Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The aim of this study was to investigate the influence of crop rotation and soil tillage on the soil water balance and water use efficiency of wheat, canola, lupin and medics in the Swartland sub region of the Western Cape. This trail was conducted as a component study within a long-term crop rotation/tillage trial during 2012 and 2013 at the Langgewens Research Farm (33016’42.33” S; 18042’11.62” E; 191m) of the Western Cape Department of Agriculture near Moorreesburg. The experiment was laid out as a randomized complete block, with a split-plot treatment design and replicated four times. Three crop rotation systems, continues wheat (WWWW), wheat/medic/wheat/medic (WMcWMc) and wheat/canola/wheat/lupin (WCWL) were allocated to main plots. . Each main plot was subdivided into four sub-plots allocated to four tillage treatments namely: zero-till (soil left undisturbed and planted with zero-till planter), no-till (soil left undisturbed until planting and then planted with a tined no-till planter), minimum-till (soil scarified March/April and then planted with a no-till planter) and conventional tillage (soil scarified late March/early April, then ploughed and planted with a no-till planter). All straw, chaff and stubble remained on the soil surface and no-grazing was allowed on all tillage treatments. Three replicates were included in this current study. Only the no-till (NT) and conventional till (CT) were included in this current study as main tillage treatments. The volumetric soil water content was monitored at weekly intervals during the active growing season (May-October) and once a month during the fallow period (November-April) using a Diviner 2000 soil moisture meter. The Diviner 2000 was used to record the soil water content at every 100 mm depth increment up to the maximum depth of the profile. At the end of the growing season the total biomass, grain yield and quality parameters were determined. The soil water balance data calculated from the 2012 season were found to be inconclusive due to too shallow installation of soil water monitoring tubes and big variations in the depth complicating any attempt in comparing data from treatments and cropping systems. Soil water monitoring tubes was installed to a depth of 900 mm in the 2013 season. Complications during planting in the 2013 season resulted in very poor emergence in the CT sites. Weed counts revealed that only 38 % of CT sites were covered by crop, 31 % with weeds and 31 % were completely bare. The NT sites had 40 % crop coverage, 50.5 % grass weed coverage and only 9.5% bare surface. As a consequences crop rotation had no effect on the soil water balance, while the tillage treatments showed a response. The effect that tillage had on the soil water balance was clearly shown in the 2013 season, in which 79 mm more rainfall occurred than the long-term average. NT retained more soil water in the profile in the drier first half of the season when only 30 % of the total rainfall in the 2013 season occurred. There was no real difference in the soil water retention in the second half of the season where 70 % of the total rainfall in the 2013 season occurred. Crop rotation did have a positive effect on grain yield. Wheat monoculture was out performed by legume based cropping systems. This trend was also observed in the biomass production. No significant difference between tillage treatments were recorded when comparing grain yield data. However wheat mono culture was again out-performed by the McWMcW, CWLW and LWCW systems producing on average significantly higher biomass. The data from both seasons suggest that in seasons where more rainfall than the long term average occurs, there is no difference in the RUE between cropping systems or tillage practices.. This study highlighted the major effect that the prevailing weather conditions have and that the expected advantages associated with NT most likely only come into play in dry conditions when plant water availability is limited. