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Wool staple stretched to show position of break.
Position of Break (POB), measured in conjunction with staple strength, is a measure of the position in the staple (base, mid or tip) where it will break given enough force.
Both sections of the broken staple are weighed after the strength test, with the results converted into values indicating whether the staple was broken in the base, middle or tip region.
POB indicates to the processor where fibres are likely to break during processing and the length of the broken fibre sections.
For example, if a staple breaks at the tip, then the broken fibres are either very short (and probably lost as card waste or noil) or rather long. If the staple breaks in the middle, both fibre sections are about equal length and relatively short.
Despite higher fibre losses during processing, low mid-break wools are usually preferred by processors as they give a longer average length in the top (hauteur). Longer wool tops receive a higher price for the topmaker, so greasy wool buyers usually pay premiums for low mid-break wool.
Price differences for POB can be seen across the entire clip. In fine wools, differences of around 150 cents can often be seen between a very low mid-break of single figures, and a mid-break in the 80 to 90% range. Most mills now specify a maximum mid-break for a delivery, making POB an important measurement for both woolgrowers and buyers.
Chart of price discounts for POB in fine wool.
Chart of price discounts for POB in medium wool.
The following charts display the trends for POB discounts since 1995. Medium and high mid-breaks are shown as a discount compared to low mid-break wools, in both fine and medium wool categories.
The market discounts higher mid-break wool. Discounts are more severe for the finer microns. After reaching historical highs in the 2000 to 2001 period, the discounts steadily contracted before making lows around four years ago. Since then penalties have increased as buyers increasingly seek out the better specified wools in response to the demands of topmakers and spinners.
Chart of price discount trends for POB in fine wool.
Chart of price discount trends for POB in medium wool.
Nutrition and time of shearing are the best ways to reduce the percentage of mid-breaks in wool.
Manage sheep nutrition throughout the year to maintain an even profile along the length of the fibre. Sudden changes in nutrition, for example the winter "break" in winter rainfall areas, can cause breaks in the wool fibre. The key is to maintain the supply of nutrients to the follicles during these stress times, particularly when midway between shearing dates.
Supplementary feeding just prior to and during these periods may reduce the impact of seasonal breaks. Identifying the most appropriate times for joining and lambing to match feed supply to peak feed demand can help maintain a more appropriate plane of nutrition for the sheep.
The second management tool involves time of shearing. If it is difficult to reduce mid-break or increase strength via nutrition management techniques, the break can be managed by altering shearing dates. While a weak point will still appear in the wool, shearing at or near the seasonal break will shift the POB towards either the tip or base.
If the break is within 10mm of either end of the staple, the Length and Strength test is less likely to break the staple at this point, increasing the overall strength measure.