pointed to recent Veterinary Medicines Directorate funded Animal and Plant Health Agency research, which found there was no advantage in blanket worming ewes at lambing, and no difference in faecal egg counts or growth rates of lambs reared on ewes that were wormed, compared to those that were not treated at lambing.
In light of this, Lesley Stubbings, of SCOPS, advised leaving a minimum of 10-20 per cent of ewes in each grazing mob untreated.
She said: “The rationale behind treating a ewe is that it removes the worms in its gut and hence the number of worm eggs contaminating the pasture. The problem is that this can be very selective for resistance.
“We know not all ewes exhibit the peri-parturient rise (PPR) so, if we can identify these and only treat the ones likely to put out the most eggs, we can reach a practical solution.
“We can use BCS rather than litter size to determine the need to treat. Flocks that have adopted this approach have significantly reduced the number of ewes they treat around lambing.”
In the briefing Dr Fiona Kenyon, researcher at animal disease research centre Moredun, also spoke about a project which is aiming to encourage the uptake of precision livestock farming (PLF) across the sheep sector.
Working as a collaborative group that includes farmers, advisers, software developers and researchers, the Smart Sheep project is aiming to encourage the uptake of PLF approaches by accelerating the development of tools to control worm burdens.
She explained that PLF was a way to use tools or monitoring equipment to optimise output on an individual animal basis, rather than whole flock approach.
A PLF approach which utilises EID tags to optimise lamb worming has already been developed, but without a user-friendly method for farmers to access the algorithm, uptake had been hindered.
Dr Kenyon said: “Essentially we have an algorithm that can be used to predict lamb liveweight gain over a short period of time which can be used to treat animals on the basis of whether they have or have not reached a weight gain target.
“This is known as targeted selective treatment and means only lambs which need it are treated, rather than all animals in a flock or group.”
The project, launched in September last year, will facilitate the integration of the algorithm into a user-friendly technology that can be easily used on-farm.