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die invloed van grondbewerking en gewasproduksiestelsels op die grondwaterbalans en doeltreffendheid van watergebruik te ondersoek in die koringproduserende gebied van Malmesbury. Hierdie eksperiment is uitgevoer as 'n komponentstudie binne 'n langtermyn grondbewerking/gewasrotasieproef gedurende 2012 en 2013 op die Langgewens Navorsingsplaas (33016'42 .33 'S; 18042'11 0,62' E, 191m) van die Wes-Kaapse Departement van Landbou naby Moorreesburg. Die eksperiment is uitgelê as 'n volledige ewekansige blok, met 'n gesplete perseel behandelingsontwerp met vier herhalings. Drie gewasproduksiestelsels naamlik, koring monokultuur (WWWW), koring/medic/koring/medic (WMcWMc) en koring/canola/ koring/lupiene (WKWL) is elk toegeken aan persele en vier keer herhaal. Elke hoofperseel is onderverdeel in vier subpersele en bewerkingsbehandelings is soos volg toegeken: Konvensionele bewerking (CT) - grond gebreek in Maart/April, en daarna geploeg en geplant met geen bewerkingsplanter. Minimum bewerking (MT) - grond gebreek in Maart/April en daarna geplant met 'n geen bewerkingsplanter. Geen bewerking (NT) - grond is heeltemal onversteur gelaat tot planttyd en daarna geplant met 'n geen bewerkingsplanter. Zero bewerking (ZT) - grond tot planttyd met rus gelaat en dan geplant met 'n sterwielplanter. Alle strooi, kaf en stoppels het op die grondoppervlak gebly en geen beweiding is toegelaat nie. Slegs drie herhalings is ingesluit in die huidige studie en slegs die geen bewerking (NT) en konvensionele bewerking (CT) is in die huidige studie as hoof bewerkingbehandelings ingesluit. Die volumetriese grondwaterinhoud is weekliks gemonitor tydens die aktiewe groeiseisoen (Mei - Oktober) en een keer 'n maand gedurende die braaktydperk (November - April) met behulp van 'n Diviner 2000 grondvogmeter. Die Diviner 2000 is gebruik om die grondwaterinhoud by elke 100 mm diepte tot die maksimum diepte van die profiel te bepaal. Aan die einde van die seisoen is die totale biomassa, graanopbrengs en kwaliteitparameters bepaal. Die data vir grondwaterbalans van die 2012-seisoen is buite rekening gelaat weens te vlak installering van moniteringsbuise en groot variasie in die dieptelesings wat enige poging om vergelykende data van rotasie en behandelings te verkry, bemoeilik het. Moniteringsbuise vir grondwater is geïnstalleer tot op 'n diepte van 900 mm in die 2013-seisoen. Komplikasies tydens die plantaksie in die 2013-seisoen het gelei tot 'n baie swak opkoms in die CT-persele. Slegs 38 % van die CT-persele was bedek deur die gewas en 31 % met onkruid, terwyl 31 % van die oppervlak onder CT-behandeling heeltemal kaal was. Die NT-persele het 40 % gewasbedekking, 50.5 % grasbedekking en slegs 9.5 % kaal oppervlak gehad. Dit het die poging, om die effek van wisselboustelsels op die grondwaterbalans, in die wiele gery. Alhoewel wisselbou skynbaar geen effek op die grondwaterbalans gehad het nie, het die tipe bewerking egter wel ‘n effek gehad. Die effek van grondbewerking op die grondwaterbalans het duidelik na vore gekom in die 2013-seisoen. In hierdie seisoen het 79 mm meer reën geval as die langtermyngemiddelde. Geen bewerking het meer grondwater in die droër eerste helfte van die seisoen in die profiel behou, toe slegs 30% van die totale reënval in die 2013 geval het. Daar was geen beduidende verskil in die grondwaterretensie in die tweede helfte van die seisoen toe 70% van die totale reënval in die 2013 geval het nie. Wisselbou het egter 'n positiewe uitwerking op die graanopbrengs gehad. Koring monokultuur is in opbrengsyfers geklop deur stelsels met peulplante as komponent. Hierdie tendens is ook waargeneem in die biomassaproduksie. Bewerkingsbehandelings het geen beduidende verskil in graanopbrengste tot gevolg gehad nie, hoewel die biomassaproduksie van koring monokultuur weer geklop is deur die McWMcW-, CWLW- en LWCW-stelsels. Die data van beide seisoene dui daarop dat in seisoene waar meer reën as die langtermyn gemiddelde voorkom, daar geen verskil in die RUE tussen verbouingstelsels of bewerkingspraktykes was nie. Hierdie studie beklemtoon die groot invloed wat die heersende klimaat speel en dat die verwagte voordele wat verband hou met NT waarskynlik slegs ‘n rol speel in droër jare.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / The rapid expansion of the world wine industry has increased the pressure on wine producers to produce high quality, distinguishable wines. The use of sensory evaluation alone as a tool to distinguish between wines is limited by its subjective nature. Chemical characterisation using analytical methods and data analysis techniques are increasingly being used in conjunction with sensory analysis for comprehensive profiling of wine. Analytical chemistry and chemometric techniques are important and inextricable parts of the chemical characterisation of wine. Through this process insight into the inherent composition of wines, be it in a general sense or related to a particular wine category is gained. Data generated during chemical characterisation are typically compiled into electronic databases. The application of such information towards wine quality control includes the establishment of industry benchmarks and authentication. The current project is part of The South African Young Wine Aroma Project, a long term research initiative funded by the South