INTRODUCTION
Fibers that have proper flexibility, delicacy, enough length and
a high ratio of length to diameter are useful for producing textile materials.
In addition, sufficient strength against mechanical operations is required
for using in textile industry. In order to optimum use of Iranian sheep
wool; first, all wool characteristics including quantitative and qualitative,
mechanical and physical characteristics should be recognized, in which
quantitative and qualitative traits are of the most important due to their
importance in value-determining systems and incomes.
Iran is one of the most important greasy wool producer countries of the
world (Table 1). Also, Fig. 1, shows
Iran’s wool production trend in the recent few decades. Although, Iran
has a high annual wool production, due to high fiber diameter mean and
variability in fleeces, most of the produced wool is applicable in carpet
industry rather than textile industry and Iran has to import most of the
wool needed for textile industry (fine wool) from other countries (e.g.,
Australia, New Zealand, South Africa and etc). Allocation a part the large
outlays related to wool importation to Iran in order to improve wool quality
through genetics and breeding, nutrition and improving life conditions
may help to optimal use of internal recourses.
Naeini sheep consists of about 30% of the total Iranian sheep population.
In addition, this breed has a good wool quality among the other Iranian
breeds (Taherpoor, 1988). The kind of wool usage is greatly depends on
fiber length, fiber diameter and uniformity. Usually, there is a high
variability in fiber length and diameter for carpet wool (Dashab et
al., 2006; Coop, 1986). The appearance of Naeini sheep and its wool
quality characteristics has been reported by Dashab et al. (2006).
All breeding plans for increasing wool production should include staple
length. Staple length is an important value determining characteristic of wool.
| Table 1: |
FAO estimates of wool production for 15 highest producing
countries in 2004 (FAO, 2006) |
 |
| MT: Million Ton |
|
| Fig. 1: |
Greasy wool production trend in Iran from 1961 to 2004. This
figure is drawn based on FAO estimates (FAO, 2006). MT: Million Ton |
The wool manufacturing industry
consists of two apparel and carpet divisions. Based on fiber length and
diameter, the apparel division is categorized to worsted and woolen systems.
Woolen system can make use of wool with more variability in length and
diameter (Botkin et al., 1988). Staple length in Iranian native
breeds is ranged from 7 to 19 cm; the lowest refers to Mehraban and Sangsari
breeds and the highest staple length is related to Lori-Bakhtiari and
Kalkoohi breeds (Taherpoor, 1988; Taherpoor and Salehi, 1987). Staple
length is affecting by the length of fibers and their crimp. Fiber length
depends on fiber growth rate and the length of growth period. Growth rate
and crimp themselves are under the control of genotype and environmental
effects, especially nutrition (Coop, 1986; Botkin et al., 1988).
Generally, Iranian sheep has a high variation in staple length that causes
the staple to have a shape like cone.
Fiber strength is very important in the spinning step, because in this procedure
wool fibers should be combed and spun to produce yarn. Thus, fibers should have
enough strength to withstand against various mechanical and physical tensions.
The term sound wool is used by the trade to describe wool that is considered
strong enough to withstand versus stresses of combing operations (Botkin et
al., 1988). Various factors have been proposed for tenderness of wool fibers,
which one or a combination of them could lead to fiber thickness and loss of
strength (e.g., Genetic and environmental influences, such as a temporary reduction
in nutrients, energy, limitation of specific dietary amino acids or minerals
and finally microbial degradation of fibers during storage (Botkin et al.,
1988). Generally, Iranian sheep wool is categorized as a medium to coarse wool
type having coarse fibers which is usually applicable to carpet industries (Taherpoor,
1988).
The objective of this study was to experiment and evaluate the length
and some physical characteristics of Naeini sheep wool for using in textile
industry.
