Faecal egg count trial cuts wormer use on Welsh sheep farms

Sheep farms that have adopted faecal egg counting (FEC) to monitor parasite burdens have reported a big reduction in the frequency of wormer treatments needed.

The sheep farms were taking part in a Farming Connect Parasite Management Project in Wales.

The eight focus sites changed their approach from the routine dosing of lambs and ewes to treating according to the number of parasite eggs per gram (EPG) in sheep faeces.

See also: Wormer trial shows faecal egg counting can cut drench costs

As a result, the frequency of wormer treatments generally reduced and farmers are now targeting dosing to when it is most needed.

According to the study, there was no decline in performance on any of the farms, despite less dosing and changes to parasite controls.

Some reported improvements in performance, although other on-farm changes may have contributed to this position.

About the project

The project ran between March and September 2019 and was carried out for Farming Connect by Ceredigion-based parasite control company Techion UK.

A total of 118 sheep samples were submitted, with the majority – 84 – taken from lambs.

Analysis of these samples showed:

  • 43% were in the ‘unlikely to treat’ category
  • 38% were ‘possibly treat’
  • And only 19% had egg counts that put them in the ‘likely to treat’ category.
  • Lower egg counts were recorded in June, July and August, with counts rising in the autumn.

Without this information, many of the lambs may have been dosed as a matter of course, said Techion UK’s Eurion Thomas, who led the project.

Seasonal changes of parasites

The project also provided an interesting analysis of strongyle and nematodirus counts, says Mr Thomas.

Historically, nematodirus has been the dominant species of worms in spring, in April and May in particular. While the strongyle group of worms was more prominent from early summer, it was rare to see nematodirus later in the season.

The project showed evidence of nematodirus throughout the season, with some quite high levels recorded at times in the autumn, says Mr Thomas.

In contrast, strongyle worms were found as early as March – much earlier in the spring than anticipated. This information is hugely important when considering the choice of wormer for the first dose of lambs.

“Many of the focus farmers knew white drench wasn’t fully effective against those strongyle worms and could change to use another group, which would work better for both,” he adds.

If there had been no significant strongyle counts, white wormer would be the most appropriate treatment, he suggested.

Mr Thomas did urge caution when interpreting nematodirus egg counts.

Even though results may be in the low to medium category, the advice is to still worm if there is a known history and the conditions are favourable to the parasite.

The Nematodirus Forecast available on the Scops website is a useful tool to help with this.

None of the farms recorded a decline in performance after changing their worm control policy, which in most cases involved reducing the frequency of wormer treatments.

“This is an important message to convey, as some farmers may not engage with activities like FEC monitoring because they are worried that regular worming is required for optimal performance.

“This project has, in fact, proven that this is not the case as long as it is carried out properly and backed up by evidence,” says Mr Thomas.

Each farm was also encouraged to FEC test ewes at or around lambing; some historically wormed mid-winter or before lambing; the indoor lambing system just after lambing; and others four to six weeks post lambing, to coincide with ewe crutching and earmarking.

“During the spring, it’s easy to assume that one group or farm will be very much like another, but the findings of this project showed that not to be the case,’’ adds Mr Thomas.

Guidance for FEC thresholds


< 200 epg – Unlikely to treat, although there are exceptions

200-500 epg – possibly treat; consider other factors such as growth rates and condition

> 500 epg – likely to treat 


< 50 epg – unlikely to treat, although there are exceptions

50-100 epg – possibly treat; consider other factors such as growth rates and condition 

> 100 epg – likely to treat

Case study: Aberbranddu, near Pumpsaint, Carmarthenshire

Irwel Jones © Debbie James

One of the farms that took part in the study – Aberbranddu, near Pumpsaint, Carmarthenshire – didn’t dose ewes pre- or post-lambing after recording low FECs.

The ewes, which had not been treated since the previous spring, were in very good condition and on good-quality grass, supplemented with a high-quality protein feed.

This meant they could maintain their immune status despite the nutritional demands and stresses of parturition.

The farmer, Irwel Jones, had been FEC testing using the original on-farm microscope-based FECPAK system for several years, but using the new image-based online FECPAKG2 system meant he could test more regularly.

FECPAKG2 is a tool for remote location parasite diagnostics and decision support. It enables simple faecal egg counts to be taken on-farm without a microscope and provides FEC results quickly via email, so drenching decisions can be made in the field.

“Monitoring on a regular basis and having quick results back via email without me needing to leave the farm means I can keep on top of the situation,” explains Mr Jones, who runs an upland flock of 860 ewes and 200 ewe lambs.

“Although I don’t dose often, I have been able to dose earlier on the back of FEC results and have avoided big drops in growth rates.”

Keeping a close eye on parasite burdens and using daily liveweight gain data, he treated at the correct time and was rewarded with improvements in growth rates in some groups.

The Welsh male lambs achieved average growth rates of 170g/day, from 1 August while the corresponding group in 2018 achieved 100g/day at that same time of year.