Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Grapevine water status is considered to be the most important factor limiting plant growth and production in the Mediterranean zones. In these regions with limited summer rainfall and limited water resources for irrigation grapevines may experience water deficits for an extended period of time. The demand of water for agriculture is constantly increasing, and will continue to do so due to the rise in the world population and to the effects of climate change on rainfall and evaporative demand in these regions. The Western Cape wine region is also classified as Mediterranean and grapevines grown in this region are often exposed to water “stress” conditions due to high evaporative demand and low water availability in the soil. Plant water status of grapevines may dependent on, amongst other factors, the water potential of soil layers close to the root system, canopy size and evaporative demand. The canopy size of a grapevine can inherently be seen as a measure of grapevine vigour, and vigour variation among grapevines within a vineyard is a common phenomenon in the Western Cape. The importance of the contributions from several factors causing vigour variation within vineyards is still a subject of debate. This may be largely ascribed to the significant amount of variability in vineyards that researchers have to deal with during viticultural studies. However, the recent advances in remote sensing technology have established new methods to assess grapevine vigour variability. In the face of the recognized variation within vineyards and the importance of a sustained grapevine water status, for wine grape productivity and -quality, it is alarming to think that a vineyard block is generally managed as a homogeneous entity when it comes to irrigation scheduling. What is more alarming is the assumption that grape, juice and wine quality will be homogeneous throughout a vineyard block – even without irrigation. With this in mind, a study was conducted to study the interaction between grapevine vigour and grapevine water status within a commercial vineyard with variable vigour by implementing various irrigation regimes. Vigour variation was identified through multispectral aerial imagery and plant-based water status determinants were used to assess grapevine water status in plots of differing vigour within the vineyard. Soil water status was also assessed, and vegetative growth quantified to ultimately determine the variability in vigour and its possible contribution to the variability through the water status of the plant. Reproductive growth was monitored continually before evaluating the effect of water status and grapevine vigour on grape composition and subsequent wine quality. The various methods used to evaluate grapevine vigour showed good correspondence. Pruning mass measured at the end of the season confirmed leaf area measurement (main leaves and lateral leaves) during vegetative growth, and corresponded well, in terms of main vigour classifications with the NDVI images collected. Berry weight and volume responded to the various classifications, with a decrease in water deficits from one classification to the next accompanying an increase in berry weight and volume. Analyses of the berry composition and wines showed statistically significant differences between the classifications. This was found for sugar content per berry, total phenols, total red pigment, malic acid, nitrogen and pH for the grape juice analyses. Wine pH and total acidity also differed significantly. / AFRIKAANSE OPSOMMING: In die Mediterreense sones word plantwaterstatus beskou as `n hooffaktor wat groei en produksie van `n wingerdstok negatief beinvloed. In hierdie sones kan wingerdstokke vir lang periodes `n tekort aan water ervaar a.g.v `n tekort aan reënwater gedurende die somer en lae beskikbaarheid van besproeingswater. Die vraag na water vir landbou is ook konstant besig om toe te neem in dié sones en die tendens sal voorduur a.g.v die groei in die wêreldbevolking, die effek van klimaatsveranderig op reënvalpatrone en die hoë verdampingsfaktor. Die wingerd- en wynstreek van die Wes-Kaap word ook geklassifiseer as Mediterreens en wingerdstokke in hierdie streek ervaar dikwels waterspanning wat deur hoë evapotranspirasie en min beskikbare grondwater veroorsaak word. Van die faktore wat die waterstatus van `n wingerdstok bepaal is onder andere die waterpotensiaal van die grondlae rondom die wortelstelsel, die grootte van die wingerdlowerraamwerk en die evapotranspirasiebehoefte. Die omvang van `n wingerdstok se lower binne die prieel word beskou as `n aanduiding van wingerdstokgroeikrag en variasie in groeikrag tussen wingerdstokke is `n algemene verskynsel in die Wes-Kaap. Die rangorde, wat die effek van die verskeie faktore wat groeikragvariasie tussen wingerdstokke bepaal, word steeds gedebatteer. Die debat kan groottendeels toegeskryf word aan die beduidende hoeveelheid variasie tussen wingerde waarmee navorsers te doen kry in wingerdkundige studies. Hoewel, met onlangse vordering aangaande afstandswaarnemingstegnologie is daar nou nuwe metodes beskikbaar om wingerdgroeikrag te evalueer. Dit is kommerwekend om te dink dat `n wyndruifwingerd normaalweg as `n homogene eenheid bestuur word as dit kom by besproeiing. Veral met die wete dat groeikragvariasie tussen wingerde algemeen erken en aangeteken word, en dat volhoubare waterstatus van `n wingerdstok van kardinale belang is vir produksie en kwaliteit van wyndruiwe. Die aanname dat wyndruiwe, die sap- en ook wynkwaliteit homogeen sal wees regdeur `n wingerdblok is egter meer kommerwekkend. Na aanvang van dié denke is daar `n studie geloods om die interaksie tussen wingerdstokgroeikrag en wingerdstokwaterstatus te evalueer. Met die studie is verskeie besproeiingsregimes aangebring binne `n kommersiële wingerd wat interne groeikragvariasie tentoonstel. Groeikragvariasie was geïdentifiseer deur middel van multispektrale lugfotos terwyl die wingerdstok se waterstatus geëvalueer is met behulp van plantgebaseerde metings in die verskillende groeikragareas. Die waterstatus van die grond is geëvalueer tesame met die vegetatiewe groei van die wingerd sodat die groeikragvariasie en die invloed van die plantwaterstatus op die groeikrag bepaal kon word. Die reproduktiewe groei is deurlopend gemonitor voor die effek van wingerdstokwaterstatus en wingerdstokgroeikrag op druifsamestelling en wynkwaliteit bepaal is. Daar was `n goeie ooreenkoms tussen die verskeie metodes wat gebruik is om wingerdgroeikrag te bepaal. Snoeimassa aan die einde van die seisoen was ooreenkomstig met die blaaroppervakte (hooflootblare en sylootblare) wat tydens vegetatiewe groei gemeet is, en het ook goed korreleer, met die multispektrale lugfotos se hoof groeikragklassifikasie. Korrelgewig en -volume het reageer op die verskeie besproeiingsregimes, en daar was `n toename in korrelgewig en -volume saam met die afname in watertekort van een regime tot `n ander. Daar was beduidende verskille tussen die verskeie klassifikasies t.o.v. korrelsamestelling analise en wynevaluasie. Die suikerinhoud per korrel, totale fenole, totale rooi pigment, appelsuur, stikstof en pH het verskil in druiwesap analises. Die pH en suur van die wyne het ook beduidend verskil.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Because of long-term climate changes, apparently associated with higher temperatures and fewer rainfall events, factors such as water-use efficiency and site selection for new cultivars are a matter of increasing importance for viticulture. Within this context, the root system is expected to play a key role. Its relevance to grapevine functioning is due to the numerous functions in which it is involved. In the light of this, the development of the root system is highly relevant to the viticulturist because of the fact that grapevine growth and functioning are dependent on the development of the root system. Differences can, therefore, be expected in terms of berry ripening on single grapevines of the same scion for situations with differing development of root systems, despite being grafted on the same rootstock. Root growth is influenced by several factors, among the ecological aspects. Soil parameters have a predominant influence on root growth and distribution but also annual root production can be altered by canopy manipulation. Due to the importance of root growth to the aboveground development of the vine, it is critical to gain understanding of the relationship between soil factors and root growth and distribution, and the central role that the subterranean environment plays in the concept of terroir. This study aimed to investigate the effect of selected soil physical and chemical parameters on root growth and distribution and to investigate whether having very different canopies influences root growth. In order to achieve these goals, two experiments were conducted; the first was performed in two commercial Sauvignon blanc vineyards each grafted onto Richter 110, non-irrigated, with two treatments: undisturbed lateral growth and complete lateral removal. The second study included the analysis of eight commercial Sauvignon blanc vineyards grafted onto Richter 99 and Richter 110 located in the Stellenbosch Wine of Origin District. Measurements of physical and chemical soil parameters, root growth and distribution, canopy growth and functioning, vine water status and berry composition were performed. The edaphic factors appeared to be one of the most important parameters that affected root development by changing soil water availability and possibly causing physical or chemical limitations on root growth. From the results of this study, it is clear that severe water stress and a pH (KCl) lower than 4.5 play a key role in the limitation of root growth. Due to the fact that most of the soils from the Stellenbosch Wine of Origin District, especially the subsoils, are acidic, this is a factor to consider before planting. On