More Science Stuff

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It is impossible to talk about histograms without putting them into the proper context. A histogram is a tool for evaluating Alpaca fiber at a given point in time.  This tool must be used as part of an assessment protocol that includes  a number of other criteria to evaluate the fiber of any individual animal.

What we hope to do here is provide a very basic, but thorough, outline of how to understand a histogram and put it into the proper context with the other evaluating factors so that you can make decisions about Alpaca fiber with more information and confidence.

What is a Histogram?  

A histogram is a graphical representation of a set of data. There are now several types of testing that are represented in histograms that look very different.

OFDA – Optical Fiber Diameter Analysis

Laserscan – End Cut Laser scanning

Laserscan

A Laserscan histogram represents the data from a 2” X 2” sample of fiber, usually from the mid -side of an alpaca.  Some breeders will take multiple samples from shoulder, hip and mid-side.  This is called Grid Sampling.  In a Grid Sample, all of the samples are tested and the results averaged. The standard sample is cut as close to the skin as possible and the cut end of the fiber is evaluated. This is important because it is the most recent growth and best represents the current environmental factors in the Alpaca’s growth such as diet, stress, pregnancy and lactation. The sample of fiber is scanned by a laser device  which measures each fiber diameter and then plots that data into a histogram.

OFDA

An OFDA report contains two elements; a histogram and an historical evaluation chart.

In this type of testing both the end cut and the entire length are tested. Fiber samples taken even an inch above the skin can give a very different set of data because of varying factors that affect the alpaca throughout the year. Using OFDA, fiber samples are tested along the entire length of the staple which provides a set of data representing an entire years growth. 

How to read a Histogram

Look at the graph table.  The fiber diameters are listed on the horizontal axis (across the bottom). The number of fibers is listed as a percentage of the whole sample on the vertical axis (Left side).   Be aware that the numbers across the bottom will be a slightly different range on each histogram based on the highest micron detected in the sample.  Some graphs will range from 4 to 40 microns and others will range from 4 to 55 or 65 microns.

When you view the bell curve of data you look for a tight grouping with fiber size variations no more than 3-5 microns off the average fiber diameter. You also want to be aware of the highest microns detected so that you can put the bell curve into perspective.  Also remember to read the Age, Sex, Color and date sample taken as they are all important factors in the evaluation of the fiber. 

Histogram Terminology Explained

Micron -   A micron is 1/1000 of a millimeter.  A human hair ranges from about 60 to 90 microns in diameter so imagine fibers 1/1000 the diameter of one of your hairs. Obviously this is a very fine fiber and would be incredibly difficult to detect differences using only ones sense of touch. I have met two breeders who can take a few Alpaca fibers between their fingers and correctly determine the micron but this is a very rare occurrence. Histograms give us an accurate way to measure this diameter.

AFD (Average Fiber Diameter) –  Exactly what it says.  The fiber sample is scanned and the number of fibers of each micron are counted.  The Average Fiber diameter will be the total microns combined divided by the total number of fibers counted. 

Example:

Sample Analysis: 

 3 fibers X 15 microns = 45 microns

 3 fibers X 16 microns = 48 microns

 20 fibers X 18 microns = 360 microns

 20 fibers X 21 microns = 420 microns

 20 fibers X 24 microns = 480 microns

Total Fibers - 3+3+20+20+20 = 66 fibers measured

Total Microns - 45+48+360+420+480 = 1,353 total microns measured

Final Equation - 1,353 divided by 66 = 20.5 Average Fiber Diameter

SD (Standard Deviation) -  A term which represents an average of individual deviations (stated in plus or minus micron values) from the Average Fiber Diameter. In other words the amount of deviation between each individual fiber’s diameter and the Average Fiber diameter.  

Example:

If the AFD = 20.5 then another average is calculated  using an equation that determines the distance of each fiber in the sample, in microns, from 20.5 microns.  As I recall from my college days in statistics, the equation is about 4 feet long and requires several calculators and a couple of pencils to figure it out.  I will leave that to the computers.  But if we use the same grouping that we used for our example of Average Fiber Diameter you can easily see that none of the micron counts is more than 5.5 microns away from the AFD of 20.5.   You can surmise that the Standard Deviation for this particular sample would be quite low.

The bell curve on a sample with a good Standard Deviation will have a very close grouping that is tall and narrow meaning that the fibers in the sample are not that far off the average.  The smaller the Standard Deviation, the more uniform in diameter is the sample.

CV (Co-efficient of Variation) – The Standard Deviation divided by the Average Fiber Diameter, multiplied by 100 and reported as a percentage.  

Example 1.

