Measurement of fibre density and fibre bundles in the skin of sheep from different breeds

Abstract

A procedure for analysing digitised scanning electron microscope (SEM) images of impressions of sheep skin has been developed and tested. The new technique for measuring fibre densities and fibre bundles was applied to a small number of sheep from the Romney, Border Leicester, and Suffolk breeds, and in fine- and strong-woolled Merinos. Skin impressions were taken from small shaved areas of the skin, and fibres in digitised SEM images of the skin impressions were counted and assigned to bundles. Estimates were made of the density of epidermal follicles, the proportion of these which branch, the number of fibres (follicles) per bundle, and the proportion of skin left bare of follicles. An average distance between neighbouring epidermal follicles, Λ _E, was also measured. Λ _E was found to be correlated with fibre diameter. The total density of fibres (follicles) in the animals sampled ranged from 10 to 100 follicles/mm² , and fibre diameter ranged from ~35 to ~15µm. Despite this wide range, all animals examined were observed to have derived (branched) follicles. The fraction of epidermal follicles which branched varied from ~0·15 to ~0·45, and the average number of fibres (follicles) per bundle ranged from 2·2 to 3·8. Λ _E was used to calculate an indicator of the fraction of skin which is bare of follicles. This was found to be substantial, varying between 0·4 and 0·7. Measurements were also made using both serial transverse and serial longitudinal skin sections. The results obtained with the different techniques were compared.