Ferguson, M. B., McGregor, B. A. and Behrendt, R. 2012, Relationships between skin follicle characteristics and fibre properties of Suri and Huacaya alpacas and Peppin Merino sheep, Animal production science, vol. 52, no. 7, pp. 442-447.
DOI: 10.1071/AN11233
This is the accepted manuscript.
©2012, CSIRO Publishing
Reproduced by Deakin University with the kind permission of the copyright owner.
Available from Deakin Research Online: http://hdl.handle.net/10536/DRO/DU:30049702
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5 Relationships between skin follicle characteristics and fibre properties of Suri and Huacaya alpacas and
6 Peppin Merino sheep
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10 M.B. FergusonA, B.A. McGregorB,D,Eand R. BehrendtCD
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12 A Department of Agriculture and Food Western Australia, South Perth, W.A., 6151, Australia
13 B Centre for Material and Fibre Innovation, Deakin University, Geelong, Vic., 3220, Australia
14 C Livestock Production Sciences, Future Farming Systems Research Division, Department of Primary
15 Industries, Hamilton, Vic., 3300, Australia
16 D Formerly Wool Quality Department, Department of Primary Industries, Attwood, Vic., 3030,
17 Australia
18 E Corresponding author E-mail address: [email protected]
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20 Short title: Follicle and fibre properties of alpacas and sheep
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24 Abstract.
25 We aimed to quantify the number, type and arrangement of skin follicles in Huacaya and Suri alpaca
26 skin and correlate their follicle characteristics with fibre traits of harvested fibre and compared these
27 relationships with those of Merino sheep. Fibre and skin samples were collected from the mid-side of 12
28 Huacaya alpacas, 24 Suri alpacas and 10 Merino sheep. The mean fibre diameter (MFD ± s.e.) of the
29 Huacaya and Suri were: 35.5 ± 0.9 µm and 28.3 ± 1.0 µm respectively. The follicle groups found for
30 alpacas were very different from the normal trio of primary follicles found in sheep and goats. The
31 follicle group of the alpacas consisted of a single primary follicle surrounded by a variable number of
32 secondary follicles. The mean ± s.e. primary follicle density was 3.1 ± 0.3 and 2.7 ± 0.1 follicles/mm2
33 for Huacaya and Suri, respectively. The mean ± s.e. secondary follicle density (SFD) was 13.7 ± 1.2 and
34 17.5 ± 0.6 follicles/mm2 for Huacaya and Suri respectively. The mean ± s.e. ratio of secondary to
35 primary follicles (S/P ratio) was 5.1 ± 0.5 for the Huacaya and 7.3 ± 0.2 for the Suri alpacas. The sheep
36 had higher S/P ratios and SFD, lower MFD and produced significantly heavier fleeces. The key
37 correlations found between traits in alpacas include a negative correlation between SFD and MFD (r = -
38 0.71, P = 0.001) and a negative correlation between S/P ratio and MFD (r = -0.44, P = 0.003) and a
39 positive correlation between S/P ratio and total follicle density (r = 0.38, P = 0.010). The study revealed
40 that important relationships exist between alpaca skin follicle characteristics and fibre characteristics. It
41 was the number of secondary follicles in a group that imparts density and a corresponding reduced
42 MFD.
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45 Additional keywords: fibre diameter, fibre quality, live weight, tenacity, fibre curvature
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47
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48 Introduction
49 The alpaca (Lama vicugna) is a South American camelid which has two genotypes, the Huacaya and the
50 Suri, both having distinctive fibre characteristics. Despite their long period of domestication, little is
51 known about the skin characteristics of alpaca and their relationship with fibre quality and quantity.
52 Preliminary research suggests that, in alpacas, primary follicles are in “groups” of one, and that the
53 typical trio follicle group seen in sheep and goats is rarely seen (Calle-Escobar 1984; McGregor 1995).
