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Fibre production and hides


Fibre

Yak produce two types of fibre: coarse outer hair and a fine down fibre, which grows prior to the onset of winter as additional protection for the yak against cold. The down fibre would be shed in early summer if not harvested. Since the 1970s, the down has been used extensively by the textile industry as an alternative to other fine animal fibres. Fabric made from yak down has better lustre than wool and handles well. It provides a high degree of heat insulation. The income the herder receives from yak fibre is, at present, small relative to the income that can be obtained from yak milk and meat. None the less, the economic value of the down is leading to consideration of developing strains of yak with improved fibre production.

The amount of fibre produced by individuals and the proportions of coarse hair and down varies with the region where the yak are kept and the associated climate, and with breed, sex, age and the season and method of harvesting the fibre.

Breed, sex and location

In general, yak of the Henduan Alpine type have a higher yield of fibre than those of the Plateau type. The highest amounts are obtained from a "fibre line" of Jiulong yak, especially selected for greater fibre production. Exceptional individuals of that breed are claimed to produce as much as 25 kg fibre, of which 50 percent is down fibre. This is ten-fold the yield of most ordinary yak (Cai Li et al., 1980a). Table 6.27 provides some results from different breeds at different locations for adult male, female and steer yak.

The results in Table 6.27 suggest considerable differences in the amount of fibre harvested at the different locations. The hair was harvested, at all these locations, by first raking the fleece to extract down fibres and then shorn to harvest the remaining down and other hair. The conditions were not, however, uniform for all the animals and these are likely to contribute to some of the variation. The outstandingly high fibre yield of the Jiulong males is consistent with the yield expected from this line of Jiulong yak specially developed for fibre production. The yield from the same type of females, however, is lower not only on account of their smaller body size and other sex-related differences in hair growth, but also because, in common with all females coming into lactation, they start to lose quantities of fibre with the onset of lactation. Similarly, steers tend to lose fibre when used for work. The differences in yield between the sexes therefore reflect more what happens in practice than something solely attributable to biological causes.

A study by Chang Y. S. et al. (in: Research Co-operative Group, 1980 - 1987) (Table 6.28) showed that the total yield of fibre harvested increased as the animal became older and bigger. It showed, in particular, that the proportion of down in the fleece declined from nearly 70 percent in one-year-old male yak to less than 20 percent in those six years old. For females the reduction in the proportion of down fibre was less. Another study on Jiulong yak by Zhong Guanghui et al. (1996c) indicated that the hair production of male yak increased year by year until five years old and decreased thereafter, while in female yak the amount remained relatively constant up to three years old and declined after that. The fibre output did not differ between male and female yak when the animals were one to two years, but above the age of three years the males produced significantly more than the females.

Table 6.27 The total yield of fibre (coarse hair and down) (kg) in adult yak of different breeds at different locations according to sex of animal (conditions of harvesting not uniform)

Province

Breed or location

Male

Female

Steer

Source

No.

Mean

SD

No.

Mean

SD

No.

Mean

SD

Sichuan

Jiulong (selected fibre line)

19

13.9

2.4

16

1.8

0.7

10

4.3

0.9

Cai Li et al., 1987*

Yunnan

Zhongdian

21

3.6

0.3

139

1.3

0.3




Duan Zhongxuan and Huang Fengying, 1982.

Tibet

Alpine

7

1.8


50

0.5


4

1.7


Research Co-operative Group, 1980-1987

Qinghai

Plateau




5

1.2

0.5

8

1.9

0.4

Lei Huanzhang et al., 1983

Qinghai

Menyuan (county)

4

3.6

0.7

11

1.6

0.6

15

2.6

0.6

Zhang Yinsong, 1985.

Gansu

Tianzhu White

9

4.0


24

2.9


7

2.1


Zhang Rongchang, 1975

* Cai Li's 1979 results, in a large report

Table 6.28 Total yield of fibre and proportion of down at different ages of yak in Menyuan county of Qinghai province [Source: Chang Y. S. et al., in: Research Co-operative Group, 1980 - 1987]

Age (years)

No.

Male

No.