the other hand, the combination of favourable edaphic conditions, such as a subsoil pH of higher than 5.0, light- to mediumtextured subsoil and moderate water stress, allow increased growth of thin roots. However, the effect of canopy management on root growth cannot be discounted due to its importance in the variation of carbohydrate demand by competing sinks. This study showed that lateral removal done from when the berries are at pea size results in an increase in the number of thin roots (0.5-2.0 mm). The secondary leaf area represents at least the same leaf area as the primary leaf area in all the vineyards evaluated, which reveals the relative importance of the laterals in the total leaf area of the vine and the potential importance in terms of microclimate and leaf area available for photosynthesis. Studies of root growth should take the vineyard canopy architecture into account. / AFRIKAANSE OPSOMMING: As gevolg van langtermyn klimaatsveranderinge wat toegeskryf kan word aan die voorkoms van hoër temperature en laer reënval, is faktore soos effektiwiteit van waterverbruik en liggingseleksie vir nuwe kultivars van kardinale belang vir wingerdkunde. Binne hierdie konteks, speel die wortelsisteem ‘n belangrike rol. Die belangrikheid hiervan vir wingerdfunksionering kan toegeskryf word aan die talle funksies waarby dit betrokke is. Die ontwikkeling van die wortelsisteem is dus hoogs relevant vir die wingerdkundige, omdat wingerdgroei en funksionering afhanklik is van die ontwikkeling van die wortelsisteem. Verskille kan daarom dus verwag word in terme van korrelrypwording op ‘n enkele wingerdstok van dieselfde onderstok vir gevalle met verskillende ontwikkeling van die wortelsisteem, ten spyte daarvan dat dit op dieselfde onderstok geënt is. Wortelgroei word, onder ekologiese aspekte, deur verskillende faktore beïnvloed. Grondfaktore het meerendeels ‘n predominante invloed op wortelgroei en -verspreiding, terwyl jaarlikse wortelproduksie deur lowermanipulasie beïnvloed kan word. Weens die belangrikheid van wortelgroei vir die bogrondse ontwikkeling van die wingerd, is dit krities om kennis op te doen oor die verhouding tussen grondfaktore en wortelgroei en –verspreiding, asook die sentrale rol wat die subterreinomgewing op die terroir-konsep speel. Die studie was daarop gemik om die invloed van geselekteerde fisiese en chemiese parameters van grond op wortelgroei en -verspreiding vas te stel, en ook te ondersoek of verskillende lowers wortelgroei sal beïnvloed. Om laasgenoemde doelwitte te bereik, is twee eksperimente uitgevoer. Die eerste is uitgevoer in ‘n kommersïele Sauvignon blanc-wingerd wat geënt is op Richter 110, sonder besproeïng en met twee behandelings, naamlik onversteurde sêkondere lootgroei en volledige sêkondere lootverwydering. Die tweede studie het die analise van agt kommersïele Sauvignon blancwingerde geënt op Richter 99 en Richter 110 in die Stellenbosch Wyn van Oorsprong Distrik. Metings van fisiese en chemiese grondfaktore, wortelgroei en -verspreiding, lowergroei en -funksionering, plantwaterstatus en korrelsamestelling is uitgevoer. Dit blyk dat edafiese faktore een van die belangrikste parameters is wat wortelontwikkeling beïnvloed deur beskikbaarheid van grondwater te verander, en wat moontlik fisiese en chemiese beperkings op wortelgroei kan veroorsaak. Uit die resultate van die studie is dit duidelik dat intense waterspanning en ‘n pH (KCl) laer as 4.5 ‘n belangrike rol in die beperking van wortelgroei speel. Aangesien die meeste van die grondsoorte in die Stellenbosch Wyn van Oorsprong Distrik, veral al die subgronde, suur is, is dit ‘n faktor wat in oorweging geneem moet word voor aanplantings. Die kombinasie van gunstige edafiese toestande, soos ‘n subgrond met ‘n pH hoër as 5.0, ‘n lig tot medium tekstuur en matige waterspanning, sal dus aanleiding gee tot ‘n toename in die groei van dun wortels. Die effek van lowerbestuur op wortelgroei kan egter nie buite rekening gelaat word nie weens die belangrikheid daarvan in die variasie van koolhidraataanvraag deur kompeterende vraagpunte. Hierdie studie toon dat, indien sêkondere lootverwydering tydens ertjiekorrelgrootte toegepas is, dit aanleiding gee tot ‘n toename in die dun wortels (0.5 tot 2.0 mm). Die sêkondere blaaroppervlakte verteenwoordig minstens dieselfde blaaroppervlakte as die primêre blaaroppervlakte in al die wingerde wat ondersoek is, wat dui op die belangrikheid van sêkondere lote in die totale blaaroppervlakte van die wingerd en die potensiële belangrikheid daarvan in terme van mikroklimaat en blaaroppervlakte wat vir fotosintese beskikbaar is. Studies van wortelgroei moet lowerargitektuur in ag neem.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: One of the most striking qualities of wine is its tart, sour taste. The sensory perception of sourness is mainly attributed to the presence of hydrogen ions (protons) at high concentrations. Large amounts of weak carboxylic acids (organic acids) are the main sources of these ions within wine. Once wine enters a person's mouth, the dissociable protons of the weak organic acids within wine are partially neutralized or, in other words, titrated by the saliva secreted inside one's mouth. This explains why the duration and intensity of a wine's sourness is related to its titratable acidity content. The sour taste of wine is usually considered refreshing and it helps balance wine flavour. In fact, wines become watery when its titratable acidity content is too low. After alcoholic fermentation, the titratable acidity of wine will usually be less than that of the grape juice from which was made due to ethanol-induced precipitation of potassium bitartrate crystals and partial consumption of malic acid by fermenting wine yeasts. Occasionally however, increases in titratable acidity are observed during alcoholic fermentation. If wine is produced from grape juice with optimum levels of titratable acidity, unforeseen increases in titratable acidity during alcoholic fermentation can be detrimental to the quality of the final product. Although the net production of malic acid by wine yeasts contributes to increases in titratable acidity seen during grape juice fermentations, the production of succinic acid is regarded as the primary contributor. In fact, succinic acid accounts for approximately 90% of the non-volatile acids produced during fermentation of grape juice. Between 0.5 and 1.5 g/L succinic acid is normally found in wine, but higher concentrations thereof (up to 3.0 g/L) have been detected within certain red wines. Acidity adjustments should preferably be carried out before the onset of alcoholic fermentation to allow better integration of the added compound(s) and to ensure that conditions during fermentation favour the quality and microbial stability of the final product. In doing so unfortunately, winemakers run the risk of ending up with wines that may taste too sour if they are unable to accurately predict and take into consideration the amount of succinic acid produced during alcoholic fermentation. Knowledge with regard to the factors involved in succinic acid's production by fermenting wine yeasts is therefore required in order to manage the titratable acidity of wines more accurately. Ever since Louis Pasteur first noticed succinic acid amongst the by-products of alcoholic fermentation, attempts have been made to determine the metabolic pathways and factors involved in its production by fermenting wine yeasts. Up until now however, it remains unclear why wines sometimes end up with exceptionally high levels of succinic acid. For these reasons it was decided to investigate the possible causes of very high succinic acid concentrations within wine. Due to complexity of grape juice's chemical composition and the problems associated with sterilizing grape juice, fermentation experiments were conducted within a chemically defined grape juice-like medium. Succinic acid production by nine different industrial wine yeast strains was studied under various conditions with regard to the nutrient status of the synthetic grape juice, temperature and availability of molecular oxygen during alcoholic fermentation. The amount of succinic acid produced during alcoholic fermentation was found to depend on the yeast strain, fermentation temperature and chemical composition of the synthetic grape juice. Out of the nine commercial yeast strains selected for this study, strain WE372 produced the largest amount of succinic acid in synthetic grape juice at 28°C. Strain WE372 produced significantly smaller amounts of acetic acid than the other yeast strains of this study and very little acetic acid at 28°C, which indicated that strain WE372 may have less acetaldehyde dehydroganase activity than the other yeast strains of this study under the conditions tested. The effect this has on NAD: NADH balance is the probable cause for its ability to form more glycerol, succinic and malic acid than the other strains. Results from our study show that succinic acid production is influenced primarily by the metabolizable fraction of YAN, which we termed metabolically available nitrogen (MAN). Succinic acid production by fermenting yeasts will be favoured by moderate to high fermentation temperatures (20°C to 28°C) in grape juice with a nicotinic acid and/ or nicotinamide deficiency, high sugar content (200 g/L to 240 g/L), moderate amounts of metabolically available nitrogen (300 ± 50 mg/L MAN), the presence of flavonoids and large supplies of unsaturated long-chain fatty acids. Even higher concentrations of succinic acid were produced when oxygen was made available to fermenting yeasts by aerating the fermenting grape juice. Fermentation temperatures below 18°C, too much metabolizable nitrogen (> 450 mg/L MAN), very high concentrations of fermentable sugar (> 240 g/L), lipid deficiencies and a lack of pantothenic acid, thiamine, biotin or pyridoxine will decrease the amount of succinic acid produced fermenting yeasts. / No Afrikaans summary available.

