Studies of the effects of the gene N on body growth and fleece development of the New Zealand Romney. II. The development of the fibre population

Abstract

An investigation of factors affecting fleece density in the N-type and ordinary Romney lamb is reported. The number of fibres per sq. centimetre on the loin position were estimated at birth, at 6 weeks of age, and at an average age of 24 weeks. At birth N/ + lambs had a lower fibre density than +/ + lambs and a high density of halo-hairs was associated with a lower density of other fibres. From birth to 6 weeks N/+ lambs added more fibres to the fleece than did +/ + lambs. In addition more fibres were added by lambs of both genotypes showing better body growth. For lambs showing poor body growth a high density at birth was associated with less new fibres at 6 weeks. Fibre density at 24 weeks was slightly but significantly lower for the N/+ lambs and, for both genotypes, was related to the 6-week density but not to the intervening body growth. The possible factors underlying these results are discussed.