The study, funded by the European Innovation Partnership (EIP) Wales, involved five commercial sheep farms
New data emerging from a study involving Welsh sheep flocks shows good potential to significantly reduce the number of ewes that need to be wormed around lambing time.
A study involving five sheep farms clearly links increased worm burden in ewes before and after lambing, commonly known as the âspring riseâ, with low body condition and nutritional stress.
Using that knowledge, gained from taking faecal egg count (FEC) samples six weeks before and six weeks after lambing, and with close attention to ewe diets with forage analysis to ensure ewes werenât underfed, farmers were able to treat the least number possible.
Project specialist and independent sheep consultant Lesley Stubbings said the project, funded by the European Innovation Partnership (EIP) Wales, had shown that it is not necessary to blanket treat ewes.
She said it is likely that around 80 percent of pasture contamination is caused by as few as 20 percent of ewes.
âWe have to question why we worm at lambing time," Ms Stubbings told farmers attending a recent joint EIP Wales and Farming Connect event at Aberystwyth.
âThere is the perception that it is because it does the ewe good. This is the bit that we must try to separate from. It is really all about reducing the number of worm eggs the ewes drop on to pasture in their dung, which then become a challenge to lambs later in the season."
Worming at lambing is deeply ingrained in the industry, she admitted. âIt is what farmers were brought up to do.
"But this project has shown that it is often not necessary, that a eweâs immunity to worms is much more to do with the effect on them when their nutrition is under the most pressure."
Fit adult ewes have immunity to worms by the time they are 12-18 months old, with the exception of the barber pole worm, Ms Stubbings pointed out.
âThey are still ingesting worm eggs but they have a nice relationship with them as in they will allow a few to exist and choose which to stay in their gut and which to shed."
That immune system works well until the ewe is under pressure â it then wanes and the ewe will produce high levels of eggs and shed them in her dung.
A need to control the volume of worms contaminating pasture is a reason why farmers have wormed every ewe, in the mistaken belief that it is necessary.
Ms Stubbings said the data from the study clearly showed that if a ewe is not under nutritional stress, she does not need to be wormed as FEC samples taken during the study show that she is not shedding large numbers of eggs.
It even applies to leaner ewes, she said. âThe message has always been that you have to treat your leanest ewes, but just because a ewe is thin it might not be necessary to drench, it is the nutritional pressure point that matters."
For instance, on several of the farms, FECs increased when ewes were short of grass.
Monitoring body condition score (BCS) will allow farmers to identify which ewes to treat, leaving a higher proportion untreated.
âCombined with some FEC monitoring, they can also pinpoint the time to give a treatment for maximum effect," said Ms Stubbings.
The findings of the study will also help farms save money. âThere is a cost element to this. If we are trying to keep costs under control, there is no point in treating if we donât have to," she advised.
But the most important reason for not using anthelmintics if unnecessary is to protect flocks from resistance.
The policy of blanket use of long-acting moxidectin 2% wormers must be revised because of the impact this policy could be having on resistance.
However, correctly using products with moxidectin as the active ingredient on ewes could reduce flock use overall, suggested Ally Ward of Zoetis, and fewer lambs are likely to need treating.
Year on year use of long-acting moxidectin in ewes around lambing is unadvisable in a flock, and simply rotating it with other wormer groups within a season is not enough, said Ms Ward.
âIf ewes are treated with long-acting moxidectin, some must be left untreated â 10% is the absolute bare minimum and this project shows that in many cases the proportion that require treatment is much lower â but if it is being used to treat scab then everything should be treated."
It should not be used more than once in any one year, she added. Ms Ward urged flock keepers to observe a high level of accuracy when dosing â they can do this by weighing animals, ensuring equipment is correctly calibrated and using best practice.
Monitoring FECs in the EIP study was done by Techion UK. Its general manager Eurion Thomas said the project had demonstrated a strong case for this approach.
âMonitoring FECs is more than just looking at lambs in the summer. There is an argument for using it to inform which ewes to treat and when. That changes from farm to farm and from year to year.
âIf you use it to get the timing of dosing right, you are not wasting that product and not building up resistance."