African Wine Industry with the ultimate aim to establish a comprehensive, up-to-date, database of the volatile composition of young wines. The data generated during this thesis represent the first contribution towards realising this ambition. Three clearly defined aims were set for this project, the first of which is the chemical characterisation of South African young wines in terms of selected volatile and non-volatile compounds and Fourier transform infrared spectra, with particular focus on the volatile composition. FTMIR spectra are information rich and non-specific instrumental signals that could provide invaluable information of the inherent composition of the wines. The second aim is the evaluation of the analytical methods used to generate the data and in the last instance, the optimisation of FTMIR spectroscopy for rapid quantification of major wine parameters and volatile compounds. The concentrations of 27 volatile compounds in South African young wines were determined by gas chromatography coupled to flame ionisation detection (GC-FID) using liquid-liquid extraction of the analytes. Wine samples of the 2005 and 2006 vintages produced from six of the most important cultivars in the South African wine industry, namely Sauvignon blanc, Chardonnay, Pinotage, Cabernet Sauvignon, Merlot and Shiraz were used. The producing cellars were from four major South African wine producing regions, namely Stellenbosch, Paarl, Robertson and Worcester. The data captured made a significant contribution to the establishment of the Aroma Project Database. Univariate statistics showed wide variations in the chemical composition of the wines. Red wines were generally characterised by high levels of higher alcohols and white wines by high levels of esters. Most of the differences between vintages were cultivar dependent and phenological differences between cultivars were suggested as a possible cause. Fusel alcohols, iso-acids and esters of fusel alcohols were particularly responsible for differences between red wines. A combination of fatty acids and higher alcohols were responsible for differences between production regions. However, using univariate statistics alone was limited in identifying characteristic features of the chemical composition of the wines. In order to explore the correlations between the volatile components, FTMIR spectra and nonvolatile components the data were further investigated with multivariate data analysis. Principal component analysis was successfully employed to distinguish between wines of different vintages and cultivars. The role of the volatile composition was more influential in the separation of vintage and red wine cultivar groupings than the non-volatile components or the FTMIR spectra. Almost all the individual volatile components contributed to the separation between the vintages and cultivars, thereby highlighting the multivariate nature required to establish the distinguishing features pertaining to each of these categories. The FTMIR spectra and the non-volatile components were more important than the volatile components to characterise the differences between the white cultivars. It was not surprising that both the volatile components and the FTMIR spectra were needed to distinguish between both red and white cultivars simultaneously. It was of interest the full spectrum, including all wavenumbers were required for a powerful classification model. This finding supports the initial expectation that the non-selective but information rich signal captured in the FTMIR spectra is indispensable. No distinction could be made between the production regions, which was not surprising since the wines used in this study was not of guaranteed origin. Furthermore, no clear correlation could be established between the chemical composition or the FTMIR spectra and the quality ratings of the wines. Limitations in the dataset were pointed out that must be taken into account during further investigations in the future. The liquid-liquid extraction method used during the analysis of the volatile components was evaluated for precision, accuracy and robustness. Generally good precision and accuracy were observed. There were slight indications of inconsistencies in the recoveries of analytes between the red and white wine matrices. Certain parameters of the protocol, namely sample volume, solvent volume, sonication temperature and sonication time, were identified as factors that had a major influence on quantification. The results obtained in this study made a major contribution towards establishing this technique for routine GC-FID analysis in our environment. Due to the high sample throughput in wine laboratories, the use of rapid