The fibre diameter profile of wool staples from individual sheep

Abstract

Variation in fibre diameter along the staple was measured on duplicate staples from five sheep from each of four lines selected for high and low staple length and high and low fibre diameter. It was found that the high and low fibre diameter lines differed in mean diameter and in variance along the staple, but did not differ in coefficient of variation along the staple. The high and low staple length lines also differed in mean diameter, but did not differ in variance or coefficient of variation along the staple. Individual sheep within selection lines differed in mean, variance along the staple, and coefficient of variation along the staple.

The measurement technique was found to be highly repeatable between duplicate staples sampled from the same animal.

Susceptibility to seasonal effects at particular positions along the staple was tested by analysing the interaction between staple segments and other factors, and was described by regressing the diameter at a position on the average diameter of all sheep at that position. It was found that the high and low fibre diameter lines differed in susceptibility (thus described) while the high and low staple length lines did not so differ. Individual sheep within selection lines also differed in susceptibility.

The application of measured variation in diameter along the staple to sheep breeding must await more extensive genetic studies. The present study simply unmasks some previously unnoticed genetic and phenotypic differences and checks on the accuracy of the measurement method. It shows that there are non-susceptible individual animals and selection lines for which the variance of diameter along the staple is very low, and hence there exists the potential to reduce this variation on a nation-wide basis, or in local areas, if such a reduction be thought desirable from a woolprocessing viewpoint.