Sorting Lines of Wool with the OFDA2000
Brent Roeder, Rodney Kott, and Brenda Robinson
Montana State University Wool Lab,
Montana State University, Bozeman, MT
Background
There is growing interest in using new technology to sort fleeces at shearing to target markets and marketing options for fairly specific fiber diameter requirements. In many cases the micron requirements of these markets are so precise that visual classing is not applicable. A particularly attractive area for US finewool producers was to try to sort fleece lines finer than 18.5 µm to take advantage of the high LDP rates. Australian researchers found a strong correlation between the averaged OFDA2000 mean fiber diameter and the certified core test and speculated that building lines to specification is feasible using the OFDA2000. However, previous US research has suggested that the accuracy of predicting the average fiber diameter for OFDA2000 classed lines is lower than required to justify the expense of testing for this specific purpose alone. Objectively classing wool into specific micron lines in America would allow producers to be more competitive on the international market, generate more income from the Wool LDP program, and offer more flexible marketing options. To explore these opportunities, Montana State University conducted research using the OFDA2000 to build lines of wool from 2004 through 2007.
PURPOSE STATEMENT
The objective of the trial was to determine practicality of the OFDA2000 in adding value to the clip by building 18.5 µm lines of wool to meet contractual requirements.
SUMMARY OF FINDINGS
The trail was conducted at Helle Land and Livestock in Dillon, Montana and utilized approximately 25,000 head of Rambouillet sheep of varying age over a four year period. After a sample was measured on the skirting table with the OFDA2000, the fleeces were sorted into line bins according to micron. Core samples of bale lines were shipped to Yocum-McColl Testing Laboratories for yield, fiber diameter, standard deviation, and coefficient of variation.
The ability to build lines of wool with the OFDA2000 on-farm is dependent on the correlation between the predicted average fiber diameter of the line and the certified core test of the line. The correlation between the predicted OFDA2000 mid-side sample lines and the certified core test lines on data collected over four years on sheep of varying ages was 0.79. Two problems encountered when using the OFDA2000 to build lines of wool was micron "creep". Micron "creep" is a function of incorrectly sorting fleeces simply due to the error of sampling and measurement. Each line will contain some fleeces measured too coarse from the adjacent lower line, and some fleeces measured too fine from the adjacent upper line, and the effect will on average balance out. However, in the finest line there is no balancing for erroneous measurements from the finer end. So it will contain some fleeces from the adjacent coarser line, and the average of the line will therefore be greater than anticipated. A similar effect occurs in the coarsest line. The OFDA 2000 tended to under-estimate the finer lines by about 0.3 µm and over-estimate coarser lines by about 0.7 µm when compared to the certified core test results (table 1). As a result, we successfully classed 18.5 micron lines about 50% of the time.
| Table 1. Four year results building 18.5 µm lines of wool from sheep of varying age. | ||||||
|---|---|---|---|---|---|---|
| Year | Flock Core µm | Line Core µm | OFDA Mid-side µm | Percent fleeces in line | Difference (OFDA estimate minus core) | |
| Ewe | 2007 | 19.8 | 18.3 | 18.3 | 18 | 0 |
| 2006 | 20.0 | 18.9 | 18.4 | 14 | -0.5 | |
| 2005 | 19.8 | 18.4 | 18.2 | 24 | -0.2 | |
| 2004 | 20.3 | 18.8 | 18.3 | 23.5 | -0.5 | |
| Lamb | 2007 | 19.2 | 18.7 | 18.4 | 66 | -0.3 |
| 2006 | 19.0 | 18.5 | 18.4 | 56 | -0.1 | |
| 2005 | 19.2 | 19.1 | 18.4 | 80 | -0.7 | |
| 2004 | 18.6 | 18.5 | 18.1 | 78 | -0.4 | |
CONCLUSIONS
When used for fleece classing, the OFDA 2000 mid-side samples produce lines of wool of different diameters in the direction as expected (the finer can be sorted from the coarser). However targeting a specific micron is more difficult. Using the OFDA 2000 as a tool for fleece classing with the goal of targeting a specific micron is possible, but its application for this purpose is not as precise as one would like and must involve a subjective evaluation of OFDA 2000 results. These data suggest that the OFDA 2000 can be utilized to sort fleeces at shearing into fairly specific fiber diameter lines of wool. Parameters utilized to sort these fleeces vary and should be determined by OFDA 2000 results, flock micron history and an estimated percent of fleeces that should be in line.
APPLICATION
In certain instances such as in years of high wool LDP rates on specific microns of wool, producers can add substantial value by sorting their clip into specific grade lines of wool. These data suggest that the OFDA 2000 can be utilized to sort fleeces at shearing into fairly specific fiber diameter lines of wool. However, its application for this purpose is not as straight forward as desirable.
The OFDA 2000 has and probably always will be better suited as a management tool rather than a wool sorting tool. Its use as a tool in sheep selection in purebred sheep operations is extremely valuable. Large numbers of individual sheep (such as replacement ewe lambs) can be measured fairly inexpensively.
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