Kemps may be defined as hairy fibres which are shed after a short period of growth. Birthcoat kemps are succeeded by fibres in the same follicle, and there may be varying amounts of this second generation that are also shed. Thus, successions of kemp often continue throughout the life of the sheep making the fleece uneven in a way usually undesirable. Previous studies have shown that selection against high abundance of halo-hairs is effective in elimination kemp. Although kemps are associated with coarse fleeces with high abundance of halo-hairs, they are not always present. A hairy birthcoat follicle after growing and shedding a kemp may produce fibres of persistent growth; hence this study should have significance for breeders of Mountain Sheep which characteristically have hairy birthcoats. It is understood that a thick, hairy birthcoat of halo-hairs with a minimum of kemp in the adult fleece is desirable in the Scotch Black-face lamb.
The various characteristic fibre types of the sheep's fleece have been studied and classified by Dry (1933). According to the collection of these types present in one sample of wool, certain characteristic arrays can be recognised (Dry 1934). There arrays can be arranged in a series:- those with sickle fibres are non-Plateau with few halo hairs and include Salle, Ravine, Valley and Plain arrays; those without sickle fibres are Plateau, coarse arrays with many large hairy halo-hairs. The former type of array, non-Plateau, is found on finer woolled sheep such as Wensleydales, fine Romneys ets. while the latter type of array, Plateau, is found on N-type Romneys and Mountain breeds such as Scottish Blackface.