MSc (Agric) -- University of Pretoria, 2005. / Includes bibliographical references (leaves 117-123)

[From Introduction]. Navorsing oor hierdie proefskrif het meegebring dat die Bemarkingswet (soos gewysig) en die Suid-Afrikaanse Sybokhaarbedryf, intensief behandel en ontleed moes word om gevolgtrekkings te maak. Die navorsing het 'n baie wye veld gedek en aan die einde van elke hoofstuk, wat voltooi is, is die bron van inligting wat nageslaan is, genoem. Aan die einde van hierdie verhandeling en sitasie, sal die geografiese verwysings meer volledig aangetoon word. Daar was so baie bronne van navorsing dat alleenlik die belangrikste volgens my mening genoem en opgesom kon word. Omdat opsommings en gevolgtrekkings gemaak moes word van die bestaande inligting in sy geheel, is daar nie spesifiek kwoteer van waar sekere inligting bekom is nie. Deel I van hierdie proefskrif behandel die Bemarkingswet, sy ontstaan, kritiek en beginsels. Deel II handel oor die Sybokhaarraad, sy ontslaan, soos dit onder die Bemarkingsraad as In Beheerraad ressorteer, hoe hy daarin geslaag het om die Bemarkingswet toe te pas en sekere aanbevelings en opmerkings met betrekking tot die werkinge daarvan.

Fibres used in textiles can be classified broadly into natural fibres and synthetic fibres. Natural fibres can be either animal, such as wool, mohair and camel hair, or vegetable such as cotton, flax and hemp. In the development of synthetic fibres numerous polymers have emerged which have no real natural counterpart and are unique in their mechanical and chemical behaviour. Often the synthetic counterpart of a natural fibre has properties with certain advantages from the textile point of view, but, simultaneously, may exhibit other properties which have disadvantages. Nylon 6 and nylon 6-6, for exemple, are extremely strong and generally easier to dye than animal fibres. On the other hand, they absorb relatively little water vapour and therefore do not give the buffering action characteristic of hygroscopic fibres, once they are woven or knitted into cloth. All textile fibres belong to the chemical class of polymers, i.e. they are made up of repeating molecular units which are linked together to form long chains. In wool the chains are made up of amino-acids which cluster together to form protein chains. Three of these protein chains, coil around each other to form what is termed a proto-fibril. The proto-fibrils make up the micro-fibrils, each of these consisting of eleven of the three chain proto-fibrils. The micro-fibrils, in turn, pack together in bundles which run parallel to the length of the wool fibre and are termed macro-fibrils. Sulphur rich amino-acids fill up the spaces between the micro-fibrils forming a matrix which binds the system into a continuous material. Intro., p. 1.

Textiles have always been one of the essential materials for people and have a great variety of uses such as in clothing, agriculture, medical, automotive and aerospace applications. The sort of properties needed for any type of fabric basically depend on the structure of the fibre surface. Of many geometric attributes that can be used to describe the surface appearance of a fibre, yarn, or fabric sample, one of the more common is lustre. Mohair and wool fibre surface structure have been studied using optical microscopy and Atomic Force Microscopy (AFM). Optical microscopy was also used to take fibre diameter measurements. Another technique, goniophotometry, was used to make quantitative lustre measurements of mohair and wool fibres. The surface structure of mohair has got a faint pattern of scales where the scales are generally unpronounced or flat and relatively long. Wool has got a scaly surface structure where the scales overlap leading to interlocking of fibres. The scale configuration on the surface of mohair and wool fibres also differs. A qualitative connection between fibre lustre and the fibre surface structure was found. Because of its smooth surface relative to that of wool, mohair reflects a greater amount of incident light specularly whereas wool reflects most of the incident light diffusely. In general, mohair fibres have a higher lustre than wool due to its less prominent cuticle structure found on its surface. Furthermore, mohair fibres with the smallest diameters give an even higher lustre.

