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3. On Farm Fibre MeasurementKen Whiteley (updated Kevin Atkins & Cheryl Pope 2010)

Learning objectivesOn completion of this topic you should be familiar with:

The curvilinear nature of the price/diameter curve and its commercial significance The use of in-shed testing as an effective tool for producing sale lots of different average

fibre diameter The technical and commercial factors that influence the efficacy of in-shed testing OFFM as an aid to selection The prospects of utilising OFFM of other characteristics for clip preparation and sheep

selection

Key terms and concepts Position and shape of the price/diameter relationship, accuracy, precision and bias in testing, Sirolan Fleecescan, OFDA 2000, shrinkage of OFFM results, components of fibre diameter variation, processing significance of additional characteristics, OFFM as an aid to sheep selection.

Introduction to the topicKnowing the diameter of wool fibre is important for sheep selection (particularly Hoggets) and in times of high micron premiums can be used in clip preparation to ensure maximum return from fleece sales.

Available technology allows clip preparation to effectively produce lines that differ significantly in average fibre diameter. This is likely to be more profitable than producing one larger line for the fleeces from a mob of sheep whose average fibre diameter lies near the inflexion point of the curvilinear relationship between price and fibre diameter. The process is dependent upon the variation among fleeces, the accuracy of the in-shed measurement techniques and prevailing prices for different fibre diameter categories.

3.1 OFFM for clip preparationThe preceding lectures have examined the components of variation of important wool characteristics within and among the fleeces from a mob of sheep. These have been used to gain an understanding of the influence of clip preparation upon the characteristics of classed lines and their subsequent processing performance.

The development of rapid methods for the measurement of fibre diameter and their use in-shed during shearing has opened up new opportunities in clip preparation. The main aim is to take advantage of the curvilinear nature of the price/diameter curve (Figure 3.1). As can be seen, the curve is comparatively linear for medium and broad merino wool then rises up sharply due to the premiums paid for finer wools. In general, high premiums are associated with high price levels.

Some researchers have represented the price/diameter curve as two adjoining linear portions with an inflexion or “elbow” at about 20–21µm (Charlton & David 1987). If a mob of sheep produces wool that has an average fibre diameter near this elbow, and the fleeces can be sorted into lines whose average fibre diameters range above and below it, then the total returns for these lines would be greater than would have been the case had all the fleeces been sold in one line.

©2012 The Australian Wool Education Trust licensee for educational activities University of New England

WOOL422/522 Wool Marketing & Clip Preparation_______________________________________________________3-1

The relationship between fibre diameter and clean price of wool

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Notes – Topic 3 – On Farm Fibre Measurement

Alternatively, if the fine and coarse lines all fell in the linear portions either above or below the elbow then there would be no advantage.

Figure 3.1 The relationship between fibre diameter and clean price of wool. Source: Atkins and Semple (2003) and average prices from 2001-2004 and 2005-2008

The concept of taking advantage of the non-linear relationship between price and average fibre diameter is not new. The Australian Wool Testing Authority offers a system called Every Sheep Tested (AWTA 1991) involving the measurement of midside samples taken before shearing followed by measurement in the laboratory (Stadler & Gillies 1994; Gilles & Stadler 1997). Objective Clip Preparation (OCP), as described earlier, was developed to replace a procedure in which fleeces were grouped into smaller lines on the basis of “fineness” or quality number and yield to produce one major fleece line for each mob. This line was sold with a pre-sale test certificate for yield, vegetable matter and fibre diameter. the conclusions of this earlier work concerning classing and the processing results of lines prepared by the OCP method remain valid.

OFFM provides the opportunity to divide the major OCP line into a number of smaller lines by measurement of the fibre diameter of individual fleeces during shearing. The term “Objective Clip Preparation” or OCP is now often applied to wools that have been prepared using OFFM. In this topic, OCP retains its original definition and OFFM is applied to wools that have been prepared using OFFM.

A number of issues need to be addressed, namely:

What is the variation in fibre diameter among fleeces of the same mob? How accurate is in-shed testing and how does it relate to the pre-sale certificate tests that

determine the price paid? How can it be established whether the average fibre diameter of the mob falls near the

elbow? What will be the position and shape of the price/fibre diameter relationship at the time the

wool is sold? What will be the extra cost of OFFM including measurement, marketing and testing of the

smaller lines resulting from this process?

The classing of fleeces using fibre diameter measurement can be treated in exactly the same manner as the use of quality number in traditional classing. As the pre-sale certificate test published in the sale catalogue is the ultimate determinate of the “fineness” of the sale lot, then the measurement of individual fleeces on-farm, and their allotment to fibre diameter categories, can be considered as an indirect method of fleece selection in the same manner as quality


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number. The critical issues are, therefore, the variation among fleeces in the mob and the correlation between the measurement in-shed of the average fibre diameter of the lines prepared in this manner and the pre-sale, certificate tests used in the market place that determine the price paid.

