Weaner Worm Control and Summer Drenching 

Weaner drenching

Weaners are a problematic member of the flock when it comes to worm control. Weaners are vulnerable to worm infections as their natural immunity, which protects them against worms, doesn’t develop until about 12-18 months of age. In addition, their immunity is further compromised by the stressors associated with the weaning process, including access to nutrition.  

This can be particularly relevant in winter rainfall areas of Australia. With the last few seasons being warmer and wetter than we experienced during the drought, the worm threat this year is high. It is important to be proactive when considering weaner management this year, not reactive.   

If you are experiencing moderate to high rainfall this year, you need to be vigilant when it comes to weaner worm management. Ensure all lambs are drenched with an effective drench at weaning. If lambs were born later in the season and received a drench at marking to coincide with the first summer drench, then it is important to stay proactive and Worm Test to determine if a drench is required.  

If lambs are weaned early- before October, it is too early to make the one drench do two jobs. A weaning drench and a separate, later, First Summer Drench should be given. Delaying the weaning drench (thus combining the 2 drenches) may lead to unnecessary infections and increase larval pasture contamination for the whole flock.  

In Western Australia a weaning drench is more often given in mid-to late spring.  

Top Tips for Summer drenching:

• In moderate to high rainfall climates, the first summer drench is usually given in November/December. Don’t delay if the season holds- It is important to remove existing worm burdens and prevent larval pasture contamination keeping the pasture clean for the next season (autumn). 

• This forms an important component when preparing low risk paddocks for weaners after the autumn break.  
• The principles of preparing a low worm-risk paddock are the same anywhere: stop further contamination and allow existing larvae to die over a period of 3 months during hot weather, increasing to 6 months during very cold weather. 
• A Second Summer Drench is based on a worm egg count, rather than being routine. This drench is important to consider for sheep that will graze paddocks to be used by weaners in the next autumn and winter. 
• By contrast, Western Australia (Mediterranean climate, typified by long, hot and completely dry summers) is a little different to the more eastern winter rainfall areas (where occasional summer rains are more likely). Adult sheep should NOT generally receive a first summer drench; instead, they are treated in autumn. When pastures dry off completely or stubbles are available, all young sheep and goats up to 18 months old can be drenched.