Staple Crimp Frequency Research Articles

Ultrafine wools: comfort and handle properties for next-to-skin knitwear and manufacturing performance

This study aimed to quantify the skin comfort and handle properties of a range of wool fabrics produced from ultrafine wool (13.7–15.1 µm) and in doing so determine if differences in fiber diameter and staple crimp frequency (5.3–7.1 crimps/cm) were important in these properties. The fabrics were evaluated using a range of subjective and objective measurement techniques, including the Wool ComfortMeter, the Wool HandleMeter and in wearer trials. This work indicated that single jersey fabrics made from ultrafine wool are approaching the limit of objective and subjective evaluation of next-to-skin comfort. The results from the Wool ComfortMeter, Wool HandleMeter and the wearer trial show that there were no significant effects that can be attributed to wool staple crimp (fiber curvature) in these ultrafine wool fabrics. The work also demonstrated a difference in the manufacturing response when knitted fabric made from wools of different fiber diameter (13.7–23.7 µm), and using yarns of the same count, resulted in a progressively higher fabric mass per unit area as mean fiber diameter was progressively reduced.

Influence of nutrition, fibre diameter and fibre length on the fibre curvature of cashmere

Raw and dehaired Australian and Chinese Liaoning cashmere were evaluated for cashmere fibre curvature, cashmere fibre length, resistance to compression, and mean fibre diameter. Tested cashmere originated from commercial lots, and previous experimental samples. In Australian goats, cashmere fibre curvature was dependent on nutrition. Goats fed to lose weight grew cashmere with significantly (P<0.05) increased fibre curvature compared with goats fed to gain weight (61 v. 47°/mm) but total fibre curvature (fibre curvature × fibre length) was not affected by nutrition treatment. In raw Liaoning cashmere, there was a significant (P<0.001) difference between each age and sex group in fibre curvature (bucks 52; does 65; kid bucks 78°/mm). Increasing Liaoning cashmere staple crimp frequency by 1/cm was correlated with an increase in fibre curvature of 6.5°/mm (r2 = 0.61). In raw and dehaired Australian and Liaoning cashmere, increasing mean fibre diameter and cashmere fibre length was associated with decreasing fibre curvature (for each 3 μm increase in mean fibre diameter fibre curvature declined 10–41°/mm; for each 10 mm increase in cashmere fibre length fibre curvature declined 3–13°/mm). Increasing cashmere mean fibre diameter was positively correlated with dehaired cashmere fibre length (for each 3 μm change in mean fibre diameter there was a change of 7–23 mm in length). In Australian and Liaoning cashmere, the direction of responses to changes in cashmere fibre attributes measured on the fibre curvature was similar. In raw Australian and Liaoning cashmere, increasing the ratio of cashmere fibre length:mean fibre diameter was associated with reduced fibre curvature. It was concluded that the high fibre curvature of Liaoning cashmere may be a consequence of low mean fibre diameter and short fibre length resulting from a production system where goats are relatively poorly fed. The results suggest that for Australian cashmere, only a certain number of crimps are produced. As such, crimp frequency in Australian cashmere is time dependent and not length dependent. Producers can manipulate the fibre curvature attributes of their cashmere by altering cashmere production via nutrition management. Preparation and testing procedures for the selling of raw cashmere and definitions of cashmere may need to be revised to include fibre curvature.

Response to selection for ultrafine Merino sheep in New Zealand: I. Wool production and wool characteristics of ultrafine fibre diameter selected and control Merino yearlings

Merino ewes were screened for low fibre diameter from 15 000 yearlings within 12 flocks to establish a foundation flock in 1987, which was expanded to 500 ewes over the subsequent two years. Ewes were selected on fibre diameter BLUP breeding values. For comparison, a control flock of 100 ewes was randomly selected from the same sources. Data from approximately 2000 progeny over five birth years within 70 sire groups were analysed. Traits measured were live weight, greasy and clean fleece weight, yield, mean fibre diameter (FD), staple length, staple strength, staple crimp frequency, resistance to compression, Commission International de l'Eclairange (CIE) tristimulus value for scoured wool and coefficient of variation in fibre diameter. The ultrafine progeny had 2-μm finer FD, 0.6 units less yellow and had 0.6 more crimps/cm (all P<0.001) than their control counterparts. This experiment suggests that formation of an open nucleus breeding population by intensive screening for fibre diameter from a commercial population will improve selection response relative to traditional within flock selection without screening or to screening rams only.