quantitative analytical methods such as FTMIR spectroscopy is becoming increasingly important. Enzymatic-linked spectrophotometric assays and high performance liquid chromatography (HPLC) methods were evaluated for their suitability to serve as reference methods for optimising and establishing FTMIR calibrations for glucose, fructose, malic acid, lactic acid and glycerol. Pigmented and phenolic compounds were identified as sources of interference in the determination of organic acids in red wines with both enzymatic assays and HPLC. The use of fining treatments for the decolourisation of red wine samples was investigated. Activated charcoal was more efficient in terms of colour removal than polyvinyl polypyrrolidone (PVPP), but neither were compatible with the specific enzymatic method used in this study. Solid phase extraction (SPE), a method commonly used during sample clean-up prior to HPLC analysis of organic acids in wine, and PVPP fining were evaluated as sample preparation methods for HPLC analysis to optimise the quantification of organic acids in red wine. Four different types of SPE cartridges were evaluated and the SPE method was optimised in order to recover the maximum amount of organic acids. However, low recoveries, in some instance less than 50%, for the organic acids in wine were reported for the optimised SPE method. In this respect one was the worst. On average, excellent recoveries were observed for the organic acids using the PVPP method that were in excess of 90%. This method therefore provides a very valuable and simple alternative to SPE for sample-cleanup prior to HPLC analysis. One aspect that still needs to be investigated is the reproducibility of the method that should still be optimised. In general, enzymatic analysis was more suitable for the determination of glucose and fructose, while HPLC analysis were more suitable for the quantification of organic acids. Efficient glycerol quantification was observed with both enzymatic and HPLC analysis, although a lower measurement error was observed during the HPLC analysis. Apart from reliable reference methods, successful FTMIR calibrations also rely on the variability present in the reference sample set. The reference sample set used to establish FTMIR calibrations must ideally be representative of the samples that will be analysed in the future. Commercial, or so-called global, FTMIR calibrations for the determination of important wine parameters were evaluated for their compatibility to a South African young wine matrix. The prediction pH, titratable acidity, malic acid, glucose, fructose, ethanol and glycerol could be improved by establishing a brand new FTMIR calibration, thereby clearly indicating that the South African young wine matrices were significantly different from the samples of European origin that were used to establish the commercial calibrations. New preliminary calibration models were established for a young wine sample matrix and were validated using independent test sets. On average the prediction errors were considered sufficient for at least screening purposes. The effect of wavenumber selection was evaluated. Relatively successful models could be established for all the compounds except glucose. Wavenumber selection had an influence on the efficiency of the calibration models. Some models were more effective using a small amount of highly correlated wavenumbers, while others were more effective using larger wavenumber regions. Preliminary FTMIR calibration models for the screening of volatile compound groups in young wines were evaluated. Compound groups were compiled based on chemical similarity and flavour similarity. Good linearity were observed for the “total alcohol”, “total fatty acids”, “esters” models while an interesting polynomial trend was observed for the “total esters” model. Relatively high prediction errors indicated the possibility of spectral interferences, but the models were nevertheless considered suitable for screening purposes. These findings are a valuable contribution to our environment where fermentation flavour profiles must often be examined. The important role sound and validated analytical methods to generate high quality analytical data, and the subsequent application of chemometric techniques to model the data for the purpose of wine characterisation has been thoroughly explored in this study. After a critical evaluation of the analytical methods used in this study, various statistical methods were used to uncover the chemical composition of South African young wines. The use of multivariate data analysis has revealed some limitations in the dataset and therefore it must be said that wine characterisation is not just reliant on sophisticated analytical chemistry and advanced data analytical techniques, but also on high quality sample sets.