Kemp in New Zealand Romney Sheep and its Significance for Mountain Breeds

Abstract

SELECTION against kemp in the Romney is a simple matter, scarcely amounting to a breeder's problem, but facts learnt from Romneys may be offered to breeders of mountain sheep that characteristically have hairy birthcoats. In Romney sheep, selection against high abundance of halo-hairs is a sufficient safeguard against kemp, and selection against halo-hairs is effective. On the backs of lambs with abundant halo-hairs (large birthcoat kemps of generation I, G₁), there may or may not be secondary kemp. Birth-coat kemps are shed around the third month after birth. Halo-hairs are nearly always all shed. Occasionally an odd halo-hair is of indeterminate growth. Super-sickle-fibres, whether in non-plateau or plateau arrays, sickle-fibres which are the key type in non-plateau arrays, and hairy-tip-curly-tip fibres which are the key type in plateau, vary in their shedding from all to none. The shed birthcoat fibres are succeeded by other fibres which when they are shed are later, or secondary, kemps. In non-plateau, later kemp is grown mostly in the follicles of the halo-hairs, occasionally, as we conclude, in some super-sickle-fibre follicles, scarcely ever in those of sickle-fibres. In plateau, super-sickle-fibres and hairy-tip-curly-tip fibres, as well as the very abundant halo-hairs, are readily followed by kemps, so that there is often a huge amount of secondary kemp in N-type lambs.