Worming sheep is a very complex issue nowadays and we have moved a long way from traditional practices of worming at regular intervals and so-called "dose & move" strategies. Our vets are happy to work with you and your flock to develop robust farm-specific worming protocols.
Adult sheep very rarely, if ever, need worming as they develop immunity.
A good way to monitor worm burdens in lambs and make informed decisions about when to worm, what wormer to use and which pastures are high risk is by carrying out faecal egg counting. If eggs are found in the faeces, it shows adult egg-laying worms are present in the animal. A high count indicates a high worm burden.
It is important to note that the Nematodirus battus worm will cause morbidity and mortality in lambs BEFORE eggs are seen in the faeces. If you are targeting this worm, you may need to drench strategically, based on Nematodirus forecasting (www.nadis.org.uk).
How to sample a batch of lambs for faecal egg counting:
Collect the group onto a clean concrete yard. Wait for 10-15 minutes and watch them pass muck. Collect a minimum of 10 fresh samples from a minimum of 10 different random lambs into individual pots or bags. You need approximately 3g of faeces per lamb. Try and exclude air from any bags. Try not to pick particularly poor lambs or particularly fit lambs – the samples are supposed to be random. Do not mix the samples from different lambs.
Less than 10 samples, or selection of animals in the group, will not give you useful information.
Keep the samples in the fridge if there is any delay. Hand in the samples to reception, preferably the same day, no later than 24h after collection. When you submit the samples, if possible, please provide information on when they were last wormed, which product you used and what condition they are in. This will help us give you more valuable feedback.
If you plan on testing the efficacy of a wormer then mark the 10 lambs you have sampled. They can then be re-tested at a set time after you worm them, depending on which product you use. Please ask for further details if this is something you would like to investigate.