Fibre Testing and Histograms

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The only way to know what quality fleece your alpacas are producing is to have it professionally tested. There are several wool testing services available (this is sheep country after all!). There seems to be quite a range of charges too! Whichever service you choose, you should be supplied with a “histogram” for each individual alpaca sampled as well as a summary sheet listing all your results. A good testing service will also help you to understand your histogram if you require it.

As well as keeping you fully informed, knowing the quality of your fleece has other applications. For example, when selling a fleece, the buyer will require some indication of its value. If you have a stud, being able to quote his fleece statistics may help sell his services to other breeders.

Histograms do not give the full story on fleece quality however! A histogram measures fleece diameter (fineness)*, and the evenness of distribution of that fineness. It does not take into account the age of the animal, environmental factors that may affect fleece diameter, nor does it give any indication of fleece density, shear weight, lustre or evenness of colour – all factors influence the value of the fleece, and the alpaca that grew it.

* Fleece diameter is measured in “micron”, abbreviated as µ

Any alpaca has its finest fleece as a cria. Providing environmental and other factors do not change, the greatest rate of coarsening occurs between the first shear (usually done at around 12 months of age) and the second shear at around 2 years old. The next 5 years normally sees a continuing deterioration in the micron, although other fleece characteristics such as density and crimp and staple should remain unchanged. For this reason, when offered a “fleece statistics” on an animal you are considering using for stud, or purchasing, you should check at what age the histogram was taken. “2nd shear statistics” (at 2 years of age) are usually accepted as giving a good indication of an adults fleece quality.

Environment plays a major part in determining fleece fineness. Many alpacas in South America have fleeces considerably finer than most NZ alpacas – it is not uncommon to find adult South American alpacas with fleeces of 18 micron or less – but import one of these alpacas to the Western world, and in a matter of months the fleece will “blow-out” by 10 micron or more. This is because of environmental factors – particularly as regards feed quality. It has been found in Merino sheep that sparse, poor quality feed produces the finest fleece, and the same rule applies to alpacas also. Many South American alpacas are on a semi-starvation diet; bring them to NZ put them on lush, good quality pasture, and the fleece coarsens immediately.

Most New Zealanders would be unwilling to subject their beloved alpacas to semi-starvation in order to achieve a finer fleece – and indeed, if you are running pregnant females, you would be most unwise to do so. However, the type of pasture you graze your alpacas on can be modified – the rye grass beloved of farmers for fattening livestock is not the pasture of choice for growing fine fleece!

While a histogram should not be the only criteria for selecting stud stock, it has great value in two applications: determining the fleece quality and improvement in your own herd (internal application), and also as a trading tool (external application).

As an internal tool (for yourself): Conformation, fleece density, shear weight, lustre, crimp, colour etc, are all factors which can be assessed visually or with scales. Accurate assessment of micron cannot be determined by either method. So, when assessing stock, use your histogram in combination with visual evaluation. Keeping annual records will also help determine which individuals maintain lower micron fleece to the greatest age and can indicate whether your breeding programme is going according to plan.

As a trade, or external, tool (for a buyer): just like you, buyers can make many assessments about the quality and suitability of a fleece they are considering purchasing, with the exception of fineness. Most will want to know the micron or grade of fleece as an aid to determining the value of the product they are about to buy. All alpaca fleece has some marketable application, but generally speaking a purchaser will expect to pay less for coarser fleece. You may well find if you are unable to provide proof of fineness for a fleece, that you miss out on a sale.

Taking a sample:

A histogram is created by taking a sample of fibre from a fleece and measuring the micron* of each individual hair. Normally a single sample is taken from a mid-side point as pictured. This spot is supposed to be an average representation of the blanket, as it will contain some finer hairs from higher in the blanket, and some coarser ones as the fleece deteriorates towards the belly. It is important to take the fleece from the correct spot, as too high a site can give a finer histogram than is accurate and too low a site, will give too coarse a result. Take a good handful of fibre – and a second one if you want to keep a sample for yourself.

A more accurate fleece representation can be achieved by laying a fleece flat on the floor, placing a wire grid on top, and then taking a small sample from the centre of each square. This is seldom done, but not only gives you a better representative reading of the whole fleece, but overcomes the difficulty of accurately siting your sample.

Courier your sample(s) in plastic bag (preferably not airtight) to your chosen testing service. Each sample must clearly identify the animal the sample was taken from. You should receive individual histograms plus a summary sheet showing results for all the samples you despatched. Histogram(s) should be filed in a safe place for future reference.

A histogram is simply a graph plotting the finest through to the coarsest hair, and which micron was present in the greatest number. The micron diameters are plotted along the base of the graph, and each bar of the graph represents the number of fibres at that micron. 

On the histogram pictured, the finest fibre measured was 11µ (on left side of diagram) and the coarsest 43µ (on right side of diagram). The most fibres gathered at 20micron (the highest point), and the arithmetic average of all fibres was 22.66.

A good histogram is one that has a good height, and little breadth, with as short as possible a tail out to the right. This indicates that most of the fibres were close to the average, with little guard hair.

Along with the graph, you should be provided with statistical information that “interprets” the histogram. Most alpaca owners focus on only 4 of these measurements:
* Mean diameter (µ): in the case of the pictured histogram, 22.6µ. This is the figure normally quoted in “shear statistics”
* Standard Deviation (SD): In this case, 5.05µ. The SD measures the uniformity of the fleece. 95% of the fibres will fall within 1 standard deviation of the mean – or 95% of fibres will fall between 17.61µ (22.66µ – SD) and 27.71µ (22.66µ + SD).
* The Co-efficient of Variation (CV): Many people find this measurement a little confusing, as it is a mathmatical calculation,
which re-expresses the SD in terms of how even the fleece is. The calculation used is:
SD divided by mean micron multiplied by 100
* % of Fibres over 30µ: Often indicates whether an animal has a significant quantity of guard hair which may become a problem during processing. Can be irrelevant if the alpaca has an overall coarse fleece!
* Comfort Factor: This measurement is a reverse recording of the amount of guard hair present in a fleece. The actual measurement is done on the % of guard hair in the sample – this is the “prickle factor”. Because the term “prickle factor” gives a negative connotation, the % is reversed to give the “comfort factor” i.e if 5% of your sample is guard hair, then the comfort factor is quoted as 95%.  Rule of thumb: If you find all of the above confusing, relax! A simple rule of thumb is that all measurements, except for comfort factor, should be as low as possible!