MATERIALS AND METHODS
The experiment of this study was conducted in 1999 on Naeini sheep
herds which were under the supervision of nucleus ram scheme of Animal
Husbandry center of Agriculture organization in Isfahan province. Herds
were chosen randomly from 6 different regions of Isfahan province; including
Isfahan city, Naein, Ardestan, Najaf-Abad, Moorchekhort and Varzaneh.
Wool samples were taken from a 10x10 cm2 surface on the mid-side
of each animal. However, staple length of different body parts (side,
britch (lower thigh of rear legs) and shoulder) was obtained prior to
shearing by measuring an unstretched lock of wool, with a stiff ruler.
Wool samples were collected in specific envelopes marked by a label of
the animal registration ID, including 36 rams and 191 ewes in 7 age classes
(year). Then, samples were transferred to the Animal Science Laboratory
of the Isfahan University of Technology for measuring some wool quality
traits such as fiber diameter and its variability, the percentage of different
kinds of fibers (true, heterotype and modulated) and scales accumulation
(the number of scales in 100 μm length of fiber). Afterwards, 5 samples
were chosen randomly from each herd and consequently at least 30 fibers
were taken incidentally from each randomly selected sample which then
transferred to the Fiber Physics Laboratory of the Isfahan University
of Technology, in order to measure some physical characteristics on wool
fibers of Naeini sheep. After fixation of individual fibers on special
frames, breaking strength and fibers elongation at break were measured
on the basis of centi-Newton and millimeter, respectively, by the Zwick
instrument. In order to provide similar conditions for samples, the movement
speed of jaws were set on 25 mm min-1 and the distance between
jaws were set on 20 mm (ASTM., 1997). Then, elongation at break
was rescaled on the percentage of the initial length (20 mm). Overall,
breaking strength, elongation at break and tenacity were measured for
about 1,000 fibers. Breaking strength is the force (Newton) that leads
to the rapture of yarn. Elongation at break is the increase in length
produced by stretching a sample to the breaking point expressed as a percentage
of the initial length. Tenacity of fibers was estimated as follows (Thornton
and Pearson, 1973):
 |
where cN, d and s were breaking strength (centi-Newton), fiber diameter
(μm) and its standard deviation, respectively. ρ was the prolonging
index for sheep wool fibers, equals to1. 3 (Thornton and Pearson, 1973).
Statistical analyses were performed applying SAS/STAT software (SAS Inst.,
1997) and the mean comparisons were done using Duncan test by the following
models:
where; Y is the record of observation, μ is the overall population
mean, Herd, Age and Sex are the related fixed effects; e and ε are
within sample and random residual errors, respectively.
RESULTS AND DISCUSSION
Mean±standard deviation for staple length of shoulder, side
and britch parts were estimated 10.8±2.36, 9.71±3.14 and
10.99±2.49 cm, respectively (Table 2). Staple
length of the britch part was estimated higher relative to the two other
parts, which was in consistent with the other reports (Taherpoor and Salehi,
1992; Botkin et al., 1988; Coop, 1986). Side samples had the lowest
mean and the highest variation in staple length. Staple length of Naeini
sheep is shorter than reports on staple length for some other Iranian
sheep such as Lori-Bakhtiari (14-16.94 cm), Sanjabi (12.6-14 cm), Afshari
(12.8 cm) and Baloochi (12-15.56 cm) breeds and longer than Mehraban (8.8-9.3
cm), Ghezel (7.73 cm) and Marivan (7.9 cm) breeds (Taherpoor, 1988). However
those breeds have coarser fibers of lower quality.
Fleece weight is directly related to staple length and fiber diameter
(Botkin et al., 1988). So, according to the relatively high Coefficients
of Variation (CV) for the staple length of Naeini sheep (21.85, 32.34
and 22.66 for shoulder, side and britch parts, respectively), fleece weight
can be improved by selecting individuals with longer staple length and
lower fiber diameter mean to maintain its quality as well. In the present
study, high correlations were found between staple lengths of different
body parts (0.71 and 0.76 between side with shoulder and britch, respectively
and 0.77 between shoulder and britch). Therefore, a staple length measurement
from one of these parts could be a good representative for the staple
length of other parts; it reduces the need for having several measurements
of staple length per animal and animals can be compared for staple length
based on one measurement (side measures which are more common in use).