In recent years computer programs have been developed to enable the grower to evaluate the potential for OFFM (Vizard & Williams 1993; The Virtual Wool Classer, Atkins & Semple 2003). These programs require information on the mob and the prices expected for different micron categories. The programs then produce a division of the fleeces into micron categories so that returns are maximised. An example is illustrated in Table 3.1.

Results obtained to date suggest that the OFFM technologies are able to substantially improve the ability of growers to divide up their fleeces into a wider range of fibre diameter categories and that the premiums for fine wool experienced in recent years have produced substantial profits. From past records they are also able to determine where their clip may lie on the price/fibre diameter curve. They can confirm such estimates by measurement of a preliminary sample of 30 – 40 fleeces.

It is more difficult to estimate the average price that will be received or the shape of the price/diameter relationship at the time of sale.

Figure 3.2 Differences in the average fibre diameter of sale lots that could be achieved using OFFM based on the inputs listed. The prices and potential profit compared with selling the wool in one major line are based on average prices from the 2007 / 2008 Selling Season




3.2 Clip preparation in practice In Table 3.1 actual results obtained by sorting fleeces on the basis of fibre diameter are reported (Dominik & Pope 2002).

In, Figures 3.3 and 3.4, the price differential that could be achieved at high and medium premiums using OFFM for these mobs is compared with the price that would have been paid had the wool been sold as one lot similar to the original OCP proposals. Each premium level is considered at low, medium and high market indicators and the cost of the OFFM procedure is also represented to indicate the level of profitability.

Table 3.1 Differences in the average fibre diameter (MFD) of sale lots achieved using OFFM for 11 South Australian mobs. Notes: SE = South Eastern, P = Pastoral, MN = Mid North and W = West Coast. Source: Dominik and Pope (2002).

Property Location ClipMFD (µm)

Mean FD of multiple sale lots (µm) and number of bales (italics)

1 2 3 4 5 6

1 SE 19.9 19.2 19.3 20.2(1) (1) (4)

2 SE 21.4 20.1 21.3 22.5(11) (13) (14)

3 SE 19.3 17.5 18.7 19.1 20.0 21.4(4) (5) (5) (7) (3)

4 SE 19.8 17.9 18.3 19.4 20.8(3) (3) (9) (13)

5 WC 19.5 17.0 18.1 19.0 20.0 21.3(1) (2) (3) (3) (3)

6 MN 17.7 17.0 18.1 18.7(3) (15) (8)

7 MN 18.1 16.5 17.3 18.2 19.0 20.0(4) (6) (8) (5) (3)

8 P 20.1 18.3 18.8 19.5 20.6 21.9(1) (2) (2) (4) (2)

9 WC 24.6 21.9 24.1 26.6(3) (15) (8)

10 P 21.5 19.0 21.1 22.8 24.2(6) (16) (5) (5)

11 WC 20.2 17.0 18.0 19.0 19.8 20.0 21.5(3) (11) (2) (2) (2) (1)




Figure 3.3 Price differences achieved using OFFM with a high micron premium at low, medium and high price levels compared to selling wool in one single lot. The heavy horizontal line represents the extra cost of using OFFM. Source: Dominik and Pope

(2002).

Figure 3.4 Price differences achieved using OFFM with a medium micron premium at low, medium and high levels compared to selling wool in one single lot. The heavy horizontal line represents the extra cost of using OFFM. Source: Dominik and Pope

(2002).

Generally high premiums for fineness and high market indicators go together. There have been times of low prices when little, if any, premium was paid for fine wool. From the Figures it can be seen that, in times of high premiums and high market indicators, a substantial profit was obtained in seven out of the eleven clips studied.

OFFM was only just profitable for Clip No. 6 at the high premium level and high market indicator because all three lines produced fell in a narrow range and all above the elbow of the curve. Clip No. 1 was similar but only a very narrow range of fibre diameter was obtained among the lines (1µm). Clip No. 9 also represented a poor result for OFFM because all the results fell on a relatively linear portion of the curve on the coarser side of the elbow.

As already indicated, the greatest advantage is to be expected when the average fibre diameter of the mob falls on or near the elbow and the testing of the fleeces allows the preparation of lines whose average fibre diameters bridge the elbow. Clips 3, 5, 7, 10 and 11 are good examples.

With a medium premium and indicator the clips maintain their order but only Clips 5, 7 and 11 are clearly profitable.

3.3 The OFFM technology ©2012 The Australian Wool Education Trust licensee for educational activities University of New England



The primary needs of the technology for OFFM are a representative sample and accurate measurement, both at acceptable cost. The Sirolan Fleecescan (Hansford 1999; Humphries et al. 2001) and the OFDA 2000 (Baxter 2001) devices are remarkable pieces of equipment and are modified versions of the Laserscan and the OFDA 100 devices recognised by the International Wool Textile Organisation (IWTO) for certificate testing of the average fibre diameter and CV fibre diameter of raw wool and wool tops (Laserscan: IWTO-12-00, OFDA: IWTO-47-00). They are also recognised by the Australian and New Zealand Standards Associations for testing fleece samples in the laboratory (AS/NZ Standard 4492.4:2000). Neither technology was designed originally for in-shed testing and there are no standardised procedures for in-shed testing.

