It took us a few years to catch on to the degree fiber diameter plays on fleece weight. Early on we had heard rumblings how the fleece show scoring system had become counter-productive to rewarding density but it wasn’t until I did the math did the reality hit home. It became instantly obvious that if we wanted to breed for fineness and density we had to find another way to identify leading producers.
The attached PDF document that helped us visualize the role fiber diameter plays in determining density through three of the most commonly used methods, weight, sight and feel.
The first issue is that fiber diameter is two dimensional. When dealing with diameter, dimensions take on a very different value than what most of us deal with every day. In determining the area of a round object, like fiber, a diameter of 12 is not half or 50% of 24. It is 1/4 or 25%. An area with a diameter of 18 is 1/2 or 50% the diameter of 24. So, in other words if your beautiful, 10lb, 24 micron fleece could be magically changed to 18 micron it would loose 1/2 it’s weight AND VOLUME. Also, If you were to physically examine two animals, one with a MFD of 18 and the other 24, side by side, without the knowledge of the actual MFD, the 24 micron animal would most likely be chosen as being more dense, when actually they would be the same density. The 24 micron fleece described only has more volume and weight, not more follicles. What this demonstrates is that if fleece weight is used without a proper relationship to fiber diameter then one would be selecting for increased fiber diameter.
An examination of the three diagrams on the bottom of the page demonstrates how misleading using volume (fills hand when grasped) or amount of visible skin when the fleece is parted can be without exact knowledge of what the fiber diameter is that you are looking at or comparing.
The chart at the top of the page shows the percentage relationships based upon diameters.