The objective of the research was to determine the extent to which marketing in general, and the Mohair Scheme in particular, played a part in the re-emergence of South Africa as the world's leading mohair producer. The two major components of the Scheme, the 'voorskot', or initial payment, and reserve prices were analysed separately. In an adaptive expectations, distributed lag model of supply adjustment, only the weighted rainfall and the average real net price of mohair during the previous season, were found to be important determinants of mohair production. The significant negative correlation between the average real net 'voorskot' price and mohair production was contrary to expectations, and probably due to the 'voorskot' always having been set well below the market price. The 'voorskot' may nevertheless have played an important part in making the Scheme as a whole acceptable to producers. As no record is kept of the reserve price, its influence was tested indirectly in two stages. In the first, its influence on price stability was determined by a comparison of ranges, standard deviations and variances, and by several multiple linear demand regressions. Three of the four models showed clearly that price stability was increased by the Mohair Scheme. In the second stage, formulae and diagrammatic analyses were used to assess the welfare gains and losses resulting from the Mohair Scheme. There was a welfare gain to local producers and most of the welfare costs of the Scheme were borne by foreign consumers. With this gain to producers and the more stable price, it was concluded that the reserve price had stimulated mohair production. It was therefore established that the Mohair Scheme had played a major part in the re-emergence of South Africa as the world' s leading mohair producer. Nevertheless, in view of the massive stockpiling in recent seasons, because the reserve price was set too high, the result was a substantial loss to the Scheme; it was therefore recommended that the Mohair Scheme be discontinued or, at least, that the reserve price should be set at a much lower long-run, market clearing level.

To improve the quality and the marketability of wool and mohair, it is important to encourage, ensure and preferable certify that the baled fibre is free of contaminants. Anything other than the fibre that is within the bale can be classified as contaminants; this may be in the form of metal and wooden objects, plastic materials, paints, and vegetable matter such as grass and seed. The internationally accepted method for detecting and classifying these contaminants are highly labour intensive and costly. The ultimate goal of the present research is to develop a non-invasive and nondestructive technique that can be used to detect contaminants, particularly plastic (polymer) materials within wool and mohair bales. Such a technique can be implemented in the wool industry and also could be applied to other fibres, such as cotton. The immediate objective of this study was to evaluate the capability and the limitation of X-rays as a technique to detect such contaminants. It was found that X-rays were suitable for detecting foreign objects, or contaminants, such as metals, but not for detecting plastic materials, such as polypropylene and polyethylene.

This work investigates the tensile behaviour of non-uniform fibres and fibrous composites. Wool fibres are used as an example of non-uniform fibres because they're physical, morphological and geometrical properties vary greatly not only between fibres but also within a fibre. The focus of this work is on the effect of both between-fibre and within-fibre diameter variations on fibre tensile behaviour. In addition, fit to the Weibull distribution by the non-brittle and non-uniform visco-elastic wool fibres is examined, and the Weibull model is developed further for non-uniform fibres with diameter variation along the fibre length. A novel model fibre composite is introduced to facilitate the investigation into the tensile behaviour of fibre-reinforced composites. This work first confirms that for processed wool, its coefficient of variation in break force can be predicted from that of minimum fibre diameters, and the prediction is better for longer fibres. This implies that even for processed wool, fibre breakage is closely associated with the occurrence of thin sections along a fibre, and damage to fibres during processing is not the main cause of fibre breakage. The effect of along-fibre diameter variation on fibre tensile behaviour of scoured wool and mohair is examined next. Only wet wool samples were examined in the past. The extensions of individual segments of single non-uniform fibres are measured at different strain levels. An important finding is the maximum extension (%) (Normally at the thinnest section) equals the average fibre extension (%) plus the diameter variation (CV %) among the fibre segments. This relationship has not been reported before. During a tensile test, it is only the average fibre extension that is measured. The third part of this work is on the applicability of Weibull distribution to the strength of non-uniform visco-elastic wool fibres. Little work has been done for wool fibres in this area, even though the Weibull model has been widely applied to many brittle fibres. An improved Weibull model incorporating within-fibre diameter variations has been developed for non-uniform fibres. This model predicts the gauge length effect more accurately than the conventional Weibull model. In studies of fibre-reinforced composites, ideal composite specimens are usually prepared and used in the experiments. Sample preparation has been a tedious process. A novel fibre reinforced composite is developed and used in this work to investigate the tensile behaviour of fibre-reinforced composites. The results obtained from the novel composite specimen are consistent with that obtained from the normal specimens.

No description available.

South Africa is currently the world leader in mohair production and emphasis is placed on mohair traits to ensure the production of a high quality clip. Accurate and complete pedigree information is a prerequisite for accurate selection and estimation of breeding values that in turn can improve the traits associated with fleece quality and yield. South African Angora goats are farmed under extensive breeding conditions in relatively large herds. As a result breeders make use of mating systems that tend to limit accurate parentage recording. Incorporation of genetic parentage testing into the breeding plan can improve the accuracy of pedigree records and lead to increased selection accuracy. Microsatellite markers were evaluated for inclusion into a parentage verification panel, to be applied in the South African Angora goat population. The panel of 18 microsatellite markers was constructed, optimized and tested in 200 South African Angora goats. These goats represented different family structures, including candidate parents alone as well as known and candidate parents. The microsatellite markers were evaluated based on the number of alleles, allele frequency, PIC, HE, HO and CPE of each individual marker and as a panel. Four microsatellite markers were excluded from the panel based on their poor performance for the above mentioned parameters. The panel of 14 markers allowed a cost effective panel with the highest exclusion power. The CPE1 of the 14 microsatellite marker panel was 99.73%. The use of molecular parentage verification may aid Angora goat breeders in improving the accuracy of the parentage records of their animals. Copyright / Dissertation (MSc (Agric))--University of Pretoria, 2010. / Animal and Wildlife Sciences / MSc(Agric) / Unrestricted

