Celyn Mawr Case Study


"It has been a real eye-opening experience for me. FEC testing has certainly helped us time the dosing of lambs much better. Now we know we have issues with White wormer and Ivermectin wormers we can avoid using them and hopefully see an improvement in lamb performance."

Posted: Wednesday May 20, 2020

Name: Hywel Davies

Farm Name: Celyn Mawr. Llanwddyn, Oswestry

Farm Type: Upland

Stock Numbers: 500 Ewes, 150 ewe lambs, 650 lambs, 40 Suckler Cows and calves (sold as stores)

Land Area: 350 acres


Key Findings

  • 21 tests submitted from May to September
  • Better timing of lamb wormin
  • Surprised by Ivermectin inefficacy


Parasite Control History

End of May all lambs wormed with a White Drench against Nematodirus. Drenching of lambs after then is not set – intervals between 1 and 2 months depending on clinical signs and conditions etc. Clear drench (3ML) given as 2nd wormer and yellow drench as the 3rd wormer.

Didn’t worm ewes regularly in the past. Only if seen to be going backwards or if Fluke dose given midwinter, they sometimes get a Fluke and Wormer at that point. During 2018, they were given Cydectin LA before lambing due to a scab issue. This year all ewes were wormed with Levamisole in early February following a problem. Ewes were really suffering late Autumn / early Winter, and this was put down to nutritional stress. Problem’s continued into the New Year with ewes losing condition rapidly. In end they diagnosed a significant lungworm issue, very high egg counts were also reported (from memory around 1800 epg). Ewes improved dramatically after worming.


FEC Monitoring Results

The results of the 21 samples submitted by Hywel are summarised here.


Multiple tests completed at the end of July showed variation between different groups of lambs (last wormed early June). These were weaned around the end of July / early August and only 2 groups out of the 5 tested needed worming; normally all lambs would have been treated at weaning.

FEC levels stayed low until end of September when 1 group of tup lambs in ‘Odan Hafan Heulog’ shot up to 1400epg, and these were used in the efficacy test.

The other tup lamb group were much lower on the same day and the worming of these was delayed for a further 2 weeks.

There was a small saving in wormer treatments as most lambs normally had 3 wormers, if not 4 in a season and this year some selected lambs would only have had 2 wormer doses.


Wormer Efficacy

Part of the project was to determine the efficacy of the four main classes of wormers. A simple efficacy test was carried out in a controlled manner by Techion’s technicians, and based on pre and post pooled samples. Although not as accurate as the gold standard full Faecal Egg Count Reduction Test (FECRT) it provides a good indication of efficacy. The results are summarised here, a full detailed report on the wormer efficacy was provided separately (see WormerCHECK report).







The results show a definite lack of efficacy for the white and Ivermectin group of wormers. Althoug

h the Moxidectin wormer result shows only a 86% reduction, we had less confidence in this result due to a lower FEC test for that group on the day of treatment and only 1 egg was counted post treatment, so we would suggested this group should be tested again.

The results for Ivermectin was unexpected and disappointing as this wormers is used as a 2nd mid-season dose for all the lambs.


Stock Performance

Although the timing of wormers has changed and some groups wormed less often, this hasn’t been to the detriment of lamb performance. The male lambs have hit their target weights for selling slightly easier this year, In mid-October there were still approximately 300 lambs left to sell between the males and females which is normal.

It is worth noting that the wormer efficacy test wasn’t complete until the very end of the project, so efficacy levels were unknown until then. The lamb performance this year was based on worming in early August with what we now know as being the not fully effective Ivermectin wormer. Had this wormer changed to a wormer with better efficacy we may well have seen better performance again from the lambs? It may be possible to sell more lambs earlier in the season and reduce the cost of carrying so many lambs through into the Autumn and Winter.


Future Advice

Continue the good work and keep monitoring and using that as the basis of treatments. We advise the strategic use of the two new 4th and 5th wormer groups (Zolvix and Startect) to help maintain the efficacy rates at the current level. These should ideally be used in mid-season and would be an ideal choice to replace the ineffective Ivermectin wormer. Other on farm management strategies can help such as grazing management, using alternative forages in the pasture and sheep bred for natural resistance against worms.


Our associates

New Zealand, Techion
Invermay Agriculture Centre
Block A, 176 Puddle Alley, Mosgiel, 9092, New Zealand
0800 332 725
+64 3 477 7555

UK and Europe, Techion
Peithyll Centre, Capel Dewi, Aberystwyth, SY23 3HU, Wales
+44 0 1970 821 918

Australia, Dawbuts Animal Health
9 Mitchell Street, Camden, New South Wales, 2570, Australia
+61 2 4655 6464