Method & Materials

Samples

Three (3) sets of samples with different histories of contact with Damara sheep were chosen for this trial:

• 5 lots as a control set (no contamination);
• 6 sale lots prepared from dry ewes (expected low levels of contamination); and
• 14 sale lots prepared from wet ewes (expected heavy contamination).

For the potentially contaminated lots, core samples were obtained from 20 Sale Lots from three properties in one region in Western Australia with a history of contact with Damara sheep. The wool from 6 of these lots was from dry ewes from flocks in which Damara lambs were being raised. It was expected that these lots would have a low to negligible level of Dark Fibre contamination. The ewes were drafted off from the main mobs and shorn separately.

The remaining lots were from the ewe mothers of these mobs. Because of the continuing contact of these ewes with the crossbred lambs it was expected, based on research conducted by SARDI, that the wool from these ewes would have significant levels of contamination.

Core samples from a further set of 5 Sale Lots with no contact with exotic sheep were also included in the trial as a control set.

Trial Design

Six (6) 10g sub-samples were drawn from the presale core samples from each of the 25 lots. Two of these were measured as blind replicates by AWTA Ltd. The other 4 were provided to SARDI as follows:

• 2 x 25 x 10g webs Shirley Analysed at AWTA Ltd; and
• 2 x 25 x 10g scoured core material (fibres to be separated and blended by SARDI).

The reason for this was to check whether or not the preparation systems used by both laboratories affected the results.

Thus three sets of results are reported as follows:

• AWTA results;
• SARDI (AWTA preparation); and
• SARDI (SARDI preparation)