Fibre density is one of the most misunderstood traits of
alpacas. High fibre density is strongly correlated with low average fibre
diameter. Conversely, low density is strongly correlated with high fibre
diameter. By the way, science to date has shown us there is little causal
relationship between the two traits - in other words, there is something deeper
occurring that influences their relationship. The problem is that broad fibre
will feel denser than finer fibre because of its greater mass. In other words, a
broad fleece will feel denser because of its diameter, than a finer fleece,
even though the finer fleece is likely to be more dense.
Performance trials with sheep and alpacas have shown that
comparing fleeces using an index on fleece weight with AFD is the most effective
way to increase fleece value and will have a positive effect on density.
The most effective traits to breed for are fibre diameter and
standard deviation because they are the most important traits in terms of
processing performance. The positive coincidence is that these two traits are
the two most heritable fibre traits. Heritability scores of about .55 and
.40 respectively. Fibre density is about .30.
Paul Valleley
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