Breeding alpacas with soft, silky fleeces.
There are two types of wool follicles in the alpaca’s skin (Figure 1). These follicle types are different in appearance and function. Primary fibres produce the outer coat of the newborn cria. The secondary fibres form the undercoat, and represent the majority of fibres in the fleece.
Guard hairs are coarse and medullated primary fibres that impair fleece and textile quality.
The diameters of the primary fibres and the secondary fibres are to a large degree, independently genetically regulated. In alpacas, primary fibres are, on average, about 10 microns coarser in diameter than the secondary fibres. Consequently, most alpacas contain guard hair and most textile products made from alpaca wool contain guard hair. (unless dehaired -an expensive procedure).
In 1988 I devised a new breeding approach for fleece coated animals (sheep, alpacas, angora goats) which recognizes and addresses the fundamental issue that the genetic regulation of primary fibres and secondary fibres is different. It is based on selecting for low primary fibre diameter and high levels of fibre density and fibre length.
These fibre traits can be estimated visually as well as measured. If direct selection is placed on reducing primary fibre diameter, the genetic response is swift since this trait is highly heritable ( h 2 = 0.7). It allows us to reduce the mean diameter of the primary fibres of the alpaca from its current and unacceptably high level of about 35 microns to less than 17 microns in order for medullation to disappear.
If the alpaca also has high fibre density and length, that is, many fibres on its body and these fibres are long, then the alpaca will produce a high fleece weight of fine diameter wool of high quality.
Reducing primary fibre diameter
The first step is to estimate the diameter of the primary fibres in the fleece by examining individual fibres on a black velvet board (Figure 2). A white board is used for dark coloured alpacas.
In the two fleece samples shown in Figure 3, guard hair is present in similar amounts. It is not obvious in the sample on the right but becomes readily apparent when individual fibres are examined on the black velvet board.
The visual clues for fibre density in the alpaca are very thin staples (about 1 to 3 millimetres wide) that are packed closely together and have exceptional softness and lustre (Figure 4).
This staple arrangement is a silhouette of the follicle patterning in the skin. It indicates that the distance between the follicles within each skin follicle group is small, and the follicle groups are also closely packed together.
The visual clues for fibre length in the Huacaya alpaca are high crimp amplitude and low crimp frequency. In the Suri, the fleeces is simply long and gently coiling.
A ruler can be used to measure fleece length
Figure 4: The high density and length fleeces of the Huacaya alpaca (left) and the Suri alpaca (right) consist of long and closely packed, thin staples.
Measuring these key fibre traits
Primary fibre diameter, density and length are all measurable.
Primary fibre diameter and density are measured under the microscope on horizontal sections cut from a midside skin sample. Fibre length is measured on the overlying fleece sample.
|Trait||High density alpaca
|Avarage density alpaca
|Primary fibre diameter (microns)||73||35|
|Secondary fibre diameter (microns)||28,9||39,6|
|Density (follicles per square millimetre)||19,9||26,3|
It is certainly possible to breed alpacas that are a lot denser, finer and longer than the current levels.
The SRS® objective is to breed alpacas that have:
• primary fibres finer than 17 microns and finer than the secondary fibres
• follicle densities above 85 follicles per square millimetre
• secondary fibres that are less than 20 microns 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 the animal’s life.
The scope for genetic improvement of both fibre density and length is at least two-fold, or a four fold increase 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.