Thesis (MScAgric (Viticulture and Oenology)--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: ‘Crimson Seedless’ is currently one of the most important and popular table grape cultivars produced in South Africa, and as such it is of great economic value for table grape producers. Major concerns with ‘Crimson Seedless’ is that it is prone to inadequate colouring, and with increased yields the berry size decreases. An additional difficulty is that methods used to increase berry size, further impede berry colouring. A plant growth regulator (PGR) commonly used in table grape production, to enhance colour formation, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In recent years significant research has been done on the effect of sunlight on anthocyanin production in grapes, although this has primarily been on wine grape cultivars. Currently, there is limited knowledge on the effect of sunlight on table grapes, and how this might influence their anthocyanin composition and content. The effect of ethephon on colour of grapes and other fruit have been extensively researched and well documented. However, the effect of ethephon on the anthocyanin composition of ‘Crimson Seedless’ is not well known. The current study aimed to explore the effect of sunlight (by matter of exclusion) and management practices, namely defoliation and ethephon application, on the anthocyanin profile and content of ‘Crimson Seedless’. Four different treatments were applied to two ‘Crimson Seedless’ vineyards, the first site located in Paarl, and the second in De Doorns. The treatments were: 1. Naturally exposed bunches, 2. Exposed bunches treated with ethephon, 3. Bunches kept in shade boxes, 4. Shaded bunches treated with ethephon. At the De Doorns site an additional defoliation treatment was superimposed over the above treatments. An HPLC technique was modified for the separation and detailed profiling of ‘Crimson Seedless’ anthocyanins and was used to analyse the effect of the reported treatments on the anthocyanin profile of berry skins. The predominant anthocyanin in ‘Crimson Seedless’ is peonidin-3-glucoside (Pn-gluc), and this was found to be significantly increased only by ethephon application, and was not altered by sunlight or leaf removal. The responses of the other anthocyanin types varied according to the respective treatments applied. However, a general observation was that ethephon application more consistently increased the concentration of anthocyanins in berry skins than did sunlight. Leaf removal had the least significant effect on anthocyanin concentration. / AFRIKAANSE OPSOMMIMG: ‘Crimson Seedless’ is tans een van die belangrikste en gewildste tafeldruif cultivars wat in Suid-Afrika verbou word en daarom is dit van groot ekonomiese waarde vir tafeldruifprodusente. ‘Crimson Seedless’ is egter daarvoor bekend dat dit te swak kleur (volgens uitvoer spesifikasies) en tweedens is die cultivar geneig om kleiner korrels te ontwikkel wanneer die oeslading vermeerder word. ‘n Addisionele probleem is dat die praktyke wat in die industrie gebruik word om korrels te vergroot ‘n verdere negatiewe impak op ‘Crimson Seedless’ se kleur ontwikkeling kan veroorsaak. Die plant-groei-reguleerder wat algemeen in tafeldruif verbouing gebruik word, ten einde beter gekleurde druiwe te produseer, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In die laaste paar jaar was daar baie navorsing gedoen oor die effek wat sonlig het op die antosianien produksie van druiwe, maar navorsing was gefokus op wyndruif cultivars. Huidiglik is daar beperkte tegniese kennis oor die effek wat sonlig op tafeldruiwe het, en hoe dit moontlik die antosianien samestelling en inhoud kan beïnvloed. Daar is ook reeds verskeie studies gedoen en data gepubliseer oor die invloed wat ethephon op die kleur het van druiwe en ander vrugte, maar die invloed wat ethephon op die antosianien samestelling van ‘Crimson Seedless’ het, is nie wel bekend nie. Die doel van hierdie studie was om die effek van sonlig (deur uitsluiting) en bestuurspraktyke (blaarverwydering en ethephon toediening) te bestudeer en hoe dit die antosianien samestelling van ‘Crimson Seedless’ beïnvloed. Vier verskillende behandelings is toegedien in twee ‘Crimson Seedless’ wingerde, die eerste proefperseel in die Paarl en die tweede proefperseel in De Doorns. Die behandelings was: 1. Natuurlik blootgestelde trosse, 2. blootgestelde trosse met ethephon, 3. Trosse met skadubokse omhul, 4. Skaduboks trosse met ethephon. By De Doorns is ‘n addisionele blaarverwydering proef bygebring. ‘n HPLC tegniek was aangepas om die antosianien samestelling en inhoud van ‘Crimson Seedless’ te bepaal, en om die effek van die behandelings te ondersoek. Die HPLC data het getoon dat peonodien-3-glukosied (Pn-gluc) die primêre antosianien in ‘Crimson Seedless’ is met die hoogste inhoud van al die antosianiene. Pn-gluc was betekenisvol beïnvloed deur ethephon toediening, terwyl die ander behandelings geen betekenisvolle effekte daarop gehad het nie. Die effekte wat die ander antosianiene gehad het, het gevarieer volgens die behandelings wat toegedien was. ‘n Algemene observasie was dat ethephon toediening die antosianien konsentrasie in ‘Crimson Seedless’ druiwe skille meer konsekwent vermeerder het as die sonlig blootstelling. Die blaarverwydering het die minste betekenisvolle effek op die antosianien inhoud van ‘Crimson Seedless’ gehad.

Thesis (MSc Agric.)--Stellenbosch University, 1987. / NO Abstract Available

Thesis (PhD(Agric))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Exogenous fibrolytic enzymes (EFE) as additives in ruminant feeds are being researched worldwide. Promising effects on dry matter intake (DMI), digestibility and production in especially dairy cows, but also feedlot steers and even sheep have been observed. However, lack of or negative effects are also reported and the need arises for clarity on the mode-of-action of EFE. Forages are characterised as being highly heterogenic and contain varying concentrations of fibre. The fibre, in turn, varies greatly in digestibility, due to the chemical as well as anatomical build-up of this complex carbohydrate. Fibre, however, presents a major source of potential energy for ruminant animals and EFE is a viable option to increase the digestibility of forages. Therefore, a study with the aim of establishing whether EFE can affect the digestibility of forages, how it affects the digestibility and the clarification of the mode-of-action was drafted. From the literature, the first objective was readily attained and clear indications exist that EFE can indeed improve animal performance when their diets are treated with such enzymes. From the current study, it was shown that EFE can alter the rate and extent of gas production of certain forages (lucerne, kikuyu and weeping love grass) and also improve the in vitro digestibility thereof (P < 0.05). This is in agreement with other research findings and it was concluded that these effects were likely exerted during the early stages of digestion. A complete feed for sheep, when treated with the EFE, showed positive effects on the in sacco digestibility, as well as on the digestion kinetics of the feed (P < 0.05). The in vitro digestibility of the complete feed was also improved due to EFE treatment (P < 0.05). The observations on in vitro digestibility were less marked when a purified xylanase, obtained from the partial purification of the EFE cocktail, was used as the sole fibrolytic enzyme treatment. It is apparent, therefore, that enzyme specificity plays a major role in obtaining positive effects on digestibility of forages and feeds. In agreement with the literature, it is proposed that the approach to improve the digestibility of forages should be to use EFE cocktails containing various enzymes, matching the complexity of the substrate. The major aim of the study was, however, an in depth investigation of the mode-of-action of EFE. This aim was approached by observing changes in plant tissue material at the histological level upon treatment with EFE and incubation in buffered rumen fluid. Results showed that EFE had subtle, yet significant effects on cell wall material for the various tissues studied (P < 0.05). The major effect observed here was that EFE had a thinning effect on the cell wall thickness (P < 0.05). It was deduced that as EFE affected the cell wall of the plant material, earlier access by microorganisms could be achieved. Also, nutrients caught in the cell wall matrix could then be released for digestion. Therefore, observations that EFE increases the rate of digestion, as well as the extent of digestion of not only fibre, but also protein, were explained by the enzyme’s action on cell wall material. It was concluded that there is definite merit in the use of EFE to improve the digestibility of ruminant feeds and that this is partly related to effects on the cell walls of the forages. The effects can be expected to occur during the early stages of digestion, thereby potentially increasing the passage rate of digesta from the rumen. Additionally, the effect of the EFE is not limited to fibre and increased digestibility of all nutrients can be expected, thereby increasing the overall digestibility of the feed. Future research should further elucidate the mode-of-action of EFE using advanced technologies routinely employed in the plant sciences. Additionally, the main potential advantage of EFE treatment lies in improving the digestibility of poor quality roughages. Unfortunately, this is an area where limited positive effects are observed and in depth investigations should be undertaken to classify the specificity and optimum conditions of EFE to better match the complexity of the substrate being treated. / AFRIKAANSE OPSOMMING: Eksogene fibrolitiese ensieme (EFE) word tans wêreldwyd ondersoek vir die gebruik daarvan as voerbymiddels vir herkouers. Belowende effekte op DMI, verteerbaarheid en produksie van vernaam melkbeeste, maar ook voerkraalbeeste en selfs skape is al gerapporteer. Swak en selfs negatiewe effekte word egter ook waargeneem en