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Variation in and Sampling of Alpaca
Updated: January 2007
ISSN 1329-8062
Bruce McGregor, Attwood
Introduction
diameter of fibres growing from primary and secondary skin follicles in an alpaca may be more than 20 µm. Many Evaluating the attributes of alpaca fleeces subjectively by medullated fibres in alpaca fleeces are more than 10 µm eye is difficult and unreliable as alpaca fleeces show large coarser than the mean fibre diameter (McGregor 1999a). variations in attributes. In addition, our eyes (and brain) are limited in their ability to discern fibre diameter, the Along the fibre
average of other attributes and the extent of naturally Changes occur in the fibre diameter, dust, grease and occurring contaminants. Alpaca fleeces are also affected vegetable matter content as the fleece grows during the by environmental conditions, in particular humidity, but year. In the example shown in Figure 1 (McGregor 1999b) also by storage conditions. These same limitations apply diameter varied from a low of 21 µm to a maximum of 27 µm. During the first few months of life the mean fibre To assist in the commercial trading of fibre for textile diameter ranged from 21 to 23 µm (15 to 11 cm) and then processing, a range of testing procedures have been increased to 25 to 27 µm (10 to 4 cm) before declining to 21 developed to help reduce the errors associated with to 22 µm. Nutritional changes, weaning, rapid growth, the subjective assessment. These testing procedures are affects of disease and reproduction all influence fibre approved by the International Wool Textile Organisation (IWTO) as the basis for the international trade in wool and other animal fibres. The IWTO Technical Committees take this task very seriously and convene international meetings to assess new or suggested changes to protocols based on new information, new technology or better scientific methods and analyses. Associated with objective tests are a range of errors related to the sampling and testing procedures. With objective testing it is possible to quantify the likely extent of the errors associated with the testing procedures employed. To help breeders evaluate alpaca fleece attributes the starting point is understanding the types of variation found Figure 1.Changes in the mean fibre diameter along a staple from in and between fleeces; the most appropriate method of a tui alpaca sampled in November (McGregor 1999b) sampling alpaca fleeces; and the application of this Different positions within the fleece
information for evaluating fibre test results. This article is Fibre length, fibre diameter, incidence of medullated based on research conducted in Australia. fibres, grease, suint, dust and vegetable matter This Agriculture Note discusses the sources and extent of contaminants vary with the position in the fleece. These variation within the alpaca fleece and suggestions are variations are discussed in greater detail in this Agnote. made as to the most appropriate method of sampling alpaca fleeces. Differences between animals and herds
Within a herd of animals, between herds and between Variation in animal fleeces
properties, alpacas will differ in their fibre diameter The variation in the attributes within the fleece of animals attributes and in their level of grease and other contaminants. This is discussed elsewhere for Australian alpacas in greater detail (McGregor and Butler 2004, Within a staple
Most of the variation in fibre diameter occurs between Briefly, mean fibre diameter (MFD) of alpaca fibre was fibres within a staple. The difference between the fibre influenced by farm, year, age, breed, live weight and State of Victoria, Department of Primary Industries
Variation in and Sampling of Alpaca Fleeces
colour of fibre. The influence of farm and age are shown in Figure 2. MFD increased to 7.5 years of age. Figure 2. Responses of mean fibre diameter to age at shearing after adjustment for year, live weight, colour of fleece and breed on five different farms (modified from McGregor and Bulter 2004). Each symbol represents a different farm Coefficient of variation of fibre diameter (CVD) was influenced by farm, year, age, breed, and colour of fibre. Figure 3. Location of the saddle, neck and fleece components Impact of variation in animal fleeces
that form the pieces (front legs including apron, belly and back The large variation in animal fleeces affects fibre legs) in alpacas and the site for mid side sampling. preparation (fleece classing), fleece value, processing and Table 1. Variation in attributes of Alpaca fleece
the interpretation of fibre testing results. measured from mid side samples and fleece
component grid samples including mean fibre diameter
Variation due to position in alpaca
(MFD) and coefficient of variation of MFD (CVD).
