Nutritional effects on fibre growth cycles and medullated fibre production in Angora goats

Abstract

‘Ihe effect of nutrition on fibre growth cycles and medullation in skin of Angora goats was investigated by microscopy of transverse sections of hair follicles. Samples of skin and fleece were taken at regular intervals between August 1989 and August 1990 from non reproducing does fed either maintenance (MPA) or ad libitum (HPA) pasture alIowances. There were no differences in follicle activity between nutritional treatment groups for any of the 11 sample dates. Primary follicles grew and shed their fibres seasonally, with the main growth period from September to May and the mean nadir of 26ct 6% in August. Mean secondary follicle activity did not fall below 95% in HPA goats, or below 85% in MPA goats, however, them was large between animal variation. Primary central follicles grew kemp fibres. primary lateral follicles produced both kemp and gare fibres. Secondary fohicles grew mostly unmedullated mohair, but gare fibres were grown by some earlier developing secondary follicles. Goats on higher feed intake had greater degree of medullation in fibres of lateral ptimaty follicles in Gctober and February, and in secondary follicles in February, March and May. These data suggest that nutritional effects on kemp ccntent of the fleece are achieved through a shift in fibre type within all follicle types.