SRS® Alpacas Int ernat ional Pt y Lt d ABN: 82 121 968 3 3 PO Box 2604 Bowral NSW 2576 Australia T: +61 (0) 2 4862 2050 F: +61 (0) 2 4862 2290
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The SRS® Breeding System for Alpacas by Jim Watts
Breeding Objective The objective of the SRS® breeding system is to reduce the diameter of the primary fibres in order to eliminate eliminate guard hair whilst increasing the density and length of fibres grown by the alpaca. If there are many fibres on the animal’s body, and these fibres are long, then the alpaca will produce a high fleece fleece weight. Also, since high fibre (follicle) density is genetically correlated with low fibre diameter, the fleece will have a high value because it is fine and there is a lot of it.
Fleece markers An example of the distinctive fleece structure of the Huacaya alpaca with measurably high levels of fibre density and length is shown in Figure 1.
Figure 1.
The fleece structure of a Huacaya fleece with measurably high levels of fibre density and length 1
An example of the distinctive fleece structure of the Suri alpaca with measurably high levels of fibre density and length is shown in Figure 2.
Figure 2.
The fleece structure of a Suri fleece with measurably high levels of fibre density and length
Genetic regulation of follicle and fibre development The density ,length and fineness fineness of wool fibres appears to be regulated genetically by the number, distribution pattern and activity of pre-papilla cells in the foetal skin. The working hypothesis for maximising fibre density and length is: pre-papilla cells regulate wool follicle formation and fibre size. a large starting population of pre-papilla cells need to be available in the foetal skin to create the potential for a large number of wool follicles to be formed. pre-papilla cells need to be distributed as small small clusters clusters to form a high density of wool follicles because all the clusters are small, the fibres, fibres, whether originating from from primary follicles or secondary follicles, will be fine in diameter these small clusters need to emit strong signals from the base of the wool follicles to stimulate the growth of long fibres.
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The genetic regulation of fibre diameter differs between primary follicles and secondary follicles. Primary fibres, if left left to natural selection or inappropriate artificial selection, become coarse in diameter, even though the secondary fibres may remain fine in diameter. Inappropriate artificial selection is any breeding system that leads tto o an undue thickening of the animal’s skin. Primary fibres are produced by the first-formed first-formed follicles in the unborn cria’s skin. The secondary fibres, which greatly outnumber primary fibres, develop later in foetal life.
Follicle patterning The follicles are arranged as ‘follicle ‘follicle groups’ (Figure 3).
Figure 3.
Diagrammatic representation representation of a follicle group in the skin.
There are only 3 primary follicles follicles per group. The number of secondary follicles per group is much higher and is a genetic characteristic for a particular alpaca but can vary widely between animals (in our studies, from 17 to 50). The S/P ratio, or ratio of secondary follicles to each primary follicle, defines the number of follicles per group. Adult alpacas considered of good fleece quality by current industry standards have, on average, an S/P ratio of 10 to 1 and about 40 follicles per square millimetre. Primary fibres are usually no more than 10 microns coarser than the average diameter of the secondary fibres. The average diameter of the secondary fibres is usually less than 25 3
microns. The length growth rate of the fibres of adult animals of less than 4 years of age is at least 0.35 millimetres per day. Figure 4 shows a cross section through the oval-shaped follicle groups of an adult alpaca with a much higher follicle (fibre) density of 73 follicles per square millimetre.
Figure 4.
Horizontal skin section (magnified view) of an adult alpaca with a high density of 73 follicles per square millimetre.
In Figure 4, the primary fibres are so fine as to be virtually indistinguishable from the secondary fibres. This is an important point. Primary fibres need to reduced in size (by selective breeding) in order for the number of follicles per group (expressed as S/P ratio) and follicle density (expressed as follicles per square millimetre) to increase. By reducing primary fibre diameter, ‘guard hair’ is also eventually eliminated. Note that in this high density animal, none of the fibres are medullated and all are fine and uniform in size and shape. It is certainly possible to breed animals that are a lot denser, finer and longer than the current standards. The SRS® objective is to breed adult alpacas that have:
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primary fibres finer than the secondary fibres follicle densities above 85 follicles per square millimetre secondary fibres that are less than 20 microns for for average fibre diameter fibres that are as uniform in size and shape as possible fibres that grow in length at a rate of at least 0.70 millimetres per day or more and maintain this length throughout much of the animal’s life.
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Fibre Length Fibre length is greatest in fleeces which not only have long fleeces but also have high crimp amplitude and low crimp frequency.
Diagram of a single wool fibre. fibre. The vertical arrows arrows indicate crimp crimp amplitude. The horizontal arrows indicate crimp frequency. If a semi circle is the maximum expression of a crimp wave, the fibres will be, on average, about 50% longer than the fleece. This high crimp amplitude is is linked to high fibre elasticity and excellent drape in finished products.
Fleece quantity and quality The scope for genetic improvement of both fibre density and length is at least two-fold, or a four fold increase in in the fibre production of the animal. This would change the fleece production of an alpaca, for example, from producing 3 kgs of 25 micron wool per year to one producing about 7.5 kgs of 20 micron wool or 4.2 kgs of 15 micron wool per year.
Medullated and pigmented fibres In horizontal skin sections, and pigmented fibres can be identified and counted within each follicle medullated type. Medullated fibres and pigmented fibres (in white alpacas) are unwanted fibres which spoil the appearance of fabrics. Whilst medullation is ffound ound predominantly in the primary fibres, secondary fibres can also be affected. And whilst, medullation tends to disappear as the fibres become finer, this is not always always the case. In some animals, medullated fibres can still be present in fine diameter fibres and numerous among the secondary fibres. Skin testing allows us to identify, and remove from the breeding pool, animals with these ‘hidden’ problems.
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