Sampling site
CVD Clean washing
Components of the alpaca fleece
The physical attributes of alpaca fleeces vary considerably over the body. During the preparation of alpaca for sale, the fleece is commonly divided into three components: # Within attributes, sampling site values with a different superscript are significantly different. According to standard industry practice, the skirtings The fibre from the mid side site was 1.2 µm finer than consist of the fibre shorn from the belly, the top of the fibre from the saddle and neck, 3.7 µm finer than the mean back legs, the top of the front legs and apron (area between for the entire fleece and 10.1 µm finer than fibre from the front legs and neck) providing it is free of guard hair pieces. Fibre from the saddle was 2.4 µm finer than the mean for the entire fleece and 8.8 µm finer than fibre from The site used for taking mid side samples, which is discussed in the next section, is part of the saddle There was a large variation in the over the body. The CVD of mid side fibre was 2.7% lower than fibre from the Variation in fleece attributes
saddle, 3.8% lower than the mean for the entire fleece and 4.3% lower than for neck fibre. Australian alpaca fleeces show large differences between the attributes of fibre from the mid side, saddle, neck, and The significantly lower clean washing yield of the mid the remainder of the fleece (pieces) and the mean for the side and neck compared with that of the saddle and pieces entire fleece (Tables 1 and 2, Aylan-Parker and McGregor shows that the distribution of dust, dirt and grease content are not equally distributed over the body of alpacas. In these alpacas there was significant variation in the mean fibre diameter over the body and this variation was associated with high variation in the coefficient of variation of fibre diameter (CVD). State of Victoria, Department of Primary Industries
Variation in and Sampling of Alpaca Fleeces
Table 2. Variation in medullated fibre attributes of white
diameter and other fibre attributes will be seriously over Alpaca fleece measured from mid side samples and
fleece component grid samples.
The mid side sample mean fibre diameter has been Sampling site
Incidence by
Medullated fibre
reported in Merinos and Alpacas to actually test finer than number# %
diameter µm
the average for the whole fleece. In the study of the Merino wool, this was particularly so for the finer sheep in the population. It was suggested that in Merino sheep this was due to intense selection over the years for finer fleece based on the mid side sample rather than selection for a finer entire fleece (Stadler and Gillies 1994). # Within attributes, sampling site values with a different While the mid side sample is highly correlated with the superscript are significantly different. mean fibre diameter of wool top (wool processed up to the The incidence of medullated fibres at the mid side site was spinning stage), the mid side sample can be finer and the 8.7% less than in the saddle, 10.8% less than the mean of differences may not be consistent (Fleet et al. 1993). This the entire fleece and 20.1% less than in the pieces. Similar suggests that the mid side sample may not be a reliable differences were seen in the diameter of medullated fibres. predictive tool for the diameter of top. In summary, for each fleece attribute, fibre at the mid side Some of these differences may be due to the effect of fibre site had lower values than fibre from the saddle and the breakage and subsequent loss during carding and noil mean of the total fleece. For each fleece attribute, except for clean washing yield, the saddle had lower values than Grid sample method
fibre from the pieces and the mean of the total fleece. Grid sampling has been used for more than 20 years. The Sampling methods
grid sample includes differences due to position within the There are two main methods of fleece sampling available fleece and so can detect variations in the fleece that the for alpaca breeders: the mid side and the grid sampling mid side sample does not detect. For example, Butler et al. methods. Each method has it own advantages and (1991) found that processed wool top produced from Merino wool was better predicted by grid sampling than by mid side samples. Mid side sample method
Grid sampling is the best method for taking samples from Since 1947, the accepted method for testing sheep wool cashmere goats as the mid side sample overestimates the has been to take a mid side sample (Turner et al. 1953). commercial yield of cashmere and underestimates The mid side sample has been used to test characteristics cashmere fibre diameter (McGregor 1994). of importance such as fibre diameter, fibre population, Method used for grid sampling
staple length, density of fibres per unit area and staple crimp. In sheep, the theory behind using a mid side sample is that 1. laying out the shorn fleece to be tested on a flat a mid side sample test result is close to the mean of both surface, ideally on a table measuring about 3 m2. The the top to underside and the front to rear variation found in a fleece. For this to be true the mid side sample has to be 2. take 16 to 32 random grab samples from the surface of either mini-cored or tested after carding. entire fleece. To help this process it is common for If a mid side sample is tested after butt cutting, as is breeders to lay a physical grid over the fleece and to common in the United States of America, then this take a sample from each grid. A suitable grid can be assumption is incorrect. A butt cut is a fibre sample taken made from plastic garden trellis mesh with a mesh only at the end of the fibre closest to the skin. A butt cut size of approximately 10 cm x 10 cm. The idea is to sample does not include any of the along the fibre take unbiased samples by pulling a tuft of sample variation or differences due to position within the fleece. Location of mid side sample
