Wormwise vets Ginny Dodunski and Mary Bowron stress the importance of ensuring your lamb drench is effective early in the season.
Lamb drenching is a part of the early summer routine on sheep farms. The aim is to remove parasite burdens in lambs while helping to reduce larval contamination on pasture.
Whether it is the first or the second drench, it’s important to know that the drench is doing the job you need it to do.
You may think you’ve done all the right things by calibrating the drench gun, weighing lambs to ensure the correct dose is given and reminding staff ‘it’s not a race!’ But what about the product itself? Can you assume it’s working one hundred percent?
Unfortunately, no. With one in three sheep farms in New Zealand likely to have triple drench resistance, there is a high chance that the drench that has been given to those lambs may not be completely effective.
There may be no immediate signs that drenches are failing on your farm, but you don’t want to wait until you are seeing major animal health issues before taking action.
An effective drench kills all (or nearly all) adult and immature worms in the gut. For the following three weeks, treated lambs do not pass worm eggs and are not major contaminators of the pastures they’re grazing.
But what if drench-resistant worms are surviving your treatments? These resistant ones can quickly build in numbers – the environment in early summer is ideal for worm egg hatching and larval development.
For at least three weeks after an ineffective drench, the only worms laying eggs and raising the larval challenge on pasture are those that have survived that lamb drench.
Using an ineffective drench will not only directly affect your lamb growth this season. It can continue to impact in subsequent seasons with increased larval challenge, more obvious signs of drench resistance and poor stock performance. Not to mention the additional financial cost of buying a product that isn’t working properly.
To check that the drench you’ve used has actually worked, carry out a drench check 7 -10 days after drenching.
Collect at least 10 fresh poo samples and get a faecal egg count done.
If the drench check comes back with all egg counts zero, that’s great, your drench is working. If there are some eggs present, then a conversation needs to be had with your animal health advisor.
Persisting with ineffective drenches will rapidly accelerate the development of drench resistance on your farm.
Testing your drench early in the season not only ensures you’re using an effective product to kill any worm burden in your lambs, but it can also be used as an early indicator of your drench not working one hundred percent. It is better to find out sooner rather than later that your drench isn’t performing. Leaving it too long can allow the population of resistant parasites to grow, causing production losses and potentially animal health issues. This ultimately affects your bottom line.
Don’t just stop at one drench check in a season, check a couple of times and ensure the drenches you are using are working effectively. All you need to do is collect a bit of poo.