FLEECE HISTOGRAM
You can test this out yourself by using the results from some of your better alpacas in these formulas. You should get a similar value from each formula. THE SCORE OF UNIFORM MICRON The graph at Figure 3 is a plot of FD+SD against CF for my herd of 122 alpacas and shows that there is indeed a very strong negative correlation between the two. I have called the FD+SD the Score of Uniform Micron or SUM where SUM=FD+SD. It is evident from the graph that when the SUM is less than or equal to 21 then the CF will usually be 100% and fibres are unlikely to be over 30Îź. It is also evident that when the SUM is less than or equal to 26 the CF will usually be at least 95% and no more than 5% of the fibres are likely to be over 30Îź. The line of best fit on the graph indicates that the strength of the correlation between SUM and CF starts to decrease as the SUM exceeds about 26 and the CF falls below 95%. It is therefore not uncommon to find fleece results in which the 36 | Autumn 2012 | ALPACA WORLD MAGAZINE
SUM is more than 26 when the CF is still at or above 95%. This strong correlation between SUM and CF indicates that the SUM can reliably be used to compare fleeces from alpacas of similar age that have a CF greater than 95% and is particularly relevant when the fleeces being compared all have the same CF of 100%. The SUM takes over when the CF reaches 100%. An advantage of using the SUM rather than the CF is that, although it is referred to as a score, its unit is microns. This gives it mathematical advantages when estimating the extent of medullation in a sample since the coarsest 5% of fibres will generally be above the micron obtained from the formula SUM+SD. This micron could also be obtained from the formula FD+CEM or FD+SD+SD.
CONCLUSIONS So what are the hidden secrets within the fleece histogram? I have shown that the SD determines the extent to which the histogram skews towards the coarse micron tail and that 2SD approximately equals the CEM. This means that the coarsest 5% of fibres will not only be above FD+CEM microns but also generally above SUM+SD microns. You can test this out yourself by using the results from some of your better alpacas in these formulas. You should get a similar value from each formula. I have also shown that the FD and SD together determine the CF and indicates that the CF is much more than a comfort measurement. It is also an indication of both the fineness and uniformity of a sample. The strong correlation between FD+SD and CF also indicates that the CF can be expressed in terms of microns as well as a percentage. This means that the SUM can be used to compare fleeces that all have the same CF of 100%. It also means that it can be used to estimate the extent of medullation in a sample. Most importantly however I have shown you that the FD, SD, CEM and CF are all intimately related and that the CEM and CF are determined by the FD and SD. In the next two articles I will show you how you can use the sum of these two values, or the SUM as I have called it, to help you assess the performance of your breeding program and to class your fleece to a high micron uniformity.
REFERENCES Watts, J., 2010. SRS Alpaca Newsletter: June 2010. Kingwell, R., 2010. Can Guard Hair Be Bred Out Of Alpaca Fleece? Alpacas Australia Issue 60: Winter 2010.