Phenotypic Links Between Skin Thickness, Follicular Density, And fibre Growth Rates in Alpacas
By Ian Watt, Alpaca Consulting Services USA
One of the benefits of objective measurement of phenotypic alpaca traits is that the resulting measurements can be collected and analysed for additional insights that can benefit the industry as a whole. Breeders who commission these analyses of their animals, as well as the organisations that provide them, play an important role in advancing the understanding of alpaca trait relationships and their possible underlying genetic links.
Aggregated skin biopsy data represents a relatively unexplored research resource for the alpaca industry. Data collected from skin biopsy samples traditionally includes measures of density (follicle count, typically expressed as the average number of follicles appearing in a millimeter-square area of skin); primary and secondary fibre population average fibre diameters (AFDs) and the standard deviations of diameters (SDs); and the number of secondary follicles relative to primary follicles, known as the S:P ratio.
At our laboratory, we also measure and record the thickness of the skin and the daily growth rate of the fibre (calculated by measuring the length of an accompanying sample of fibre and dividing that length by the number of days since the animal was last shorn.) We record this additional information because we are aware of both genetic and phenotypic research on sheep that supports links between follicular density, fibre fineness, and fibre growth rates. As individual fibre traits like fineness, uniformity of micron, curvature, and staple length share similar relationships and are comparably heritable in both sheep and alpacas, we suspected that similar links between skin thickness, density, fineness and staple length may also hold among alpacas.