A.  Standard Deviation  - 4.1, Average Fiber Diameter – 21.4

      4.1 / 21.4 = .192 X 100 = CV 19.2%

B.   Standard Deviation – 4.2, Average Fiber Diameter – 25.9

     4.2/ 25.9 = .161 X 100 = CV 16.1%

In the above example, equation B would mathematically be the more uniform fleece.

But don’t let math be your only guide.  Compare equation B with equation C 

Example 2.

B.   Standard Deviation – 4.2, Average Fiber Diameter – 25.9

     4.2/ 25.9 = .161 X 100 = CV 16.1%

C.   Standard Deviation – 8.4, Average Fiber Diameter – 51.8

     8.4/ 51.8 = .162 X 100 = CV 16.2%

the CV in these two equations is almost identical but you would definitely feel a difference between an animal that had an AFD of 25.9 and one that was 51.8.

This CV is a very mathematical way of saying that you want to compare two different things.  The CV is most useful when comparing two separate fleeces.  If the fleeces have he same Standard Deviation and one has a higher Average Fiber Diameter. Mathematically, the fleece with the higher Average Fiber Diameter is the more uniform fleece.  

What the numbers infer is that if you take this sample and apply it to the entire area of fleece you would have more uniform characteristics. When comparing two fleeces the CV is a more useful measure of uniformity of the entire fleece.  You want a minimum amount of variation throughout a fleece so the lower the CV, the better.

Fibers over 30 Micron – this measurement shows the coarse edge that effects what the fiber will be used for.  If the percentage number of fibers over 30 micron is very high in a sample, the fleece will have a higher “prickle” factor that we associate with strong fibers.

If we use the examples from our CV calculations and apply the fibers over 30 micron information the picture changes drastically.

Example .

A.  Standard Deviation  - 4.1, Average Fiber Diameter – 21.4

Co-efficient of Variation -  19.2%, Fibers over 30 Micron - 2.6%

B.   Standard Deviation – 4.2, Average Fiber Diameter – 25.9

Co-efficient of Variation  -16.1%, Fibers over 30 Micron  -13.1%

C.   Standard Deviation – 8.4, Average Fiber Diameter – 51.8

Co-efficient of Variation  -16.2%, Fibers over 30 Micron – 27%

Sample A Would be the overall finest fleece with the lowest “Prickle factor, Sample B would be the easiest to process commercially because of it’s uniformity and Sample C would be rug fiber based on it’s over 30 Micron percentage.

CF: Comfort Factor.  The percentage of fibers under 30 microns.   100% comfort factor would represent that all the fibers in the sample were under 30 microns. 70% comfort factor would represent that 30% of the fibers in the sample were over 30 microns.  This term has shown up in the last year or so and seems to be directed more toward marketing terminology than scientific terminology

CRV: Curve or Fiber Curvature.  Another new measurement that gives the average curvature of all the fibers in a sample.  It is specifically a measurement for Huacaya fleece as Suri has very little curve.  It measures degrees of curve per one millimeter of fleece length.  A higher CRV would represent a deeper crimp in Huacaya fiber.

Again, you have to put all the pieces together to form the big picture. The pieces of a histogram form a single indicator in the evaluation of alpaca fiber.  It is important to remember that the histogram needs to be used in conjunction with other subjective and objective factors in determining fleece quality.  The following glossary of terms is important to understand the entire fiber picture from both the processor and producer’s perspective.

OBJECTIVE CRITERIA – can be definitively and scientifically measured

Staple Length – the length of the fibers in a sample from end to end.  When we refer to staple length we are talking about the length of the fiber.  In Huacaya this is usually the length after one year of growth.  In Suri it could be anywhere from one to three years growth.  Commercial processors use staple of 6 mm or about 3.5 inches, anything longer than that is cut to size.  For hand spinners, the longer the staple the better because it makes it easier to spin together.  Again, you have to remember the end use of the fiber.

Tensile Strength  - the measurement of a fiber’s strength before it snaps under pulling pressure.  Fiber affected by poor nutrition or poor health will break easily.  If you shear 12 pounds of fiber off an animal but it cannot withstand the rigors of processing or normal human use then the fiber is not very useful and will not have a very high value.

Fleece Weight – the weight of fiber sheared from an animal.  Usually divided into blanket and neck and leg fiber and weighed separately.  Average weight of a fleece is currently 4-6 pounds per year.  Increased fleece weight is one of the areas that breeders are currently working on.  Note that the same weight in Suri fiber will have much less volume because of the locking character of the fleece.

SUBJECTIVE CRITERIA – Cannot be measured by machine.  These items are measured by the experienced eye and hand of the sorter and breeder.  