daarom is ʼn deeglike ondersoek na die metode van werking van EFE van belang. Ruvoere word gekenmerk deurdat dit heterogeen van aard is en bevat variërende vlakke van vesel. Vesel maak op sy beurt ʼn wesenlike deel uit van die ruvoer, maar varieer baie in verteerbaarheid weens die chemiese sowel as anatomiese samestelling van hierdie komplekse koolhidraat. Ruvoer verteenwoordig egter ʼn goeie bron van potensiële energie vir herkouers en EFE word voorgestel as ʼn haalbare behandeling om die verteerbaarheid daarvan te verhoog. Dus is ʼn studie beplan met die doelwit om die effekte van EFE te definieer, hoe dit verteerbaarheid beïnvloed en die metode van werking daarvan te ondersoek. Vanuit die literatuur is dit duidelik dat daar wel baie positiewe effekte is waar ruvoere met EFE behandel is en dat diereproduksie wel bevoordeel word daardeur. Vanuit die studie is dit getoon dat die tempo en hoeveelheid gasproduksie van sekere ruvoere (lusern, kikuyu en oulandsgras) verbeter word deur EFE behandeling (P < 0.05). Hierdie bevinding was ondersteun deur verbeterde in vitro verteerbaarheid van die ruvoere (P < 0.05). Dit is in ooreenstemming met literatuur en die gevolgtrekking is gemaak dat hierdie effekte tydens die vroeëre stadia van vertering verwag kan word. ʼn Volledige skaapvoer wat met EFE behandel is, het positiewe effekte op in sacco verteerbaarheid en verterings kinetika data gehad (P < 0.05). Weereens is die in vitro verteerbaarheid van die voer verbeter (P < 0.05). Waarnemings op in vitro verteerbaarheid was veel minder opvallend wanneer ʼn gesuiwerde xylanase as enigste fibrolitiese ensiem behandeling gebruik is. Dit is dus duidelik dat ensiem spesifisiteit ʼn belangrike rol speel in die verkryging van positiewe resultate in die verteerbaarheid van ruvoere en veevoere. In ooreenstemming met literatuur word dit voorgestel dat ensiemmengsels wat verskeie ensieme bevat as EFE gebruik behoort te word ten einde aan die kompleksiteit van die substraat te voldoen. Die hoof doelwit van die studie was egter ʼn indiepte ondersoek na die metode van werking van EFE. Hierdie doelwit is benader deur die effekte van EFE op selwand strukture van plantmateriaal op ʼn histologiese vlak te ondersoek. Die ruvoere was vooraf met EFE behandel en in vitro geïnkubeer in rumen vloeistof. Die resultate het getoon dat EFE ʼn matige, dog betekenisvolle effek op die selwand materiaal van die onderskeie weefsels gehad het (P < 0.05). Die belangrikste waargeneemde effek was dat EFE ʼn verdunningseffek op die selwande gehad het. Dit is afgelei dat as EFE die selwand kan beïnvloed, mikro-organismes vroeër toegang tot die inhoud kan kry. Verder, nutriënte vasgevang in die selwand matriks raak ook beskikbaar vir vertering. Hierdie afleiding en die effek van EFE op selwande verklaar waarnemings dat EFE die tempo van vertering sowel as die vlak van vertering van nie net vesel, maar ook proteïen kan bevoordeel. Die gevolgtrekking is gemaak dat daar definitiewe meriete is in die gebruik van EFE om die verteerbaarheid van herkouervoere te verbeter en dat dit verband hou met die ensiem se werking op selwande van die ruvoere. Die effekte kan verwag word tydens die vroeë stadia van vertering om dus deurvloeitempo van digesta te verbeter. Die effek van die EFE is verder nie beperk tot vesel nie, maar positiewe effekte op ander nutriënte kan verwag word en vervolgens ʼn algehele verhoging in die verteerbaarheid van die voer. Navorsing behoort in die toekoms verder die metode van werking van EFE te ondersoek deur gebruik te maak van gevorderde tegnologie wat alledaags gebruik word in die Plantwetenskappe. Die belowendste aanwending van EFE lê in die verbetering in vertering van swak kwaliteit ruvoere. Dit is ongelukkig juis hier waar min positiewe resultate gerapporteer word en indiepte navorsing moet onderneem word om ensiem spesifisiteit en optimum kondisies te definieer sodat EFE beter opgewasse is teen die kompleksiteit van die substraat.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Aquaculture has proven to be a viable operation in multi-used irrigation reservoirs (also referred to as farm dams) in the Western Cape province (WCP) of South Africa. Many studies found that the fitness-for-use of these reservoirs for both net cage culture of fish and irrigation of crops is feasible. However, practising intensive fish farming in existing open water bodies can increase the nutrient levels of the water through organic loading, originating from uneaten feeds and fish metabolic wastes. Under such conditions the primary (irrigation) and secondary (drinking water and recreation) usage of the dam could be compromised by deteriorating water quality. Rainbow trout (Oncorhynchus mykiss) farming is done in Mediterranean climatic conditions of the WCP. This type of climate presents short production seasons with fluctuating water quality and quantity. The study investigated the dynamics of water physico-chemical parameters and assessed the long term impact of rainbow trout farming on irrigation reservoirs. Furthermore, associated land-use in the catchment of such integrated aqua-agriculture systems is described, and mitigation to minimise the impact of fish farming evaluated. The investigation concluded with assessing the contribution of aquaculture to rural and peri-urban communities. The aim is to present an integrated, socio-ecologically balanced farming system for irrigation reservoirs with associated aquaculture activities. A total of 35 reservoirs, including both fish farming and non-fish farming ones, were selected as research sites. They were located in three geographical regions namely, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) and Breede River (Ceres/Worcester). Reservoirs were <20 ha in surface area and the volume ranges from 300 000 to 1 500 000 m3. Water samples were collected monthly and seasonally for the different investigations and analysed for a range of water quality parameters, including: transparency (Secchi disc), temperature, dissolved oxygen (DO), pH, sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), chloride (Cl), carbonate (CO3), bicarbonate (HCO3), manganese (Mn), copper (Cu), zinc (Zn), boron (B), total phosphorous (TP), orthophosphate (PO4), total ammonia nitrogen (TAN), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), aluminium (Al), total suspended solids (TSS), total dissolved solids (TDS), alkalinity, hardness and sulphate. Phytoplankton samples were also collected, genera identified and biomass calculated. The water quality data were analysed in terms of surface and bottom strata in both fish farming and non-fish farming reservoirs based on repeated measurements at the same site location at different times using the procedure General Linear Models of Stastical Analysis System (SAS, 2012). Values p<0.05 were considered as statistically significant. A Principal Component Analysis (PCA) biplot was used to graphically depict all the sites and measured water quality variables with the purpose of trying to see whether the fish farming and non-fish farming ones showed any groupings and how the sites were related to the measured variables. Structured questionnaires and informal discussions were used to collect additional information on the water use, production data and socio-economic effects on fish farmers. Categorical data gathered from the interviews (21 aquaculture projects) were analysed for frequency of occurrence using the Statistical Product and Service Solutions (SPSS) computer programme (SPSS Systems for Windows, Version 12.0). Results are presented in publication form with research chapters focusing on the subject areas of water quality impact, catchment land-use, potential mitigation measures and aquaculture contribution. Results for the water quality analyses indicated that as a collective, the farm reservoirs’ overall minimum, mean and maximum values for the physico-chemical parameters were fit-for-use for trout farming. The depth of the reservoirs ranged from 1.2 - 21.6 m with the low value taken during the summer season. Values lower than 5.0 m can cause management problems for floating cages that require a minimum of 4.0 m for net suspension and 1.0 m of free space below for adequate lateral flow. The Secchi disc reading of the reservoirs ranged from 10 – 510 cm. Higher transparencies were recorded after the winter rains when sand, silt and clay settled. Trout feeding is dependent on visibility and transparencies of more than 50 cm are required for good feeding conditions. The dissolved oxygen (DO) ranged from 0.3 – 16.4 mg/L with values below 5.00 mg/L recorded during summer when extraction and temperatures were high and provided conditions unable to sustain trout farming. The situation reverses with the onset of winter when the dams fill and DO rises above 5.00 mg/L as required for trout farming. The phosphorous (P) levels ranged from 0.001 – 0.735 mg/L. Higher concentrations were recorded during the winter turnover phase when bottom and surface waters mixed. Concentration above 0.01 mg/L can cause eutrophication of the water bodies. Total ammonia nitrogen (TAN) ranged from 0.015 - 6.480 mg/L. Higher concentrations were recorded during summer when temperatures were high and depths were low. TAN can be toxic to fish when the pH and temperature are high. The generally low least square means (LSM) for TAN were indicative of minor environmental impact of trout farming operations conducted during the colder, winter rainfall months. Trout farming coincided with conditions where the water temperatures were low, dam levels were high and dams were overflowing. The difference in bottom and surface water quality of reservoirs and the site location were found to be more important than the absence or presence of fish farming. The difference in bottom and surface water is directly linked to the ecological status of the sediment, which serve as nutrient sinks. In monomictic dams found in Mediterranean areas, mixing occurs during the winter turnover phase. Nutrients are released due to surface and bottom water mixing, brought about by torrential rains and wind