The comparative ability of some lousicides to reduce cockle in sheep pelts

Sheep naturally infested with the biting louse, Bovicola ovis were treated with a range of organophosphorus and synthetic pyrethroid dip formulations. 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 saturation with dip formulations produced more high quality pelts than did sheep treated with low volume, pour-on or spray-on dips. These differences are suspected to arise because louse populations decline more slowly 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 to the dyed crust leather stage highlighted lesions in the same pelts that were not apparent at the pickle stage and lead to a substantial increase in the number of downgraded pelts.