The pattern of follicle activity and fibre growth on the neck, mid side and rear leg of 12 Scottish Cashmere (SC) and nine Siberian (S) goat kids was examined from birth to 255 days of age. In both genotypes maximum secondary to primary follicle (S/P) ratio was reached earliest on the neck (P < 0·05) but was proportionately 0·21 and 0·28 (P < 0·001) lower than that on the rear leg and mid side respectively. Secondary follicle activity ceased earlier on the rear leg than the mid side or neck (P < 0·001) and this was associated with lower staple lengths and patch weights of undercoat. Fibre weight and diameter were compared on six body parts: neck, front leg, mid side, rear leg, rump and belly at 255 days of age. Patch undercoat weights and diameter were greatest on the neck, front leg and rump and lowest on the belly.
The estimated annual production of undercoat, calculated from patch weights and skin area measurements on the six parts of the body at 255 days of age was 138 (range 42 to 260) g for SC kids and 525 (range 377 to 661) g for S kids (s.e.d. = 39·4, P < 0·001). Mean undercoat diameter was 16·15 (range 15·32 to 17·51) and 18·94 (range 17·25 to 19·89) μm for SC and S kids respectively (s.e.d. = 0·376, P < 0·001).
Correlation coefficients between fibre traits, measured at approximately monthly intervals and estimates of annual production and undercoat diameter at 255 days were calculated. For SC kids mid-side patch undercoat weight was consistently and strongly related to estimated annual production (mean correlation coefficient, 0·85, s.e. 0·036). For S kids the only variable to show a consistently strong relationship with estimated annual production was mid-side undercoat staple length × diameter2 (mean correlation coefficient 0·66, s.e. 0·067). Thus the best fibre traits for ranking annual production differed between genotypes. In both cases the accuracy of the ranking increased with age. Undercoat fibre diameter measured from 4 to 5 months of age was closely related to estimated undercoat diameter at 255 days of age in both SC and S genotypes (mean correlation coefficient 0·92, s.e. 0·009). Prior to 4 months of age the mean correlation coefficient for SC and S genotypes was 0·53 (s.e. 0·20).
It is concluded that goat kids can be ranked for annual production and diameter of the undercoat, prior to first harvesting, based on fibre traits measured on samples of the fleece.