Livestock

Winter worm burdens in sheep

By Dr Jeff Cave

Jul 11, 2025

Worms should be considered in all ill-thrifty or scouring sheep, regardless of when the sheep were last drenched.

Worms and scours can be a significant problem in weaners and lambing ewes, especially with limited feed and the cold stress of winter.

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Winter conditions provide ideal conditions for the survival of worm larvae on pastures. What is more, feed may be short.

Sheep that are nutritionally stressed and in light condition grazing short pastures are likely to be affected by worms and scouring this winter.

Worms should be considered in all ill-thrifty or scouring sheep, regardless of when the sheep were last drenched.

To help establish whether worms are the cause of ill-thrift or scouring it is worth considering the following:

Nutrition of the sheep including the feed availability, supplemental feeding, and stocking rate.
Class and condition of the sheep including their body condition score.
Drench program including the product/s used and date/s drenched, particularly the time since the last treatment.

To know for sure, faecal samples from at least five affected and five non-affected sheep should be submitted for worm egg counts.

To help manage worms in sheep during winter:

Provide adequate feed for weaners and lambing ewes on low worm pastures such as those prepared by smart grazing over summer, those previously grazed by cattle, or those used for cropping.
Weaners and lambing ewes need to be in a condition score around 2.5. If lighter, they will need preferential treatment and feeding.
Check worm egg counts by Wormtest (samples from 10 representative sheep) every four to six weeks through winter.
Confirm the drench worked by Wormtest at the time of drenching and 10 to14 days later.
Check worm egg counts in lambing ewes about four weeks before lambing.

For further information, contact your local veterinarian or Agriculture Victoria animal health or extension staff, or in NSW your Local Land Services, or use WormBoss at: https://wormboss.com.au/

Dr Jeff Cave is a senior veterinary officer in Agriculture Victoria’s northern region.

By Dr Jeff Cave

Dr Jeff Cave