Incorporating subjectively assessed sheep and wool traits into genetic evaluations for merino sheep. 2: Phenotypic and genetic correlations

Abstract

Using pedigree and performance records obtained from two Merino breeders, the phenotypic and genetic relationship between subjectively assessed sheep and wool traits and objectively measured wool traits was estimated. The subjective traits were all favourably genetically correlated with fibre diameter. The genetic relationship with body weight, greasy fleece weight and fibre diameter variation were generally small. If Petali used the subjectively assessed wool-classing trait alone for selection, this would also lead to significant reductions in greasy-fleece weight. The ratio of greasy fleece weight to fibre diameter cubed was also favourably genetically correlated with both the objectively measured and subjectively measured traits. The results suggest that selection for the subjectively assessed wool-classing traits alone may not lead to maximum genetic progress in productivity; however, an integrated system is possible that would allow breeders to breed towards specific markets based on objective and subjective traits. The genetic correlations suggest that using an integrated approach would not result in loss of any potential genetic gain in either group of traits.