The first drench given to calves can set the scene for the rest of the season. The first drench should not be seen as a treatment for the calves – more as a treatment for the paddocks for the season to come. Drenching calves early in the season, with a highly effective drench, reduces the larval build- up of parasites on pasture. This reduces challenge and worm burdens later on in the season, meaning that you are always front-footing the parasite into summer and autumn rather than chasing its tail.
A triple combination drench is currently the most effective drench that you can use. The triple drench contains three different drugs that all act in different ways to kill internal parasites. This means that, if a parasite is resistant to one or even two of the drugs, it will still be killed. Triple combination drugs should be used to enable the control of parasites in the presence of single or multiple drug resistance and to slow resistance development to these important drugs. Using a product with three different drugs to kill worms should kill more worms and reduce the likelihood of resistance development on farm – this comes with a big IF! IF there is adequate refugia.
What is refugia? Refugia is actually pretty easy to achieve. If you do not treat your animals with a drug, the parasites do not become resistant and you have created refugia – lots of it. The only downsides are terrible growth rates and productivity, clinical disease and even death in some circumstances. Obviously, this is not acceptable to anyone and so we drench. However, with skill, using the right drench and monitoring, a balance can be struck between optimizing productivity and maintaining enough refugia. Your vet can give you advice around this, as a ‘one size fits all’ approach is usually inadequate.
In calves under 4 months of age (<120kg as a rule of thumb) abamectin can be toxic and is not recommended for use. This means that many of the triple active combinations have been avoided in this age group. However, there is a triple active drench available containing ivermectin, which is safe to use in calves, instead of abamectin. It is called Iver MATRIX® Mini-dose Hi-mineral (also called Iver MATRIX® Calf). It is available in 5L and it can be used in calves from 80kg.
Iver MATRIX® is available at your local Vetlife clinic.