TREAT – Treatment options

Once you know your worm burden, and having spoken to your vet you agree you need to treat the livestock, what is the best way to treat for livestock health and to reduce impact on dung beetles?

Any long-acting drugs should be avoided where possible. These drugs may create resistance and do not allow the animals immune system to become challenged during their efficacy.

Clear wormers (Avermectins or Macrocyclic Lactones) currently have the least reported resistance in sheep (the opposite is true in cattle) and as such, we should be trying to protect them for use when necessary. It can be tempting to use these products as a first line treatment because they are cheap, do not often require a second dose and have some residual activity but do you really need to?

A general rule of thumb is clear wormers (Avermectins or Macrocyclic Lactones) and synthetic pyrethroids are considered the most detrimental to dung beetles.

More comprehensive and up-to-date information on the type of wormers available, what they treat, and their withdrawals is available in the AHDB Parasite control guide.

Every time you worm your livestock, you should do a Faecal Egg Count Reduction Test (FECRT) – make it routine. It is important to know how well your wormers are working!

Targeted selective treatment (TST)

By treating only stock that require it, you leave some parasites unexposed to treatment or 'in refugia'. This is thought to slow the development of resistance. It also always results in some non-treated dung on the pasture, which is likely beneficial for dung beetles.

This strategy has used indicators such as anaemia [1], faecal egg counts and traits including body condition score, milk production and daily liveweight gain to determine if animals require treatment.

In a 2016 study in sheep in Scotland [2] demonstrated that by using a program called The Happy FactorTM only animals that were not achieving 2/3 of their expected daily live weight gains (DLWG) were treated and compared with a control group. This approach proved that TST had negligible effects on production with significantly less wormer use.

TST in sheep requires accurate data collection including regular weighing of animals before it is embarked upon to reduce the risk of production losses. Speak to your vet.

TST in cattle using DLWG does not appear to be as effective and should be approached with caution.

Milk yield may be another area that can be targeted in milking animals.

Correct usage

Incorrect storage can reduce the efficacy of worming products – store them away from sunlight and extreme temperatures (some may even require fridge storage) - be sure to have a quick check on the packaging!

Underdosing can increase the risk of anthelmintic resistance

Ensuring animals are weighed and dosed correctly will reduce the risk of resistance. At the very least – weighing the heaviest in the group and dosing for that weight. If there is a wide range of weights, split the group and weigh the heaviest in each smaller group

Weighbands can be used effectively in first year grazing cattle and have been shown to be more effective than estimating ‘by eye’.

Before using each time, ensure that the correct amount of product is being dispensed by calibrating any drenching / pour-on guns:

  1. Fill the dosing gun with water to the desired amount
  2. Empty water into a bowl
  3. Pull water it into a syringe
  4. Check the number of millilitres in syringe against the desired volume of the dosing gun.

This will tell you if your dosing guns are accurate.

When dispensing, keep pour-on guns upright and ensure they are filling with product each time and not just air!

Livestock should be clean of organic matter on the skin may impede absorption of the product if a pour-on is used.

Sacrificial fields

We believe toxicity of dung reduces over time, although there is currently no definitive research as to how long toxicity of wormers / flukicides last either on pasture or in slurry. It appears to be very variable and dependent on many factors such as light and oxygen availability, seasonality and more.

We are therefore unable to offer any meaningful advice at this time, however, we have made some assumptions below.

The quantity of any active product within an animal reduces over time. This is where withdrawal times are developed from. We therefore assume that the dung containing the most anthelmintic product is passed soon after treatment, although using withdrawal period does not in any way guarantee that excreta is no longer toxic.

Keeping stock on a sacrificial field for 4 weeks after treatment, or even a few days, may reduce the impact on dung beetles across the rest of your fields.

The ‘sacrifice’ refers to the dung fauna in this area to protect the rest of the farm’s dung invertebrates.

field should also be well away from watercourses too to reduce contamination here.

If animals are treated within a shed before they are turned out onto pasture, then the affected dung goes onto a dung heap / slurry tank and not the pasture. This should reduce the toxicity of the dung to beetles by the time it is spread. So, if possible, treat your livestock a number of weeks before turning them out, not as you turn them out.

Above all, administering worming / flukicide treatments (anthelmintics) only when necessary will help reduce the negative effects on dung beetles, reduce the risk of anthelmintic resistance and help save the pennies.

There are studies that show that avermectins are persistent in soils and may even accumulate over time, dependent on soil biology and cultivation practices (Litskas et al, 2012[3]). Routine worming strategies without diagnostics may contribute to this.

Milk withdrawals

For animals that are being milked, the problem of which drug to use becomes increasingly difficult as the only ones on the market that have zero milk withdrawal are the Macrocyclic Lactones (MLs). Again, only using them if they are required to reduce both resistance and negative effects on dung fauna.


  1. Van Wyk, J. A. & Bath, G. F. 2002. The FAMACHA system for managing haemonchosis in sheep and goats by clinically identifying individual animals for treatment. Veterinary Research, 33, 509-29.
  2. Mcbean, D., Nath, M., Lambe, N., Morgan-Davies, C. & Kenyon, F. 2016. Viability of the Happy Factor™ targeted selective treatment approach on several sheep farms in Scotland. Veterinary parasitology, 218, 22-30
  3. Litskas, V., Dosis, I., Karamanlis, X. & Kamarianos, A. 2012. Occurrence of priority organic pollutants in Strymon river catchment, Greece: inland, transitional, and coastal waters. Environmental Science and Pollution Research, 19, 3556-3567.