The development and moulting of the birth and first adult coat of two genotypes of cashmere-bearing goats, a highyielding Siberian (S) and low-yielding Icelandic × Scottish feral (IF), were examined. Samples of fibre from the neck, mid side, belly and rear-leg areas and of mid-side skin were obtained monthly from five male and five female kids of each genotype from birth to 13 months of age. Guard hair and undercoat length, secondary/primary (S/P) skin follicle ratio and the proportion of skin follicles containing a non-growing fibre with a brush end were recorded. S/P ratio reached an asymptote between 4 and 5 months of age and was higher fP < 0·01) in S (10·7) than in IF (6·7) kids. In both genotypes peaks of brush formation in primary follicles occurred between 2 and 4 months and again between 8 and 11 months of age. In contrast to primary follicles, secondary follicles had only a single peak of brush formation occurring at 10 and 8 months of age for S and IF kids respectively. Guard hair moulted from the birthcoat, but there was no loss of undercoat prior to 12 months of age and harvesting of cashmere prior to this time is unnecessary.
The secondary follicles of S kids had a longer growing period and fibre length increased at a greater rate than that of IF kids, resulting in more than a two-fold difference in the maximum undercoat length. Assessments to estimate the final weight and proportion of cashmere, made prior to completion of growth of the fleece, are likely to underestimate these parameters for high-yielding goats in comparison with their low-yielding counterparts. However, it is unlikely to alter the ranking, and hence the selection, of animals for retention in the breeding herd.