turbulence. The concentration of organic material in the sediment and bottom waters is a function of the nutrient loading over time, irrespective whether the non-point sources were fish farming or agricultural activities and therefore it is difficult to partition causes and effects. In cases where reservoirs were already eutrophic due to past agricultural practices, implementing aquaculture could exacerbate the poor water quality status of the reservoir. There was a statistically significant difference between fish farming and non-fish farming for phosphorous, Secchi disc, total suspended solids and nitrite-nitrogen (p<0.05) and no statistically significant difference between fish farming and non-fish farming for dissolved oxygen, total ammonia nitrogen and nitrate-nitrogen (p>0.05). There was a statistically significant difference between surface and bottom waters for P and TAN (p<0.05). One reason for higher P and TAN concentrations in bottom waters is the accumulation of both in the sediment and subsequent release in the water column when the water mixes. A two-dimensional scatter plot was generated using the score for the first two principal components. The first two principal components accounts for 40 and 17 % of the total variance respectively, and the two groups of fish farming and non-fish farming did not separate well based on the first two principal components. The occurrence and distribution of phytoplankton biomass fluctuated with dam water levels and nutrient concentrations. The prevailing phytoplankton communities are important to fish farmers for two reasons: 1. It leads to fluctuations in dissolved oxygen concentrations via users (respiration and decomposition) and producers (photosynthesis). 2. It could lead to algal taint of fish flesh when geosmin-producing phytoplankton species are present. The frequency of occurrence indicated that the Group Chlorophyta (including genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, etc) had the most occurrences (n=371) with Chrysophyta (including genera, Dinobryon, Mallomonas, Synura, etc) the least (n=34). There was a statistically significant difference between genera occurrence and season (p<0.05). The geographical location of sites had no significance influence on the frequency of phytoplankton occurrence. There was no direct link between water quality and production yield (p>0.05). The fish yield of farms were linked mainly to the quality of fingerlings and the feed conversion ratio (FCR) achieved (p<0.05). Land-use patterns in the catchment where fish farming dams were located have shown that the dams are multiple-used systems. The ecological integrity of the farm dam ecosystem is dependent on the base volume. The dam is primarily for irrigation and fish farming can be compromised when higher demand for water is required during the dry season. The dams receive about 20 % of its water from rainfall and the rest from runoffs. Farmers could not provide accurate extraction rates making it difficult to predict water levels for future fish production. Four potential mitigation measures to reduce nutrient loading were described namely, feed management (quantity, frequency, type, etc.), feeding method (demand feeders, hand feeding), feed ingredients (formulation) and floating gardens. Both feed management procedures and demand feeders were evaluated as to the efficiency of reducing feed wastage and optimising FCR’s. The small-scale fish farmers were producing approximately 6 tons and had an average FCR of 1.96:1 ± 1.15. If farmers could improve their FCR’s by 0.1 (i.e. from 1.96 to 1.86), it would translate into a reduction of 100 kg feed for every ton of fish produced and result in 5% decrease in nutrient loading. The results of the water analysis and visual assessment of faecal length and colour showed no statistically significant difference between treatments for the guar-gum based binder (p>0.05). In addition, the level of binder did not influence digestibility of the experimental diets. The floating garden study indicated that it was feasible to construct a low cost raft system that is easy to manage and can produce plant crops as a hydroponic system in conjunction with fish farming cages. The lettuces grown on farm dam water provided support for the premise that the water quality can be improved via extraction of nutrients for crop production. For the production of 3.5 kg/m2 lettuce, a ratio of 1.09 plants/fish equal to 1.84 g feed/day/plant would reduce the accumulation of soluble nutrients around floating net cage farming system. The socio-economic evaluation of the contribution of fish farming to the welfare of rural and peri-urban farming communities supported the notion that aquaculture can lead to the upliftment of participating communities. Seventy-one percent (71%) of the respondents indicated that their motivation for exploring aquaculture is to supply fish to the wholesale market in order to generate income. Sixty-one percent (61%) of the respondents conducted the sales themselves or co-opted family members to assist them. The contribution of aquaculture provided direct benefits through improvement in household income, subsistence food supply and skills development. Indirect benefits included providing an information hub for other emerging farmers, elevation of the fish farmer’s status in the community through greater wealth and knowledge creation and promoting sector diversification through new products and technology. The three main constraints to the promotion and growth of aquaculture were listed as lack of government support, insufficient market intelligence and access, and limited choice in the availability of suitable candidate aquaculture species. Irrigation reservoirs in the WCP have a history of enrichment through external sources supplying water via agricultural runoff (fertilisers and pesticides), catchment runoff (leaf litter and organic debris) and stormwater effluent (grey and black water). The incorporation of aquaculture into such dams adds extra nutrients to the water column and management is crucial to limit the nutrient loading and ensure environmental sustainability. Such an approach will ensure that commercial land-based crop farmers’ irrigation regime and water distribution operations would not be negatively affected. Therefore future research needs should focus on; firstly the prevention and minimisation of pollution deriving from aquaculture through improved production management and technology transfer, secondly the monitoring and evaluation of the catchment ecosystem as a continuum with all the external factors affecting the ecology of farm dams and thirdly, evaluating the sediment processes and dynamics as sinks for nutrient accumulation. / AFRIKAANSE OPSOMMING: Akwakultuur het getoon dat dit ‘n lewensvatbare inisiatief is vir meerdoelige-gebruik van besproeiingsdamme (ook genoem plaasdamme) in die Wes-Kaap provinsie (WKP) van Suid-Afrika. Vele studies het bewys dat die geskiktheid-vir-gebruik van die reservoirs haalbaar is vir beide visproduksie sowel as besproeiing van landbougewasse. Nieteenstaande, die beoefening van intensiewe visboerdery in bestaande buitelug watersisteme kan lei tot ‘n toename in nutriëntvlakke van die water as gevolg van organiese belading afkomstig van ongevrete voere en metaboliese afvalstowwe van die vis. Onder sulke omstandigthede kan die primêre- (besproeiing) en die sekondêre (drinkwater en rekreasie) gebruik van die dam in gedrang kom weens ‘n afname in waterkwaliteit. Reënboogforel (Oncorhynchus mykiss) boerdery word beoefen in die omliggende Mediterreense klimaat van die WKP. Die tipe klimaat verskaf kort produksie-seisoene met wisselvallige water kwaliteit en kwantiteit. Die studie het die dinamika van water se fisies-chemiese parameters ondersoek en het die impak van forelboerdery op besproeiingdamme oor die langtermyn beskryf. Verder het die studie die geassosieerde landgebruik in die opvangsgebied met geïntegreerde akwa-landbou sisteme beskryf, asook moontlike toetrede (mitigasie maatreëls) geëvalueer wat die impak moontlik kan verlaag. Die ondersoek is afgesluit deur die bydrae wat akwakultuur lewer aan landelike en semi-stedelike gebiede, te beskryf. Die hoofdoel is die daarstelling van ‘n geïntegreerde, sosio-ekologiese gebalanseerde sisteem vir besproeiingdamme met gesamentlike akwakultuuraktiwiteite. ‘n Totaal van 35 besproeiingsdamme, insluitend die met visboerdery en nie-visboerdery, is gekies as navorsingspersele. Dit is hoofsaaklik geleë in drie geografiese gebiede naamlik, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) en Breederivier (Ceres/Worcester). Die reservoirs is almal < 20 ha in oppervlakarea en die volumes het gewissel van 300 000 – 1 500 000 m3. Watermonsters is maandeliks sowel as seisoenaal versamel vir die onderskeie ondersoeke en ontleed vir ‘n reeks van parameters, insluitend: sigbaarheid (Secchi disc), temperatuur, opgeloste suurstof (OS), pH, natrium (Na), kalium (K), kalsium (Ca), magnesium (Mg), yster (Fe), chloor (Cl), karbonaat (CO3), bikarbonaat (HCO3), mangaan (Mn), koper (Cu), sink (Zn), boor (B), totale fosfor (TP), ortofosfaat (PO4), totale ammoniak stikstof (TAN), nitraat-stikstof (NO3-N), nitriet-stikstof (NO2-N), aluminium (Al), totale gesuspendeerde vaste stowwe (TGV), totale opgeloste vaste stowwe (TOV), alkaliniteit, hardheid en sulfate. Phytoplanktonmonsters is ook versamel, genera geïdentifiseer en die biomassa bepaal. Die waterkwaliteitsdata is ontleed in terme van oppervlak- en bodemstrata vir beide visboerdery en nie-visboerdery reservoirs en was gebaseer op herhaalde metings by dieselfde perseel op verskillende tye deur gebruik te maak van die Algemene Liniêre Model van Statistiese Analitiese Sisteem (SAS, 2012). Waardes p<0.05 is oorweeg as statisties beduidend. ‘n Hoofkomponentanalise bi-stipping (HKA) is toegepas om die persele en veranderlikes grafies voor te stel en te bepaal of die visboerdery en nie-visboerdery s’n enige groeperinge vorm asook hoe die persele assosieer met die veranderlikes. Gestruktureerde vraelyste en informele besprekings is onderneem om inligting in