|dc.description.abstract||Professor A.E. Henderson of the Wool Science Department, Lincoln College, has identified and bred two lines of sheep which grow consistantly 'yellow' or 'white' fleeces. This yellow colouration is removed when the wool is extracted with organic solvents suggesting that the component is in the wool wax. Wool wax is a mixture of skin-derived and secreted lipids retained by the wool fibres.
This study of skin surface lipids was directed, at first, towards identifying the components in wool wax responsible for the colouration and subsequently extended to examine other skin lipids.
The agents for yellow colouration in fleeces are diverse (Hoare 1968). Discolourations have been attributed to products of microbial origin (Mulcock et al 1965, Mulcock & Frazer 1958, Frazer & Mulcock 1956), oxidized sterol or bile-like pigments (Sidey 1931, Rimington & Stewart 1932) or possibly the carotenoid pigments as observed in adipose tissue (Kirton et al 1975).
The wax index, fibre diameter, fleece pH, percentage of free fatty acids, and iodine number were investigated. Differences were found in wax index, iodine number, and percentage of free fatty acids. There were no significant differences between the fleeces when the saponifiable and non-saponifiable fractions were analysed by gas-liquid chromatography.
In spite of extensive work the components could not be separated adequately by thin layer or gas-liquid chromatography. This was probably because of interference by products of wax which had undergone extensive oxidation. The wax, spread over the fibres in a thin film, presents a large surface area to agents like the alkaline suint salts and microorganisms. Incubation in a warm, often moist microclimate leads to the formation of a complex range of compounds.
Ear wax, which is not subject to suint action or fleece microrganisms was proposed as a more readily monitored lipid source.
The initial study to determine whether the composition of ear wax is typical of skin surface lipids was made on human ear wax.||en