A histogram is a common graphical presentation of quantitative, objective scientific data. With alpacas, it is a graphical representation of measured fiber characteristics. Usually, a “grid” sample is taken at the time of shearing from the side of the alpaca or multiple samples are taken from shoulder to hip.
Caution: When examining histogram data, it is important to note the date of birth as well as the date the sample was taken. While having a favorable histogram at six months is a good start, the initial graph should be followed with information as the alpaca ages and experiences various environmental factors. Top breeders like RobAsia will always be willing to share this information as part of the assessed value of an alpaca.
A histogram consists of the following information:
Normal Distribution: depicted as a bell-shaped curve of measured fiber snippets.
Mean Fiber Diameter (MFD): Fiber diameter measured in microns. One micron is equal to one millionth of a meter or 1/25,400th of one inch (very, very small). This is an internationally recognized measurement for the commercial wool and fiber industry. This measure is also sometimes referred to as AFD, Average Fiber Diameter.
Standard Deviation (SD): SD characterizes dispersion of individual measurements around the mean and is an important measure of variability.
Coefficient of Variation (CV): A measure of variability derived from dividing the Standard Deviation (SD) by the Mean Fiber Diameter (MFD) and used to compare uniformity between different populations. It is useful in ranking uniformity of individual animal fleeces, regardless of mean fiber diameter.
Fibers Greater Than 30 Microns: The percentage of the fibers measured over 30 microns, also known as the Prickle Factor or the coarse edge.
Medullated Fibers: A medullated fiber is an animal fiber that in its original state includes a medulla. A medulla in mammalian hair fibers is the more or less continuous cellular marrow inside the cortical layer in most medium and coarse alpaca fibers. Translation: the fiber is like a straw, hollow in the center.
Spin Fineness: This provides an estimate of the performance of the wool or fiber when it is spun into yarn.
Mean Curvature (deg/mm): Fiber curvature is related to crimp. The greater the number of degrees per millimeter, the higher the crimp frequency and the tighter the crimp.
SD Curvature (deg/mm): Curvature (and crimp) is variable in alpaca fiber.
Comfort Factor: Comfort factor is the percentage of fibers over 30 microns subtracted from 100 percent.
Mean Staple Length: Total length of fiber measured in mm. Dividing mean staple length by the number of growth days will give you growth rate per day, a very valuable number for assessing fiber-producing animals.
Final Note: Both the sample date and the date of birth should be listed on the histogram. When reviewing, always cross-reference these dates to fully understand the sample of the animal. Less than forthright breeders will advertise favorable histograms on their alpacas at first shearing. However, the true value of the alpaca is what it can maintain over time/age of the animal. Don’t be fooled – ask for historical histograms. Another area that sets RobAsia apart from the competition: we meticulously maintain these historical records.