“Sirolan fleecescan” This device operates on the principle of the scattering of a finely-focussed laser beam by a stream of fibre snippets supported in a solvent.

Laserscan was invented by CSIRO Textiles and Fibre Technology for use in testing laboratories, the first in-shed applications were carried out in 1997 (Hansford 1999). The major change for in-shed testing was the development of sampling equipment so that the whole fleece could be weighed, compressed and sub-sampled using a minicore followed by a rapid scouring procedure to clean the resulting snippets. Disadvantages are its size and the use of solvents both for the cleaning procedure and to support the snippets as they flow through the scanning system. Water can be used to replace the organic solvent.

In addition to fibre diameter and CV fibre diameter, Fleecescan also provides fibre curvature information and greasy fleece weight.

Early evidence suggested that Laserscan has slightly greater precision than the OFDA 100.

“OFDA 2000” This technology, developed by BSC Electronics, is a high-speed duplication of the traditional microscope method using digital imaging (Baxter 2001).

The system is very portable, lower in cost than the Laserscan and is applied to greasy staples. Like the Fleecescan, it provides for measurement of fibre diameter, CV fibre diameter and fibre curvature. In addition it measures medullation and produces a profile of fibre diameter along the length of the staple to demonstrate changes in productivity throughout the growing season.

There is concern about the very small sample that is used (a single staple), how it is chosen and the fact that it is measured in the greasy state. Whilst this represents a much simpler preparation procedure a correction factor has to be determined for each mob to account for the non-wool components and results are adjusted for temperature and humidity. The portability of the OFDA 2000 enables its use for examining sheep in the race but it requires protection from sunlight representative of the whole fleece as the midside.

Relative accuracyThe ultimate test of both technologies lies in their ability to facilitate the formation of sale lots that can be shown subsequently by the pre-sale certificate test to differ in fibre diameter in order to attract price premiums. Both the technologies appear capable of this but there is still substantial room for improvement in terms of their operation, data handling and accuracy.

Atkins (2005) showed that the measurement precision was strongly related to the average fibre diameter of the mob being tested. Using data from 39 datasets to estimate precision he derived a table showing predicted precision and the value that should be used in software.




Table 3.2 Precision of fibre diameter for use in softwareFibre diameter(µm) Predicted precision Suggested precision

16 0.80 0.818 1.02 1.020 1.24 1.222 1.46 1.424 1.68 1.6

3.4 Shrinkage of in shed results Any researcher who has used measurement to select extreme individuals from a population will be aware that, upon a second measurement, the differences have been reduced. The reason for this relates to the non-random selection of fleeces to form sale lots and the random error in the measurement technique (Marler 2001; Atkins & Semple 2003).

If one repeatedly measures the fibre diameter of a sale lot, results will be distributed about the mean in relation to the random errors in sampling and testing. This is not the same as selecting extremes from a population that has already been measured. For example, when selecting from a 20µm clip for extremes at the fine end of the distribution, say 18µm, the selection will include some wools that are broader, say 19µm, but have measured finer (underestimated) due to random error, and some that are finer, say 17µm but have measured broader (overestimated).

Consequently when the “nominal” 18µm fleeces are measured again, either singly or as a sale lot, the result, and any subsequent measurements, will be grouped about the “true” mean result for each fleece, or sale lot, as determined by the random error in the measurements.

Bearing in mind the shape of the distribution it can be seen that, at the fine end, there will be more broader fleeces that have measured finer (underestimates) than the reverse (overestimates). As a consequence, the mean diameter of the fleeces in the selected fibre diameter category (18µm) will be broader when re-measured as a sale lot.

By the same reasoning, the lines made from fleeces placed in the broader fibre diameter categories will measure finer on the second measurement. If fleeces are selected to represent the average fibre diameter then there will be no shrinkage as the distribution is symmetrical at this point. Thus the magnitude of the shrinkage increases with the distance of the selected category from the average of the mob.

These effects are demonstrated in Table 3.3 for a simulated study of 1000 fleeces with an average fibre diameter of 20µm and an among-fleece standard deviation of 1.5µm (Atkins & Semple 2003). Each fleece had a true fibre diameter and three fleece tests at different levels of precision (±0.4µm, ±1.0µm, ±2.0µm). The fleeces were then divided into fibre diameter categories based on the fleece tests and compared with the true values. It is assumed that there is no bias between the fleece tests and the true result.

Table 3.3 Comparison Between Fibre Diameter Results Based on Individual Fleeces and the Subsequent Predicted Result on Bales. Source: Atkins and Semple (2003).

