a1 Wool Industries Research Association, Leeds
The follicle ratio S/P and the fibre ratio Sf/Pf have been determined for various post-natal ages of English Romney lambs in six lamb crops.
A maximum site-sampling error has been determined for use in assessing the degree of significance of differences in values of the ratio S/P determined from successive skin samples from individual lambs. Variations encountered in these Romney lambs in the level of their follicle and fibre ratios, in their rates of change and in the degree of their association with live-weight changes show that rigid conclusions based on data from one lamb crop only are not justified. An intensive study of birth and 8-day old samples has shown that follicles may regress in the early post-natal life of the lamb.
Not all follicle anlagen are initiated before birth and the ‘ceiling value’ of the adult ratio Sf/Pf is not necessarily determined or set pre-natally except in the sense of there being a genetic maximum which may or may not be attained. Low restricted follicle and fibre ratios at birth may increase rapidly postnatally and high ratios at birth may increase little, if at all, post-natally. The follicle and fibre ratio may increase even between the ages of 6 and 12 months.
(Received January 20 1965)