Female

Total yield (kg)

Down (%)

Total yield (kg)

Down (%)

Mean

SD

Mean

SD

1

2

0.80


68.8

7

1.10

0.25

60.0

2

20

1.84

0.64

48.9

27

1.47

0.38

54.4

3

13

1.97

0.61

40.6

24

1.50

0.52

46.7

4

15

1.99

0.68

43.2

11

1.39

0.58

43.2

5

3

2.65

0.38

21.9

11

1.60

0.58

53.1

6

4

3.60

0.70

18.6

8

[0.83]*

[0.32]*

*

* Only the down fibre was harvested in the milking females.

Method of harvesting

Combing out the down hair prior to shearing can increase the yield of down from the total fleece by about 10 percent compared with shearing alone. In one study (Wang Jie and Ouyang Xi, 1984), the percentage of down increased from about 50 percent with shearing to 61 percent with combing.

Melatonin (MT)

Melatonin is secreted by the pineal body gland and can promote hair and hide growth of the animals, such as goats and sheep. When it was injected into Menyuan yak, the length, speed of growth and the production of down hair were greatly increased (P<0.01), although the diameter of the down hair was not affected (Table 6.29).

Table 6.29 Effect of melatonin on growth of down hair of yak in Menyuan county of Qinghai in the spring [Source: Xue Bai et al., 1999]

Group

Length* (cm ± se)

Growth (cm/week)

Diameter (m)

Production (kg ± se)

Treatment

10.0 ± 1.18a

0.39a

18 - 30

0.91 ± 0.16a

Control

7.3 ± 1.19b

0.01b

18 - 30

0.70 ± 0.06b

* Different letters (a or b) in the same column indicate significant difference /between means (P<0.01).

Fibres and staple properties

Fibre types have been examined in a number of studies (Wang Jie and Ouyang Xi, 1984; Wang Jie, 1984; Zhang Rongchang, 1975, 1977; Lu Zhonglin et al., 1982; Wu G. Y. et al., 1983; Xue Jiyin, 1981; as well as studies by Cai Li). The results can be summarized as follows:

Staple shape. This varies with the part of the yak body on which the fibre grows and differs between the coarser hair and the down.

Fibre types. The fibres of the yak can be divided into three main types: down, mid-type and coarse.

(In practical production, there is often a dividing line drawn only between "down" hair, fibres of less than 35 m diameter and "coarse" hair with a greater diameter.)

An analysis (Table 6.30) on the fibres of 60 Plateau yak by Zhao Longquan et al. (1994) indicate that the down content among fibres on shoulder, back and rump was much higher than on belly and foreleg (P<0.05). Down fibres also tended to be shorter and the other fibres longer on the belly and foreleg, but fibre diameters did not differ significantly among body parts.

Length of fibre. As shown in Table 6.30, there are considerable differences in the length of stretched fibres, depending on the type of fibre and the part of the body. Similar results have been reported by Zhang Rongchang (1989) with the length of coarse hair varying from 8.9 cm to 21.1 cm, and mid-type hair from 5.3 cm to 13 cm, with the longest in both cases on the belly and the shortest on the shoulder (and the fibres on the back intermediate in length). Down fibre length in Zhang Rongchang's report was slightly less (3.7 - 4.1 cm) than shown in Table 6.30, and in contrast to the results in that Table, the down fibres in Zhang Ronchang's study were longest from the belly and shortest from the back.

Table 6.30 Proportion, length and diameter of the different types of fibre on different parts of the body of 60 Plateau yak in Qinghai province [Source: Zhao Longquan et al., 1994] (means ± SD)

Position

Prop.

Coarse hair

Prop.

Mid-type hair

Prop.