Staple length had low correlations with fiber diameter (0.05, 0.08 and
-0.04 for shoulder, side and britch, respectively) which indicates that
breeding for increasing staple length does not make important problems
through increasing fiber diameter; however, these correlations were moderate
with uniformity in fiber diameter (0.21, 0.24 and 0.18, respectively)
which confirms that in breeding programs staple length and variability
in fiber diameter should be considered simultaneously.
Among the studied effects (sex, age and herd) only herd shown a significant
effect on fiber length (p<0.01) which is due to the genetic base and
environmental differences between herds (Table 3). More
recording programs in continuous years and generations would be required
(to produce a large pedigree structure) for separating genetic and environmental
effects. Sex and age effects had not any significant effect on the length
of fiber (p>0.05). Thus, it could be concluded that Animal’s age and
sex do not play very important roles on the fiber length of Naeini sheep.
Results of the effect of age on staple length was inconsistent with the
results of Siah-Kamari (1998) on Sanjabi sheep, Salehi and Taherpoor (1991) on Sangsari breed and Brown et al. (1966) on Merino sheep. who
found the effect of age to be meaningful on staple length.
| Table 2: |
Descriptive statistics for the measured wool parameters |
 |
| *: Each observation on the staple length and the fiber
strength traits is based on 4 and 30 fiber measurements, respectively;
§: centi-Newton |
| Table 3: |
MSs and dfs for the fiber length from different body parts |
 |
| **p<0.01 |
|
| Fig. 2: |
Mean comparisons between different sexes for staple length
of different body parts |
|
| Fig. 3: |
Mean comparisons between different ages for staple length
of different body parts |
However, the
results of the present study were in agreement with the results of Hasani (1992) on
Lori-Bakhtiari sheep. Figure 2 and 3 provide comparisons
of staple length in different body parts between different sexes and ages,
respectively.
Staple length of different body parts differed considerably between different
herds. It seems that animals in herds with better pastural and nutritional
conditions, like herds in Ardestan and villages surrounding Isfahan city
have higher fiber growth rates than animals living in herds of Naein and
herds close to desert boundaries, which have lower fiber growth rates
and more fiber loss. Staple length has a high correlation with fleece
weight. The longer the staple length, the higher the fleece weight would
be (Botkin et al., 1988).
Table 4 shows the results of the analyses of variances
for the fiber resistance traits against tension. Herd and age effects
were not significant on the fiber physical attributes (breaking strength,
elongation at break and tenacity) concerned (p>0.05). However, considerable
variations observed within samples of individual animals, which had a
significant effect on %elongation at break (p<0.05). Because the majority
of diameter variation among fibers in a fleece occurs between fibers within
locks (Botkin et al., 1988), high variation of fiber diameter in
each sample may be responsible for this effect.
To evaluate the effect of age, animals were assigned to young (<3
years) and old (>3 years) subclasses. Because in the primary model,
sex was found as a non-significant effect with a negligible influence on the fiber strength
traits, it was not considered in the final model.
| Table 4: |
Results of the analyses of variance for some physical characteristics
of fibers |
 |
| *p<0.05; §: (centi-Newton); ¤: (cN/dtex); |
Although, differences
were insignificant (p>0.05), wool fibers of young animals (<3 years)
were more resistant relative to older animals (>3 years), which were
14.73 vs. 12.46 centi-Newton for breaking strength, 29.55 vs. 28.20 for
%elongation at break and 1.24 vs. 1.20 (cN/dtex) for tenacity. Results
of the Animal’s age and sex on fiber resistance traits against elongation
are in consistent with the results of Drummond et al. (1982) and
Robert et al. (1986).
