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THE POTENTIAL TEXTILE UTILIZATION OF THE DOWN FIBRES FROM SOUTH AFRICAN DAMARA SHEEP BREED

  COUNCIL FOR SCIENTIFIC AND INDUSTRIAL RESEARCH (CSIR)

Albie Braun - 17 September 2004


Introduction

The unique and highly desirable characteristics of luxury animal fibres, such as softness and comfort, have increasingly been sought after by discerning customers world-wide. There has also been a trend towards lighter, casual and easy care garments.

 Although not classified as a luxury fibre, wool is the most widely produced and popular animal fibre, possessing highly desirable properties. Because of their superb softness and comfort, fine wool (finer than 18 micron) and cashmere are two of the worlds most sought after animal fibres today.

 In the light of the above and the fact that certain indigenous goats and sheep breeds have the potential to produce a fine "down" cashmere type of fibre, the CSIR, together with other stakeholders, has embarked on various projects aimed at investigating the economic feasibility of, and requirements for, utilising fine down components of indigenous goats and sheep breeds for producing marketable products, one such sheep breed being the Damara.

 This report addresses results obtained on fibre samples obtained from the Damara double-coated sheep breed found in South Africa.

 Sheep breeds

From a textile view point wool from sheep can be sub-divided into 3 main groups, namely (1) wool shorn from living sheep (shorn/virgin wool) (2) wool removed from skins (skin wool, slipe wool or dead wool) and (3) re-used (non-virgin) wool. Sheep breeds, which are primarily wool producers, can be sub-divided according to the type and fineness of fibre they produce and the end products made from these fibres. For example breeds, such as the merino and merino related breeds, which produce primarily apparel type wool (i.e. fine or medium wool) and those breeds which produce a coarse wool used for carpets i.e. Lincoln.

The above-mentioned wools grow throughout the entire year and the fleece is of a single component. There are other sheep breeds, such as the Dorper, which are primarily mutton producers but which also produce a medium to coarse type of wool and hair covering as a by-product to meat production. There are also the fat-tailed mutton producing sheep breeds, which possess the ability to produce a fleece consisting of two distinct coats of fine and coarse fibres, namely a fine down or undercoat and a coarse hair or guard coat. The coarse outer coat or guard hair component protects the body of the animal. The Damara, Ronderib Afrikaner, Pedi, Van Rooy, and the Blackhead Persian are good examples. Most of these breeds possess the inherent ability to respond to seasonal changes in day length and climatic conditions resulting in periods of an active fibre growth and then of fibre shedding (moulting). In South Africa, the down fibre grows actively from December to June, thereby protecting the animal from the cold in winter while shedding of the down fibres takes place during early spring (July to September) so that the animal does not suffer from excessive heat during the hot summer months. Generally, the fat-tailed sheep breeds are found in arid or semi-arid regions of the country where food is sparse.

 The Damara sheep breed possesses the ability to produce a fleece consisting of two distinct coats (fine and coarse fibres).

 Purpose of Investigation

In view of the great demand for the cashmere type of fine down world wide and the potential for employment creation and value addition, the CSIR extended its indigenous goat initiative to also include the double coated fleece of fat-tailed mutton sheep breeds, such as the Damara sheep breed found in South Africa.

Harvesting of fine down fibre

During the shedding / moulting period the animal releases the down fibre freely from its body but it can also be harvested by combing the animal and the fibre collected. The shedded/combed fibre consists of both fine down (undercoat) and coarse hair (guard coat) which requires a mechanical process, called dehairing, in order to separate the two components.

 Results and Discussion

An initial investigation of various fat-tailed sheep breeds showed that the Damara was one of the breeds with the finest down. (Table 1)

Table 1 gives a summary of the fiber properties (quality and yield) of the Damara and various other sheep breeds and compares the diameter profiles with those of dehaired Chinese cashmere and with dehaired down of the South African Boer Goat.

For easy and efficient dehairing there needs to be a clear distinction between the two fibre populations (fine and coarse). It is generally desirable that the ratio of the diameter of the outer coarse coat (guard hair) to that of the fine down fibre component at least be 4:1 and that the outer coat have a mean fibre diameter greater than 60 micron. For this reason, the presence of intermediate fibres (30 to 60 micron) in the fleece is undesirable because it is difficult to remove such fibres during the dehairing process.