Down fibre

Length (cm)

Diameter (m)

Length (cm)

Diameter (m)

Length (cm)

Diameter (m)

Shoulder

19.5

12.9 ± 1.5

79.3 ± 11.2

17.7

6.8 ± 1.1

41.7 ± 8.6

62.8

4.6 ± 0.75

17.7 ± 3.4

Back

21.1

13.3 ± 3.8

81.0 ± 12.4

15.0

8.8 ± 1.3

39.2 ± 8.2

63.9

4.6 ± 0.95

16.6 ± 3.4

Rump

20.4

17.9 ± 2.3

84.9 ± 12.1

18.9

9.6 ± 1.6

39.8 ± 9.2

60.7

4.2 ± 0.72

17.5 ± 3.8

Belly

63.6

19.0 ± 2.4

86.7 ± 12.5

29.5

10.2 ± 1.7

39.0 ± 8.9

6.9

3.8 ± 0.67

16.7 ± 3.4

Foreleg

60.3

19.3 ± 2.6

88.6 ± 13.7

33.9

10.1 ± 2.1

43.4 ± 9.1

5.7

3.8 ± 0.67

18.4 ± 3.2

Fibre diameter. Diameter varies greatly with type of fibre and with breed and sex of animal, but as shown in Table 6.30, for any given fibre type there were no significant differences in the diameter of these fibres among the various body parts.

Down fibres tend to be more uniform in diameter along their length than coarse hair fibres. In one study (Wang Jie and Ouyang Xi, 1984), the diameter was measured at the upper (outer end), middle and lower part of the fibre. Approximately 100 coarse hair fibres and a similar number of down fibres were examined from each of four yak. Results are shown in Table 6.31.

Table 6.31 Fibre diameter (m) at different parts of the fibre* [Source: Wang Jie and Ouyun Xi, 1984]


Part of fibre

Mean

[SD]

Coarse

Upper

83

15.8

Middle

75

16.6

Lower

77

4.8

Down

Upper

21

3.3

Middle

20

3.7

Lower

20

3.1

* 100 fibres from each of four yak

Fibre density. The density of fibres per unit area varies greatly with the position on the body of the yak. Some results are shown in Table 6.32. The density of down fibres per unit area is far higher than that of coarse hair. Particular note should also be taken of the high degree of variability in density among the 30 yak sampled. The coefficients of variation range from 23 to 64 percent.

Table 6.32 Fibre density of coarse hair and down hair on two different parts of the body of 30 adult yak [Source: Li Shihong et al., 1985]

Position

Hair type

Density
(fibres per sq cm of skin)

Mean

[SD]

Shoulder/back

Coarse

182

117

Down

1468

473

Belly

Coarse

201

94

Down

757

403

Fibre strength. One of the useful properties of both the coarse hair and the down from the yak is their strength. Results from a study by Xue Jiyin et al. (1981) were as follows: Down fibre (diameter 16.8 m) strength (breaking load) dry 9.8 g, moist 6.9 g; corresponding values for coarse hair (49.8 m) were 32.8 g and 25.1 g, respectively. Wang Jie and Quyang Xi (1984) reported a breaking load of 12.9 g for down hair with a diameter of 22.7 m. These breaking loads are remarkably high relative to those quoted for typical sheep wool (Ryder and Stephenson, 1968), if the methods used for determining the load are the same. Results from yak (Wang Jie and Quyang Xi, 1984) also suggest that the stretched length percentage of wet fibres (the limiting extension on the load extension curve; see Ryder and Stephenson, 1968) is of the order of 60 percent for both down and coarse hair fibres. This appears to be in the same range as sheep wool.

Other attributes of yak hair

Moisture retention. According to Wang Jie and Ouyangxi (1984), moisture retention in yak fibre increased with the air humidity as also found in sheep wool, shown for comparison in Table 6.33. Retention was higher in the coarse hair of yak than in its down fibre. The mid-type and down hair of the yak had a lower moisture retention than that of the local breeds of sheep.

Table 6.33 Moisture retention of yak fibre under different relative air humidity when air temperature equal to 20¡ãC (13 yak sampled) [Source: Wang Jie and Ouyang Xi, 1984]

Fibre type

Air humidity (%)

76

85

Moisture retention* (%)

Moisture retention* (%)

Coarse hair of yak

11.3

12.3

Mid-type hair of yak

7.8

8.5

Down fibre of yak

7.4

7.7

Wool of Tibetan sheep

9.6

11.8

Wool of Xingjiang sheep

9.4

11.0

* The range of moisture retention was approximately 10 - 15 percent of their means.