Fiber characteristics of Naeini sheep for using in textile industries
Geometric characteristics: Fiber diameter is the most important assigning
factor for the wool quality, which is measuring by either Micron (μm)
or Spinning count systems. The range of variation in fiber diameter and
the relative frequency of each range are presented in Table
5 for Naeini sheep. The frequency of fibers with lower than 25 μm
diameter was more than a half of the total fibers which shows that most
of the Naeini wool fibers are of a fine quality and by conducting selection
programs on Naeini sheep wool, the frequency of true fibers would be increase
and fiber diameter mean would be decrease.
According to Table 5, as fiber diameter increases, its
relative frequency decreases. In textile industries the wool value-determining
factor is the spinning count score, which is determining by the D3992
system (Klein, 1986). Because a minimum number of fibers are required
for yarn to be strong enough for weaving or knitting, more yarn can be
spun from finer wool than coarser one. Spinning count system provides
16 categories for describing fleece grade (Botkin et al., 1988).
Based on the total fiber diameter mean and standard deviation (28.514.33
μm) reported for Naeini sheep by Dashab et al. (2006), on
average, the spinning count score (fleece grade) of Naeini sheep was predicted
54’s regarding the specifications for grades of wool (Botkin et al.,
1988), which indicates an intermediate fleece grade for Naeini sheep wool.
It seems that the reason for this quality loss may be due to the percentage
of fibers with more than 40 μm diameter (%13.4 of the total fibers).
This shows the importance of selection against coarse fibers including modulated and heterotype fibers with 65.8 and 46.7 μm diameter mean
for Naeini sheep (Dashab et al., 2006), respectively.
| Table 5: |
The frequency of fibers in different ranges of diameter |
 |
Spinning count scores between 58’s and 80’s or finer is useful for Fustian
systems (Klein, 1986). It shows that there is a short lag between Naeini
sheep fleece grade and the fleece grades applicable in Fustian system.
This lag can be removed easily by selection against coarse fibers. Current
researches on Naeini sheep have shown that fibers with more than 40 μm
diameter are mainly consisted of kemp and heterotype fibers which are
about 5.93 and 4.38% of the total fibers, respectively (Dashab et al.,
2006). Thus, by reducing the percentage of kemp and heterotype fibers
and improving the spinning count score from 54’s to 60’s which is simply
applicable in Fustian textile system it would be possible to produce finer
and tender stuffs from Naeini sheep wool. Fleeces with 23.5-24.94 μm
fiber diameter mean are specified as 60’s grade (Botkin et al.,
1988). Thus, by 3.6 to 5 μm decline in fiber diameter mean of Naeini
sheep it would be possible to enhance its grade from 54’s to 60’s. The
reason of using finer fibers for producing of finer yarns is that finer
fibers have higher impact surfaces and compactness in yarns and as a result
the less vacant spaces between fibers would be. It makes it possible to
produce finer yarns with necessity strength.
Scales accumulation in the length of fiber is another geometric characteristic
of fibers, which is associated with fiber strength and polish (Von Bergen,
1963). Scales accumulation had light negative correlations with staple
length (-0.09, -0.05 and -0.18 for shoulder, side and britch, respectively).
Also, the correlations between scales accumulation and the fiber strength
traits were estimated negatively (-0.03, -0.22 and -0.51 for tenacity,
%elongation at break and breaking strength, respectively). So, it can
be concluded that fibers with higher number of scales in length are shorter
and tender. Dashab et al. (2006) reported that lower scales accumulation
is associated with finer fibers with a better handle character. No reports
were observed for the suitable number of scales in the length of fiber.
However, on average the number of scales was estimated 6.2 per 100 μm
length of fiber for Naeini sheep (Dashab et al., 2006).