DiameterCategory

(µm)

Precision of Fleece Test+ 1.0 µM + 2.0 µm

Fleeces True Fleeces True< 18 17.3 17.6 17.2 18.1

18 - 19 18.6 18.7 18.5 19.019 - 20 18.5 19.6 19.5 19.720 - 21 20.5 20.4 20.5 20.321 - 22 21.4 21.3 21.5 21.0

> 22 22.7 22.4 22.8 21.9




With a test method of high precision (± 0.4µm, not shown in Table 3.3) the difference at the extreme fibre diameter categories is only 0.05µm whereas at the lowest level of precision (± 2.0µm) a shrinkage of 0.9µm is observed. This could have a major effect on the level of profitability of the process. The intermediate level of precision (± 1.0µm) is reasonable and probably represents the best result that can be achieved with current in-shed procedures. Early research (Marler, Hansford & McLachlan 2002; Hansford et al. 2002) suggested that the precision of testing in-shed, including sampling and measurement errors, was approximately ±1.0µm to ±1.4 µm with Sirolan Fleecescan outperforming 0FDA 2000.A later comparison of Fleecescan and OFDA 2000 (Marler and Baxter 2004a) concluded that the methods were essentially equivalent in precision. An average 95% confidence interval for fibre diameter was estimated to be ±1.2 µm.

In addition to precision, there may be bias between in-shed results and the presale certificate test due to sampling and/or test methods and, although undesirable, this does not invalidate OFFM as a technique for separating fleeces on the basis of fibre diameter. It is, however, important to establish the magnitude and direction of this bias in order to be able to predict the profitability of OFFM as a tool for clip preparation.

In conclusion, the profitability of using in-shed testing of fleeces for fibre diameter is heavily dependent on the average fibre diameter of the mob, the variation among fleeces, the accuracy of results and the “micron premium”. OFFM achieved wide support with high prices and premiums but recent sharp declines in price have dampened enthusiasm. Growers should pay particular attention to previous test results and market prices to ascertain likely outcomes.

Figures 3.1a and b illustrate the price/diameter curves for periods between 1998 and 2008. The greatest profits were achieved in early 2001 when the relationship is flat and linear for wools broader than 20µm then rises very steeply below 20µm. By comparison, the late 1998 period revealed a relationship that had a relatively modest increase in price below 20 µm. OFFM was not profitable during this period at any fibre diameter (Figure 3.5).

The above considerations have been based on testing all animals in a mob and using the information for the preparation of lines based on average fibre diameter. There are other considerations when looking at an entire clip composed of several different mobs such as mixed-age ewes, wethers and young sheep.

Firstly, even in a clip in which adult fleeces measure 23 µm, the young sheep may be up to 2 µm finer so that measurement can be applied profitably to the young sheep to take advantage of the curvilinear price/diameter relationship.




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Figure 3.5 Net potential profit achieved using OFFM for mobs of different fibre diameter for three of the price periods . Source: Atkins and Semple

Secondly, if sheep are identified, then it is possible to reuse the results for young sheep at little cost as a basis for separation of the adult fleeces in subsequent years. Whereas some growers have used OFFM opportunistically for selecting fleeces on the basis of fibre diameter the reuse of results from young sheep would necessitate identification, effective data recording and record maintenance.

3.5 OFFM as an aid to selection Growers who use measurement as a basis for sheep selection already have identified their sheep so measurements taken at shearing can be used for clip preparation and sheep selection. In addition to the possibility of higher returns from clip preparation, measurement can be used to achieve two substantial benefits namely: the selection of replacement animals so that the average diameter of the flock is lowered and the genetic gains realized through the progeny of the replacement animals.

Price declines since 2002 have resulted in some growers halting in-shed measurement although analyses continue to indicate that optimal use of OFFM for clip preparation remains profitable in virtually all clips in the 19µm – 23 µm range. However, among finer clips, much greater benefits result from the use of OFFM in sheep selection rather than clip preparation (Atkins & Semple 2002, 2003).




Figure 3.6 Long Term economic benefits of OFFM for clip preparation and sheep selection in a flock comprising 2000 breeding ewes and 1000 adult wethers. Source: Atkins and Semple (2002).

In Figure 3.6 the average annual profits over a 10 year period for a flock of 2000 ewes and 1000 wethers are shown. The greatest benefits are achieved in the finer flocks through the application of OFFM for selection rather than clip preparation. Thus, although there has been a decline in OFFM, it does appear that it will become the norm for specialist wool producers and sheep breeders in the future.

3.6 Including fleece weight with fibre diameter for sheep selectionOn-farm measurement of fibre diameter can be used effectively to both prepare the wool clip and select animals for the breeding flock. Fleece weight, of course, is the other major determinant of wool value and can be used in combination with fibre diameter to select animals according to an index of value. But given that recording of fleece weight is an additional measurement, we need to know when the fleece weight record will make a difference to the bottom line.