Potential benefits of using grid sampling
The site for taking the mid side sample in sheep is located Grid sampling can be completed while the next alpaca is over the third last rib, halfway between the mid-line of the being shorn or can be undertaken after a fleece has been belly and the mid-line of the back (Figure 1). The mid side site is convenient to use for sampling Grid sampling avoids the problems found with core because it can be easily located during shearing and can sampling of entire fleeces. Core sampling is time even be shorn without removing the entire fleece. consuming but does include variation due to position within the fleece. However core sampling cuts staples in Problems with mid side sampling
the fleece thus reducing the fibre length. In alpacas, if the mid side sample is taken to close to the belly, it may include fibre that is really part of the pieces component. If this happens the test results for mean fibre State of Victoria, Department of Primary Industries
Variation in and Sampling of Alpaca Fleeces
Sampling and testing variability
difficulty in sampling and measuring these fibres. Contamination of saddle fleece samples with fibres from If repeat samples are taken from a fleece, differences in the the pieces and by coloured fibres will also increase the reported test measurement will usually be reported. These differences are related to two main causes. Variation between samples
Evaluating and undertaking alpaca fibre
Each sample submitted for testing is different. These differences are related to the variation in animal fleeces Use of mid side sample
discussed earlier but in this case are due to sampling variation. Samples are also frequently sub-sampled once or The mid side sample was found to be an appropriate twice and variation also occurs during these processes. sample from which to predict the mean fibre diameter and the clean washing yield. Variation between tests
The mid side sample does not measure a large enough area Variation occurs between tests. This variation can be of the fleece to detect sufficient variation in mean fibre related to preparation of the sample and the operation of diameter coefficient of variation (CVD) or in the incidence the equipment. Each sample tested by the equipment is different, so some differences in the reported measurement are to be expected. Scientific test laboratories regularly Use of the saddle grid sample
monitor their testing procedures to ensure the reliability of Breeders wishing to improve CVD and/or spinning fineness measurements of the alpaca saddle, in the most efficient way, should use the saddle grid sample, since the Interpreting test results
mid side sample is not as accurate for use in the selection Alpaca growers need to be aware that each test has an inherent error related to the variability associated with Breeders using either mid side samples or saddle grid sampling and testing procedures. This measurement error samples to improve total fleece CVD, will improve neck exists even if only one sample is taken and measured. CVD at the same time with similar effectiveness. Some growers have submitted fleece samples to different The saddle grid sample was found to be the appropriate fibre testing services and expressed criticism at the sample to predict the incidence of medullated fibres in the “difference in results” they receive. Such an outcome is to be expected. But do these “different” results really differ? Sampling procedure
Sampling variance in Australian alpaca
The large 95% confidence limits for all the tested fibre By determining the sampling variance, the 95 percent attributes indicate that alpaca breeders and advisers need confidence limits can be calculated for a particular to consider taking suitable duplicate measurements and sampling and testing procedure. The sampling variance other precautions during breeding and animal selling and confidence limits for mid side and saddle grid samples has been measured in Australian alpacas (Table 3, Aylan-Parker and McGregor 2002). Using the confidence limits
The sampling variance for the alpaca fibre mean diameter The 95% confidence limits for mean fibre diameter (± 1.6 attributes are similar to values reported for Merino wool. µm) show that alpaca breeders and advisers need to exercise Except for clean washing yield, the sampling variance for caution when interpreting absolute fibre test results. This saddle grid samples was generally 2 to 4 times greater than data indicates that breeders cannot confidently distinguish the sampling variance for mid side samples. As a between animal test results where the mean fibre diameter consequence, for most fleece attributes, the 95% differs by less than 1.6 µm. See examples below. confidence limits for the saddle grid sample were about There is only a 5% chance that two alpacas with the double those of mid side samples (Table 3). following mid side test results are different: Table 3. The 95% confidence limits for fibre attributes
measured from mid side or saddle grid samples in
Australian alpacas.
