Laboratory Testing ~ The Histogram
A histogram outlines the percentage of fibers that fall within a specific micron range in a fiber sample. If you look at the histogram of a good cashmere fibered goat, you will notice that the range of bars representing the different thicknesses of fiber is very narrow. This means there is very little variability in the sample and the statistical mean is the average of the fibers. Where the majority fall into this small range, it gives the histogram a tight, long look. This smaller range of microns being averaged is reflected in a lower standard deviation (SD) and coefficient of variation (CV).
The SD is a measure of the spread or distribution of individual fibers within a tested sample where approximately 2/3’s of the fiber diameters lie on either side of the average fiber diameter. For kids, the SD should be less than 4 and for adults it should be less than 3.5. In general, the lower the score, the better. ie: The more consistent the fiber.
The CV measures the spread of the fiber diameter variation relative to the average. CV is the SD as a percentage of the average micron. For kids it should be less than 30% and for adults it should be less that 25%. Again, the lower the score, the better.
There are problems in relying wholly on visual assessment and wholly on laboratory testing. For example, you may get very different results if you use a 3 sample site method for objective testing versus a one mid side sample method. The 3 site sample method typically takes fiber from the mid side, the neck and the rump of the animal. The number in this method will typically be higher as the neck fiber is typically coarser and less crimpy. Testing that same mid side sample only will typically yield lower results as the fiber in that section should be fairly consistent. This does make it hard to compare the result of animals whose sampling method was completed differently.
Since the perfect sampling method has not yet been developed, you will see some variability from sample to sample and from year to year, so it is best to evaluate the fleece through using your visual classification in combination with the objective data from a laboratory.
The ideal cashmere goat would of course produce very similar histograms regardless of the sampling method as their fleece would be very similar no matter where you sampled it. This is the case for some goats but we have yet to be able to call them the ideal goat when you factor in all the other traits they need to be good cashmere and meat animals, we must not forget that we are working towards the ideal and not throw wawy a lot of very good goats by focusing too greatly on one factor only. You can however, weight that criteria more heavily in your selection process as you work your way through improving all the traits towards that ideal goal. That is the purpose, challenge and fun of breeding after all!