Correlations of subjectively assessed fleece and conformation traits with production and reproduction in Afrino sheep

Abstract

Data used for this study were collected on the Carnarvon Afrino flock from 1986 to 1998, and include data records on several subjectively assessed traits, body weight and fleece traits of 3291 animals, the progeny of 127 sires and 772 dams. Reproduction data of 686 ewes born from 1986 to 1997 were also included. The heritabilities of and genetic and phenotypic correlations among the subjectively assessed traits were estimated, as well as the genetic and phenotypic correlations of these traits with body weight, objective fleece traits and reproduction. Heritability estimates for the various subjectively assessed traits ranged from 0.06±0.02 for straightness of the top line to 0.51±0.04 for softness of fleece. Positive genetic correlations, ranging from 0.33±0.18 to 0.80±0.06 were estimated amongst the conformation traits head, front quarters, top line and hocks. High genetic correlations were estimated among the subjectively assessed fleece traits and fibre diameter, where animals with lower fibre diameter had softer fleeces, better crimp definition, their fleeces were more even, less dense and had higher creeping belly scores (the extent to which belly wool tends to creep up the side into the fleece). Estimated genetic correlations between the subjectively assessed fleece traits and reproduction were variable in sign and magnitude. The most important of these is the unfavourable genetic correlation (-0.33±0.23) between creeping belly and reproduction. The conformation traits had moderate to high genetic correlations with body weight at all ages. Of the subjectively assessed fleece traits, creeping belly score had the highest genetic correlation with body weight, ranging from -0.26±0.10 for weaning weight to -0.38±0.07 for 15-month body weight. No noteworthy phenotypic correlations were discernable between the reproductive traits and any of the subjectively assessed traits. Of the objective fleece traits, only fibre diameter had some significant phenotypic correlations with the subjectively assessed fleece traits. These were similar in sign, but smaller in magnitude than the corresponding genetic correlations. It is concluded that, with the exception of two or three traits, the subjectively assessed traits would not be negatively influenced when selection is based on the economically important production traits. It is, however, important that selection priorities be based on economic values of the traits.


South African Journal of Animal Science Vol.32(2) 2002: 88-96