Physical Properties and Processing of Fine Merino Lamb's Wool

The fiber properties and handle of fine Merino lamb's and fleece wool are critically reviewed in Part 1 of this series of papers. Those objective characteristics that distin guish these two classes of raw wool and appear to account for the relative softness of hand of lamb's compared with fleece wool are presented here. The best single parameter indicating softness is resistance to compression. A reduction in staple crimp frequency or mean fibre diameter or both lowers resistance to compression and increases softness. The lower mean staple crimp frequency observed in wool grown in the first four months of a lamb's life is a visual indication of tactile softness compared with that of wool grown subsequently.

Effects of Phenylalanine and Analogues of Methionine and Phenylalanine on the Composition of Wool and Mouse Hair

Administration of the methionine analogue methoxinine (O-methyl-DL-homoserine) to sheep substantially changed the composition of wool; in addition wool fibres were weakened and the staple crimp frequency was reduced for a prolonged period. The proportions of high-tyrosine proteins were reduced by 40-45% whereas the high-sulfur proteins were usually slightly increased. The content of high-tyrosine proteins in wool was still depressed in most sheep 70 days after dosing with methoxinine. These experiments supported a previous finding that the cystine content of wool and its crimp frequency are not causally related. Ethionine, another methionine analogue, did not consistently change the composition of wool. In some sheep there was no change in the proportions of high-tyrosine proteins following administration of ethionine, even though weak wool was produced. This result, together with the lack of association between the content of high-tyrosine proteins and the strength of wool fibres in a sheep given methoxinine plus methionine, indicates that a reduction of the high-tyrosine proteins is not a prerequisite for the production of weak wool. Neither a threefold increase in the phenylalanine intake by mice nor the administration of three analogues of phenylalanine (4-fluoro-DL-phenylalanine, 4-chloro-DL-phenylalanine and beta-(2-thienyl)-DL-alanine) to sheep altered the composition of hair or wool. Fluorophenylalanine was incorporated into all the constituent proteins of wool to the extent of c. 2% of phenylalanine residues. The other analogues studied could not be detected in wool.

6—THE RELATIONSHIP BETWEEN THE RESISTANCE TO COMPRESSION OF WOOL BULKS AND FOLLICLE CURVATURE

It is shown that there are strong relationships between the resistance to compression, the felt-ball diameter, and the curvature of the parent wool follicles. The relationship of these properties with follicle curvature is stronger than that with staple-crimp frequency.

Response to selection in Australian Merino sheep. VIII.* Further results on selection for high clean wool weight with attention to quality

Results of selection for high clean wool weight per head with control of quality are reported for two selection groups over the period 1966–74. Results for the same experiment for the periods 1950–1959 and 1961–64 were reported earlier. Both groups were selected for high clean wool weight, one (S) with a ceiling on fibre diameter and degree of skin wrinkle, and the other (MS) with a lower limit on staple crimp frequency and a ceiling on skin wrinkle. Genetic progress in clean wool weight was greater in S than in MS over the 1966–74 period (0.12–0.15 lb/annum, compared with 0.06–0.09). This was to be expected from genetic correlations of clean wool weight with fibre diameter (low positive) and staple crimp frequency (high negative). The result supports the previous recommendation that staple crimp frequency is an inefficient way of controlling wool quality while attempting to improve quantity by selection, because its use severely restricts the likely progress in quantity. The actual rate of progress in the S group was similar to that in the period 1950–59, which was followed by a fall in superiority of the selected over the control group animals born during 1961–64. The recovery of response in the 1966–74 period negates the suggestion that the loss of response during the 1961-64 period was due to a 'plateau'. The most likely explanation is that a genotype x environment interaction occurred, such that the genetic gain made in the 1950-59 period could not be expressed in the poorer environments of 1960–65, but reappeared gradually under the improving environment of the 1966–74 period. Attempts to remove this interaction by regression of response on the mean clean wool weight of the unselected control group (as an index of the level of the environment) for each year, were not successful. The interaction is, therefore, not simply a case of all selection groups being equal when the environment is poor. ________________ *Part VII, Aust. J. Agric. Res., 26: 937 (1975).

Effect of stocking rate on fleece measurements and their relationships in merino sheep

The wool characteristics of Merino wethers were measured for 6 years in a stocking rate experiment. The decline in fleece weight due to increasing stocking rate from 4.9 to 12.4 sheep per hectare was usually accompanied by a reduction in fibre diameter and staple length and an increase in staple crimp frequency. The magnitude of these responses differed considerably between years; in one year clean fleece weight was reduced by 50%, with an associated reduction of 5 µm in mean fibre diameter and one of 2 cm in staple length. In four of the six years of the experiment, variation in fibre diameter accounted for at least 50% of the variation in wool production between stocking rate treatments. The relationships between clean fleece weight and fibre diameter were similar between years, mean fibre diameter being reduced by about 1.8 �m for each kilogram reduction in clean fleece weight. Fibre diameter is the major determinant of wool price, and this information should improve the prediction of economic responses to changes in stocking rate.