Using the OFFM Calculator (Version 2.1) for the market period 2002-07, Atkins and Semple examined some simple scenarios. A flock size of 2000 ewes in 5 age groups, 80% reproduction rate, hogget ewes only measured, 10% culled on physical traits and a $1.50 cost of measurement were assumed. We then used this flock structure to see the effect of selection based on a number of strategies for flocks of average diameter between 17 and 24 microns.The selection strategies were:

Select on (low) diameter only and no measure of fleece weight required Select on a micron premium (MP) index combination of diameter and fleece weight using a

14% MP (low diameter, maintain fleece weight), a 7% MP (low diameter and increased fleece weight) and a 3.5% MP (maintain diameter, increase fleece weight) SGA index.


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Diameter FD only 14%MP index 7%MP index 3.5%MP index

17 $5.74 $5.18 $3.89 $1.4618 $5.11 $4.61 $3.47 $1.3619 $3.92 $3.61 $2.78 $1.2120 $2.45 $2.43 $1.99 $1.0321 $1.03 $1.33 $1.27 $0.8922 -$0.02 $0.56 $0.80 $0.8323 -$0.57 $0.18 $0.57 $0.7524 -$0.46 $0.29 $0.62 $0.62

Figure 3.7 Average annual profit per breeding ewe from the use of measurement of diameter alone or diameter and fleece weight combined in an index.

Optimal selection policy for each micron is shown in the shaded column.

3.7 Determining the potential value of OFFM in my situation – OFFM calculatorAs most producers will obtain the maximum benefit from OFFM by using a number of the pathways, it is critical to assess the benefit of each pathway as well as the overall benefit. ‘The OFFM Calculator’ has been designed specifically for this purpose. It allows growers to input their own flock data and see the likely benefit from OFFM that will arise from selection and clip preparation.“The OFFM Calculator” has been developed by K.D. Atkins and S.J. Semple as a multi-purpose tool that can be downloaded from the web-for regular review and as an MS Excel® tool for interactive training during workshop development and workshop delivery.

Basic information on flock size and structure and average (adult) fibre diameter are required. The output is in the form of a profit map over time with some suggested changes for increasing profit by altering structure or selection method.

An up-to-date version of the tool can be downloaded from the software section of the Sheep CRC website: http://www.sheepcrc.org.au

The profit from OFFM changes with time – but not by much!

Over the last 4 years, the market values in the OFFM Calculator have been updated with a rolling 5-year average. The perception of many producers, mirrored by the usage of OFFM, has been that the early year or two of this century was the only favourable period for OFFM use and that in recent times it is not a financially attractive technology.

Current and previous versions of the OFFM Calculator have been used to determine the profitability of OFFM during the market periods 1998-2003, 2000-05 and (current) 2002-07. A


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In flocks of 20 micron average diameter or less, there was little benefit from including fleece weight in the selection of breeding ewes. That is not to say that fleece weight is unimportant, rather that fibre diameter has such a dominant effect on price that for effective selection in ewes, fibre diameter is sufficient. For ram selection, where selection intensity is greater and has a larger impact on the flock, attention to both fleece weight and fibre diameter is essential.

In flocks above 20 micron average diameter, including fleece weight as well as diameter in ewe selection is beneficial. In fact, selection on fibre diameter alone can lose money (when accounting for measurement cost) in flocks over 22 micron average. Useful profit levels in broader micron flocks can still be achieved through on-farm measurement provided fleece weight is measured.


flock size of 2000 ewes in 5 age groups, 80% reproduction rate, hogget ewes only measured, 10% culled on physical traits and a $1.50 cost of measurement were assumed for flocks of average diameter of 18, 20 and 22 microns. The figure below shows the profit from OFFM in these varying market periods after accounting for measurement costs.

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Fig 3.8 Average annual profit per breeding ewe from the use of measurement of diameter alone or an index of diameter and fleece weight in 3 market periods.

3.8 OFFM for other characteristics The measurement of a number of other characteristics in-shed has been proposed such as CVd, fibre curvature, fibre profile, medullation, staple length, staple strength and dark fibres. The first four can be measured using OFDA 2000 but there are no cost-effective methods for measuring staple length and strength in the shed. It may be that fibre profiles could be used instead of staple length and strength and in some situations CVd provides a guide to staple strength. The major issues in regard to additional measurements are:



Profit levels per breeding ewe have declined over time in all flocks, but the decline has been quite small particularly in fine wool flocks.

OFFM, for diameter alone or diameter and fleece weight, remains an attractive proposition in fine and medium flocks due largely to the benefits from selection. These benefits can be magnified in fine wool flocks by selection of wethers.

The largest fall in profit (over $1 per head) has occurred over time in medium wool flocks, largely due to the reduced value of objective clip preparation in these flocks.

Benefits in broad wool flocks continue to be modest and rely substantially on recording fleece weight since selection on fibre diameter alone has limited value in these flocks.


1. The availability of suitable sampling and testing procedures and 2. Their value for clip preparation and/or sheep selection purposes.

