Farmers are being reminded to treat all incoming sheep with a group 4 wormer and quarantine them to prevent resistant worms being brought onto farms.

While it is generally common practice to treat and quarantine newly purchased stock, sometimes this process can be overlooked for sheep that are returning from grazing.

Matt Colston, Elanco ruminant technical consultant, says it is vital not to forget these animals because they pose the same risk as newly bought stock.

“Whether sheep are grazing common land or rented ground, unless a farmer has had sole use of that land for a minimum of two years, it’s important to treat these animals as ‘incomers’,” says Mr Colston.

Below, Mr Colston outlines the best practice protocols for quarantine dosing:

Weigh stock and calibrate drenching equipment

To ensure sheep are dosed accurately, do not guess the weight of sheep. Calibrate your scales, then select and weigh the biggest sheep in the group to determine the correct dose. Split the group if you need.

Underestimating the weight of sheep can cause them to be underdosed.

Treat all incoming stock with a group 4 wormer

Currently there are only five chemical groups of anthelmintics. Research shows resistance to group 1-BZ (white), 2-LV (yellow) and 3-ML (clear) is growing rapidly.

“Once resistance to wormers has developed it’s irreversible,” says Mr Colston.

He recommends using the newer group 4 (orange) wormer Zolvix as soon as possible after the sheep arrive back on the farm as this will clear out any resistant worms the sheep might have been picked up  while grazing land away from the farm.

Quarantine sheep

The quarantine period should start as soon as sheep arrive.

Ideally sheep should be yarded for 24-48 hours to allow the treatment to work and prevent worms being passed on pasture.

Turn sheep out to dirty pasture

Following the quarantine period, sheep should only be turned out to dirty pasture.

“If resistant worms survive the treatment, this ensures they are diluted by other worms,” says Mr Colston.

For more advice on treating sheep for worms go to:

Levels of resistance on UK sheep farms:

  • In Scotland, resistance to group 1 white wormers has been found on 80% of lowland farms and 55% of upland farms, according to Moredun
  • In England and Wales, resistance to white wormers has been found on nearly 100% of lowland farms and 83% of upland farms, according to Sustainable Control of Parasites in Sheep (SCOPS)

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