Teagasc has produced a short guide to dealing with worms in sheep.

It says to dose lambs based on faecal egg count results rather than routine dosing, with advice from your adviser or veterinary surgeon, and reminds farmers to check withdrawal dates with lambs approaching slaughter.

1. Weigh lambs
Weigh a number of the biggest lambs in the group and dose according to the weight of the heaviest. Do not guess. If there is a wide range of weights, consider splitting the group, then weigh the heaviest in each subgroup.

2. Check if dosing gun/syringe is working properly
Check that the dosing gun is delivering the right amount of drench. Calibrate using a graduated cylinder, jug, or syringe, or another vessel with graduations. Adjust the gun as necessary until it is correct.

3. Maintain equipment in working order
Carefully clean with warm soapy water immediately after use. Use vegetable oil to lubricate the working parts. When injecting sheep use clean, sterile needles.

4. Drench or inject correctly
Ensure that the sheep swallow the full dose. Using the dosing gun, place the dose on top of the tongue towards the back of the mouth, taking care not to penetrate the tissues at the back of the mouth.

When injections are used, check if the product must be administered as a subcutaneous or intramuscular injection, and follow the manufacturer’s instructions.

5. Storage 
Wormers should be stored securely away from direct sunlight at 4-25°C. Check the ‘use by’ date and, once open, use within the time shown on the packaging. Shake products well before use.