Production and oxidation of wool grease after shearing

Objective To measure the production and amount of oxidation of wool grease secreted immediately after shearing. To identify components of wool grease that might act as a carrier to facilitate lateral diffusion of topically ap plied insecticides. Design Fine-wool Merino sheep were shorn and residual greasy wool was colle cted from the sheep's flank. The quantity of grease produced, and the amoun t of oxidation was measured during 18 days after shearing. Wool grease was fractionated into five component groups based on their polarity and the deg ree of oxidation in these fractions determined. Results There was a 24% increase in grease production within 2 days after s hearing but secretions returned to pre-shearing amounts after 4 days. Durin g this period wool grease oxidised rapidly. Of the grease fractions examine d, sterol and wax esters remained essentially unoxidised whereas free stero ls such as cholesterol and lanosterol, fatty acids and polar lipids, aldehy des and alcohols were extensively oxidised within 7 days after shearing. Conclusion The transient increase in grease production after shearing may f acilitate diffusion of topically applied synthetic pyrethroid insecticides. Oxidation of grease components may then contain the insecticide and limit further diffusion. Incorporating the insecticide in non-oxidising fractions of wool grease may make insecticide dispersion more efficient.