54 Primary follicles in alpacas have an associated sudoriferous gland and an erector pili muscle, as in other
55 animals. Both secondary and primary follicles have associated sebaceous glands, although the quantity
56 is reduced when compared with sheep (Calle-Escobar 1984). Preliminary studies of Australian alpacas
57 indicate a range of secondary to primary follicle ratios (S/P ratio) of 4:1 to 9:1 (McGregor 1995).
58 Antonini et al. (2004) reported that in 10 Huacaya and 5 Suri alpaca mean S/P ratios ranged from 6.9 to
59 9.4 reaching a mature ratio at about 4 months of age.
60 There has been extensive research on the follicle structures of sheep and their effect on fibre traits
61 (Rendel and Nay 1978; Williams and Winston 1987; Maddocks and Jackson 1988; Moore et al. 1996)
62 but in comparison, we found none for these associations in alpaca. Merino sheep breeders consider skin
63 characteristics as being important in determining potential wool growth and quality. In sheep, increasing
64 follicle density in the skin through increasing the S/P ratio, results in a reduction in fibre diameter and
65 usually an increase in fleece weight (Hynd et al. 1996, Barton et al. 2001). However, the rate of genetic
66 improvement through the additional use of these skin follicle measures is generally not much greater
67 than the use of measures such as clean fleece weight and mean fibre diameter alone (Skerritt 1995;
68 Hynd et al. 1997; Purvis and Swan 1997; Barton et al. 2001). Differences in follicle traits are also
69 genetically associated with subjectively assessed wool traits (Hill et al. 1997).
70 Since the number, type and arrangement of follicles in the skin of sheep can, at least in part,
71 explain differences in fibre characteristics, and considering the commonality between skin structures of
72 fibre producing animals, an analysis of skin structure of alpacas may reveal reasons for the observed
73 differences in fibre attributes of harvested fleeces. In the absence of objective data for alpaca, we aimed
74 to quantify the number, type and arrangement of skin follicles in Huacaya and Suri alpaca skin and
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75 correlate their follicle characteristics with fibre traits of harvested fibre and compared these
76 relationships with those of Merino sheep.
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78 Materials and Methods
79 Animal management
80 Twelve Huacaya alpacas (11 male and 1 female; age 4 to 13 years) provided by Australian alpaca studs
81 were grazed at the Department of Primary Industries, Attwood, Victoria (37°40S, 144°53E). They
82 grazed with 10 Merino castrate sheep (age 5 years, medium Peppin strain). Further information is
83 provided elsewhere (McGregor 2002; McGregor and Brown 2010; Judson et al. 2011).
84 As there were no Suri alpaca available for use in research herds, access was restricted to stud
85 flocks. We used 24 Suri alpacas (11 male and 13 female; age 6 months to 11 years), located at the
86 nearest stud at Trentham East, Victoria (37°24S, 144°19E).
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88 Fibre and histological measurement
89 Mid-side fleece samples were collected at shearing in midsummer after 12 months of fleece growth.
90 Skin biopsy samples were collected following shearing (Maddocks and Jackson 1988). The mid-side
91 site was located (third last rib, halfway between the mid-line of the back and the midline of the belly)
92 and fibre removed at skin level using small animal clippers. A skin biopsy was taken (1 cm trephine)
93 and immediately placed in fixing solution (10% buffered formalin).
94 The mid-side fibre samples were measured for mean fibre diameter (MFD, µm), fibre diameter
95 coefficient of variation (CVD, %), fibre medullation (%w/w) and fibre curvature (FC, °/mm) using an
96 Optical Fibre Diameter Analyser (OFDA100) (IWTO 2005a,b). Coloured fibres were not assessed for
97 medullation. The bundle tenacity (Yang et al. 1996) was determined on five staples from the mid-side
98 sample following cleaning in non-swelling conditions and re-conditioning. Staple length was measured
99 on 10 staples using a ruler to the nearest 1 mm. Lengths were adjusted to a one-year growth period to
100 allow a comparison.
