Implications to fleece evaluation derived from sources of variation contributing to cashmere fibre curvature

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Abstract

Cashmere fibre curvature (crimp) has important impact on the softness and quality of cashmere textiles, the efficiency of cashmere processing and cashmere production. This work was aimed to quantify the magnitude and direction of factors affecting cashmere fibre curvature, with data collected from 11 Australian commercial cashmere farms, using general linear model analysis. Nineteen parameters were recorded for 1244 goats. Following log transformation the best model for fibre curvature included farm, age, clean washing yield, mean fibre diameter, cashmere yield, fibre diameter standard deviation, and live weight and the interactions between these terms. The percentage variance accounted for was 71.7%. Mean fibre diameter alone accounted for 39% of the variation in fibre curvature and farm accounted for 49% of the variation. Cumulatively mean fibre diameter and farm accounted for 66.6% of the variation existing in fibre curvature. For the other terms, age added 2.2% and the other fibre measurements a further 2.9% to variation accounted for by the best model. Results suggest that within a farm, using cashmere fibre crimp frequency to estimate mean fibre diameter has a correlation of 0.72—provided the trained observers perform as well as the calibrated laboratory equipment. On the other hand, however, results indicate fibre curvature not to be a reasonable indicator of mean fibre diameter differences across farms. Farm-effects on fibre curvature are large and may explain the difficulties cashmere growers experience when they visit other farms to visually evaluate cashmere goats prior to purchase. This work indicated that heavier goats are likely to produce cashmere with a lower fibre curvature. As this relationship did not differ between farms, it is reasonable to conclude that all goats exhibit this phenotypic response. Using cashmere fibre curvature (crimp frequency) as a tool for changing mean fibre diameter or selecting homogenous batches of fibre for sale will be reasonably effective within a farm, but is not a reasonable indicator and predictor of mean fibre diameter differences between farms.

Introduction

For centuries cashmere has been regarded as the premier soft-handling animal fibre. One of the primary characteristics for the softness of cashmere is its low fibre curvature (McGregor, 2000, McGregor, 2001, McGregor, 2004). Until recently there was no objective information available on the fibre curvature (crimp) attributes of cashmere. Generally raw cashmere exhibits single fibre crimping, which can be reliably measured as fibre curvature (McGregor, 2001, McGregor, 2007). Furthermore, there are measurable differences between raw cashmere of different origins in: fibre crimp frequency; mean fibre curvature, mean fibre diameter relationships; and fibre crimp forms (McGregor, 2007). Eleven different forms of cashmere fibre crimp have been described and the occurrence of these crimp forms vary with the origin of the raw cashmere (McGregor, 2007). Commercially dehaired cashmere from more recent origins of production (Australia, New Zealand and USA) have significantly lower fibre curvature (fibre crimp) than cashmere obtained from the traditional sources such as Iran, Afghanistan, Mongolia and China. The predominant form of fibre crimping for cashmere derived from a particular origin together with the low rate of fibre crimping explains the low resistance to compression of cashmere and the differences in resistance to compression of cashmere between the different countries. The relationship between crimp frequency and fibre curvature of cashmere is quite strong, even though it covers a different range of values to those that have been observed in wool (McGregor, 2000, McGregor, 2001, McGregor, 2004).

Greater fibre curvature in raw cashmere has been associated with increased efficiency of cashmere dehairing and the production of longer dehaired cashmere (McGregor and Butler, 2008a). Furthermore the impact of fibre curvature on the processing, yarn and fabric mechanical properties of cashmere and superfine wool blend knitted fabrics have been evaluated (McGregor, 2001, McGregor and Postle, 2002, McGregor and Postle, 2004, McGregor and Postle, 2007, McGregor and Postle, 2008, Wang et al., 2006). By adding cashmere to wool, the knitted fabric softness, smoothness, flexibility and suppleness are increased, while pure cashmere fabrics have been found to be softer than pure wool fabrics. Generally, the blending of cashmere with low curvature (crimp) superfine wool has resulted in a change in the fabric mechanical properties or other physical attributes towards pure cashmere. These changes in the fabric mechanical properties are also translated as the fabric wear properties of cashmere and wool blend knitted fabrics (McGregor, 2001, McGregor and Postle, 2002).

While fibre curvature may be important in the processing and textile properties of cashmere, what are the implications for the cashmere producers? It has been established that for Australian cashmere, only a certain number of crimps are produced (McGregor, 2003). As such, crimp frequency in the Australian cashmere is time dependent, and not length dependent. Thus cashmere producers can manipulate the fibre curvature attributes of their cashmere by altering the cashmere production via nutrition management (McGregor, 2003). So, for example, well-fed goats, compared with under-fed goats, grew more cashmere which was longer and possessed a lower fibre curvature. Cashmere breeders can also manipulate the fibre crimp by genetic selection—as cashmere fibre crimp is moderately heritable (McGregor, 1997). Recently the impact of farm and age of the goat on cashmere fibre curvature was quantified, as these factors are commonly the only information available to breeders at animal sales or on farms (McGregor and Butler, 2008b). It has also been shown that cashmere fibre curvature along with cashmere staple length accounts for an additional 7–13% of the recorded variation in clean cashmere production after the farm identity and mean fibre diameter effects have been taken into account (McGregor and Butler, 2008c). The effect of reducing fibre curvature to below 70°/mm was to reduce the relative clean cashmere production.

As fibre curvature of cashmere has such an important impact on the cashmere softness, textiles, processing and production, this paper aimed to quantify the magnitude and direction of factors affecting cashmere fibre curvature (crimp), using laboratory measurements available to the cashmere producer.

Section snippets

General management

The data set and approach are the same as described earlier (McGregor and Butler, 2008c). Cashmere goats from 11 farms in 4 different states of Australia were monitored for live body weight (LW; kg) each month from December 2002 (Initial LW; kg) until June 2003 (Final LW; kg), just prior to shearing (Table 1). Some producers were unable to weigh each month (for example, during mating in autumn). Generally all goats in the flocks were monitored, but with some larger flocks 10 randomly selected

Results

The mean, standard deviation, and range in the number of sampled cashmere goats per farm were 398, 404, 70–1200, respectively. Considerable variability was recorded in the measured attributes, including fibre curvature (Table 2).

Discussion

The major share of the variation in fibre curvature of Australian cashmere is associated with mean fibre diameter and farm. Mean fibre diameter alone has accounted for 39% of the variation in fibre curvature and farm alone has accounted for 49% of the variation. Cumulatively the mean fibre diameter and farm accounted for 66.6% of the variation in fibre curvature, with age adding 2.2% and OFDA cashmere yield, initial live weight, fibre diameter standard deviation and clean washing yield combined

Conclusions

The major factors affecting cashmere fibre curvature were mean fibre diameter and farm. Using cashmere fibre curvature (crimp frequency) as a tool for changing mean fibre diameter or selecting homogenous batches of fibre for sale will be reasonably effective within a farm, but is not a reasonable indicator and predictor of mean fibre diameter differences between farms.

Acknowledgments

The cashmere producers who participated in this project, the Australian Cashmere Growers Association (ACGA), Riverina Fleece Testing Services, Albury, Mark Brims (BSC Electronics Perth) and the Rural Industries Research and Development Corporation, who partly funding this project, are thanked.

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