Crimp –  The wave created by the two parts of a fiber twisting around each other. The  paracortex and  orthocortex are parts of each individual fiber and they create crimp. The debate on crimp could go on for days.  Some think it is important, some do not.  Put simply, if you have a crimpy fiber it stretches out to a longer staple length and it allows more fibers to fit into a square inch of fleece which equates to density.  A fleece with good crimp is denser and produces more fleece from a single animal.

Density –  The number of hair follicles per square inch on an animal.  Primary follicles are the guard hairs or medulated fiber.  Secondary follicles surround each primary follicle.  The more secondary follicles, the denser the fleece.  Density can be measured by skin sampling but is not a practice commonly used in the North American Alpaca industry.  It will become more widely used as the industry grows.  

Handle –  The feel of a fiber.  Softness in Huacaya and Silkiness or slick feel in Suri.

Luster -  The shine or brightness usually associated with Suri fleece.  Caused by higher reflectivity of locks and the longer scale length in suri fiber.  Huacaya fleece will have “brightness” rather than true luster but it is a developing element.

Color – In a production environment a uniform color throughout the blanket reduces the need for sorting and separating.  Saving time and making processing easier.

Uniformity – Refers to even distribution of all the characteristics that are valued in a fleece: Diameter or Fineness, Color, Staple Length, Crimp, Density, Handle and Tensile Strength.  If all these factors are the same at the shoulder as they are on the hip then you have uniformity.

How important are these objective criteria in evaluating the fleece quality?

The Michell Company, the largest processor of alpaca fiber in the world, uses Peruvian Quechua Indian women to sort their fiber for color and fineness.  While they do test some batches, they believe that there is no better process for evaluating all the factors of a fleece than the practiced human hands of these women who have been sorting fiber for generations and generations.  To evaluate a fleece without these criteria would be a costly mistake.

Several very important pieces of information are not on any graph but they provide perspective for anyone reading a histogram.  Remember to read the Age, Sex, Color and date sample taken as they are all important factors in the evaluation of the fiber.

AGE: A study done by B.A. McGregor and K. L. Butler for Primary Industries Research in Victoria, Australia shows that age is an important variable in fleece Micron.  Fleeces from animals at 1.5 to 2 years of age compared with the same animals at 4 to 7 years of age showed significant increase in mean fiber diameter.  They state that “Sampling alpacas at under 2 years of age is likely to substantially decrease selection efficiency for lifetime fibre(sic) diameter attributes.”  Cria fleece will always be the finest fleece because it has not been affected by nutrition, hormones or outside stresses.  The best time to get a real picture of the lasting power of fleece genetics would be at age 2 or 3.

SEX: No significant difference is seen between male and female fleeces until maturity.  At this point hormones will play a large role.  A breeding male will be subject to higher levels of testosterone and a breeding female will be subject to varying levels of progesterone.  Both these hormones will impact mean fiber diameter.  So, if you are looking at a histogram of an 8 year old female who has had multiple cria you will most likely see a much higher AFD than a maiden female.

COLOR: For the last twenty years breeders in the United States have been breeding alpacas with color in mind.  We love the natural colors in this fabulous fleece.  However, in Peru, for 70 years before the U.S. ever heard of alpacas, they bred mainly white because that is what was commercially efficient.  So the white alpaca has had a great deal more development time than the color.  White fleece will most often be the finest, with the best structure because of years and years of breeding white.  Colored fleece has a long way to go to match the statistics of white fleece.  When you read a histogram, be aware of the color of the animal for perspective.

Factors that Affect Fleece Histograms

Age, diet, hormones, stress and environment can all change a histogram.

An animal that was raised in Alaska on dry lot feed can expect a change in histogram when they are moved to Texas to pasture graze.  

Example:  According to a study done at Tara Hills Stud in New Zealand, animals imported from Chile, where they were pasture grazed on rough forage, weighted 100 pounds upon arrival into quarantine.  Within one month their weight increased to an average of141 pounds.  They were shorn at this point and tested for fleece diameters.  For two successive years the animal’s fleeces were tested at shearing time and at the end of two years the average weight of the animals increased to 150 pounds (51 percent heavier than pre-quarantine weight) and fiber diameter increased by almost 7 microns, from 25.2 to 32 microns.  In some animals the increase was 9 microns and the most extreme increase was 11.5 microns. This shows a direct correlation between fiber micron and diet.

Laserscan tchnology tests the cut end only, this histogram is a measurement of a moment in time in the life of alpaca fiber.