The primary marketing of South African mohair has been the topic of much discussion and it has become a contentious issue since producer prices became unusually unstable, producer returns increasingly uncertain, and production consequently began declining. This dissertation has aimed to structure these discussions and issues and to critically analyse the South African mohair marketing system in the evolving global agribusiness environment. It is widely documented that the intangible attributes of products are growing in importance as retailers and consumers become increasingly interested in and concerned about safety, provenance, welfare, society and sustainability. Marketing systems are consequently compelled to convey not only objective but also subjective product quality attributes. Mohair is an exclusive product with niche market appeal and the central question of this dissertation is whether mohair is inherently suited to the current fifty-five year old commodity-based marketing system in a marketing environment that requires marketing systems to convey far more information than commodity-based systems do. This, in effect, boils down to the question whether the mohair clip can be considered a commodity or a niche product. Historically, mohair has been considered a commodity and the marketing system for mohair has been structured accordingly. Mohair is, however, one of the scarcer animal fibres globally, diverse in its physical properties and is suitable for use in many products all of which have different market and demand characteristics. It is therefore argued that mohair currently boasts with the characteristics of a product despite its historical development as a commodity. Mohair’s unit type (whether it is a product or a commodity) informs two theoretical frameworks used to determine an appropriate governance structure for the exchange between producers and processors. Both these frameworks reveal that the exchange between mohair producers and processors should be governed by more intensively coordinated governance structures than the current spot market. This is in accordance with global trends where there is a shift away from open market trading to more stringent coordination of the supply chain. In view of this it is proposed that the spot market, which this dissertation contends to be a “value bottleneck” in some instances, be augmented by a number of hybrid governance structures like long term contracts, cooperation agreements or some form of vertical ownership to offer additional exchange structures, where necessary, to transmit all of mohair’s attributes more effectively between producers and processors and ultimately the whole mohair supply chain when required to do so. It is proposed that these additional options should function in tandem with the current spot market which continues to be a critical exchange mechanism for mohair that is used as a generic input to the production of multi-purpose blended fibres where price and availability are the major determinants of demand and not the type of fibre or its intangible attributes. In such instances the conveyance of any attributes other than price and quantity (within the respective classing standards) is superfluous and a spot market to facilitate the exchange would suffice since it provides sufficient coordination control for the specific transaction. The discontinued or diluted use of a spot market as proposed is, however, not without pitfalls. The spot market price for mohair is the only public price forming mechanism. If the use of the spot market were to be discontinued or diluted there would be no reliable yardstick to use for negotiating prices for mohair that is exchanged by means of other governance structures and alternative mechanisms would need to be developed to determine such prices. In an attempt to keep up with global trends in agricultural marketing a South African mohair producer group recently established an “innovative” approach to the marketing of mohair. This innovation in marketing is, however, not quite complete although the producer group have instinctively made huge strides in the right direction. The producer group also continues to make use of a spot market to exchange their niche quality mohair, resulting in relatively high transaction costs that could be reduced by more coordinated governance structures. Over and above the theoretical arguments to this effect, mohair producers are also demanding vertical coordination structures that require increased levels of coordination to govern the exchange between themselves and mohair processors. The implementation of such strategies would be best undertaken by brokers or producer groups given the superior levels of trust that producers have expressed in brokers and the fact that the levels of transaction costs are the lowest between parties where the greatest levels of trust are exhibited. The inefficiencies created by an inappropriate or incomplete marketing system for South African mohair are expected to lead to a loss of consumer value and a loss of potential profit throughout the mohair supply chain. In anticipation of the ever changing, and now consumer driven agricultural marketing environment the South African mohair industry would therefore be well advised to collectively consider and to encourage the creation of exchange mechanisms that offer greater coordination within the mohair supply chain to function in tandem with the current spot market exchange mechanism and to embrace these developments in a practical and mutually inclusive manner to the benefit of the whole South African mohair industry – a challenge that would compel the industry to shake off its reputation as a sluggish adapter to the dynamic changes in world markets. / Dissertation (MSc (Agric))--University of Pretoria, 2007. / Agricultural Economics, Extension and Rural Development / MSc / Unrestricted