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101 The histological techniques, follicle differentiation and counting techniques were adapted from
102 Maddocks and Jackson (1988). Skin biopsy samples were processed for paraffin embedding and
103 sectioning using conventional histological procedures. Horizontal 5 µm sections were cut at sebaceous
104 gland level using a microtome and mounted and stained using a Haematoxylin, Eosin and Picric Acid
105 method. Follicles were differentiated and counted using a projection microscope and a square of known
106 area. Primary follicles were differentiated from secondary follicles by the association of the primary
107 with a sweat duct and bi-lobed sebaceous glands. Eight groups of follicles were identified, to ensure that
108 at least 100 follicles were counted for each sample, to determine the S/P ratio, primary (PFD),
109 secondary (SFD) and total (TFD) follicle densities. Results were adjusted for sample shrinkage that
110 occurs when fixing the skin biopsy in relation to the diameter of the trephine.
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112 Statistical analysis
113 As there was unequal variation between groups and the group data sets were often not normally
114 distributed the data was log transformed to prevent the residual variation increasing with the mean. For
115 the alpaca data, linear regression analysis and one-way ANOVAs were performed using GenStat (Payne
116 2010) to assess the relationships between variables. In the ANOVA we compared alpaca genotype
117 (Huacaya, Suri) and Merino data. For linear regression analysis we compared relationships in alpacas
118 between follicle density measurements and S/P ratio with MFD, liveweight, genotype and sex and S/P
119 ratio with follicle density measurements. Individual means were used as the unit of analysis.
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121 Results
122 Huacaya had higher liveweights compared with Suri with the Merino intermediate (Table 1). Huacaya
123 alpaca had greater MFD and FC and shorter staples than Suri alpaca (Table 1). Merino wool had lower
124 MFD, CVD, bundle tenacity and medullation, and a higher FC than the alpaca fibre (Table 1).
125 The PFD did not differ between the Huacaya and Suri alpaca populations but were greater than
126 the Merinos (Table 2). The Suri population had a significantly higher SFD and TFD (P<0.01) and S/P
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127 ratio (P<0.001) than the Huacaya population but lower than the Merinos (P<0.001, Table 2). There was
128 no effect of sex on any attribute within the Suri population (P > 0.05).
129 Regression analyses of the relationships between different traits highlighted some significant
130 correlations. A negative correlation (r = -0.71) was apparent between TFD and MFD in the alpaca
131 populations (P= 0.002) with genotype being significantly different (P= 0.002). However the
132 relationship between TFD and MFD was determined by the negative correlation (r = -0.71) between
133 MFD and SFD (P < 0.001, Fig. 1) which was affected by genotype (P = 0.004) but not PFD (P = 0.95)
134 or TFD (P = 0.95). TFD was negatively associated with liveweight (r = -0.38, P = 0.012, Fig. 2) at time
135 of sample collection and genotype was not significant (P = 0.35). However liveweight was not
136 significant (P = 0.47) when added to regressions with SFD and genotype.
137 For all alpacas, a negative correlation (r = -0.44, P = 0.003) was found between S/P ratio and
138 MFD (Fig. 3). The best equation relating S/P ratio to MFD for all alpacas retained liveweight in the
139 equation (r = -0.53, P = 0.02) which indicated that MFD declined with increasing S/P ratio but increased
140 0.98 (s.e. 0.39) µm for every 10 kg increase in liveweight. There was a significant positive correlation (r
141 = 0.38, P = 0.010) between S/P ratio and TFD which was not affected by genotype (P = 0.20 Fig. 4).
142 However the best predictor of TFD was provided by both S/P ratio and liveweight (r = 0.54, P = 0.0012)
143 where TFD increased with increasing S/P ratio but declined 0.81 (s.e. 0.30) follicles/mm2 for each 10 kg
144 increase in liveweight.
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146 Skin structures
147 The follicle group for both alpacas consisted of a single primary follicle characterised by an associated
148 sweat duct and sometimes bi-lobed sebaceous glands (Fig. 5). The primary follicle was surrounded by a
149 variable number (commonly 4-10) of secondary follicles, which may have associated sebaceous glands.
150 Within each follicle group primary follicles were generally larger than the secondary follicles and
151 always had medullated fibres, whereas the secondary follicles had both medullated and non-medullated
152 fibres.