Longer fibers require fewer swings to make yarn and so the spinning constancy
increases. Fiber length and staple length are directly correlated and
as fiber length increases staple length increases (Botkin et al.,
1988; Von Bergen, 1963). On average, the staple length of Naeini sheep
was estimated 10.5 cm regardless of the body part, which is relatively
shorter than the most Iranian native breeds (Taherpoor, 1988). However,
this length is satisfactory for textile industry.
Fiber strength traits: Fiber strength is particularly important to processors that comb
wool in preparation for the manufacture of worsted yarns. In the present
study, the mean of fiber tenacity and breaking strength were estimated
12.2 mN/dtex and 13.76 centi-Newton, respectively (Table
2) which are more than the required thresholds of the spinning line.
Wool fibers using in textile industries should have at least 6 mN/dtex
tenacity to withstand against physical and mechanical tensions and breaking
(Klein, 1986). So, it could be concluded that wool fibers of Naeini sheep
have a desirable tenacity and breaking strength for using in textile industry.
None of the studied effects were significant on the both traits (p>0.05).
Among the reported breaking strengths for Iranian breeds (Taherpoor, 1988),
only Zandi breed had a higher breaking strength (14.76 centi-Newton) relative
to Naeini breed.
The desirable percentage of elongation at break for wool fibers is between
40-50% (Klein, 1986); this value was estimated 28.95% for Naeini sheep
in the present study (Table 2). Therefore, it seems that
wool fibers of Naeini sheep have an adequate but not a desirable grade
in this physical point of view. It seems that there is a high potential
for improving physical strength of Naeini sheep wool fibers through genetic
and nutritional improvements. Energy and protein (the Sulfur containing
amino acids) content affecting wool traits considerably. The Sulfur containing
amino acids (particularly Cystine) are especially important because of
their contribution in the chemical structure of wool (Botkin et al.,
1988). Cooper is directly involved in the formation of wool fibers and
its metabolism is closely related to dietary level of Molybdenum and Sulfate,
so their balance may be more important than their absolute levels (Botkin
et al., 1988). According to the reported %elongations for Iranian
breeds (Taherpoor, 1988), only Makooi breed with 33.1% elongation at break
was superior to Naeini breed. High positive correlations were found between
%elongation of fibers with tenacity and breaking strength (0.84 and 0.52,
respectively) which indicates that fibers with high elongation character
have a more tenacity and needs more strength to break.
Although these physical experiments are relatively cost and time consuming,
the frequency of desirable genes contributing in fiber strength could
be increased in the population by conducting measurement and recording
programs on breeding rams, because each individual ram is mated to more
than one ewe and so, rams have a more contribution in the gene follow
to the next generations.
According to the results of this study, Naeini sheep has suitable wool
fibers applicable in the semi-Fustian system. Improving wool quality helps
sheepmen earn more returns, facilitates the development of textile industry
and finally may lead to a national economization. In addition, Naeini
sheep has an ability to produce finer fibers with more uniformity and
there is a high capacity to work on this Iranian native breed. By conducting
more breeding programs, improving management and modifying environmental
effects, much finer fibers with more strength will be obtained from Naeini
sheep to reach the Fustian system qualifications. By conducting well planned
designs, Naeini sheep can supply the wool needed for Fustian and fine
textile industries and there would be less need for wool importation for
this section of textile industry.
ACKNOWLEDGMENTS
We would like to thank the experts of the responsible and personnel
of the Animal Husbandry Center of the Agriculture Organization in Isfahan
province for their co operations, Animal Science Laboratory of the Agricultural
Sciences College of the Isfahan University if Technology for the wool
quality analyses and Fiber Physics Laboratory of the Textile Engineering
College of the Isfahan University of Technology for the fiber physical
analyses. We appreciate the National Scientific Research Council for the
financial support of national scheme No. 1132 (Breeding Naeini sheep for
carpet and textile industries). Also, we would like to thank Ms. Samira
Adami, the plan assistant of the national scheme (M14).
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