A rapid image analysis procedure for quantitative measurement of wool follicles and fibres in sheep skin

Fibre diameter (FD) at follicle level, and density of follicles in skin tis sue of sheep are traditionally observed with a light microscope. The purpos e of this study was to compare the measurement of these characteristics usi ng either a computer-assisted image analyser (IA) system or manual measurem ent (MM). Skin biopsies were collected at 9 months of age from 16 Merino ho ggets of an ultrafine selection flock. IA and MM methods were compared for follicle FD and density after the latter were adjusted for biopsy shrinkage . Fleece midside FD was also compared with follicle FD by IA and MM methods . A regression of method differences for follicle FD and density with their means gave non-significant slopes. Differences predicted at respective mea ns for pairs of variables were: follicle FD of LA. versus MM (r(2)=0.90, P< 0.001), -1.79 +/- s.e. 0.21 mu m (mean 14.85 mu m); wool FD versus follicle FD by TA (r(2) = 0.72, P<0.001), 1.90 +/- 0.20 mu m (14.90 mu m); wool FD versus follicle FD by MM (r(2)=0.71, P<0.001), 0.11 +/- 0.21 mu m (15.80 mu m), and IA density versus MM density (r(2)=0.89, P<0.001), 19.77 +/- 3.46 mm(-2) (175.3 mm(-2)). This study confirms that measurement of follicle FD and density by IA is an effective and rapid alternative to the more tedious MM method, albeit dependent upon an experienced operator with skills in ti ssue processing, computer imaging and follicle fibre measurement.