COV and the Histogram

Historically, cashmere is known as the non irritating, warm and lightweight fabric of choice for those that could afford it. China has always been the leader, setting the standard, a fact well known by those trying to market American cashmere.

Unfortunately, China operates with an entirely different perspective on life. The entire culture revolves around many mouths fed on limited resources. The relationship between Chinese culture and Chinese cashmere is one that reflects the industry. It would indeed be very interesting to transport some Chinese goats to America and feed them alfalfa free choice for a season. What would happen? If the Chinese had truly superior genetics, their phenotype would not change with the increase in nutrition. If the fiber were truly “hunger fine”, then would we have a bunch of cashgora goats? If they were in between, would they still be coarse on the neck and shoulder? Do the Chinese even comb the neck and shoulder? Recent reports indicate that Chinese cashmere goats have nothing to eat between November and May. When they are combed in April, they have lost up to 40% of their body weight.

But in the meantime, voices from all over America say that in order to double the profits from a cashmere goat, the growers must double the fiber grown by each goat. Sounds great, but how do we do that? If we feed the goats, we run the risk of increasing fiber diameter. If we starve the goats, we reduce the production as well as the diameter. If we select for greater follicle density, a fleece parameter separate from production, we run the risk of reducing liveweight. Can an historically underfed goat with fine fiber be presented as top quality cashmere breeding stock? They may blow out in a new home if they are fed better. Dr. Restall recommends that we challenge the genetics of young goats to express themselves by feeding them well and then cull heavily. Can we afford to feed animals that barely pay for themselves on a commercial scale? Some Texas growers who do not supplement feed think a $2-$3 return per head on cashmere is enough. Those who have to put $10-$15 per head in feed into each goat to overwinter them say “no way, we need more”.

Clearly, the American cashmere industry needs to define itself. We need a way to insure that a “cashmere” goat fits the set definition. So how do we define “the American cashmere goat”? Handspinners want length and crimp, growers want high returns per head, manufacturers want low prices for raw fleece, consumers want “classic”, non-irritating garments. Can all wishes be granted? This author submits that the goal is to breed for a goat that produces a fiber that:
…1) is identifiable as cashmere as a mature animal,
…2) that does so under the most favorable environmental conditions and
…3) that is capable of passing that quality on to a majority of its progeny.

To achieve this goal we need to stop using breeding bucks that are young and unselected, untested, and/or underfed. We need to start thinking in terms of Commercial herds and Breeding Stock herds. The key is to know what questions to ask. American cashmere must be consistent, crimpy, easily dehaired and cheap to satisfy manufacturers. It must be warm, soft and affordable to satisfy the consumer. Cashmere must be profitable to grow to satisfy the grower. What we need is a key, some common ground that will link the needs of the three groups. As it turns out, the key is called “the prickle factor”.

Prickle factor is a term that defines the amount of irritation of the finished garment against bare skin. It is easily understood by consumers, but how does it relate to manufacturers and growers? Prickle factor is graphically represented by a histogram. Commonly, the population of tested fibers, when graphed with diameter and number of fibers on the axes, results in a neat, bell-shaped curve. The histogram also reports mean fiber diameter (MFD), the standard deviation (SD, defining the parameters of the true mean), the coefficient of variation (COV, the standard deviation divided by the mean), and the yield (Y). For too long, this industry has defined cashmere based on MFD without considering what the other factors are trying to say.

For example, look at the histogram by clicking here. To the untrained eye, it looks pretty good. To the trained eye, there are some important questions to ask. The first is how old is the goat when tested and the second is how old is the goat now? Breeders that advertise kid fleece data when updated numbers should be available should be questioned as to why they do this. The next question should concern yield if it is above 30 percent. A cashmere producing goat rarely has a yield above 30 percent. Reported values of more than 30 percent may be due to several factors, only one of which is good news; that it is a truly superior goat. High yields are mostly reported on fleeces that are fine cashgora or reported due to non-random subsampling.

Mean fiber diameter is the most misleading value reported on a normal histogram. Values for MFD less than 16.5u should be questioned closely. Again, how old is the goat is the first question. Who subsampled the fleece is the next question. Then the standard deviation must be considered. What SD means is that at the 95 percent confidence level (meaning that 95 percent of the time, the stated MFD actually falls within the SD) that the true mean is plus or minus the SD. An SD of 3.7, for example and a reported MFD of 14.7, means that 95 percent of the time, the true mean lies somewhere between 11 microns and 18.4 microns. Quite a range, really.

Next, look at the coefficient of variation (COV), the most ignored and the most important of the given parameters. A COV of 25.2 means that a 25.2 percent (or one quarter) of the fibers measured fall outside of the range defined by the standard deviation. What does this mean? Granted, it could mean that fine guard hair was accidentally included in the measured sample and produced the rather obvious “tail” on the histogram. But if you look carefully at the histogram, there are actually two tails, one going from 18 microns, the upper limit for the true mean and 29 microns. Another “tail” commences at 33 microns and continues through 37 microns. It is here, between 30 and 40 microns that the errant guard hairs will reside. So what about the first tail? This is where the fiber responsible for giving a “prickly” hand to the finished garment reside. These are actually cashgora fibers and it is these that protrude from the finished garment and irritate (prickle) the skin.

The COV for Chinese cashmere or any hunger fine goat may very well be very high, ie: greater than 20 percent. The difference is that Chinese cashmere is so much finer, that the fibers in the tail section are also fine and do not prickle the skin. The dashed line in the histogram represents data for a Chinese fleece. The bell shaped curve is similar. If American growers select against goats with a COV above 20 percent and aim to produce a goat with a 15 percent COV, then we will eliminate the prickle factor. The fibers responsible for irritating the consumer skin will not be there. This type of histogram is represented by the dotted line on the histogram. The elimination of this class of fiber has other implications. First, it allows the manufacturer to more efficiently dehair the raw fleece. Cashgora fibers tend to clog dehairing machines large and small and much valuable cashmere is lost in the congestion.

Second, it allows the grower to use a scientific, objective measurement to select breeding stock. But BEWARE! COV can be manipulated by unscrupulous growers through non-random subsampling, such as selecting only midside fiber. That’s fine, if the coarser neck and shoulder portion of the fleece is unshorn or discarded. Those wild and woolly necks must be fairly represented in the tested subsample if the animal is to be sold as top quality breeding stock. Unfortunately, here we are still in the realm of Buyer Beware!

The best part about using COV to select our goats is that fleece that is very uniform in diameter, meaning that its COV is 20 percent or below, will perform like, meaning the end product will be indistinguishable from, fiber that is much finer on average. This is the golden fleece, truly! What that means to the grower is that we can grow animals that average 17 microns and the finished product will feel like the average was 15.5 microns. Coarser MFD means twice the production. Twice the production means twice the income from a single goat. COV will allow the American industry to grow well fed, coarse goats and still compete in the marketplace with the Chinese. It is our key to success.

So by using COV as our key to defining cashmere, we satisfy most of the needs of the three groups. The only thing left is crimp, that hard to measure, subjective assessment of fiber quality. Until the scientific community can come up with an effective way to test for crimp, we are stuck with depending upon trained, unbiased assessors to determine the right amount of crimp. This author hypothesizes that crimp is inextricably tied to COV, although this has not yet been tested, let alone proven. Incorporating tested COV’s into the definition of cashmere will greatly reduce the parameters of what passes for cashmere. We need to remember that it is in our own best interests to carefully define American cashmere. We have the means to determine if a garment, the fiber and the goat fits the definition, we just need to use it.

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