Small differences in MFD are unlikely to be valid grounds Attribute
Mid side Saddle
upon which to discriminate against animals. This interpretation has even greater weight when using saddle grid samples to select animals, as the sampling variance for these samples is at least twice that of mid side test Differences between years and properties
It is not valid to compare the fibre testing results obtained among properties or between years unless special Sampling variance for the incidence of medullated fibres precautions are taken during the collection and analysis of in saddle grid samples was very high, possibly due to the data. Large between year differences in the environment State of Victoria, Department of Primary Industries
Variation in and Sampling of Alpaca Fleeces
will affect alpaca fibre attributes (McGregor 2002) and McGregor, B. A., 1994. Animal Production in Australia, property and year affects can interact (See Figures 2 and 3, McGregor and Butler 2004). Thus during the design of McGregor, B.A., 1999a. In “Australian Alpaca Fibre: genetic improvement programs, arrangements must be Improving Productivity and Marketing” pp. 6 – 46. made to account for these influences if serious attempts are RIRDC Research Paper Series No. 99/140. (RIRDC: to be made at identifying real genetic differences. Correct fibre classing
McGregor, B.A. (1999b). The influence of environment, It is essential that alpaca fibre be harvested and prepared nutrition and management on the quality and production of for sale in accordance with the guidelines laid down by the alpaca fibre. Proceedings National Conference Australian industry. Correct fleece preparation is needed prior to the Alpaca Association, pp. 88–94. (Australian Alpaca taking of saddle grid samples. These guidelines can change from time to time. New guidelines can be obtained from McGregor, B.A., 2002. Comparative productivity and grazing behaviour of Huacaya alpacas and Peppin Merino sheep grazed on annual pastures. Small Ruminant Conclusions
Research 44: 219 – 232.
If alpacas are to be selected for characteristics such as low McGregor, B.A., 2004. Natural variations in alpaca fleeces mean fibre diameter and high fleece weight then the mid and interpretation of fibre tests. Proceedings National Conference Australian Alpaca Association, pp. 85-90. If alpacas are to be selected for low mean fibre diameter (Australian Alpaca Association: Mitcham, Victoria) coefficient of variation, low incidence of medullated fibres McGregor, B.A., 2006. Production, attributes and relative and other characteristics of medullated fibre, then the value of alpaca fleeces in southern Australia and saddle grid sampling technique is recommended. implications for industry development, Small Ruminant Alpaca breeders and advisers need to exercise caution when Research 61: 93-111.
interpreting absolute fibre test results. Evaluation of fibre McGregor, B.A., 2006. The affect of age, fleece weight, attributes among alpacas should take into account the 95% fibre diameter and live weight on the relative value of confidence limits of the sampling procedure. Australian alpaca fleeces. Proceedings National Conference Australian Alpaca Association, pp. 108-112. Acknowledgments
(Australian Alpaca Association: Mitcham, Victoria). The financial support of the Rural Industries Research and McGregor, B.A. and Butler, K.L., 2004. Sources of Development Corporation and the Australian Alpaca variation in fibre diameter attributes of Australian alpacas Association is gratefully acknowledged. Ms. J. Aylan- and implications for fleece evaluation and animal Parker, Ms. A. Howse and Mr. C. Tuckwell are thanked selection. Australian Journal of Agricultural Research 55:
References and further reading
Stadler, W. and Gillies, R.I., 1994. Wool Technology and Sheep Breeding, 42: 319-26. Aylan-Parker, J. and McGregor, B.A., 2002. Optimising sampling techniques and estimating sampling variance of Turner, H.N., Hayman, R.H., Riches, J.H., Roberts, N.F. fleece quality attributes in alpacas. Small Ruminant and Wilson, L.T., 1953. Division of Animal Health and Research 44: 53–64.
Production Report No.4 (Series S.W.-2), 92 pp. (CSIRO: Melbourne). Butler, K., Dolling, M., Marland, D.J., Naylor, G.R.S., Phillips, D.G. and Veitch, C., 1991. In “Proceedings Fibre The previous version of this note was published in Diameter Review Conference”, 54 pp. (CSIRO: Belmont, Fleet, M.R., Foulds, R.A. and Lampe, F.J., 1993. Wool Technology and Sheep Breeding, 41: 307-16. The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned.
The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular
purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this
publication.
State of Victoria, Department of Primary Industries

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