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
Select and weigh the biggest sheep in the group to determine the correct dose
If there is a wide range of weights, consider splitting the group and dose to the heaviest in the batch
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
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
Smaller drenchers for lambs (as opposed to fully grown ewes) are available with smaller nozzles
Squirt three or four doses and check the level each time, air bubbles coming through, resistance and worn springs all affect accuracy
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
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
Make sure sheep are properly restrained and can’t leap around when drenching, so they swallow the whole amount
Sheep can suffer serious injury, or even death, if unrestrained and the gun penetrates the tissues at the back of the mouth
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
Research has shown the efficacy of the white (1-BZ) and clear (3-ML) drenches improves by withholding food before treatment
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 white (1-BZ) products well before use
Do not mix anthelmintics with any other product before administration
No matter how often you use a product, always read the instructions as recommended dose rates and withdrawal periods do change
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
Respecting Withdrawal Periods
Withdrawal Periods do vary and the Benzimidazoles (white group) class of anthelmintics have a relatively short withdrawal period ranging from four to 24 days. The Levamisole (yellow group) class of anthelmintics generally have on average a longer withdrawal period compared to the white drenches. Depending on the product, the withdrawal period for yellow wormers range from 15 to 21 days. The Macrocyclic Lactone (clear group) class on average for oral drenches range from six to 14 days but have the longest withdrawal period of up to 104 days for injectable versions. Combinations have a wide range of withdrawal periods depending on the chemicals in question. Fluke products range from 28 to 56 days.
It is obvious therefore, that the possible withdrawal periods of animals being treated within a flock who are close to slaughter need to be considered carefully. Recording of treatment dates accurately can be made much simpler by EID tagging animals (perhaps earlier than usual) so reading and recording and can be done. Many EID Stick Readers now on the market possess Alerts helping to prevent animals being selected for slaughter too early so the danger of residues entering the food chain is prevented.
Table 1 The Classes of Anthelmintics available in the UK
Source; SCOPS *Not all products cover all the parasites listed. **Withdrawal period dependent on Product used.
Animal Health Delivery Systems (AHDS) from Simcro and NJ Phillips include a variety of sizes for adult and lamb. They are highly accurate, many with High Flow Valves (HFV) and dual fitting barbs so wider tubes can be used allowing quicker treatment and for thicker drenches to flow through smoothly. They also come with high quality tubes, connectors and springs preventing kinks in pipes again increasing flow rate and preventing air bubbles. Many in the range possess Service Kits too. Farm Resource Management (FRM) solutions from Tru-Test include EID Stick and Panel Readers so animals possessing an EID tag can have their treatment date recorded. The Tru-Test XRS2 Stick Reader has an Alerts function to identify treated animals and pre-selected animals. Weigh scale indicators with Load bars help to establish the weight of animals to be treated. The Tru-Test S3 records livestock weights onscreen or uses Bluetooth to connect to mobile devices. Livestock Identification Systems (LID) include EID tagging solutions including TagFaster, Z for sheep and Rubba tags offering accurate tagging and reading by EID Stick Readers.