A particularly attractive area for fine wool producers in the United States is to try to sort fleece lines finer than 18.5µm to take advantage of price premiums and high wool loan deficiency payments (LDP). The objective of this trial was to determine feasibility of building 18.5µm lines of wool to meet contractual requirements using the Optical Fiber Diameter Analyzer (OFDA) 2000. This trial utilized approximately 25,000 head of Rambouillet sheep of varying age over a four year period. Fleeces were sorted into various lines based on the OFDA2000 fiber diameter measurements of individual samples and a pre determined set of fiber-diameter cutoff points. After shearing, bales were weighed and cored and samples were sent to a commercial testing laboratory for determination of yield, fiber diameter, standard deviation, and coefficient of variation. The coefficient of determination (r2) between the estimated fiber diameter of the lines of wool based on the OFDA2000 measurements at shearing and the final core test results was 0.79. OFDA2000 predicted values approximately 0.20µm (range from +.62µm to -0.18µm) coarser than the certified core test. Classing fleeces based on OFDA2000 estimates at shearing produced lines of wool of different diameters in the direction to be expected. The OFDA2000 tended to under-estimate the finer lines (AAA, ALW, and AL) by about 0.3µm and over-estimate coarser lines (A and BL) by about 0.7µm when compared to the certified core test results. Specific 18.5µm lines were successfully identified in 4 of the eight lines. In cases where the targeted µm of < 18.5 was not successfully identified, the difference between the core test µm and the OFDA estimated line µm was low (0.2µm to 0.6µm). These differences were small enough that these lots could be easily combined with a small lot of finer wool to produce an overall lot that would meet contractual requirements. These data suggest that the OFDA2000 can be utilized to sort fleeces at shearing into specific fiber diameter lines of wool. However, its application for this purpose is not as straight forward as desired. Initial settings can be based on predicted OFDA2000 averages but must be modified slightly by the classer based on knowledge of the flock micron history and a percent of fleeces that the classer estimates should be in a particular line.