Coefficient of variation of fibre diameter (CVd)

CVd plays a minor role in worsted spinning. It requires a 5% change in CVd to have an effect equivalent to a change of 1µm in fibre diameter. A 5% change in CVd, however, represents almost the complete range of CVd found among fleeces in a mob of sheep and, in any case, it is correlated with fibre diameter. In view of its secondary importance to the processor it is difficult to see any reason for further subdividing fibre diameter categories into high and low CV. The differences achieved would be small and of little or no processing significance. As the measurement of CVd is already available using existing technology it could be useful in sheep selection especially for animals used for breeding purposes.

Fibre curvature

Fibre curvature or crimp has a minor role in processing and the quality of the final fabric or garment but should be kept in perspective. Low-crimp fibres of a given diameter are easier to process and produce leaner yarns and garments that have a silkier handle compared to high-crimp fibres. Industry currently produces superfine wools that exhibit the extremes of crimp usually associated with staple length i.e. long low-crimp and short high-crimp fibres. They both have special applications; the low-crimp fibres appearing to be ideal for the production of lightweight worsted fabrics or for blending with other fine low-crimp speciality fibres such as cashmere. High crimp fibres are more appropriate where bulk and fabric cover are required.

It is likely that these different types of fibre will be found in different flocks rather than by dividing fleeces from the same mob into lines that exhibit differences in this characteristic. The latter process would simply result in a return to the traditional method of sorting fleeces for fineness on the basis of crimp frequency and would be unlikely to produce sufficiently large differences in curvature to be of interest to the processor. Current measurement techniques are available but require further development.

Dark fibres

Dark fibres (pigmented or stained) are the major quality issue in clip preparation but represent a technical challenge in terms of establishing sampling and testing procedures that could be used in-shed. The techniques currently used are tedious and are not available for pre- or post-sale testing of greasy corings. Sheep management (pre-shearing crutching) and removal of stains during clip preparation continue to offer the best approach to reducing the dark fibre content of fleece lines. If a suitable technique could be developed then its main value would be in the detection and culling of undesirable animals.

Medullation

Medullation is not considered to be a problem in wool marketing or processing of fine Australian wool. Although measurement appears to be feasible from a purely technical point of view, the question of sampling would be a major issue as medullation is most likely to be found in the breech area and extremities. Its greatest value would lie in sheep selection and could increase in importance with the introduction into the Australian clip of animals that produce heavily-medullated fleeces.

Staple length and strength

These two important staple characteristics have already been discussed with the conclusion that separating fleeces is not value-adding in terms of processing although current regulations still call for separation of tender wools that receive severe discounting. Wools with a staple strength of less than 20N/ktex are usually recognised as tender using manual methods. The availability of presale test certificates for strength and length largely removes the technical reasons for separating fleeces for either length or strength. Consideration should be given also to current price discounts to determine whether any value is added by producing tender lines.

Fibre profiles




Measurements of fibre diameter taken along the staple provide an interesting fingerprint of seasonal conditions and the effects of management decisions. It may also be of value in the prediction of processing performance as it would appear to offer more information than the measurement of staple strength and position of break.

3.9 Future developments It is important that the industry establish which measurements are worthwhile and to what extent they should be introduced into sheep management and shed practice prior to devoting effort to further developments in this area.

Clearly the most important issue facing the wool industry in terms of fleece characteristics is the continuing move towards fining the clip whilst maintaining or increasing fleece weight. OFFM has the potential to make a significant contribution here.

Some clip preparation processes have served in the past to assist valuations based on visual appraisal and the advent of presale testing has largely removed this requirement. It has also been proven that efforts devoted to classing fleeces did not improve the uniformity of important characteristics nor the processing performance of the resulting lines.

The use of additional measurements such as CVd, curvature, medullation may well have some application in identifying limits of acceptance and consequent culling of undesirable animals. Their application as an aid in clip preparation appears to be marginal at best. Indeed, it could result in a loss of focus on the most important characteristics (fleece weight and fibre diameter) and the formation of small lots that would increase the cost of marketing and handling with no advantage to the processor.

The most important feature of clip preparation is the removal of fleeces exhibiting those wool faults and non-wool contaminants that have a major impact on processing and the quality of the final product. In the future, with the continuing requirement to produce finer wool, in line with other natural and manmade fibres, and to reduce processing cost that are much higher than for cotton and synthetics, continuing research and constant revision of clip preparation procedures are essential. It is certain that any of the faults that are clearly proven to lower the processing potential and or quality of the final product will attract even heavier price penalties for the wool producer in the future. It is equally important, however, to ensure that practices designed to assist the buyer in valuation based on subjective appraisal but which have no further textile or consumer significance are not allowed to hinder the development of more efficient wool production, marketing and processing operations.

OFFM can be used to advantage for subdivision of the fleeces from a single mob into fibre diameter categories but any further subdivisions based on other measured characteristics are not likely to produce benefits. On the other hand the use of OFFM for flock replacements and sheep selection purposes is very attractive for most merino flocks. It may well become the norm for specialist wool producers and sheep breeders.