Grease content. The lanolin content of yak hair is low. For Gannan yak this has been estimated as 2.7 percent and 1.7 percent of the shorn fleece for male and female yak respectively (Lu Zhonglin et al., 1982). Another study (Wang Jie and Ouyang Xi, 1984) suggests that the grease content varies with the part of the body of the yak - 3.8 percent on the back, 2.2 percent on the rump, 1.5 percent on the belly, and only 0.3 percent for hair from the tail. The melting point of the lanolin ranges from 37 o to 43o C (Xue Jiyin et al., 1981).

Specific gravity. Specific gravity of yak down fibre is around 1.32 - 1.33 g per cu cm and coarse hair around 1.22 - 1.33 g per cu cm - similar to that of sheep wool (Xue Jiyin et al., 1981).

Static electricity. Under similar conditions, the down fibres of the yak suffer less from static electricity disturbance than cashmere fibres from goats, thus giving yak fibres an advantage in processing (Xue Jiyin et al., 1981).

Amino acid content. The strength and resilience of yak down fibre has been attributed to its content of high sulphur proteins. The total amino acid content of down fibre from female yak has been measured as 79.8 percent of dry weight, with cystine, proline and serine accounting for 19.4 percent - higher than the 15.9 percent of local sheep wool with which it was compared.

Other structural properties. The structural property of yak hair differs from that of sheep wool not only in respect of its greater strength. In the yak, the angle between scale and hair shaft, on the external surface of the fibre, is small so that the scale virtually sticks to the shaft - making the hair fibre relatively smooth. This gives yak hair poor felting qualities.

Shedding of fibres

Down fibres and mid-type hair begin to shed as the weather becomes warmer in the spring and early summer. Observations by Ouyang Xi et al. (1985) showed that shedding towards the end of May, in their locality, was greatest from the belly of the yak (nearly 20 percent) and less from the back and rump (just over 12 percent). Lactating females also start to shed fibres with the onset of lactation.

In July, when air temperature is at its highest, down fibre will twine around coarse hair or will fall on pasture and shrubs if not combed out or sheared. Shedding of the coarse hair has not been observed. As the length of coarse hair increases, the growth rate of the hair declines until it virtually stops.

Hides

Yak hide is a major source of raw hide in China - about one million yak hides are produced from the Qinghai-Tibetan Plateau per year.

Weight

Fresh hide weight varies with breed and sex of yak (Table 6.34) from 13.2 - 36.1 kg for adult yak, accounting for 5.5 - 5.8 percent of live weight. Average weights of hides per 100 kg body weight were 6.1 ± 0.5 kg for female yak, 6.6 ± 0.6 kg for steers and 6.8 ± 1.3 kg for entire males (Zhang Rongchang, 1989).

Size

The size of fresh hide of adult yak steers and males is reported to be about 0.11 sq m per kg and that of females around 0.19 - 0.21 sq m per kg (Zhang Rongchang, 1989).

Thickness

Skin thickness varies with the part of the yak body. It is thickest on the back and thinnest on the neck and belly. On average, the skin of three-month-old yak calves is reported to be about 2.7 mm thick and that of 9 - 12 years old yak around 3.9 mm.

Table 6.34 Hide production of adult yak (mean ± SD) [Source: adapted from Zhang Rongchang, 1989]

Location

Breed or yak of country

Sex

No.

Fresh hide weight (kg)

Proportion of hide to live weight (%)

Tianzhu, Gansu

Tianzhu White

Steer

5

20.1 ± 3.6

7.7

Female

7

14.8 ± 2.5

6.8

Ruoergai, Sichuan (former) USSR

Mawai

Steer

8

24.2 ± 3.9

6.6

Kyrgyzstan

Male

7

36.1 ± 4.6

8.8

Female

7

13.2 ± 2.5

5.6

Quality

The quality of yak hide is poorer than that of cattle. Factors affecting the hide quality include age, sex, live weight, nutritive status and environment where the yak lives (Zhang Rongchang, 1989) and including often extensive damage to hides from warble fly and from poor skinning and processing.


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