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Objective fiber testing measurements examined by Montana State University

by Wyoming Livestock Roundup

Buffalo “Objective fiber testing can be a powerful marketing tool,” stated Lisa Surber, a research scientist at the Montana State University (MSU) wool lab.

Surber was one of several speakers at the Northeast Wyoming Sheep Symposium, held in Buffalo on Dec. 11.

She noted that the industry has been measuring, classing and sorting wool subjectively for many years.

Wool technology

“We have a lot of advances in technology in the wool industry that allow us to look at wool in a more objective fashion,” Surber said.

From a commercial producer’s point of view, she continued, objective fiber testing is important because it provides a hard figure, rather than someone’s subjective opinion about what the wool might be like.

“The industry road map has placed a big priority on the National Sheep Improvement Program (NSIP) and the use of genetic records for the improvement of the production and profitability of the sheep industry,” she stated.

A piece of equipment used by the MSU wool lab, according to Surber, is the Optical Fiber Diameter Analyzer, known as the OFTA 2000. She noted that it can be packed into a suitcase as a portable tool, making fiber measurement realistic in the lab and out on the ranch.

“OFTA measures in microns, which may be a little different than how we traditionally think about measuring wool,” she reported, adding, “A micron is one millionth of a meter.”

Using this equipment, scientists can record fiber diameter, standard deviation, coefficient of variation and curvature in a sample of wool, Surber said.

Fiber diameter

“Fiber diameter is a function of both genetics and environment, or particularly, the nutrition of the animal,” she noted.

To illustrate her point, Surber referenced a piece of wool sheared from a lamb. At the tip of the sample, furthest from the shear point, the fiber diameter was greatest, thinning out through the middle and becoming thick again closer the sheared end.

“When the lamb was nursing from the ewe, we can see the impact from the high plane of nutrition in the thick fiber diameter, and as the lamb started to rely less on the ewe and more on forage, it got a little finer,” she said.

Closest to the shear point, the thicker fiber diameter corresponded to the lamb going on to feed and getting more nutrition in its diet, according to Surber.

Breeding significance

She reported that this could be important in determining the Estimated Breeding Value (EBV) of sheep.

“When buyers are looking at rams, for instance, they are looking at that raw micron value that may be reported, but they also need to look at condition of that ram,” Surber said.

Because rams are typically fed for ram sales, she noted that they are probably in the best condition of their lives at the time of the sale.

“A micron profile lets us look at what happens from tip to base of that lock. It really gives us a window into the production of that sheep during that year,” she said.

Surber explained that fiber diameter indicates the highs and lows of the year and where there might have been stressful events or access to less nutrition.

Standard deviation 

“We know that a single fiber can be variable from tip to base, and we also know that on an animal, fiber diameter can vary from shoulder to britch a great deal,” Surber stated.

Standard deviation measures the uniformity of the wool on an animal and can also be recorded by the OFTA, Surber explained.

“Even though we use just one lock of wool, the standard deviation of that lock has a relationship to how variable that wool is on the whole animal,” she stated.

This measurement is important, she continued, because it impacts how the wool is processed. It affects the uniformity of the yarn and evenness of the product it is made into, as well.


Coefficient of variation (CV) is another measurement of variation in wool, which relates to comfort factor, Surber said.

“A lot of people are talking about comfort factor, prickle factor or the itch factor of wool,” she stated.

By measuring the percentage of fibers that measure equal to or less than 30 microns, the comfort factor of the wool can be determined, Surber explained.

“When a fiber presses up against the skin, anything greater than 30 microns isn’t going to bend, whereas fibers less than 30 microns will. If it doesn’t bend, it feels itchy or prickly,” she said.

She added knitwear, especially worn close to the skin, is big in the market right now, so comfort factor is important. 


Curvature, another measurement from the OFTA, is related to crimp, said Surber.

“We subjectively look at crimp all the time when we are grading wool. Crimp is usually a pretty good indicator. The finer and tighter the crimp, usually the finer the wool,” she reported.

Merino genetics might not align with this though, she continued. Because of their breeding, producers will see bigger crimp in much finer wool in Merino fleeces.

“Curvature has some positive effects and some negative effects. It really depends on where the wool is headed,” she stated.

Curvature is related to the bulkiness, or resistance to compression, in the wool, Surber explained. This means that for products like socks, consumers prefer more curvature, whereas it is less desirable in garments like a fine Italian suit, where a flat, consistent and smooth yarn is necessary.

“Curvature is a hot topic right now. It is one of the topics we are starting to look closer at within the NSIP,” she said.

By using the data from the OFTA 2000 and NSIP, Surber noted that breeders can select to make big improvements in producer’s flocks.

Western opportunity

Wyoming, Montana and western South Dakota produce 40 to 50 percent of wool in the 21 to 24 micron range, or midrange.

The industry is trending towards more fine wool products, Montana State Unviersity’s Lisa Surber said.

She also noted that there are a lot of sheep being bred for meat, rather than wool.

“Midrange micron wools are disappearing from a lot of production, and that allows us to be positioned very well,” she reported.

The area, she said, is producing wool that is not coming from other producers. 


Natasha Wheeler is editor of the Wyoming Livestock Roundup and can be reached at

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