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154 Discussion
155 This study revealed that important relationships exist between skin follicle characteristics and fibre
156 characteristics in alpacas. In sheep, TFD is thought to be an important trait because of its close
157 relationship with MFD (Moore et al. 1996). Selection to alter the densities of follicle types in Merino
158 sheep results in a change in MFD and fleece weight (Rendel and Nay 1978; Moore et al. 1996). A
159 negative correlation was found between TFD and MFD in this study for both genotypes of alpacas. In
160 this study, the slope of the regression line was greater for the Suri population than in the Huacaya
161 population. This is an unlikely scenario and is more likely to be a function of the populations sampled
162 which had different age profiles for example and not of alpacas in general. The most important issue is
163 that there was a negative correlation between TFD and MFD in this study for both genotypes of alpacas.
164 A similar relationship was found between SFD and MFD (Fig. 1). In alpacas SFD is the main
165 determinant of TFD and MFD, this is not unexpected considering the large numbers of secondary
166 follicles compared with the number of primary follicles.
167 In this study the Suri population had a TFD of 20.2 follicles/mm2 and the Huacaya population a
168 TFD of 16.8 follicles/mm2, a difference which may only be a result of population sampling or
169 differences in mean liveweight via its affect on skin surface area. These values are similar to the
170 preliminary report of Watts (1996), whose data suggested a TFD of 22.3 follicles/mm2 for Huacaya
171 alpacas while Antonini et al. (2004) reported Huacaya with TFDs of 18.3-22.3 follicles/mm2 from 4 to
172 10 months of age. Both Hoffman and Fowler (1995) and Antonini et al. (2004) indicate that the follicle
173 density in the Suri is less than that in the Huacaya, which from this study seems not to be the case. More
174 importantly the S/P ratio of the Suri alpacas was found to be significantly greater than the Huacaya
175 alpacas in this study whereas Antonini et al. (2004) reported that Suri had a lower S/P ratio than
176 Huacaya at 6 and 10 months of age. Antonini et al. (2004) did not provide data on liveweight of their
177 alpaca so reported differences between alpaca genotypes and between their work and the present study
178 may be due in part to differences in animal growth consequent upon differences in nutrition which are
179 likely to affect follicular development.
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180 The S/P ratio is important in determining the quality and quantity of wool produced in sheep
181 (Williams and Winston 1987). The S/P ratios found in this study are consistent with the 7.2 reported by
182 Calle-Escobar (1984), preliminary reports of McGregor (1995) 4.1-9.1 and Watts (1996) (4.6 to 9.8),
183 and those of Antonini et al. (2004) (means for animals 6 and 10 months of age 6.9-8.8). The S/P ratio is
184 expected to have an effect on TFD and MFD and we found that there was a correlation between S/P
185 ratio and MFD for all alpacas (Fig. 3), where MFD decreases with an increase in S/P ratio. TFD was
186 correlated with S/P ratio (Fig. 4). This relationship would be expected, as it has been observed in
187 Merino sheep (Williams and Winston 1987; Hynd et al. 1996). It is therefore the number of secondary
188 follicles in a group that imparts density and a corresponding increase in fleece weight and reduced
189 MFD.
190 Earlier reports indicate that in alpacas, primary follicles are in “groups” of one (Calle-Escobar
191 1984; McGregor 1995). This is consistent with the results of this experiment, with only one primary
192 follicle present in each group in most cases in both the Huacaya and Suri alpaca. The presence of a
193 sudoriferous or sweat gland and often the presence of bilobed sebaceous glands differentiated primary
194 follicles from secondary follicles (Calle-Escobar 1984; Maddocks and Jackson 1988). Sebaceous glands
195 were also found around the secondary follicles. Recently Badajoz et al. (2009) investigated the skin
196 structures of 42 young Huacaya and Suri alpaca. Similarly to other reports they found that follicular
197 groups were formed by one or more primary follicles and a variable number of secondary follicles,
198 however in the Suri alpaca, they reported groups of three primary follicles, one larger and central and
199 two smaller at each side. Calle-Escobar (1984) reported that both secondary and primary follicles in
200 alpaca have associated sebaceous glands, although the quantity is somewhat reduced as compared with
201 Merino sheep. This was also found in this study and it is suggested that the increased yield found in
202 alpaca fibre as compared with Merino wool is a direct result of the presence of fewer sebaceous glands
203 in the skin of the alpaca.
