Seasonal and between sheep differences in medullation of wool fibres
D.R. Scobie, J.L. Woods, D.B. Baird
AgResearch, P.O. Box 60, Lincoln, 8152, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1993,
53: 319-322
Twelve mature Romney ewes were housed and fed to maintain a
constant bodyweight for 14 months. Monthly midside samples were
collected and individual fibres measured by projection microscope for fibre
and medulla diameter. Medullated fibres were observed in fibre diameter
classes between 14 and 70 µm, and non-medullated fibres were observed
within the range 10 to 68 µm. The proportion of fibre cross- section occupied
by medulla was calculated from fibre and medulla diameter, assuming
circularity. Within a sample, the cross-sectional area occupied by medulla
was found to increase exponentially with increasing fibre diameter. There
was a significant effect of season (P<0.001), with the highest levels of
medullation occurring in summer. Differences between sheep were
significant, (P<0.001) and were maintained throughout the year. These
findings are discussed in relation to a model for fibre formation.
Keywords: NZSAPAB;
Medulla; wool fibre; fibre diameter; season; Romney.
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Last Updated 25-01-1997