OFDA testing and the historical evaluation chart that it presents shows breeders the evidence of change due to factors in an individual animals life. (reference Whittick Fiber Mills Ltd worksheet on reading the OFDA chart.)

What is the importance of a histogram in relation to purchasing and breeding Alpacas?

A histogram is one factor in evaluating the quality and quantity of fiber on an individual alpaca.  When someone says to you that this particular alpaca is “great” based solely on a low micron count, you need to remember that  histograms can indicate

A. Fineness at a given point in time

B. Variation in fiber diameter at a given point in time

C. Changes in fineness and variation over time (when multiple histograms or OFDA charts are present)

A single factor, like a low micron is not sufficient information to evaluate fiber.

Interestingly, when micron measurements change due to any of the environmental factors that we have discussed the Standard Deviation and Coefficient of Variation will remain relatively stable.

Remember to engage your senses to evaluate all the other qualities of fleece rather than relying solely on a histogram.

Because there are so many factors involved in assessing fiber quality, what are the questions we should ask when evaluating histograms?

1. What was the age of the alpaca when the sample was taken?  

(Tui (first year) fleeces are not good representatives of fleece quality because they are always the finest and the animal has not finished growing).  However, the OFDA chart of a Tui fiber gives you a reading from the tip of the fiber or a Genetic marker of Micron since this measurement would literally be an in-utero measurement before being affected by outside environmental influences.

If you want to look at the histogram that gives you the best averages for the animals life you would want to look at age 2.

2. Can you provide histograms for the past 3-5 years?

(Change happens.  If great statistics can be verified over 3-5 years with very little change then you could have genes that predispose offspring to great fleece characteristics and you would like to include them in your breeding program.  Be aware that herdsire fleeces change with extensive breeding while the genetics for great fiber continue to be passed to the offspring.)

3. What was the weight of the clip corresponding to each histogram?

(Great fleece will not do a processor any good if there is no quantity to process)

4. Is the animal pregnant? Is she nursing? Is this a breeding male? Were there any changes in diet or feeding levels between the histograms?

(Remember all those environmental factors that can cause change, some of which can be improved, some of which cannot.)

5.        Did the animal have any illness or extensive travel (Stress) in the past year 

6.        Ask yourself to what use you wish to put the animal?

Breeding for show -  When you breed for the showring you are looking for the individual outstanding animal.  This is where we get a great deal of our genetic improvement for the next generations.

Breeding for a fiber production herd  - We are still in the process of breeding enough animals in this country to have a commercial fiber industry.  However, when we do arrive at that point the processors are going to want maximum uniformity to reduce waste and make processing more efficient.  A breeder working toward that end might focus on producing a herd that has uniformity of fleece characteristics, not only on one animal, but on all animals in the herd.  They might look for the best average they can get in fleece weight, staple length, tensile strength, color and fineness so that all the fiber can be sold in larger batches.  A breeder working toward that type of herd would want to know the fiber classifications currently used in fiber processing.

Fiber Classifications as recognized by Inca Group, Peru

Classification Micron Range

Royal Baby Under 20 micron

Baby 20-22 Microns

Superfine 23-26.9 Micron

Suri 27 – 31.9 Micron

Adult 27.5 –31.9 Micron

Coarse 32 Micron and above

Fiber Classifications as recognized In Canada

Classification Micron Range

#1 Under 20 Micron

#2 20-22 Microns

#3 23-25.9 Micron

#4 26 – 28.9 Micron

#5 29 –31.9 Micron

#6 32.1 - 35 Micron

Fiber Classifications as recognized in Australia

Classification Micron Range

Superfine Under 20 Micron

Fine 20-23 Microns

Medium 23-26 Micron

Strong 26.1 – 30 Micron

Extra Strong 30 Micron and above

Note that each country has it’s own ideas about how to classify fleece.

Something that should be mentioned, even though we do not like to believe that it happens is fraudulent histograms.  There is currently no procedure in place for verifying that the sample being tested actually came from the animal that an individual says it came from.  No DNA testing is run on fiber samples, probably due to cost and time factors.  So if an unscrupulous person wanted to, he could send in a sample from a yearling female and state that it was from a registered 2 year old male and get a histogram back that listed that male’s information on the data for another animal. Not a very pleasant thought but one that falls under the old adage, “if it looks too good to be true, it probably is.”   It is just one more reason to make sure that you evaluate the animal fully.  Touch it, Feel fiber  samples, Ask questions about its history, then make your decisions.

Remember, a histogram is just one tool for evaluating fiber.  It provides valuable scientific information about fiber but it has to be incorporated with all the other factors that affect fleece to help the breeder determine a fantastic fleece.