204 The fleece production and fleece attributes for the Huacaya alpacas and the Peppin Merino sheep
205 are discussed elsewhere (McGregor 2002). That data, in association with the present work, supports the
206 contention that S/P ratio influences MFD and fleece weight as the clean fibre production of the sheep
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207 was 80% higher than that of the Huacaya alpacas despite the MFD being 40% less than that of the
208 alpaca. Table 3 is included as a reference and shows that there is a general relationship between S/P
209 ratio and MFD over a range of sheep breeds and the alpaca data from this study.
210 Correlations between follicle curvature and fibre traits especially FC would be an interesting area
211 for further study.
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213 Conclusion
214 This study revealed that many trends within and between skin and fibre traits that are seen in sheep also
215 hold true for Huacaya and Suri alpacas. In alpacas, S/P ratio, SFD and live weight were important
216 determinants of the MFD.
217
218 Acknowledgments
219 Ms. Andrea Howse provided technical support. Members of the Australian Alpaca Association provided
220 Huacaya alpacas and access to the Suri alpacas. The project was part funded by the Rural Industries
221 Research and Development Corporation. Mark Ferguson completed the study as part of his degree at the
222 University of Melbourne with the support of the DPI through its cadetship program.
223
224 References
225 Antonini M, Gonzales M, Valbonesi A (2004) Relationship between age and postnatal skin follicular
226 development in three types of South American domestic camelids. Livestock Production Science 90,
227 241-246.
228 Badajoz LE, Sandoval CN, Garcia VW, Pezo CD (2009) Histological description of the hair follicle in
229 the young alpaca (in Spanish). Revista de Investigaciones Veterinarias del Peru 20, 154-164.
230 Barton SA, Purvis IW, Brewer HG (2001) Are wool follicle characteristics associated with wool quality
231 and production in hogget and adult sheep? Proceedings of the Association for the Advancement of
232 Animal Breeding and Genetics 14, 289-292.
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233 Calle-Escobar R (1984) ‘Animal breeding and production of American Camelids.’ (Ron Hennig-
234 Patience: Lima)
235 Carter HB, Clarke WH (1957a) The hair follicle group and skin follicle population of Australian Merino
236 sheep. Australian Journal of Agricultural Research. 8, 91-108.
237 Carter HB, Clarke WH (1957b). The hair follicle group and skin follicle population of some non-merino
238 breeds of sheep. Australian Journal of Agricultural Research 8, 109-119.
239 Crook BJ, Purvis IW (1997) Wool follicle traits in the NSW Peppin Merino stud industry: preliminary
240 estimates from a sample survey. Proceedings of the Association for the Advancement of Animal
241 Breeding and Genetics 12, 158-162.
242 Hill JA, Hynd PI, Ponzoni RW, Grimson RJ, Jaensch KS, Kenyon RV, Penno NM (1997). Skin and
243 follicle characters II. Correlations with objectively measured and subjectively assessed wool
244 characters. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 12,
245 524-528.
246 Hoffman E, Fowler ME (1995) ‘The Alpaca book: Management, Medicine, Biology and Fiber.’ (Clay
247 Press Inc.: Herald, California)
248 Hynd PI, Ponzoni RW, Grimson R, Jaensch KS, Smith D, Kenyon R (1996) Wool follicle and skin
249 characters- Their potential to improve wool production and quality in Merino sheep. Wool Technology
250 and Sheep Breeding 44, 167-177.