ReadingsThe following readings are available on web learning management systems

1. AWI, 2001, On-farm/In-shed fibre testing in the Australian wool industry, Australian Wool Innovation.

2. Atkins, K.D. and Semple, S.J. 2005, OFFM Calculator, Version 1.33, Australian Sheep Industry CRC, International Fibre Centre, Australian Wool Innovation.

3. Dominik, S. and Pope, C.J. 2002, Case Studies on the Profitability of Objective Clip Preparation for South Australian Wool Producing Businesses, Sheep Industries Development Centre, Roseworthy, Primary Industries and Resources SA and the Wool and Fibre Development Board.

4. Semple, S.J. and Atkins, K.D. 2003, Virtual Woolclasser – User Notes, Orange Agricultural Institute, NSW Agriculture and Australian Sheep Industry CRC.

SummarySummary Slides are available on web learning management systems




The ability of the classer to separate skirted fleeces on the basis of fibre diameter depends on the level of variation among fleeces and the correlation between fibre diameter and quality number. The availability of technology to replace the appraisal of quality number with the measurement of the average fibre diameter of individual fleeces at shearing enables a greater degree of separation of fleeces into micron categories. If the average diameter of the mob lies near the inflexion of the price/diameter curve then this separation based on measurement may be profitable. The accuracy of the measurement is important as is the premium paid for finer wools. The measurements can also be used for sheep selection purposes and this may produce greater returns than its use for clip preparation.

ReferencesAtkins, K.D., 2005 A note on the Association of measurement Precision with Average Fibre

Diameter in On-Farm Fibre measurement, International Journal of Sheep and Wool Science, Vol 53, 2 pp 43-46

Atkins, K.D. and Semple, S.J. 2002, The benefits of on-farm testing in commercial Merino flocks, Proceedings of Trangie QPLUS Merinos Open Day, ed Bartlett, B.A., pp. 23-31.

Atkins, K.D. and Semple, S.J., 2003. ‘The economic benefits of on-farm testing of fibre diameter in commercial Merino flocks: (1) objective clip preparation. Wool Technology and Sheep Breeding, vol. 51(1) paper 1, pp 1-15.

Atkins, K.D. and Semple, S.J. 2003, ‘Using fibre measurements for clip preparation and selection in commercial Merino flocks’, Wool Technology and Sheep Breeding, vol. 51(2), pp. 127-129.

AWTA, 1991, The EST Concept, www.awta.com.au.Baxter, B.P. 2001, On-farm classing of animals and fleeces with the OFDA2000, Wool

Technology and Sheep Breeding, vol. 49(2), pp. 133-155. Charlton, D. and David, H.G. 1987, ‘The myth of the fine line’, Wool Technology and Sheep

Breeding, vol. 35 (2), pp. 131-141.Dominik, S. and Pope, C.J. 2002 Case studies on the profitability of objective clip preparation

for South Australian wool producing businesses, Sheep Industries Development Centre, Roseworthy, Primary Industries Resources SA and the Wool and Fibre Development Board.

Gillies, R.I. and Stadler, W. 1997, A four year study of the ongoing effectiveness of flock ranking following a single testing for mean fibre diameter, Wool Technology and Sheep Breeding, vol. 45(1), paper 4, pp. 27-34.

Hansford, K.A. 1999, Real-time measurement on-farm of mean fibre diameter, fibre diameter variability and fibre curvature using Sirolan Laserscan, Wool Technology and Sheep Breeding, vol. 47(1), paper 2, pp. 19-33.

Hansford, K.A., Marler, J.W. and McLachlan, I. 2002, A comparison of on-farm OFDA2000 and In-Store FLEECESCAN – Sheep selection and fleece classing, Proceedings of IWTO, Technology and Standards Committee Meeting, Barcelona, Report No. CTF09.

Humphries, W., Lukovic, L., Aspros, W.A. and Higgerson, G.J. 2001, Sirolan fleecescan: performance and benefits of in-shed individual fleece testing, Proceedings of IWTO, Technology and Standards Committee Meeting, Shanghai, Report No. CTF04.

Marler, J.W. 2001, The impact of test result precision on on-farm decisions, Wool Technology and Sheep Breeding, vol. 49(4), paper 6, pp. 284-301.

Marler J W and Baxter, P. 2004a The 2003 Australian Wool Innovation on-farm measurement instrument evaluation trial, Part 1: Accuracy and precision trials. Wool Technology and Sheep Breeding 52:43-96

Marler, J.W., Hansford, K.A. and McLachlan, I. 2002, A comparison of the OFDA2000, FLEECESCAN and LASERSCAN – The precision of the measured fibre characteristics of a fleece, Proceedings of IWTO, Technology and Standards Committee Meeting, Barcelona, Report No. CTF08




Peterson, A.D. and Gherardi, S.G., 2001. ‘The ability of the OFDA2000 to measure fleeces and sale lots on-farm’. Wool Technology and Sheep Breeding, vol. 49(2), pp 110-132.Stadler, W. and Gillies, R.I. 1994, A case study for the use of mid-side samples to predict the mean fibre diameter of classed lines, Wool Technology and Sheep Breeding, vol. 42(4), paper 5, pp. 319-326.

