Using OFDA2000 and FLEECESCAN to Prepare Lots for Sale and Sheep Selection: A Case Study

Abstract

Traditionally, fleece testing using midside samples has been conducted in a laboratory, commonly using the Airflow, SIROLAN-LASERSCAN or OFDA100 instruments. A new generation of testing technologies has recently allowed testing to be performed on-farm, in a classing race (OFDA2000) or during shearing (SIROLAN-FLEECESCAN). Commercial usage has determined each system’s costs and practical advantages/ disadvantages, but little information is available that evaluates their precision limits or technical performance.

Based on a fine-medium Merino flock, this study compares the performance of OFDA2000 operated in a race prior to shearing with FLEECESCAN operated in a central store. A further comparison is made with snippets sampled by FLEECESCAN but tested under standard laboratory conditions (referred to as LAB LASERSCAN). OFDA2000 and FLEECESCAN results were used to allocate fleeces to four Mean Fibre Diameter (MFD) categories and two “Elite” classes. It was stipulated by the classer that Elite fleeces be ≤19.0 µm and Semi-Elite fleeces be ≤20.0 µm. The average fleece MFDs for all sale lots were compared to their corresponding IWTO Coretest results. Both OFDA2000 and FLEECESCAN were able to class fleeces into four distinct diameter categories. However, in this trial, the OFDA2000 results exhibited a coarse bias that resulted in the allocation of fewer fleeces to Elite classing lines. This highlighted the importance of measurement accuracy when classing to a micron cut-off.

The ranking of a single trait, MFD, was used to compare the testing technologies. When selecting a large proportion of a flock, e.g. retain 65%, the three systems had 85-90% of sheep in common. However, when selecting a tail of the distribution, e.g. retain 5%, the systems only had 40 - 50% of sheep in common. This highlighted the importance of measurement precision. In these circumstances, it is advisable to use the test system with the best precision and if possible, further improve the precision through testing more samples (for FLEECESCAN) or more sites (for OFDA2000).

The comments/recommendations in this paper are based on the results of this trial. Both OFDA2000 and FLEECESCAN testing facilitated the differentiation of fleeces into four MFD categories. As the different test systems do not rank animals in the same order and/or may have different biases, in a commercial situation it is not recommended that comparisons of results from different test systems be made. For example, do not make decisions about sheep tested using OFDA 2000 with sheep tested using FLEECESCAN. High levels of accuracy are required in order that specific clip preparation strategies involving micron cut-offs can be achieved, for example, preparation for a contract with defined MFD categories. Under these circumstances, it is essential that a close relationship between the test system and Coretest results be assured.

Citation

"Using OFDA2000 and FLEECESCAN to Prepare Lots for Sale and Sheep Selection: A Case Study", K.A. Hansford , J.W. Marler & I.M. McLachlan, Paper 35, Wool Industry Science & Technology Conference, October 2002, Hamilton, Victoria, Australia