The appraisal of fineness in greasy wool sale lots

SUMMARYRelationships among quality number, crimp frequency and. fibre diameter of sale lots are reported for a wide range of Australian wools, the quality number appraisals being those of the selling broker and the successful bidder at auction.Results show that sale lots classified as having the same quality number exhibit a 95% confidence interval of ± 2·5 μm about the mean value. This variation is attributed first to the dependence of quality number on staple crimp frequency and secondly to the strength of the relationship between crimp frequency and fibre diameter.

Influence of nutrition on the crimping rate of wool and the type and proportion of constituent proteins.

When the nutritional level of sheep is restricted, the staple crimp frequency of the resultant fleece increases substantially whereas the cystine and high-sulphur protein contents decrease. This is in marked contrast to the direct relationship between crimp frequency and cystine content among sheep. These observations can be reconciled by assuming that variations in crimp frequency are attributable solely to a combination of follicle shape and fibre length growth rate without recourse to the more generally accepted theories relating to the proportion and distribution of ortho- and paracortical cells in the firbre cortex. The major portion of the decrease in the cystine content of high-crimp wools is due to the decreased synthesis of a specific protein fraction (ultra-high-sulphur protein) as would be expected from the results of dietary supplementation experiments. Low-crimp wools do not appear to contain this protein fraction and in this respect they may differ from high-crimp wools.

13—SOME OBSERVATIONS ON THE OBJECTIVE CHARACTERISTICS OF CLASSED WOOL CLIPS PART I: DISTRICT ANALYSIS

Some relations between fibre diameter, quality number, and staple-crimp frequency among classers' lines are reported. There is a strong over-all relation between quality number and crimp frequency. The within-clip relations do vary, apparently as a result of a tendency among appraisers of superfine wools to allot classed lines from the same clip into different quality-number categories on the basis of small differences in staple-crimp frequency. This effect disappears when data from different clips are pooled. The relation between fibre diameter and quality number is also strong, but the slope of the regression line of fibre diameter on quality number varies markedly between districts, even when individual clip data are pooled. These two relations, taken together, reveal that the classification of fleeces on the basis of the quality-number system is not particularly effective in producing lots that differ significantly in fibre diameter.

Compositional studies of high- and low-crimp wools.

Merino wools with high staple crimp frequency contained 20% more cystine than poorly crimped wools of the same strain. These differences were reflected in both the quantity and composition of those components of the high-sulphur fraction of wool keratin that are richest in sulphur. It was found that this greater concentration of disulphide cross-linkages in high-crimp wools was associated with a marked reduction in swelling and supercontraction but has no effect on the stress of single fibres at 30% extension in water.

Response to selection in Australian Merino sheep. V.* Inheritance of abnormal staple crimp: Crimp abnormalities in groups of breeding ewes selected for high and low values of clean wool weight and its components

Correlated responses in crimp abnormality in wool (i.e. irregularity of staple crimp frequency, to which the term "doggy" wool or "rough fleece" is applied when the crimp frequency is markedly reduced) are reported for two groups of Peppin Merino sheep selected for high clean wool weight, and for eight pairs of groups under selection for high and low values of the following single characters: clean wool weight per head, clean wool weight per unit area of skin, body weight, wrinkle score, fibre number per unit area of skin, fibre diameter, staple length, and percentage clean yield. In the first two groups the correlated responses in crimp abnormality were small and for practical purposes negligible. However. there appeared to be slight increases in crimp abnormality following changes in selection criteria, although this period coincided with adverse seasonal conditions. In the eight pairs of groups selected for single characters, correlated increases in crimp abnormality occurred in the groups selected for high clean wool weight per head, high and low fibre number per unit area of skin, high fibre diameter, and low percentage clean yield, and correlated decreases occurred in the groups selected for low clean wool weight per head, low fibre diameter, and high percentage clean yield. The responses were due mainly to the initial, intense selection of the foundation animals, and the responses to continuing selection were small. Environmental factors (year of fleece growth, maternal handicap, and lambing performance) did not have large effects on crimp abnormality. Crimp abnormality increased with age, and the rate of change was altered by selection in each of the single character groups in which correlated responses in crimp abnormality occurred, the responses being more pronounced at older ages.

The variability of yield in pastoral flocks

Mid-side yield was determined on 5,410 fleeces from 49 Merino, 3 Polwarth, and 4 Corriedale flocks from Victoria, South Australia, and Tasmania. Yield decreased as staple crimp frequency increased and as mean fibre thickness decreased. There were fewer exceptions in the former than in the latter. The mean mid-side yield of a flock was negatively correlated with its coefficient of variation. The range of yield in the various staple crimp or mean fibre thickness classes in the flock was surprisingly wide and only slightly less than that for the whole flock.