Vizard, A.L. and Williams, S.H. 1993, A model to estimate the economic value of using individual fleece fibre diameter measurements to class wool, Agricultural Systems, vol. 41, p. 475.




Glossary of terms

Additivity Greasy wool characteristics (staple length, staple strength, fibre diameter, yield, vegetable fault) can be given appropriate weightings and simply added together to predict fibre length in the top. Examples are the TEAM formulae that apply even to very mixed lots of wool such as fleeces blended with lower lines

BWT Body Weight

Carding The process of converting scoured wool in a sliver of randomized fibres in preparation for combing. Much of the vegetable matter is removed during this process. The next step in worsted processing, combing, short fibres (noil) together with remaining vegetable matter particles are removed and the remaining fibres are converted into a parallel array (top)

Card Waste Wool that is lost during the carding process in the form of fibres entangled with vegetable fault, wool that falls from the card (“sweepings”) and fibres that become airborne (“fly”)

CEM Course Edge Micron. The number of microns above the mean diameter where the broadest 5% of fibres lie

CF Comfort Factor. Is the Percentage (%) of fibres equal to or lessthan 30 microns

CFW Clean Fleece Weight

Clip Preparation Clip preparation involves two major steps: Separating the belly wool skirtings, locks, stains etc from the fleeces and the subsequent classing of the skirted fleeces on the basis of quality number, yield, length, strength together with fleeces containing specific faults. The finer skirted fleeces were classified as AAAM unless heavier in condition and/or shorter. These fleeces were classified as AAM. The broader fleeces were classified as AAACOM or AACOM respectively. Very short fleeces were usually combined into an A or ACOM line if they were present

CRV Fibre curvature expressed in degrees/millimeter. This measurement is related to crimp frequency

CVD Is the Standard Deviation (SD) as a Percentage (%) of the micron

Dark Fibres Fibres that are discoloured due to the inclusion of natural pigment during fibre synthesis (pigmented fibre) or to contamination with urine (stained fibre)

FPFT Finest Point from the Tip. A measurement in millimeters from the tip to the finest micron point in the staple

Fibre Profile Measurements of fibre diameter taken along the length of the fibre that provide valuable information about seasonal conditions throughout the growing period and indicate the strength of the fibre and its likely processing performance

Fine Ends Is the difference between MFE and Micron (MFE-Micron)

GFW Greasy Fleece WeightMax Mic Maximum Microns. The broadest point expressed in microns along

the staple

MFE Mean Fibre Ends. The average fibre diameter of the fibre ends (tip and base) expressed in microns

Micron The average fibre diameter of the tested sample expressed in Microns




Micron Profile Shows the variation of fibre diameter along the staple during the growing period

Min Mic Minimum Microns. The finest point along the staple expressed in microns

Noil Short fibre that is removed from the sliver during combing

OCP Objective Clip Preparation (OCP) represents a system of clip preparation under which the four major fleece lines: AAAM, AAM, AAACOM and AACOM were not made but the fleeces were combined into one major line. This was based on research that demonstrated the inefficiencies of the traditional procedures in producing lines that differed significantly in fibre diameter, staple length and yield. Pre-sale certificate tests for diameter and yield were required for the OCP method. The term OCP has now been adopted for procedures for dividing fleeces on the basis of fibre diameter measurements on individual fleeces at the time of shearing. The original basis of the term is used in these lectures.

Part Tender Staples having strengths in the 25N/ktex region

%<15 The Percentage (%) of fibres less than 15 microns

SD Standard Deviation. Is the statistical distribution or probability in microns that represents approximately 70% of the fibres either side of the average fibre diameter measured within the sample

SDC Standard Deviation of Curvature is the Standard Deviation (SD) of all fibres measured for curvature

SL Staple Length expressed in millimeters

SP Spin Fine is a calculation of micron and Coefficient of Variation of Diameter (CVD) to represent the spinning quality expressed in microns

Staple Strength The maximum force required to break a staple corrected for staple thickness. The units are Newtons/kilotex (N/ktex). Values range from 0 – 100 N/ktex

Sound Staples Staples having strengths greater than 20N/ktex

Subjective Appraisal Traditional methods of appraisal for quality number, yield, vegetable fault and staple length were largely visual. Staple strength was estimated by breaking staples by hand. These were the only tools available to the buyer prior to the introduction of presale testing. On Farm Fibre Testing has now made fibre diameter results on individual fleeces available to the classer

Tender Staples Staples having strength s less than 20N/ktex

VM Vegetable Matter



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