Best Practise Drenching

With UK land at a premium the sheep industry certainly in more lowland flocks has intensified. Reliance on pastures grazed only by sheep has increased so dependence on anthelmintics for parasite control has become fundamental. Two new groups of anthelmintics (groups 4 and 5) offer the opportunity to maintain good worm control for many years through strategic use as a quarantine treatment and as mid-to-late season dose for lambs but care in correct usage is key. Use of faecal egg counts (FECs) to monitor the level of worm burden and to test the effectiveness of treatment is especially useful and many should adopt this.


Other worm control tools also exist such as understanding of life cycles, grazing and pasture management. But most (if not all) units rely on some level of drenching during the season. So, there are also several very simple management practises often overlooked particularly when administering oral drenches for sheep that can also be undertaken.

Weigh to remove guesswork & risk of under-dosing

  1. Select and weigh the biggest sheep in the group to determine the correct dose

  2. If there is a wide range of weights, consider splitting the group and dose to the heaviest in the batch

  3. Check that the weigh-crate is accurate, remove any build-up of woolly dags -even consider changing to a digital weighing system upgrading the faithful and well used dial scale.

Calibrate & maintain the drench gun & delivery tubing

  1. Check the right amount is being delivered using a calibration tube, the neck of a 10ml syringe or a container with accurate calibration marked on it

  2. Smaller drenchers for lambs (as opposed to fully grown ewes) are available with smaller nozzles 

  3. Squirt three or four doses and check the level each time, air bubbles coming through, resistance and worn springs all affect accuracy

  4. Drench guns need regular cleaning with warm soapy water after use, check springs and tubes to make sure there are no kinks that will form air bubbles

  5. Service kits are available for some drenchers or replace old guns with a new purchase.


Drench correctly as correct technique is a vital part of ensuring that wormers do their job

  1. Make sure sheep are properly restrained and can’t leap around when drenching, so they swallow the whole amount

  2. Sheep can suffer serious injury, or even death, if unrestrained and the gun penetrates the tissues at the back of the mouth

  3. Place a hand under the head and tilt slightly to the side. Slot the nozzle in the gap between molar and incisor teeth and then over the back of the tongue. You must get the nozzle over the back of the tongue. If the wormer is just put into the mouth, it will by-pass the rumen as it escapes down the oesophageal groove. Particularly important for white (1-BZ) drenches.


Hint & Tips

  1. Research has shown the efficacy of the white (1-BZ) and clear (3-ML) drenches improves by withholding food before treatment

  2. Wormers should be stored securely, away from direct sunlight at 4-25°C 

  3. Check the use by date and, once open, use within the time shown on the packaging

  4. Shake white (1-BZ) products well before use

  5. Do not mix anthelmintics with any other product before administration

  6. No matter how often you use a product, always read the instructions as recommended dose rates and withdrawal periods do change

  7. EID tagging lambs earlier allows tag readers to then assist in monitoring the required withdrawal periods easily and more accurately.


Worm challenges through the season in sheep