251 Hynd PI, Ponzoni RW, Hill JA (1997) Can selection for skin traits increase the rate of genetic progress
252 in Merino breeding programs? Proceedings of the Association for the Advancement of Animal
253 Breeding and Genetics 12, 752-759.
254 International Wool Textile Organisation (2005a) ‘Measurement of the mean and distribution of fibre
255 diameter of wool using an optical fibre diameter analyser (OFDA).’ IWTO-47. (International Wool
256 Textile Organisation: Ilkley, UK)
257 International Wool Textile Organisation (2005b) ‘Determination of medullated fibre content of wool and
258 mohair samples by opacity measurement using an OFDA.’ IWTO-57. (International Wool Textile
259 Organisation: Ilkley, UK)
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260 Judson GJ, McGregor BA, Howse AM (2011) Blood mineral, trace-element and vitamin concentrations
261 in Huacaya alpaca and Merino sheep grazing the same pasture. Animal Production Science 51, 873-
262 880.
263 Maddocks IG, Jackson N (1988) ‘Structural studies of sheep, cattle and goat skin.’ (CSIRO: Blacktown)
264 McGregor BA (1995). Alpaca fleece development and methods of assessing fibre quality. Proceedings
265 International Alpaca Industry Conference, Geelong pp. 55-78. (Australian Alpaca Association: Forest
266 Hill, Victoria)
267 McGregor BA (2002) Comparative productivity and grazing behaviour of Huacaya alpacas and Peppin
268 Merino sheep grazed on annual pastures. Small Ruminant Research 44, 219-232.
269 McGregor BA, Brown AJ (2010) Soil nutrient accumulation in alpaca latrine sites. Small Ruminant
270 Research 94, 17-24.
271 Moore GPM, Jackson N, Isaacs K, Brown G (1996) Development and density of wool follicles in
272 Merino sheep selected for single fibre characteristics. Australian Journal of Agricultural Research 47,
273 1195-1201.
274 Payne RW Ed (2010) ‘The Guide to GenStat®; Release 13. Part 2: Statistics.’ (VSN International:
275 Hertfordshire, UK)
276 Purvis IW, Swan AA (1997) Can follicle density be used to enhance the bate of genetic improvement in
277 Merino flocks? Proceedings of the Association for the Advancement of Animal Breeding and Genetics
278 12, 512-515.
279 Rendel JM, Nay T (1978) Selection for high and low ration and high and low primary density in Merino
280 sheep. Australian Journal of Agricultural Research 29, 1077-1086.
281 Skerritt JW (1995) There is no benefit in using follicle density, secondary to primary follicle ratio or
282 primary follicle density as additional selection. Proceedings of the Australian Association of Animal
283 Breeding and Genetics 11, 228-232.
284 Thomas IR (1981) In ‘A Manual of Australian Agriculture.’(4th ed., Ed. R.L. Reid). (W. Heinmann:
285 Melbourne)
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286 Watts JE (1996) Elite Alpaca production: breeding from fibre to fabric. (Coolaroo Alpaca Stud: N.S.W.,
287 Australia)
288 Williams AJ, Winston RJ (1987) A study of the characteristics of wool follicle and fibre in Merino
289 sheep genetically different in wool production. Australian Journal of Agricultural Research 38, 743-
290 755.
291 Yang S, de Ravin M, Lamb PR, Blenman NG (1996) Wool fibre bundle strength measurement with
292 Sirolan-Tensor. Proceedings of Top-Tech 96, 293-304. (CSIRO: Geelong)
293
294
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295 Table 1. The mean (±se) liveweight, fibre diameter (MFD), coefficient of variation of fibre
296 diameter (CVD), incidence of medullated fibres (MED), fibre curvature (FC), staple length and
297 bundle tenacity. Values within rows with different letters differ P<0.05.
