20 December 2022


A three-year European Innovation Partnership (EIP) Wales study on dairy farms in Ceredigion resulted in all three farms managing their R2 yearling heifers at grass without the need to treat them for gut round worms; one farm found that it didn’t need to treat its R1 animals for gut worms once they had been vaccinated for lungworm.   

The other two, whose farms have a higher worm burden, wormed their R1s less often. They also switched to using white (1BZ) drenches and yellow (2LV) drenches after efficacy testing showed a reduced efficacy of the clear (3ML) wormers.

The data collected during the EIP study showed that there were similar growth patterns to previous years when clear wormers were used and heifers were dosed routinely therefore the changes in worming treatments had no obvious negative effects on performance. 

One of the experts involved in the study, Professor Diana Williams, from the University of Liverpool’s Veterinary Parasitology Research Group, said the study demonstrates that the advice around worming needs to change.

“Traditionally the advice to farmers was to dose first season grazing calves in the early part of the season to prevent disease mid-season but because of lots of factors such as climate change and wormer resistance that advice needs to change.

“This project has demonstrated that we can reliably use FEC, alongside growth rate data and calf condition, as a means of monitoring infection during the grazing season and only treat when the animals actually need it rather than dosing by calendar date.’’

Cooperia oncophora was the dominant worm species in the FECs and Ostertagia ostertagi was also present in every sample.

Infections with C. oncophora alone are not normally associated with clinical disease in UK, although they may exacerbate disease caused by the more pathogenic Ostertagia ostertagi.

Climate change, with warmer temperatures earlier and later in the season and changes to rainfall patterns, is making the epidemiology and lifecycle of parasites much less predictable. 

“Temperatures of 20°C in mid-November as we have seen this year are not normal,’’ said Professor Williams, who sits on the steering group of Control of Worms Sustainably (COWS) https://www.cattleparasites.org.uk.

Whilst white and yellow wormers can be used during the grazing season, there is a place for using clear wormers, particularly at housing during the autumn and winter.  

Gut worms, picked up in the autumn, particularly after a cold spell, go into an arrested stage of development and sit in the wall of an animal’s gut through the winter, causing severe disease in the spring when they wake up and start developing again.

Yellow wormers are not effective at destroying parasites in that arrested stage, Professor Williams advised. “If a clear wormer is to be used, this is the time to use it and, by using it only when it is needed, the risk of increasing resistance levels is much lower.’’

The EIP study showed big differences in EPG levels on each of the farms in the trial, despite all three having spring calving, and similar grazing systems.

The researchers said that this highlighted why a standard blueprint to roundworm control cannot be implemented.

One of the issues thrown up by the study is the threat of lungworm when wormer used to control gutworms is reduced.

Dealing with the risk of lungworm, and sometimes Type II ostertagiosis, was a factor that confused treatment decisions on the trial farms.

“If you are starting to think about FEC to control gastrointestinal worms you can’t forget about lungworm,’’ warned Professor Williams. “Seek veterinary advice if there is any reduction in growth rates or animals are coughing.’’

Quarantine treating all incoming stock will reduce the risk of bringing lungworm onto the farm and R1 heifers can be vaccinated before turnout to protect against lungworm.


Wormer resistance

The project found a significant lack of efficacy of the 3ML group of anthelmintics on two of the farms where several Faecal Egg Count Reduction Tests (FECRTs) using Techion UK’s FECPAKG2 system were carried out. 

This was found in wormers where both ivermectin, and the longer acting moxidectin, were the active ingredient.

On one of the farms, treatment with a pour-on clear wormer showed that on one occasion it had an efficacy rate of just 8% and it was never higher than 81%.

In contrast, benzimidazole and levamisole – white and yellow wormers – were fully effective, giving a 100% reduction.

A FECRT is a useful field test for detecting if a wormer is losing efficacy.  

The results from a FECRT give a picture of possible resistance, said Eurion Thomas, of Techion UK.

He recommends a FECRT every two to three years to ensure that the wormers that are being used are working. 

As a result of this testing the study farms have significantly reduced their use of clear wormers.

Mr Thomas said the research highlighted why farms shouldn’t rely on one class of wormer and that farmers fully understand which active ingredients are in the product they are using.


Case study

FEC sampling in combination with vaccination for lungworm and changes to grazing management enabled one of the project farms to administer no wormer treatments to youngstock at grass in 2022.

The Mossman family, who run 100 R1 and 100 R2 heifers, previously followed the standard practice of routinely worming heifers three weeks after turnout and every five weeks thereafter during the grazing season.

But with testing showing consistently low egg counts the Mossmans had the confidence to not treat their R1 and R2 heifers at all.

“We surprised ourselves because we didn’t think it would be possible,’’ said Chris Mossman, who farms with his wife, Debbie, and daughter, Bella, at Nantybach, Llangrannog.

Withdrawing wormers did however result in a lungworm challenge.

All R1 heifers have now been vaccinated for lungworm and next year the beef youngstock will be vaccinated too.

“Vaccination is costing us £12 an animal which isn’t cheap but for any farmer who is keen to reduce wormer use then I think it is something that must be considered,’’ said Mr Mossman.

The business has made financial savings by cutting back on wormer use, even when balanced against the cost of vaccination, but Mr Mossman said cost cutting was never the intended goal from reducing treatments.

“For us it was never about the cost, wormers are relatively inexpensive, and that is one of the reasons why our generation of farmers have been reaching for them without thinking about the other consequences.’’

Soil health and the long term impacts wormers have on dung beetle populations were the main considerations for the Mossmans. 

Overuse of some livestock wormers have reduced dung beetle populations across the UK with evidence showing that when there are no beetles to breakdown a pat, the dung does not decompose to enrich the soil with organic matter. There is also a significant impact on other soil fauna.

Mr Mossman believes that the farm’s consistently low worm egg levels are in part a result of its low stocking rate.

Nantybach has lost a significant number of animals to bovine TB and, by default, its stocking rate has reduced from three livestock units (lu) a hectare to two.

“It has given us a lot more scope to change our grazing management,’’ said Mr Mossman.

There is a leader-follower system in place with calves grazing designated paddocks five to six days ahead of the herd of 315 crossbred cows and daily moves.

This was initially put in place to combat coccidiosis infection.

“After introducing leader-follower grazing we took dung samples every 12 days and got to the point where we found no infection,’’ said Mr Mossman.

It has reduced populations of other parasites too and is a reason why the FECs in the EIP study showed consistently low egg counts, he added.

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