Withholding periods for worm, lice and fly treatments for sheep

Withholding periods are mandatory with all registered veterinary products used to treat sheep for worms, flies or lice. These periods have been developed to indicate when the chemical residue that remains in or on meat and wool products will not exceed the maximum residue limit.

These limits are set in Australia to ensure that:

  • Lamb and sheepmeat is safe to eat.
  • Wool is safe to handle.
  • Wool scour effluent is safe for the environment.

There are three withholding periods:

  • The Meat Withholding Period (Meat WHP) is the time from chemical application to when an animal is slaughtered for domestic use.
  • The Milk Withholding Period (Milk WHP) is the time from chemical application to when milk can be taken from the animal for human consumption.
  • The Wool Harvest Interval (WHI) is defined as the time from application of a chemical to when the wool can be harvested to satisfy Australian environmental requirements (also includes crutching).

Other important intervals that need to be observed:

  • The Export Slaughter Interval (ESI) is the time from chemical application to when an animal is slaughtered for export.
  • The Sheep Rehandling Interval (SRI) is the time between treatment and when wool/sheep can be safely handled without the need for protective clothing.

The meat WHP appears on the labels of all registered veterinary products.

A Trade Advice statement (such as an ESI) may not appear on labels of older registered veterinary products, however, all new products will now include a Trade Advice statement.

All current ESIs can be found on the APVMA website: http://apvma.gov.au/node/10806, see ‘Export Slaughter Intervals and Chemical Withholding Periods’.

The WHP information for all registered veterinary products can be found at https://portal.apvma.gov.au/pubcris.

If a lice or fly treatment does not state a Wool Harvest Interval (WHI) or a Sheep Rehandling Interval (SRI), then a default one-month period applies for mob treatments or for wound dressings. Flystrike treatments for individual sheep have a default withholding period of at least one month for wool.

Always consult the product label and follow the directions for use.