Wool yellowing and pH within Merino and Romney fleeces
R.M.W. SUMNER, S.R. YOUNG AND M.P. UPSDELL
AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton,
New Zealand
NZSAP 2003 Abstract No. 38
Proceedings of the New Zealand Society of Animal Production
63: 155-159
Fleece samples were taken from the back, side and belly of three
adult ewes in one Merino flock and three adult ewes in one Romney flock
in each of six regions of New Zealand (Waikato, Manawatu, Wairarapa,
Marlborough, Canterbury, Otago). Each fleece was 12 months growth. These
samples were used to compare factors associated with wool yellowing as
measured by tristimulus (Y-Z) values. Neither the region of New Zealand
where the sheep grazed nor the measured dimensional fleece
characteristics, were related to fleece yellowing. The pH of an aqueous
extract of greasy wool was strongly related (R2 = 0.93) to
tristimulus (Y-Z) (base yellow) at shearing but less strongly related
(R2 = 0.70) to tristimulus (Y-Z) after the sample had been
incubated at 40°C and 100% RH for 6 d. Merino samples had a lower
tristimulus (Y-Z), both before and after incubation, at a particular pH
than Romney samples. Back wool did not increase in yellowness as much
during incubation as side or belly wool possibly on account of
photo-oxidation following prolonged exposure to sunlight. These data
indicate a close relationship between pH of a water soluble component of
greasy wool and the extent of wool yellowing that was influenced by
sheep breed and body site.
Keywords: NZSAPAB;
wool; Merino; Romney; yellowing; body site; pH
Last Updated 8/07/2004
