College Farm Case Study


"Testing for wormer efficacy is well worthwhile and we had some interesting results with the levamisole issue in particular an unexpected one. It’s scary to think how many of us farmers pay for wormers that simply don’t work."

Posted: Wednesday May 20, 2020

Name: Nicola Drew

Farm Name: College Farm, Trefecca, Brecon

Farm Type: Lowland

Stock Numbers: 550 Ewes + 50 Ewe Lambs, 15 Suckler Cows + Calves (Sold as Stores)


Key Findings

  • Discovery of wormer inefficacy, 16 tests submitted from April to September.
  • Reduced wormer treatments, but improved lamb performance.


Parasite Control History

Since Nicola had taken over the farm from her father, she had started to carry out a small number of FEC tests through her vet and uses that to help with worming decisions on occasion. Previous to that, lambs were wormed at regular intervals with an Ivermectin (3ML) oral wormer. Ewes were historically wormed at 6 weeks post lambing, but this had recently changed to worming at turnout from the lambing shed.


FEC Monitoring Results

Below is a summary of the 16 results that Nicola submitted using the online FECPAKG2 system. Nicola commented that she knew she should have done some more testing but still found what she was able to do helped a lot with worming decisions: -

Ewe FEC’s at point of lambing confirmed the need for turnout wormer. As the singles were lower than twins it was advised only to worm the poorest looking singles to leave a percentage of ewes untreated.

The intervals between worming lambs was extended and this varied between groups. Some groups had by now received their 3rd wormer treatment, whereas normally by the end of September all lambs left on the farm would have received their 4th treatment.

In particular please note group A which are a group of singles and only received 1 wormer in early May and had low FEC’s throughout and have performed very well with most lambs now sold as fat.

Cattle tests - the heifers are bucket reared and therefore a susceptible group but low FEC and good condition meant they weren’t wormed. Important to note lungworm must also be considered carefully.

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, 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 are a concern as it shows inefficacy to 3 out of the 4 wormers tested. These are reported with a fairly high level of confidence due to the FEC results observed and it is most likely that the lack of efficacy was down to wormer resistance.

The results for the white wormer and Ivermectin weren’t a great surprise to Nicola as so

me post treatment testing through the vet in previous years had suggested this. However, the result for levamisole was a surprise as Nicola didn’t believe they had used much of that wormer at all in the past. In further discussions it became apparent that some fluke treatments given to ewes would often be combination worm and fluke treatments such as Combinex where the wormer ingredient would be Levamisole.

Having received these results in early August meant Nicola was able to change the choice of wormer treatment in late August and September to Moxidectin.

Stock Performance

This year Nicola reports that lamb’s performance has been better than normal. At the end of September, the same number of fat lambs have been sold as last year but they have been between 1 and 1.5 kg heavier in liveweight. She also would have sold 50 store lambs by now but these will all go as finished lambs this year as they have reached target weight and condition (just waiting to see if price improves before selling them).

Although difficult to put this improvement in performance down to better worm control alone, it is encouraging to note that this increased performance was achieved with less wormer treatments required. The favourable early season conditions of hot, dry weather following last years drought would have helped lower the worm challenge on pasture and contributed to this improved performance.


Future Advice

Due to evidence of multiple anthelmintic failure, controlling parasites effectively in the future will be challenging. However, by continuing to regularly monitor FEC and following SCOPS guidelines the situation can be managed. We advise the strategic use of the two new 4th and 5th wormer groups (Zolvix and Startect) to ensure roundworms are controlled effectively in the future. However, we must be careful of these two groups and only use when necessary so we don’t develop resistance to them as it could happen very quickly.

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