298
Parameter Huacaya Suri Merino
n 12 24 10
Liveweight 76 ± 3.5a 59 ± 4.5b 65 ± 2.5ab
MFD (µm) 35.5 ± 0.88c 28.3 ± 1.00b 20.6 ± 0.65a
CVD (%) 26.1 ± 1.22b 24.6 ± 0.60b 17.9 ± 0.27a
MED (% w/w) 50.2 ± 11.39b 24.7 ± 2.72b 0.2 ± 0.02a
(n = 3) (n = 23) (n = 10)
FC (°/mm) 25.8 ± 1.31b 12.3 ± 0.44c 79.9 ± 3.57a
Staple length (mm) 76.9 ± 2.84a 151.9 ± 8.96b 79.9 ± 3.57a
Bundle tenacity (cN/tex) 12.4 ± 0.29b 11.3 ± 0.31b 9.5 ± 0.26a
299
300
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301 Table 2. Mean (±se) for primary, secondary and total follicle density (follicles/mm2), and
302 secondary to primary follicle ratio (S/P ratio) for alpacas and sheep. Values within columns with
303 different letters differ P<0.05.
304
Group n Follicle density S/P ratio
Primary Secondary Total
Huacaya 12 3.1 ± 0.28b 13.7 ± 1.24a 16.8 ± 1.42a 5.1 ± 0.46a
Suri 24 2.7 ± 0.12b 17.5 ± 0.64b 20.2 ± 0.73b 7.3 ± 0.23b
Peppin Merino 10 2.0 ± 0.40a 41.4 ± 7.58c 43.5 ± 7.63c 21.0 ± 5.07c
305
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306 Table 3. A summary of the range in mean fibre diameter (MFD), total follicle density and S/P
307 ratio for several sheep breeds (Carter and Clarke 1957a, 1957b; Thomas 1981; Crook and Purvis
308 1997) and the alpaca and sheep data from this study.
Animal type MFD Follicle density S/P ratio (µm) (follicles/mm2) Saxon Merino 19-20 30-118 11.2-32.8
Peppin medium Merino 21-22 27-114 7.2-115.7
South Australian Merino 23-26 37-82 10.7-28.3
Corriedale 25-32 13-42 7.9-14.0
Romney Marsh 32-38 16-28 4.1-8.2
Lincoln 40-48 11-18 3.4-7.0
Peppin MerinoA 17.5-25.3 29-70 18.3-33.6
Suri alpacaA 21.8-41.7 12-28 5.1-9.4
Huacaya alpacaA 31.2-41.2 10-26 2.9-7.9
309
310 A data from this study
311
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312 Figure captions
313
314 Fig. 1. The relationship between secondary follicle density (SFD) and mean fibre diameter for
315 each of; Huacaya () and Suri () alpacas. Lines represent regression equations fitted to the data for:
316 all alpacas (), y = 45.1 (s.e. 3.20) - 0.91 (s.e. 0.19) SFD; Suri alpacas (--), y = 44.1 (s.e. 4.71) - 0.91
317 (s.e. 0.26) SFD; and Huacaya alpacas (⋅⋅⋅⋅⋅), y = 39.5 (s.e. 3.16) - 0.28 (s.e. 0.22) SFD.
318
319
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320 Fig. 2. The relationship between liveweight and total follicle density. The regression equation was
321 not affected by genotype: y = 24.77 (s.e. 2.14) – 0.087 (se 0.033) liveweight, r = -0.38. Symbols:
322 Huacaya (), Suri ().
323
324
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325 Fig. 3. The relationship between S/P ratio and mean fibre diameter for Huacaya () and Suri ()
326 alpacas. The line represents a regression equation fitted to the data for all alpacas (y = 40.9 (s.e. 3.49 –
327 1.61 (s.e. 0.512) S/P ratio, r = -0.44).
328
329
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330 Fig. 4. The relationship between S/P ratio and total follicle density for all alpacas. The regression
331 line: y = 12.1 (se 2.75) + 1.10 (se 0.404) S/P ratio, r = 0.38. Symbols: Huacaya (), Suri ().
332
333
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334 Figure 5. Horizontal section of Suri alpaca skin at sebaceous gland level, magnified x 100, showing
335 a follicle group of one primary follicle (P) and ten secondary follicles (S). The sebaceous glands
336 (G) and sweat duct (D) are shown. Some fibres exhibit a medulla (M). This animal displays the
337 following densities: primary follicle density, 2.04 follicles/mm2; secondary follicle density, 16.88
338 follicles/mm2; total follicle density, 18.92 follicles/mm2; and S/P ratio: 9.
339
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340