|dc.contributor.advisor||Cronje, P. J.||
|dc.contributor.author||Van der Linde, Hendrik Johannes||
|dc.description.abstract||Samples obtained from fleeces exhibited at a
National Merino Fleece Wool Competition were analysed
for physical and chemical properties.
Standard methods of analyses anda modified method
for determining disulphides and thiols polarographically
with methyl mercury iodide are described.
The accuracy of judging was calculated through
r2-values from correlation coefficients. The interrelationship
between different characteristics was
estimated by correlation coefficients.
The accuracy of calculating clean wool weight from
greasy fleece weight by means of the estimated yield
value, was very high (83 percent). The low accuracy
of estimating yield· seems to have a negligible effect
and for practical breeding and classing purposes it
can be disregarded.
While the accuracy of judging length is low, in
practice the error is negligible because a length
difference of one inch is allowed in wool from the
same bale. Judges tend to underestimate length.
Spinning count estimation seems to be more dependent
on crimps per inch than on fibre thickness.
Judges tend to underestimate spinning count as a
result of the undercrimping in the wool. While
the Duerden standard, laid down in 1929, is still
used, it is emphasised that a re-evaluation of the
crimp fibre thickness relationship in the South
African Merino wool must be made. The internationally
eccepted A.S.T.M. standards seem a much more
accurate basis for judging spinning count of South
African Merino wool.
The large number of fleeces disqualified for being
overstrong is alarming. If disqualifications had been
based on measured fibre thickness, a smaller percentage
of the fleeces would have been disqualified while the
use of A.S.T .M. standards seemsa more realistic basis
and only 13.8 percent of the fleeces would have been
disqualified in comparison with the actual 38.5 percent.
The greasy fleece weight is positively correlated
with the amount of scoured wool ~~ and
staple length.\audn~\ve1y witb spinning count.
The amount of scoured wool is positively correlated
with greasy fleece weight and staple length and negatively
correlated with spinning count.
Spinning count is negatively correlated with
The use of greasy fleece weight as a selection
criterium is recommended.
The use of length and a lower spinning count as a
selection measure to increase the amount of scoured
wool is discussed. Selection f~r length to a
maximum of 3! inches is recommended while a decrease
in spinning count as a method ';to increase the amount
of scoured wool is strongly disapproved of.
While no significant correlations were found
between quality and other physical wool properties it
would seem from the literature that finer wool has
the better quality. This corresponds with the definition of quality in the trade.
Although data are limited9 it would seem that
differences in quality can be ascribed to differences
in the chemical composition of the keratin fibre and
that chemical decomposition of the tip sections
affected the estimation of quality.
An increase in wool production as a result of an
increase in length may be the reason for the positive
correlation between the amount of scoured wool and
the thiol content and the negative correlation between
the amount of scoured wool and the disulphide bond
status. A positive correlation was also found
between greasy fleece weight and thiol content.
Highly significant correlations were found between
yield and alkali solubility (positive), total
disulphides + thiols and thiols (negative). This
may possibly be due to the amount of yolk present in
the wool. Longer fibres tend to contain less yolk
than short fibres. This results in the decomposition
of the exposed tip section of long fibres and
consequently the production of thiols from disulphides.
The bilateral structure of wool is responsible for
crimp formation and the paracortex contains more and/or
different disulphide linkages than the orthocortex.
A significant positive correlation between spinning
count and disulphide bond status and a negative correlation
between spinning count and thiol content were
found. Although data are rather limited it would
seem that finer fibres contain more disulphide bonds
than coarser fibres, possibly as a result of a higher
degree of keratinization in the paracortex.
Accuracy of judging is dicussed and a re-evaluation
of crimp fibre thickness relationship for South
African standards is recommended.
Interrelationship between different wool traits
is summarised and the practical applications thereof
A possible reason for the non-significant correlations
in the ram sample group between physical and
chemical properties seems to be the lower variation
in the ram sample.||en_ZA
|dc.publisher||University of the Free State||en_ZA
|dc.subject||Dissertation (M.Sc.Agric. (Sheep and Wool Science))--University of the Free State, 1968||en_ZA
|dc.title||A study of fleeces exhibited at a national merino fleece wool competition||en_ZA
|dc.rights.holder||University of the Free State||en_ZA