In many wool-growing businesses, Staple Strength (SS) is an important profit driver affecting clean price. SS is heritable and good responses to direct selection have been shown over a reasonable number of years. However direct measures of SS on individual animals is expensive and for many years breeders have used Coefficient of Variation of Fibre Diameter (FDCV) as a proxy for direct measurement of SS, since FDCV is measured and reported automatically when Fibre Diameter is now measured. FDCV is genetically moderately strongly correlated with SS. This makes FDCV a useful indirect indicator of SS, without incurring the expense of measuring individual sheep directly for SS. In recent years, breeders have been measuring their sheep at earlier ages and in shorter wool. There have been questions raised regarding the effect Staple Length (SL) has on the accuracy of SS breeding values.
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