te samel op watergebruik, produksie-data, en die sosio-ekonomiese invloed wat akwakultuur bied aan visboere. Kategoriese data wat deur die onderhoude (21 akwakultuurprojekte) ingesamel is, is ontleed vir die frekwensie van aanwesigheid deur die gebruik van Statistiese Produk en Dienste-oplossings (SPDO) rekenaarprogram (SPSS Systems for Windows, Version 12.0). Die resultate vir die verskeie ondersoeke is beskryf en saamgestel in publikasie-vorm met die navorsingshoofstukke wat gefokus het op die areas van waterkwaliteitsimpak, opvangsgebied landgebruik, toetrede-meganismes en die bydrae van akwakultuur. Die resultate vir die waterkwaliteitsanalises het getoon dat gesamentlik die reservoirs se oorhoofse minimum, gemiddelde en maksimum waardes vir die verskillende fisies-chemiese parameters geskik is vir forelboerdery. Die diepte van die reservoirs het gewissel van 1.2 - 21.6 m, met die laagste waarde aangeteken gedurende die somermaande. Waardes laer as 5.0 m kan bestuursprobleme vir drywende hokstelsels versoorsaak want ‘n minimum van tenminste 4.0 m vrye spasie onder die hokke word benodig vir voldoende laterale vloei. Die Secchi-skyf lesing (sigbaarheid) van die reservoirs het gewissel van 10 – 510 cm. Hoër sigbaarheidswaardes is aangeteken na winterreëns wanneer sand-, slik- en klei deeltjies uitgesak het. Forel voer op sig en sigbaarheid van > 50 cm word benodig om goeie voeding te handhaaf. Die OS het gewissel van 0.3 – 16.4 mg/L met waardes onder 5 mg/L aangeteken gedurende somer wanneer wateronttrekking en temperature hoog was. Dit het gelei tot ongunstige toestande vir forelboerdery. Die situasie swaai om met die begin van winter wanneer die damme vol reën en die OS bo 5 mg/L styg soos benodig vir forelboerdery. Die P-vlakke het gewissel van 0.001 – 0.735 mg/L. Hoër waardes is aangeteken gedurende die winteromkeerfase wanneer die bodem en oppervlak se water meng. Konsentrasies bo 0.01 mg/L kan tot eutrofikasie van watersisteme lei. TAS het gewissel van 0-015 – 6.480 mg/L. Hoër konsentrasies is aangeteken gedurende die somer wanneer temperature hoog is en damvlakke laag. By hoë pH’s en temperature kan TAS toksies wees vir vis. The algemene lae kleinste kwadaat gemiddelde (KKG) waarde vir TAS het getoon dat daar ‘n klein impak op die omgewing was wanneer forelboerdery bedryf word gedurende die koue, winter reënvalmaande. Forelboerdery val saam met omstandigthede wanneer die watertemperature laag is, damvlakke hoog en die reservoirs oorloop. Die verskil in die bodem- en oppervlak water in die besproeiingsdamme en die ligging van die perseel is vasgestel om meer belangrik te wees as die teenwoordigheid of afwesigheid van visboerdery. Die verskil in die bodem en oppervlak is toe te skryf aan die toestand van die sediment waar nutriënte kan opgaar. In monomiktiese damme soos gevind in Mediterreende areas, vind vermenging plaas gedurende die winteromkeerfase. Nutriënte word vrygestel a.g.v. die vermenging van die oppervlak en bodem se water wat dan veroorsaak word deur harde reën en windturbulensie. Die konsentrasie van organiese materiaal in die sediment en bodem water is ‘n funksie van die nutriëntlading met tyd, ongeag of dit afkomstig was vanaf visboerdery of landbou-aktiwiteite. Dit is dus moelik om die spesifieke oorsaak van besoedeling af te baken. In gevalle waar die reservoirs alreeds eutrofies is a.g.v. aangewese landbouaktiwiteite, kan die toestand van die waterbron vererger indien akwakultuur toegepas word. Daar is ‘n statistiese noemenswaardige verskil tussen visboerdery en nie-visboerdery vir P, Secchi-skyf, totale gesuspendeerde vaste stowwe en nitrite-stikstof (p<0.05), en geen statistiese noemenswaardige verskil tussen visboerdery en nie-visboerdery vir OS, TAS en nitraat-stikstof (p>0.05). Daar is ‘n statistiese noemenswaardige verskil tussen oppervlak- en bodem water vir P en TAS (p<0.05). Een moontlike rede vir hoër P en TAS konsentrasies in die bodemwater, is die akkumulasie van beide parameters in die sediment en gevolglike vrystelling in die waterkolom wanneer die water gemeng word. ‘n Twee dimensionele spreidingstipping is geprodueer deur die waardes te gebruik van die eerste twee hoofkomponente. Die eerste twee hoofkomponente dra by 40 % en 17 % van die totale variansie onderskeidelik, en die twee groepering van visboerdery en nie-visboerdery het nie duidelik getoon nie. Die voorkoms en verspreiding van phytoplankton biomassa het gewissel met die verandering in damvlakke en nutriëntkonsentrasies. Die aanwesige phytoplanktongemeenskappe is belangrik vir die visboer vir twee redes: 1. Dit kan wisselende OS-vlakke versoorsaak deur die verbruik (respirasie en dekomposisie) en produksie (fotosintese) daarvan. 2. Dit kan lei tot alge na-smake van vis wanneer geosmin-produserende phytoplankton spesies aanwesig is. The frekwensie van voorkoms het getoon dat die Groep Chlorophyta (insluitend die genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, ens.) die meeste voorkom (n=371), met Chrysophyta (insluitend die genera, Dinobryon, Mallomonas, Synura, ens.) die minste (n=34). Daar is ‘n statistiese noemenswaardige verskil tussen genera voorkoms en seisoen (p<0.05) vir phytoplankton. Die geografiese ligging van die perseel het geen noemenswaardige invloed op die frekwensie van phytoplankton voorkoms nie. Daar is geen statistiese noemenswaardige verbintenis tussen waterkwaliteit en visproduksieopbrengste nie (p>0.05). Die visopbrengste by plase is hofsaaklik afhangende van die kwaliteit van die vingerlinge en die voeromsettingsverhouding (VOV) wat bereik is (p<0.05). Die landgebruikspatrone in die opvangsgebied waar visboere gesetel is, het aangedui dat die besproeiingsdamme meeldoelige sisteme is. Die ekologiese integriteit van die plaasdam-ekosisteem is afhanklik van die basisvolume. Die dam is hoofsaaklik daar vir die besproeiing en visboerdery kan in gedrang kom wanneer daar ‘n hoër aanvraag vir water gedurende die droë seisoen is. Die damme het omtrent 20 % van die water vanaf reënval ontvang en die res van aflope. Boere kon nie akkurate inligting verskaf van waterontrekking nie wat dit moeilik gemaak het om te voorspel wat die beskikbare watervlakke in die toekoms sou wees vir visproduksie. Vier potensiële toetrede meganismes om die nutriëntlading te verminder, is beskryf naamlik voedingsbestuur, (kwantiteit, frekwensie, tipe, ens.) voermetodes (aanvraagvoeder, handvoeding), voerbestandele (formulasies) en drywende tuine. Beide voedingsbestuur prosedure en aanvraagvoeders is geëvalueer as ‘n metode om die voervermorsing te verminder en die VOV te verbeter. Die kleinskaalse visboere het ongeveer 6 ton produseer met ‘n gemiddelde VOV van 1.96:1 ± 1.15. Indien die visboere hul VOV’s met 0.1 kan verbeter (bv. van 1.96 tot 1.86), sal dit beteken dat daar ‘n vermindering van 100 kg voer bewerkstellig word vir elke ton vis geproduseer. Dit kan ook lei tot ‘n vermindering van 5 % in die nutriëntlading. Die resultate van die wateranalises en die visuele waarneming van faeceslengte en kleur het geen statistiese noemenswaardige verskil tussen die behandelinge vir die guar-gom binder getoon nie (p>0.05). Verder, die hoeveelheid van die binder het nie die vertering van die eksperimentele diëte beïnvloed nie. Die studie op die drywende tuine het getoon dat dit haalbaar is om ‘n lae-koste sisteem te bou wat maklik is om te bestuur en gewasse kan produseer soos in ‘n hidroponiese sisteem tesame met visproduserende hokstelsels. Die kropslaaie se groei het getoon dat die waterkwaliteit van besproeiingsdamme kan verbeter word deur die opname van nutriënte wanneer plante verbou word. Vir die produksie van 3.5 kg/m2 kropslaaie, sal ‘n verhouding van 1.09 plante/vis of 1.84 g voer/dag/plant die akkumulasie van opgeloste nutriënte rondom die hokstelsels verminder. Die sosio-ekonomiese evaluasie van die bydrae van visboerdery tot die welvaart van die landelike en semistedelike plaasgemeenskappe ondersteun die feit dat akwakultuur verbetering kan bewerkstellig, veral onder deelnemende gemeenskappe. Een-en sewentig persent (71 %) van die respondente het getoon dat hul oorweging vir die bedryf van akwakultuur is om vis te voorsien aan die grootmark en daarvolgens geld te maak. Een-en-sestig persent (61 %) van die respondente het aangedui dat hulself die vis verkoop of vir familie-lede vra om met die verkope te help. Die bydrae van akwakultuur het direkte voordele aan die deelmers voorsien deur ‘n verbetering in huishoudelike inkomste, voedselvoorsiening vir selfgebruik en die ontwikkeling van vaardigthede. Indirekte voordele sluit in dat die deelmers ‘n bron van inligting geword het vir opkomende boere, hul status in die gemeenskap het verbeter omdat hul kennis verbreed het en dit het verder gelei tot diversifisering in die sektor a.g.v. die skepping van nuwe produkte en tegnologie. Die drie hoof struikelblokke wat die groei en bevordering van akwakultuur belemmer is o.a., ‘n tekort aan staatsondersteuning, onvoldoende markinligting en toegang en ‘n beperkte keuse in spesies vir boerdery. Besproeiingsdamme in die WKP het ‘n geskiedenis van verryking deur eksterne bronne wat water voorsien vanaf landbou-afloop (bemestingstowwe en pesbestrydingsmiddels), opvangsgebied-afloop (blare en ander organiese debris) en stormwateruitlaat (gruis- en swart water). Die implementering van akwakultuur in sulke damme voeg addisionele nutriënte tot die waterkolom en bestuur is krities om die lading te verminder en te verseker dat omgewingsvolhoubaarheid behou word. Indien die regte praktyke en bestuur toegepas word, sal dit beteken dat die kommersiële boer se besproeiing en waterverspreiding nie negatief beïnvloed word nie. Vervolgens moet toekomstige navosingsbehoeftes fokus op eerstens, die voorkoming en vemindering van besoedeling afkomstig van akwakultuur deur verbeterde produksie-bestuur en tegnologie-oordrag, tweedens, die monitoring en evaluering van die opvangs-ekosisteem as ‘n kontinuum met al die eksterne faktore wat die ekologie van die plaasdam kan beïnvloed en laastens, die ondersoek en evaluering van die sediment se prosesse en dinamika as ‘n sisteem wat nutriënte ophoop.

