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Wednesday, December 16, 2015

How do wool strength and yield vary with staple length?

By Andrew Woods, ICS  |  Source: AWEX, Holmes Sackett, ICS

Key points

  • Staple strength decreases as staple length increases.
  • Yield increases as staple length increases.
  • The appropriate micron, staple length and staple strength need to be used when comparing prices for wool from shearings of different intervals.
  • It is quite possible that shearing at shorter staple lengths will result in more greasy wool but the same volume of clean wool.

In November, Mecardo looked at the price relativities for different length merino wool. This analysis showed little difference in price between 60 and 120 mm length wool, with a premium for 80 mm length wool. In that article, we assumed different staple strengths for the different staple lengths. This article explores the variation in wool specification by staple length further.

Various parts of the industry are encouraging an increase in the frequency of shearings in order to reduce the staple length of wool being offered for sale in Australia. In order to analyse whether this is a worthwhile exercise, some assumptions need to be made regarding volumes and wool specifications. This is needed to see if the additional cost incurred by extra shearings and changing farm production systems is offset by increased income.

In the November article, Mecardo assumed that staple strength would be higher for the shorter staple length wool, and lower for the over length wool in relation to the 80-90 mm “standard” length. Table 1 shows the average measured staple strength for all wool sold at auction in 2014-15 by staple length (down the left hand side) and by micron groupings (across the top).

As a rule, staple strength increases with decreasing staple length. For 120 mm length wool, the average staple strength in 2014-15 was in the order of 30-34 N/ktx, while 60 mm length wool had an average strength in the order of 45-55 N/ktx. When comparing potential prices for different length wool, the appropriate staple strength should be taken into account.

Table 2 shows a similar analysis for yield (Schlumbger Dry in the main, for the technically-minded) again from the 2014015 season. It shows that the average yield increases as staple length increases, with roughly a 5% difference between the yield for 60 and 120 mm length wool.

Sheep increase their appetite after shearing, which can lead to a short term increase in wool production. However, Sandy McEachern at Holmes Sackett says that this increase can be easily swamped by other factors such as lambing or a lack of feed.

The assumption then is that clean wool production is relatively constant on a per annum basis regardless of the frequency of shearing. If clean wool production is constant then, given the lower yields for shorter staple length, it is quite possible that more greasy wool will be produced by shearing at short staple lengths.

2015-12-15 Prem Shorn TBL 1 Lge

2015-12-15 Prem Shorn TBL 2 Lge

What does this mean?

The variation in wool specification according to staple length requires some care in comparing potential prices from prospective changes to shearing frequencies. In addition, calculations should be done on a clean basis rather than greasy because the yield is likely to vary according to staple length.

Mecardo information is provided to assist in your marketing decisions. It contains a range of data and views on the current market. It is not intended to constitute advice for a specific purpose. Before taking any action in relation to information contained within this report, you should seek advice from a qualified professional. The information is obtained from a variety of sources and neither Mecardo nor Ag Concepts Advisory will be held liable for any loss or damage whatsoever that may arise from the use of information or for any error or mis-statement contained in this report. 


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