The information contained in a histogram report is a valuable tool when assessing the quality of alpaca fiber. Yet, the histogram results may be the least understood factor for prospective or new alpaca owners, and even experienced breeders.

The results of a histogram, using a “good” sample (as outlined by Yocom-McColl Testing Laboratories), provide objective information regarding some of the characteristics and quality of the fiber produced by an individual alpaca. When tracked over time, histograms provide useful information related to the genetic propensity of an alpaca to maintain those qualities.

The basics: AFD, SD, CV, %> 30

AFD: Average Fiber Diameter is the measurement commonly known as the micron count and represents the average diameter of the fiber sample measured in microns. Of the four basic standards of measurement, the AFD is the most easily affected by variables, yet is often the one measurement that receives the most attention and consideration when making buying and breeding decisions. The three primary variables are: age, sex, and nutrition. Age is a factor because as an animal matures, the fiber tends to become coarser (higher micron value). Also, nursing cria may have a higher count because of the nutritional composition of the mother’s milk. Males frequently have a higher micron count than females due to the influence of testosterone. Nutrition can have a great affect. Often, overfed animals produce higher micron counts. A fourth and lesser influence affecting AFD is the color of the fiber. Whites and fawns tend to have lower AFD readings than the darker colors due to the lower color pigment of the fiber.

SD: Standard Deviation represents the variation from the AFD. Statistically, about 68% of all the fibers will have a micron count that is plus or minus one SD of the AFD. For example: an alpaca with an AFD of 24 and an SD of 4 will have about 68% of the fibers in the fleece measuring between 20 and 28 microns. Generally, the smaller the SD the better.

CV: Coefficient of Variation represents SD as a percentage of AFD. In the example above the CV is 16%…..4(SD) divided by 24(AFD) = .16 or 16%.
Breeding for uniformity (consistency) is a major goal in a breeding program and the CV is a good indicator of uniformity. Typically, an alpaca with a good “handle” will have a relatively low CV (<20%).

%>30: Represents the percentage of fibers greater than 30 microns and determines the CF (Comfort Factor). Essentially, the CF is the percentage of fibers smaller than 30 microns. The CF is calculated by subtracting the percentage of fibers greater than 30 microns from 100%. For example, if the %>30 is 2.0 the CF is 98%. The closer the CF is to 100 the more comfortable the fiber will feel next to the skin.

When making alpaca purchasing and breeding decisions there are many factors to consider (density, coverage, fiber architecture, conformation, phenotype, and genotype), that are not assessed by a histogram. When considered with these other factors, and clearly understood and used properly, histogram results are an effective marketing tool for sellers and a useful filter for buyers.
When you buy an alpaca or a breeding, keep your eye on the numbers…..the objective results of the histogram indicated by the AFD (aka micron count), SD, CV, and CF.

Jack and Dianna Jordan
Alpacas of Somerset Farm