Mean fibre diameter is a measurement in micrometres (microns) of the average diameter of fibres in a sale lot. This measurement is the single most important characteristic of greasy wool and has been responsible for between 70% and 80% of the price over the long term.

The importance of fibre diameter has led to a lowering of the average fibre diameter over recent years, with production of fine and superfine wool increasing sharply as a total percentage of the wool clip.  Australia now dominates supply of fine wool to the international trade, accounting for over 90 per cent of global production of merino wool of 19.5 micron and finer. 

This has largely been in response to an increase in global demand for fine wool as manufacturers and processors have sought more fine wool to satisfy the global consumers’ demand for lightweight garments with next-to-skin comfort, particularly in women’s wear.

The present relationship between micron and price is shown below.  It shows that the finer the wool the higher the price that it receives with the micron premium increasing as fibre diameter diminishes.  Between 17.0 and 20.0-microns there is over 100-cents difference for each full micron which falls to less than 50 cents between 21.0 and 22.0-microns.  Finer than 17.0-microns the premium for each micron can be 200 to 400 cents.  Lower styles and lower strength types tend to display a much flatter micron/price curve.

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Wool diameter trends

Fine wool

After peaking in 00/01 and then again in the 02/03 season, fine-wool prices fell away before initially bottoming out in November 2003. A brief rebound followed before continuing to drift lower towards the most recent low in late 2005. The market has since recorded solid increases over the past 2.5 years with prices easing in mid 2007 only to make solid gains to mid 2008. At this point pieces again fell dramatically, and have only now at end 2009 begun to recover some ground.

Stylish wools have generally underperformed recently with traditional buyers appearring reluctant at this point in time. Only the very best Spinner’s styles are attracting any sort of premium over the lower styled types.

Medium Wool

Medium and broader microns have followed the pattern of the finer microns, with prices well below their peak in season 2002/03. Rises in mid to late 2007 have given way to a slight easing of recent times, due in part to a decline in the yields and Nkt performance of the wools available. The 28 microns continues to trend sideways, “lowest common denominator” preparation being the greatest influence on price.

The third chart displays the micron differentials over time. It tracks the quarterly averages for the 21 & 23 Northern and Southern Region Micron Price Guides for the last 8 years, comparing them with 21-microns (x-axis).

It shows that the premium for 19-micron wool is now tracking in a range of approximately 150 cents, with this figure falling around 50 cents since October 2008. The 23 microns have increased their margin to the 21 micron axis, mainly due to the increase in demand for mid micron Merino fleece wool.

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Wool diameter tips

The most important decision you can make as a woolgrower, with respect to the price you will receive for your wool, is the fibre diameter you choose to produce. This decision should be based first and foremost on your view of market requirements in the medium to long term.

Failing this, long term historical price relativities are a better guide than recent, short term price margins.

Breeding is the critical determinant of fibre diameter. Environment plays some role in the type of sheep you can run, but this is over-rated; fine wool sheep have been successfully run in pastoral areas. Fine wool sheep do not necessarily cut less wool.

You may wish to compare a few ram sources to decide whether you should change bloodlines. Wether trial and sire evaluation information can help you to identify the most productive sheep.

Variation in fibre diameter (CVFD) is also of some importance, especially as high CVFD is usually associated with low staple strength. CVFD is under genetic control. It is also influenced by fluctuations in nutrition.

Ways to influence diameter

Set breeding objectives for your flock, and design a breeding program that ensures you will meet those objectives. It is vital to choose a ram source with similar objectives to yours, and which provides objective information on its sires so that you know what you are buying.

'Fining up' the flock through breeding is a long-term process but need not compromise your wool cut or other traits.

In higher rainfall areas, run the sheep at a high stocking rate, to maximise wool cut per hectare. Understocked sheep cut more wool per head but less per hectare, and the wool has a higher fibre diameter. Also consider lambing in spring rather than autumn to match feed availability with supply.

Through grazing management techniques, maintain a reasonably constant plane of nutrition to minimise fluctuations in diameter along the fibres. Also consider lambing in the spring rather than autumn to better match feed availability with supply.

Utilise tools such as rapid in-shed micron testing with Laserscan or OFDA. This not only assists in the achievement of breeding objectives, but it also makes it possible to prepare premium finer fleece lines during classing.

However, the basic rule is to keep all the wool from similar sheep together. A fine line strategy is only likely to give a net benefit if you have individual measurements for each fleece (visual classing is not precise enough), and where there is a steeply increasing premium for decreasing fibre diameter (that is, the clip should average below 21um as a guide only).

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