The following document was provided to the ARI Board of Directors in 2009 as the Board sought expert opinions on the discussion of use of butt (base) cut testing versus staple length profile testing for use in an Expected Progeny Differences program.
What is the difference between butt (base) cut fibre testing and staple profile testing?
As in any testing situation, the wider the range of sampling, the more opportunity for accuracy of the results across a population.
Base cut sampling involves guillotining 2 mm fibre snippets, via a single cut, from the base of the fibre staples. These fibre staples are provided within a 4” x 4” sample of fibres shorn at a midside site, at the skin, of a fibre producing animal.
A 4” X 4” fibre sample provides hundreds of individual fibres from which the snippets are cut. A minimum of 4000 of these fibre snippets from the sample are then measured to obtain AFD, SD, CV, SpnF, CF, Curve, and Medullation. Furthermore, 10 fibre staples are randomly pulled from the entire sample to measure MSL, SDL, and CVL.
Staple profile involves measuring one fibre staple shorn from a specific location on the fibre producing animal. This location can be the midside. The single staple taken from a fleece does not provide the varied population of fibre for measurement. It simply provides the number of fibres within that one staple (approximately 100 fibres more or less), which can vary considerably from one animal to another. The measurement data will provide AFD, SD, CV, SpnF, CF, and Curve. This single staple measurement will not provide a medullation reading and length can only be calculated on the length of the staple being measured at the time.
“…The OFDA200 is an instrument primarily designed to measure fibre diameter and its distribution on single greasy staples outside the confines of a laboratory…The OFDA2000 was close to the precision of commercial midside fleece testing when one greasy staple was measured from the midside …” Peterson, A.D. and S.G. Gherardi. 2001: “The ability of the OFDA2000 to measure fleeces and sale lots on-farm.” Wool Technology and Sheep Breeding 49(2).
Staple profiling was developed to quickly provide a fleece measurement in the shearing shed during the shearing of large flocks. This quick measurement created greater efficiency in the shearing sheds namely as a means of objectively identifying the fineness of the fleece on each sheep within the flock being sheared, thus aiding the Classing of the wool into specific lines and acting as a tool for genetic selection for fine wools. When presented for sale, fleeces that have been staple profiled still have to be cored sampled and tested under IWTO and ASTM approved conditions.
Staple profiling is not approved by the IWTO (International Wool Testing Organization) or ASTM. Staple profiling is not conducted under a controlled environment i.e. controlled temperature and humidity, therefore test results can be affected at any given time. For the EPD program, measurement of the actual quality of the fleece is what is required. The breeder, the prospective buyer of the alpaca, as well as the prospective processor and manufacturer of the fibre and fibre products, must know the quality of the fibre being produced by respective animals/national herd. This information must include the variation in length and the amount of guard hair present. Only with complete information can one determine the type and quality of product that can be produced and whether or not these qualities can accurately be repeated. Accurate information is also required for genetic selection. Alpaca fleeces are not yet uniform in their various characteristics across the fleece and from one side of the alpaca to the other. Therefore, accuracy of measurement as well as the range of fibres representing each fleece, is of utmost importance to an industry.
Base cut sampling does provide a greater range of fibres per sample than does the one staple profile method. Therefore, base cut sampling should be the method preferred over staple profiling for the EPD program.