Sheep Drenching & Vaccinating in the Riverina

The most reliable way to determine when drenching is needed is through regular faecal egg counts, which give you an accurate picture of the worm burden present in your mob at any given time. Drenching based on egg counts rather than calendar dates helps avoid unnecessary treatments and reduces the risk of drench resistance building up in your flock over time. Seasonal conditions, pasture contamination levels and the class of sheep being managed all influence how frequently drenching is likely to be needed across your operation.

Drench resistance occurs when a proportion of the worm population in a flock survives treatment because they carry a genetic resistance to the active compounds in the drench being used. It develops gradually through repeated use of the same drench class and is now widespread in sheep producing regions across Australia. Rotating between drench classes, using combination products where appropriate, dosing accurately based on the heaviest animal in the mob and avoiding underdosing are the most practical strategies for slowing the development of resistance in your flock.

Combining sheep drenching and vaccinating with other handling events such as crutching, EID recording or condition scoring is standard practice on most properties and makes efficient use of the time involved in getting a mob through the yards. Planning the order of work carefully so that each task flows into the next without creating bottlenecks keeps the job moving and minimises the time sheep spend in the yards. Discussing the full scope of work with your contractor before the day ensures the right equipment and personnel are available to get everything done in one well-organised run.

Drenching is giving sheep a dose of liquid worming treatment, usually by mouth, to control internal parasites. It's a routine part of keeping a flock healthy and productive.

It varies with season, rainfall and worm test results — some mobs need it a few times a year, others less. Best practice is to drench based on worm egg count testing rather than a fixed calendar.

Internal parasites such as roundworms and barber's pole worm, which cause weight loss, scouring and anaemia. Controlling worms protects growth rates, fertility and overall condition.

Often around key points like weaning, before lambing, and during high-risk warm, wet conditions — guided by worm egg counts.