ASSESS – Know your worm burden before treatment

Knowing your worm risk and worm burden before you reach for chemicals is a great start. There is no need to treat livestock if you do not have to, it is both better for the dung beetles and your pocket! It will also reduce the risk of wormer resistance.

To start, work with your vet / SQP to adopt a diagnostic approach to worming. Using signals such as coughing, wet tails, irritability and loss of thrift, typical signs of a worm burden can let you know that your animals require treatment. However, once we get to this point – much of the damage caused by the parasites has already been done and it is likely you will have had a drop in production.

Utilise results from regular Faecal Worm Egg Counts (FWECs), daily live weight gain, body condition scores and milk yield, as an early warning system, be proactive and either change your management practices or treat as required.

Animals need exposure to worms to build resistance to them. Traditional, continuous dosing strategies throughout the grazing season without diagnostics hamper this, as they do no not allow for any exposure, inhibiting animals from creating their own natural immunity. Allowing some exposure and treating only when required will help build this immunity.

Pepsinogen testing - cattle

Pepsinogen is a proenzyme which is converted to ‘pepsin’. Most mammals, including cows use pepsin for protein breakdown in the stomach. If the lining of the stomach wall is damaged by worms burrowing into it to overwinter, pepsinogen is released into the bloodstream and higher than normal levels can be seen on a blood test.

If you have not wormed for the duration of the grazing season, you may want to consider a housing dose based on the history of disease on your farm, pepsinogen results and in conjunction with your vet.


Do not underestimate the value of doing postmortem examinations on animals that die on farm. These can turn complete losses into a useful diagnostic tool. Parasitic damage, along with other disease processes is often easily visible and all farmers should get their vet involved in these circumstances.

Lungworm diagnostics

When looking for lungworm infection, your vet will be able to use faecal samples, bronchoalveolar lavage, bulk milk elisa and other tools. Speak to them if you have concerns about lungworm, if you see coughing in cattle or if you are considering changing your worming routine.

Parasite forecast

The NADIS parasite forecast should also be taken into consideration and is kept up-to-date regularly with new information. Nematodirus in lambs, for example can have a high mortality rate, so knowing when it could be a problem on your farm can really help reduce losses.

Pasture risk map

Creating a map of your grazing platform and assigning a risk value to it, then grazing appropriately can help you decide how you use your paddocks and reduce the risk of heavy parasite burden year on year.

Parasite burdens depends on several factors including weather, season, stocking rate, time spent on pasture.... The list goes on.

Paddocks/fields can be categorised into high, medium, and low risk:

  • Low risk paddocks are those that have not been grazed before such as a new ley or forage crop.

    Rotating cattle with other livestock, rotating silage and grazing fields, using break crops, rotating younger animals with older ones in alternate grazing seasons are all practices that will help reduce the level of exposure that young stock will encounter.

  • Medium risk paddocks grazed by only adult stock the previous year. Adult animals excrete less larvae than youngstock.

  • High risk pastures are those that have had youngstock or stores on the year before or earlier in the season. If you continually put youngstock on the same paddocks year on year, the risk of heavy parasite burdens in those animals and the likelihood that they will require worming is increased.

    Allowing a field/paddock at least one grazing season free from youngstock would be a good start.

    By using adult animals as ‘vacuums’ you can use them to clean up high risk pastures as they will not act as ‘multipliers’ in the same way youngstock do, due to the resilience they have built up.

Our very own Bruce Thompson uses this Traffic Light Grazing technique on his farm and will explain how this looks in more detail this coming spring.