THE COMPARATIVE ABILITY OF SOME LOUSICIDES TO REDUCE COCKLE IN SHEEP PELTS

Sheep naturally infested with the biting louse, Bovicola ovis were tre ated with a range of organophosphorus and synthetic pyrethroid dip for mulations. The sheep were killed 42 days after treatment and the pelts examined for evidence of cockle, a nodular condition that appears in some sheep as a response to the presence of lice. Sheep treated to sat uration with dip formulations produced more high quality pelts than di d sheep treated with low volume, pour-on or spray-on dips. These diffe rences are suspected to arise because louse populations decline more s lowly after treatment with pour-ons or spray-ons than with saturation dips. The removal of lice and regression of cockle resulted in a high percentage of first grade pickled pelts. However, processing through t o the dyed crust leather stage highlighted lesions in the same pelts t hat were not apparent at the pickle stage and lead to a substantial in crease in the number of downgraded pelts.