Dr. Scobie et al., WOOL FIBER TENACITY IN ROMNEY SHEEP GENETICALLY DIFFERENT IN STAPLE TENACITY, Australian Journal of Agricultural Research, 47(8), 1996, pp. 1203-1212
Wool from lines of Romney sheep selected for improved or reduced stapl
e tenacity was examined to determine if the difference in staple tenac
ity was explained by a difference in fibre tenacity. A random sample o
f ewe hogget wools (n = 32) was chosen from each of the 2 selection li
nes. Fibre tenacity was measured by breaking 10 fibres from each wool
sample using an Instron to measure peak force, and then a fluorescence
microscope attached to an image analyser to measure cross-sectional a
rea of the fracture surface. Staple tenacity was measured on 5 staples
per sample, by placing each staple in a Staplebreaker set to 40 mm be
tween clamps, and the peak force to break the staple was recorded. Pri
or to clamping, each staple was adjusted so that the thinnest point me
asured 1.5 mm(2) in cross-section and this point was positioned 20 mm
from each clamp. Although the difference in staple tenacity between th
ese 2 groups was highly significant (P = 0.002), there was no differen
ce in the tenacity of individual fibres (P = 0.903). Staple tenacity w
as not significantly correlated with fibre tenacity (r = 0.090). Simil
arly, there was no significant correlation between work to break the s
taple and either work (r = 0.118) or peak force (r = 0.195) to break t
he fibre. It is proposed that other components of staple tenacity, suc
h as the profile of cross-sectional area along the fibre and the varia
bility of crimped fibre length within the staple, may be more importan
t determinants of staple tenacity in these selection lines.