Abstract

Skin and fleece samples were taken from 637 ewes of Romney (R), Superfine Merino (SFM), Local Merino (LM), Superfine Merino x Romney (SFMxR), Local Merino x Romney (LMxR) and Backcross (BX) (3/4 SFM) genotypes. Secondary to primary follicle ratio (S/P), total follicle density (n(P+S), primary follicle density (nP), mean fibre diameter (MFD), quality number (QN), staple length (SL); total crimp number (TCN); live weight (LWT) and greasy fleece weight (GFW) were evaluated. Differences between the various genotypes, ages, years of sampling and birth/rearing ranks for these follicle and fleece characteristics were analysed. There were between genotype differences in significance of fixed effects. Genotypes having Merino ancestry with much large follicle populations had more significant fixed effects, but year of sampling and birth/rearing rank were seldom significant. Repeatability estimates for follicle and fleece characteristics ranged fr4om 0.44 to 0.89. Total follicle density and primary follicle density were positively correlated but the degree of association was higher between S/P and n(P=S). Both within and across genotypes, the correlations between S/P and MFD were negative. The low correlations between nP and GFW reflect the genotypes studied, nP having less effect on GFW and MFD in breeds with Merino ancestry. Heterosis was estimated in several ways, the means of groups representing the parent breeds being compared with the mean of each generation of the crossbred genotypes. The follicle traits, as well as MFD and QN showed negative heterosis. Live weight and GFW showed positive heterosis in the F1 SFMxR and LMxR groups of 6.84 kg, 5.99 kg and 0.18 kg and 0.47 kg respectively. The crossbreds weighed more and produced heavier fleeces than the purebreds but with no concomitant increase in MFD over the parental breed mean.

MJ, Young, and AR Sykes

Proceedings of the New Zealand Society of Animal Production, Volume 48, , 157-162, 1988