Follicle, Density and in-Skin Micron Count Data

Density and Length Profiles of Alpacas
A preliminary report prepared by J.E. Watts
Samples collected 29 March 2005

Introduction

The SRS® breeding objective of increasing the density and length of fibres grown by fleece-coated animals is based on the pre-papilla cell research of Moore et al (1998), "Pattern and Morphogenesis in Skin", Journal of Theoretical Biology, 191:87-94, and later unpublished data.

This work has demonstrated that the density and fineness of fibres is controlled by the size of the pre-papilla cell clusters formed in the foetal skin whilst fibre length is thought to be regulated by the 'signal strength' of mitogen(s) produced by these cells (see www.srswool.com for details).

Pre-papilla Cells

High fibre density requires a large starting population of pre-papilla cells in the foetal skin and for these cells to be distributed as small clusters to both the primary wool follicles and secondary wool follicles. Follicle formation is completed before the animal is born. Fibre length is also a measurable response of pre-papilla activity. So the 'package' of desirable follicle and fibre characteristics we are seeking to breed in alpacas are:

very fine primary fibres of uniform diameters (eventually finer than the secondary fibres) - this allows a greater proportion of the pre-papilla cells to be available to form secondary wool follicles
high follicle density associated with high levels of secondary follicle branching (the latter equates to high secondary follicle to primary follicle [S/P] ratio - this is an expression of many pre-papilla cells being available to form secondary follicles which, in turn, are formed by small clusters. Hence the secondary fibres are also fine, uniform in diameter and highly aligned.
If 1. and 2. are in place, the profiles will show two steep and narrow fibre diameter distribution curves with the red one (primary fibres) to the left of the blue one (secondary fibres)
very long fibres of uniform length

These features are associated with skins that are thin and loose (Watts, unpublished data).

Medullated Fibres

Medullated fibres are unwanted fibres which spoil the appearance of fabrics.
In horizontal skin sections, medullated fibres can be identified and counted within each follicle type.

This is an important capability. Whilst medullation tends to reside mainly in the primary fibres and disappears as fibres become finer, this is not 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.

Pigmented Fibres

Skin testing also allows us to identify pigmented fibres in each follicle type. This also is an important diagnostic function.

For example, in a white alpaca we can determine if any pigmented fibres are still to be found and which follicle type(s) are affected. We can also determine whether pigmentation is a problem of coarse diameter fibres, and likely to disappear as fineness and uniformity of fibres improve, or is generally distributed throughout fibres.

Industry Standards

Alpacas considered of good fleece quality by current industry standards have, on average, a follicle density of about 40 follicles per square millimetre and an S/P ratio of 10 to 1.

Primary fibres are mostly medullated and about 10µ coarser than the secondary fibres. The average fibre diameter in adult animals generally varies from about 20µ to 30µ.

The fibre length of young adult animals averages about 0.40 millimetres per day, and in old animals, about 0.25 millimetres per day. The higher the fibre length to staple length ratio, the higher crimp amplitude (that is, the deeper the crimp) is likely to be.

It is certainly possible to breed animals that are a lot denser, finer and longer than current industry standards.

The SRS® breeding goals (as stated above) are to breed alpacas that have primary fibres finer than the secondary fibres, secondary fibres that are up to 10µ finer than currently seen in adult animals, follicle densities above 85 follicles per square millimetre and S/P ratios above 20 to 1. Ultimately, no fibres should be medullated, irrespective of the age of the animal or the follicle type. The objective is also to improve fibre length to 0.70 millimetres per day or more and maintain this length throughout much of the animal's life.

Density Profiles

The density results for the alpacas are listed in Table 1.
Download a report here (PDF, 187KB, new window)

Table 1. Follicle and fibre characteristics of the Huacaya alpacas. Bracketed figures are standard deviations.

Animal	Color	Dp	Dp Med.	Ds	Ds Med.	Fn	S/P Ratio	Skin Thickness	FL	FL/SL
Malato (12) JW0350	Black	37.8 (10.7)	-	28.4 (3.9)	-	32.8	7.6	2.26	99.0	1.06
Marquite (13) JW0351	Black	35.6 (8.0)	-	24.9 (4.0)	-	28.7	8.4	2.02	104.9	1.04
Missel (14) JW0352	Black	41.7 (7.6)	-	24.8 (2.2)	-	34.5	8.5	2.60	82.1	1.14
Anana (15) JW0353	Black	48.6 (9.9)	-	31.1 (4.9)	-	14.8	7.8	1.77	75.4	0.97
Cielo (16) JW0354	Black	39.5 (3.8)	-	25.8 (3.8)	-	36.9	9.9	1.80	77.4	1.10
Esbelta (17) JW0355	Black	38.8 (8.6)	-	26.2 (4.1)	-	26.6	7.9	1.77	79.5	1.13
Pr. Charming (18) JW0356	White	30.0 (3.4)	96%	24.2 (3.5)	66%	48.8	11.3	2.38	103.3	1.18

Legend:

Dp	primary fibre diameter in microns
Dp med.	percentage of medullated primary fibres
Ds	secondary fibre diameter in microns
Ds med.	percentage of medullated secondary fibres
Fn	follicle density (per square millimetre)
FL	fibre length growth rate in millimetres per day
FL/SL	ratio of fibre length to staple length

Density Profiles - Case Study

Anana(15) in Table 1 (above) is the dam of Marquite (13) with Missel (14) as the sire.
These three animals clearly illustrate the SRS® breeding objective of increasing the density and length of fibres.
Their histograms clearly show the influence of a superior sire over an average female - imagine if the next sire were an elite animal bred over the daughter (Marquite (13)).
Clearly, identifying density counts, primary and secondary ratios and fibre length in sires provides an excellent selection tool for progressive and forward thinking breeders.

For further information, contact Ian Watt at

Alpaca Consulting USA
1540 San Bernardo Creek Road
Morro Bay California 93442
+ 1 805 772 1774
info@elitealpacabreedingsystems.com