According to Table1, the fine fibre component of the Damara compares favourably with cashmere down in terms of fineness, down fibre and guard hair diameter ratio (1:4) with a good diameter profile i.e. without indications of intermediate fibres. Nevertheless, the down fibre yield is comparatively low at 39%.

 Processing of Damara hair

It was also considered necessary to determine the acceptability of the fine down fibre as a textile fibre, i.e. in terms of textile processing performance and conversion into acceptable garments. To this end Mr. Mr Dennis Steenkamp of the Damara breeders Association were approached to supply fibre for processing purposes. The 350kg of combed fibre supplied was scoured (washed) in South Africa and dehaired (mechanical separation of the coarse guard component from the fine down fibre component) in the UK after which the down fibre was processed into yarn and knitted garments by the CSIR. Garments were produced from pure Damara wool as well as from blends of Damara wool with either viscose fibre or Mopanie silk. Because the dehaired fibre is very short ( 16mm), processing into yarn was carried out on short staple machinery.

 Processing stages

Process                                                                         Product

 

1. Scouring (washing)                                                     Scoured fibre

2. Dehairing (mechanical separation)                               Coarse hair component

                                                                                      Fine down component

3. Carding of down component                                      Card sliver

4. Drawing                                                                     Sliver

5 Roving                                                                         Roving

6. Spinning                                                                     Spun yarn

7. Twisting                                                                     Plied yarn

8. Dyeing                                                                       Dyed yarn

9. Knitting                                                                     Garment

 

Economic Potential                                             Fibre Yield per animal*/ Fibre weight (g.)

Raw fibre                                                                                         50

Scoured fibre (74% of greasy fibre)                                                  37

Down fibre (39% of scouring yield)                                                   14

Final Down Yield (after processing and making-up)                           13

Down fibre per animal in final product                                                13

 The above indicates that assuming that an animal producers 50 grams of raw fibre which yields 13grams of fine down fibres and a knitted garment of 500grams means that the down from 39 sheep is required to produce the garment.

Conclusion

 

The availability of the Damara sheep breed offers an opportunity for the diversification of existing agricultural resources without a large capital outlay. The utilization of the fibres as an additional source of income (value addition) could make this mutton breed more profitable. The fibre characteristics, notably fineness and yield, of the Damara sheep breed were therefore investigated with a view to assessing the potential of the undercoat as a textile fibre and for value addition. It was found that the Damara sheep breed showed potential in terms of the utilisation of their fine undercoat fibres in the high value added textiles with an African design. Nevertheless the yield per sheep of fine down fibre would need to be substantially increase for this to become a reality

The recent acquisition of a dehairing facility in South Africa provides the opportunity for South Africa Damara sheep farmers to exploit the potential and ability of the Damara sheep breed to produce fine, high quality unique garments.

 

Results obtained on double-coated indigenous sheep breeds found in South Africa

 

TABLE 1

 

Sample

Scoured Yield

Down

Guard hair

Down Yield

Percentage of Fibres in Specific

Diameter Classes

MFD

SD

CV

MFD

SD

CV

SPECIFIC DIAMETER CLASSES

(%)

(m)

(m)

(%)

(m)

(m)

(%)

(%)

1-20m

21-25m

26-30m

31-60m

61-300m

 

Blackhead Persian

64

16.2

3.6

22.1

96.1

47.3

49.2

34

80.4

9.4

1.4

2.7

6.2

Pedi

95

16.2

3.1

19.2

116.4

54.0

46.4

51

89.1

8.1

0.7

0.5

1.7

Ronderib Afrikaner

85

18.3

3.7

20.5

66.0

24.2

36.7

55

69.1

19.6

3.9

3.3

4.1

Van Rooy

80

18.6

3.6

19.2

123.8

75.5

60.9

57

71.4

23.2

3.7

0.6

1.1

Damara

74

16.0

3.3

20.7

146.5

56.5

38.6

39

88.2

7.8

1.3

0.4

2.3

SA Boer Goat

93

16.7

3.3

19.7

109.1

57.2

52.4

64

85.4

12.1

1.0

0.4

1.1

Chinese Cashmere

0

15.6

3.0

19.2

104.8

52.7

50.2

79

94.0

5.2

0.0

0.2

0.5

 

MFD = Mean Fibre Diameter

SD = Standard Deviation

CV = Coefficient of Variation

m = Micron

 

 

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