If drenching is to be effective, a drench must be given correctly. Incorrect or poor drenching practices can promote the development of drench resistance.
Do not underdose. Weigh a sample of the mob and dose to the heaviest animal in the mob. Split the mob into weight ranges if there is a large weight range variation.
Check the drench gun is working properly and is accurately calibrated. Squirt several doses of the drench into an accurate measuring vessel before use. If the dose is not correct adjust the drench gun accordingly.
Read all labels carefully and take note of the following:
Method of application.
Handling (shake well before use).
Good drenching technique is extremely important. It doesn’t matter how good a drench is, it’s performance will be compromised if it is not given properly.
Hold the animal gently with the head horizontal.
Carefully introduce the nozzle of the gun into the side of the mouth and over the back of the tongue.
Administer the drench slowly and withdraw the gun.
Ensure the animal swallows before it is released.
Check the accuracy of the gun each time after drenching about 200 animals.
Do not rush.
Drench gun injuries to the throat, or drench that enters the lungs can be fatal.
Animals must be dry and clean before being injected.
Use sharp, clean needles.
Change the needle every 50 doses, or if they become bent, burred, blunt or contaminated.
Inject with the bevel of the needle turned outwards.
Inject under the skin in the front half of the neck.
Tent the skin prior to giving the injection, and inject at a 45 degree angle to avoid injecting into the muscle.
Use a needle with the smallest gauge that the product can be injected through easily and of a length that deposits it under the skin, not in the muscle.
Careless injections can cause infections or carcass damage and downgrading at slaughter.
Take a Drench Check
This test is a simple and quick way to check if the drench you are using is effective. It is done by simply doing a Faecal Egg Count on faeces from drenched animals about ten days after the drench was given.
If there are worm eggs present on this test it can mean several things.
It can mean that the drench was not fully effective and has left some worms still laying eggs.
That the FEC was extremely high before the test and the residual egg count at ten days is not unexpected.
That the animals were not drenched correctly, either the dose rate was insufficient, or the administration was not correct, or not all animals were drenched.
Drench Gun Cleaning
Good hygiene is very important when handling drenching equipment, both for operator safety, and ensuring future efficacy of the equipment.
Wash out/squirt through tubing and drench guns.
Dismantle guns and carefully wash barrel with warm water and detergent.
Check valves for foreign material.
Ensure all parts are fully dry before reassembling.
Lubricate barrel using recommended oil.
Reassemble gun carefully ensuring washers are not damaged and valves are correct way around (springs always face nozzle end).
If anything is obviously broken, fix it immediately.
The information in this section has been adapted from the Wormwise Handbook 2019. www.wormwise.co.nz