Thesis (PhD(Agric))--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This study set out to determine (co)variance components for the important production, reproduction and conformation traits of a South African fine wool resource flock that was established at the request of the South African wool industry. A secondary aim was to assess progeny of these animals under pastoral conditions in areas where the production of fine wool is uncommon. The Cradock fine wool Merino stud was established in 1988 with ewes bought from producers with the finest clips in South Africa. Data collected from 1988 to 2010 were used to estimate the (co)variances for the genetic fine wool resource flock. The quantification of the interdependencies of fibre diameter (FD) with production, reproduction and subjective traits were the main objective of this study. It is evident from the results of this study that FD is a highly heritable (0.63 ± 0.03) trait, which can lead to marked genetic progress provided that there are adequate levels of phenotypic variation available during selection. Fibre diameter was unfavourably correlated with body weight (0.30 ± 0.05), clean fleece weight (0.24 ± 0.05) and reproduction (0.59 ± 0.18), which implies that selection for reduced FD can have a detrimental effect on all these traits. Despite these unfavourable genetic correlations genetic gain in the other economical important traits was achievable in the stud (-0.129 ± 0.033). These results were supported by the results obtained during the evaluation of progeny of this stud under pastoral conditions where the production and reproduction of the fine wool animals were comparable with medium wool animals. It can therefore be concluded that selection for reduced FD can be practiced without detrimental effects on the economically important traits and subsequently the profitability of the sheep enterprise, as long as breeders have a reasonable selection objective based on economic considerations. / AFRIKAANSE OPSOMMING: Hierdie studie het dit ten doel gehad om (ko)variansie komponente vir die belangrike produksie, reproduksie en subjektiewe eienskappe in 'n Suid-Afrikaanse fyn wol hulpbronkudde, wat gevestig is op versoek van die Suid-Afrikaanse wolbedryf te bepaal. 'n Sekondêre doel was om die nageslag van hierdie diere onder veldtoestande te evalueer in gebiede waar die produksie van fynwol ongewoon is. Die Cradock fynwol Merino stoet is in 1988 gestig met die aankoop van ooie van produsente met die fynste skeersels in Suid-Afrika. Data wat ingesamel is vanaf 1988 tot 2010 is gebruik in die bepaling van (ko)variansie komponente vir hierdie genetiese fynwolkudde. Die kwatifisering van die interafhanklikheid van veseldikte (VD) met produksie, reproduksie en subjektiewe eienskappe was die hoofdoel van die studie. Dit is duidelik uit die resultate van die studie dat VD `n hoogs oorerflike (0.63 ± 0.03) eienskap is, wat tot vinnige vordering in VD kan lei indien genoegsame fenotipiese variasie beskikbaar is tydens seleksie. Veseldikte is ongunstig gekorreleer met liggaamsgewig (0.30 ± 0.05), skoonvaggewig (0.24 ± 0.05) en reproduksie (0.59 ± 0.18), wat beteken dat seleksie vir ʼn verlaagde VD nadelige vordering in hierdie eienskappe tot gevolg kan hê. Ten spyte van hierdie ongunstige genetiese korrelasies was die genetiese vordering in die ekonomies belangrike eienskappe haalbaar in die kudde wat ondersoek is (- 0.129 ± 0.033). Die laasgenoemde resultate word ondersteun deur die bevindinge dat die nageslag van hierdie stoet se produksie en reproduksie ooreengestem het met medium wol diere onder veldtoestande. Die gevolgtrekking wat gemaak kan word uit die studie is dat VD verlaag kan word sonder nadelige gevolge in die ekonomies belangrike eienskappe, asook die van `n skaapboerdery onderneming. Om dit te vermag moet telers `n aanvaarbare benadering tot seleksie, gegrond op ekonomiese beginsels, volg.

Dissertation (PhD (Agric))--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: A breeding programme aimed at the genetic improvement of growth rate of rainbow trout was initiated in 1988 by the Department of Genetics, University of Stellenbosch, in collaboration with the local trout producer's organisations. The first phase of the breeding programme included the collection, evaluation and selection of the best available genetic material from 13 different genetic groups (nine local and four overseas) to make up two separate base populations as odd and even year-groups. This was done to establishment a base population with high genetic merit and variation at the onset of the breeding programme. Statistically significant and commercially valuable genetic differences in terms of weight and length gain were detected between the various hatchery groups. The next two generations of the breeding program included a series of single and double crosses in order to increase the levels of genetic variation in the base populations, and to investigate possible heterosis and specific and general combining ability among the crosses. Significant levels of heterosis (6.7% to 9.6%) and general combining ability was found for weight and length gain during consecutive growth stages. No evidence was found for specific combining ability among the crosses. The crossing of selected offspring from the original genetic groups followed by the application of intensive multi-stage selection for growth rate within progeny groups has led to the establishment of second and third generation parental populations with higher levels of genetic variation and improved individual genetic merit with regard to growth rate. The exploitation of non-additive genetic variation within the base populations through crossbreeding and heterosis during the early stages of the selection programme was delayed in favour of the utilization of additive genetic variance through a procedure of multi-stage selection that incorporated high intensities of selection within and between family groups. The estimation of genetic parameters during the fourth generation on the basis of a hierarchical half-sib family structure confirmed the presence of high levels of additive genetic variation within the respective populations/year-groups. High heritability values in the range of 0.40 to 0.53 were recorded for body weight and length at 150 days. Genetic correlations between the traits were also high, in the range of 0.74 to 0.82. The cumulative realized response of 50% in body length for the EVEN year-group after six generations of selection (8.3% per generation), and the 33% for the ODD year-group after five generations of selection (6.6% per generation) confirms the efficiency of the multi-stage selection procedure to exploit the available additive genetic variation for growth rate within the respective populations. The programme is still ongoing, entering its 7th generation in 2004 and is supplying about 50-60% of commercial material through direct supplies of broodstock, ova and fingerlings and indirect supplies via multiplier stations (commercial hatcheries). The programme was the first of its kind in relation to aquaculture species in the Southern African region, and has since initiated the introduction of programmes of genetic improvement in three other indigenous species, namely tilapia (Oreochromis mossambicus), African catfish (Clarias gariepinus) and abalone (Haliotis midae). / AFRIKAANSE OPSOMMING: ‘n Teelprogram gerig op die verbetering van groeitempo in reënboogforel is in 1988 ingestel onder toesig van die Departement Genetika aan die Universiteit van Stellenbosch, in sameweking met die plaaslike forelprodusenteverenigings. Die eerste fase van die teelprogram behels die versameling, evalasie en seleksie van die beste beskikbare genetiese materiaal vanuit, 13 verskillende genetiese groepe (nege plaaslike en vier van oorsee) om twee basispopulasies te ontwikkel in elk van die gelyke en ongelyke jaargange. Die doel daarvan was om ’n basispopulasie met hoë genetiese meriete en variasie te ontwikkel met die aanvang van die teelprogram gerig op genetiese verbetering, deur middel van seleksie. Statisties betekenisvolle en ekonomies belangrike genetiese verskille in massa- en lengtetoename is aangetref, tussen die onderskeie genetiese groepe. Die daaropvolgende twee generasies binne die teelprogram behels die uitvoering van ’n reeks enkel- en dubbelkruisings ten einde ’n verdere toename in genetiese variasie in die basispopulasies te bewerkstellig, sowel as om die voorkoms van heterose en algemene, sowel as spesifieke kombinerings-vermoë tussen die kruisings te bepaal. Betekenisvolle vlakke van heterose (6.7% tot 9.6%) sowel as algemene kombineringsvermoë, is aangetref ten opsigte van massa- en lengtetoename in opeenvolgende groeifases. Daar kon geen aanduiding van betekenisvolle, spesifieke kombineringsvermoë gevind word nie. Die kruising van geselekteerde nageslag vanuit die oorspronklike genetiese groepe, gevolg deur ‘n multi-fase seleksiemetode vir groeitempo binne nageslaggroepe, het bygedra tot die ontwikkeling van ‘n tweede en derde generasie broeipopulasie wat beskik oor hoër vlakke van genetiese variasie en verbeterde individuele meriete ten opsigte van groeitempo. Die benutting van nie-additatiewe genetiese variasie binne die basispopulasies deur middel van kruisteling en heterose tydens die vroee stadium van die teelprogram is uitgestel ten gunste van die benutting van additatiewe genetiese variasie deur middel van ‘n multi-fase seleksiemetode, wat berus het op die toepassing van hoë vlakke van seleksie-intensteit binne en tussen familiegroepe. Die beraming van genetiese parameters tydens die vierde generasie het die voorkoms van hoe vlakke van additatiewe variasie binne die onderskeie jaargroepe bevestig. Hoë oorerflikhede van 0.40 tot 0.53 is beraam vir ligaamsmassa en -lengte op die ouderdom van 150 dae. Genetiese korrelasies tussen die kenmerke was ook hoog met waardes van 0.74 tot 0.82. Die saamgestelde gerealiseerde seleksierespons van 50% vir liggaamslengte vir die “EVEN”-jaargroep na afloop van ses generasies van seleksie (8.3% per generasie) en die 33% van die “ODD”-jaargroep na afloop van vyf generasies van seleksie (6.6% per generasie) het die doeltreffendheid van die multi-fase seleksiemetode bevestig ten opsigte van die benutting van die additatiewe variasie vir groeitempo binne die onderskeie basispopulasies/jaargroepe. Die teelprogram duur steeds voort en sal die 7de generasie in 2004 bereik. Die program voorsien nagenoeg 50-60% van die kommersiele materiaal vanuit direkte voorsiening van teelmaterial, eiers en vingerlinge asook die indirekte voorsiening via kommersiële teelstasies. Die teelprogram was die eerste van sy soort met betrekking tot akwakultuurspesies in Suider Afrika en het bygedra tot die implimentering van programme van genetiese verbetering in drie inheemse spesies, naamlik die tilapia (Oreochromis mossambicus), die baber (Clarias gariepinus) en die perlemoen (Haliotis midae).

Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Plums with good taste, aroma and eating quality lead to repeat purchases and sustained demand. Taste includes non-volatile compounds, e.g. sugars and acids, and has been well researched to meet the consumers’ preferences. Plum aroma, however, has not enjoyed the same attention. Limited literature is available on the aroma of Japanese plums and none could be found on the effects of relatively long cold storage on the profiles. The main aim of this study is to investigate the changes in aroma compounds of Japanese plums throughout maturation and ripening and the effects of commercial cold storage regimes. Near infra-red (NIR) spectroscopy was also evaluated as a non-destructive method to determine plum quality parameters aimed at minimising sample variability. In Paper 1, NIR spectroscopy was used to develop prediction models for total soluble solid (TSS), total acidity (TA), sugar-to-acid ratio, firmness and weight in three cultivars (Pioneer, Laetitia and Angeleno) and a multi-cultivar model. Samples were collected for seven consecutive weeks and repeated over two seasons. TSS results showed excellent predictability (R2 = 0.817-0.955; RMSEP= 0.453-0.610 % Brix) but the TA models did not perform well. The sugar-to-acid ratio models had results comparable to that of TSS. Both the firmness and weight models had acceptable results. The models of ‘Pioneer’ and ‘Laetitia’ had a better predictability capacity than the ‘Angeleno’ model. Although the multi-cultivar models outperformed the single cultivar models on R2 values it had higher prediction errors. The robustness of all the TSS, TA and firmness models is high in terms of seasonality, range and cultivar. Papers 2 and 3, the main focus of the study, are concerned with the aroma profile dynamics of Japanese plums. HS-SPME was used in both papers to extract the aroma compounds followed by GC-TOFMS for separation and identification. In Paper 2, the aroma volatile compounds of three cultivars (Pioneer, Laetitia and Angeleno) were determined for a seven week period including samples from three maturity stages (immature, harvest and tree-ripe). A total of 35 compounds were identified of which ten were generic. Each cultivar had five unique compounds resulting in different aroma profiles for each of the maturity stages and distinct separation patterns using discriminant analysis. The study was extended in Paper 3 where the aroma volatile compounds of six cultivars (Pioneer, Sapphire, Laetitia, Songold, Larry Anne and Angeleno) and one plumcot (Flavor King) were determined at three functional stages (commercial harvest, tree-ripe fruit and cold stored fruit). A total of 62 compounds were identified and classified into three groups (‘unique’ (31), ‘generic’ (11) and ‘frequent’ (20)) based on their frequency of occurrence. The aroma profiles of ‘Larry Anne’ and ‘Flavor King’ are the most affected by cold storage conditions and ‘Pioneer’ appears to be the least affected. All the cultivars have significantly different aroma profiles at all three of the functional stages with ‘Sapphire’, ‘Larry Anne’ and ‘Flavor King’ showing the largest differences. ‘Flavor King’, a plumcot, presented a ripe aroma profile that was much diverged from that of the true plums. / AFRIKAANSE OPSOMMING: Pruime met ‘n goeie smaak, aroma en eetkwaliteit lei tot herhaalde verkope en volhoubare aanvraag. Smaak sluit die nie-vlugtige stowwe (suikers en sure) in en is goed nagevors om die verbruikersvoorkeure te bevredig. Pruim aroma het egter nie dieselfde aandag geniet nie. Daar is beperkte literatuur beskikbaar wat handel oor die aroma van Japanese pruime en geen kon gevind word oor die effekte van lang koelopberging op die aromaprofiele nie. Die hoof doel van hierdie studie is om die veranderinge in die aromatiese komponente van Japanese pruime te ondersoek tydens die volwassewording- en rypwordingsprosesse asook die effekte van kommersiele koelopberging. Naby infrarooi (NIR) spektroskopie is ook geevalueer as ‘n nie-destruktiewe manier om pruim kwaliteitsparameters te bepaal met die doel om monstervariasie te beperk. In Artikel 1 is NIR spektroskopie gebruik om voorspellingsmodelle vir totale oplosbare suikers (TOS), totale suur (TS), suiker-tot-suur verhouding, fermheid en gewig te bepaal in drie kultivars (Pioneer, Laetitia en Angeleno) asook ‘n multi-kultivar model. Monsters is vir sewe opeenvolgende weke versamel en herhaal oor twee seisoene. TOS resultate toon uitstekende voorspelbaarheid (R2 = 0.817-0.955; RMSEP= 0.453-0.610 % Brix) maar TS modelle het egter nie so goed gevaar nie. Die suiker-tot-suur verhoudingsmodelle se resultate was vergelykbaar met die van TOS. Beide die fermheid- en gewigsmodelle het aanvaarbare resultate opgelewer. Die modelle vir ‘Pioneer’ en ‘Laetitia’ het ‘n beter voorspelbaarheidskapasiteit getoon as die van ‘Angeleno’. Alhoewel die multi-kultivar model beter presteer het as die enkel kultivar modelle op die R2-waardes was daar meer voorspellingsfoute. Hoe robuustheid is gevind i.t.v. seisoene, datagrense en kultivar vir al die TOS, TA en fermheidsmodelle. Artikels 2 en 3, die fokuspunt van die studie, handel oor die dinamika van die aromaprofiel van Japanese pruime. HS-SPME is in beide artikels gebruik on die aromatiese verbindings te ekstraeer gevolg deur GCTOFMS vir skeiding en identifikasie. In Artikel 2 is die aromatiese stowwe van drie kultivars (Pioneer, Laetitia en Angeleno) bepaal vir sewe opeenvolgende weke en sluit monsters van drie volwassenheidsstadiums in (onvolwasse, oes en boom-rypgemaakte pruime). ‘n Totaal van 35 verbindings is geidentifiseer waarvan tien as generies beskou kan word. Elke kultivar het vyf unieke komponente gehad en het gelei tot verskillende aromaprofiele vir elk van die volwassenheidsstadiums en diverse skeidingspatrone tydens die gebruik van diskriminant analise. Die studie is uitgebrei in Artikel 3 waartydens die aromatiese vlugtige stowwe van ses kultivars (Pioneer, Sapphire, Laetitia, Songold, Larry Anne en Angeleno) en een plumcot (Flavor King) bepaal is tydens drie funksionele stadiums (oes, boom-rypgemaak en koelopgebergde pruime). ‘n Totaal van 62 verbindings is geidentifiseer en in drie groepe geklassifiseer (‘uniek’ (31), ‘generies’(11) en ‘gereeld’ (20)) gebaseer op voorkomsfrekwensie. Die aromaprofiele van ‘Larry Anne’ en ‘Flavor King’ is die meeste deur die koelopberging geaffekteer en ‘Pioneer’ die minste. Al die kultivars het kenmerkend verskil t.o.v. hul aromaprofiele in al drie die funksionele groepe en ‘Sapphire’, ‘Larry Anne’ en ‘Flavor King’ het die grootste verskille getoon. ‘Flavor King’, die plumcot, het ook ‘n ryp aromaprofiel gehad wat baie van die van die egte pruime verskil het.