Animal health

The best things to do to slow wormer resistance

The most important thing to think about with wormer is animals build resistance over time. It is just like humans with antibiotics. So, ideally you want to minimise how often you need to give animals the drugs. There are several other things you can try to slow the build-up. We want to have a closer look at them today so you know what you should be doing with different types of livestock and horses.


Firstly, you should target animals and only treat those that need it. Dosing when it isn’t necessary will be building the resistance with no benefits. Keep in mind that your goal should be to have a low level of parasites. It is unlikely you will ever be able to get to a point where you are entirely worm free. Trying to do so can mean you’re putting your animals at risk too; they could end up with a heavy burden of resistant parasites.


Next, be conservative and favour over rather than under dosing. If you don’t give animals a sufficient dose, you won’t kill the parasites and can instead massively boost their resistance. You should do all you can to avoid this. Remember that wormers are typically safe so you can be cautious and add a little extra to doses.

Worm and move

One of the most important things to avoid is worming animals and then immediately moving them to a new pasture. This can lead to the development of a resistant worm population. Instead, dose with wormer and then keep animals on the same pasture for a while before you move them.


Another good idea is to keep animals together in groups as much as possible. This way you can keep them all on the same schedule. It also reduces the chance of animals introducing parasites from outside the group.

Cleaning up

Worm larvae in dung becomes mobile within a week. So, you should get into the habit of cleaning it up as soon as you can. Typically the best idea is to clean up twice weekly. You can then ensure you are moving the dung away from the pastures to reduce the risk of re-infestation.

If you do this, the best option is to keep dung piles as far away from grazing land as you can. Larvae can move one metre per day if it is dry. This increases to three metres when it is wet. So, keep that in mind and ensure there is plenty of distance so they can’t make it back to animals.

Cross grazing

Some worms are cross species, but the majority are specific to one. So, it can be a good idea to have different species of animals grazing together. This can ensure that any worms ingested by the wrong hosts will die rather than infesting the right ones. It can reduce your worm loads and mean you don’t need to resort to using wormer.

Animal introduction

If you are planning to introduce new animals, keep them separate and test to find out their parasite burden. Then, if you need to worm them, do so and wait a few days before testing again to make sure you got the best reduction in worms. You can then introduce them once you are happy.

General management

Finally, make sure stay on top of managing general things like food and water troughs, field shelters, stables, and other facilities. Your goal should be to prevent any worm eggs from being re-ingested.

Be careful with wormer to slow resistance

All of the things above can play a part in helping to reduce worm infestations and reliance on wormers. So, they can slow the building of resistance. Ultimately that should mean that whenever you do need to deworm, you shouldn’t have issues. You should also make sure you are rotating products to avoid relying on the same one. Parasites are more likely to become resistant if you use the same product every time.

If you need any advice about wormer, you can also speak to us. We have a lot of knowledge about the various products we offer. So, we can share it with you to ensure you can get the best results.