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Little scientific information regarding the effect of different geological parent materials on grapevine performance is currently available in South Africa. This aspect is of special significance for the Helderberg area, where parent material may change from granite to shale over a short distance. This results in shale- as well as granite-derived soils often occurring within the same vineyard. The objectives of this study were to (i) quantify the nutritional status and other soil properties of different parent materials (shale and granite) and overlying soils (ii) investigate the impact of geological differences in the soil on the vine nutritional status and certain vine parameters. This study was done over two seasons (2006/2007 and 2007/2008). Two Sauvignon blanc and two Cabernet Sauvignon vineyard blocks were selected at two different localities for each cultivar in the Helderberg area, South Africa. Shale- and granitederived soils were identified within each block. Kaolinite was the dominant mineral, whereas quartz and feldspar were sub-dominant. Traces of mica were also present in some shale- and granite-derived soils. Granite- contained significantly higher contents of coarse sand than shale-derived soils, whilst the opposite occurred in terms of fine sand. These differences affected the water holding capacity, in general making it higher in shale- than granite-derived soils. Shale-derived soils had higher concentrations of total K but granite-derived soils had a higher ability to release K as they contained higher concentrations of soluble K. The Q/I parameters, potential buffering capacity of K (PBCK) and equilibrium activity ratio of K (ARK) showed no consistent responses to geological differences. Potassium concentrations were higher in the leaf blades (obtained before harvest in 2007) from Sauvignon blanc grapevines on granite- than on shale-derived soils. Potassium concentrations in the Cabernet Sauvignon juice (obtained in 2007) tended higher in juice from granite- than from shale-derived soils. In 2008, K concentrations tended higher in juice from shale- than from granite-derived soils for both cultivars. The pH of the Sauvignon blanc juice (obtained in 2008) tended higher in juice from shale-than from granite-derived soils, thus corresponding with the K concentrations in the juice in this season. Nitrogen concentrations were higher in Cabernet Sauvignon juice (obtained in 2007) and Sauvignon blanc juice (obtained in 2008) from shalethan from granite-derived soils. In terms of vine water status, vines on granite-derived soils appeared more stressed than those on shale-derived soils in both seasons at one of the vineyards. In these Sauvignon blanc and Cabernet Sauvignon vineyards, the K nutritional status was not affected by geology in a consistent manner but there were some noticeable tendencies for a specific cultivar during certain seasons. On account of vines being planted on shale- and granite-derived soils within the same block, soil preparation was done similarly for both soils, and they were exposed to similar irrigation schedules, canopy management strategies and climatic conditions. Therefore, there is a high probability that all these practices may have negated the effect of geology on the K status of soils and especially on juice K concentration at the time of harvest. It was clear that seasonal differences and fertilisation affected the nutritional status of the vines more than geology. / AFRIKAANSE OPSOMMING: In Suid-Afrika is daar tans min wetenskaplike inligting oor die effek van verskillende geologiese moedermateriale op die prestasie van wingerd beskikbaar. Hierdie aspek is veral van belang in die Helderberg-area, waar moedermateriaal oor ‘n baie kort afstand van graniet na skalie kan wissel. Dit lei daartoe dat skalie-, sowel as granietgronde, dikwels binne dieselfde wingerd voorkom. Die doelwitte van die studie was om: (i) die voedingstatus en ander grondkundige eienskappe van die verskillende moedermateriale (skalie en graniet) en oorliggende gronde te kwantifiseer (ii) die impak van geologiese verskille in die grond op wingerd se voedingstatus en sekere wingerdkundige parameters, te ondersoek. Hierdie studie is oor twee seisoene (2006/2007 en 2007/2008) gedoen. Twee Sauvignon blanc en twee Cabernet Sauvignon wingerdblokke is geselekteer by twee verskillende lokaliteite vir elke kultivar in die Helderbergarea, Suid-Afrika. Beide skalie- en granietgrond is binne elke blok geïdentifiseer. Kaoliniet was die dominante mineraal, met kwarts en veldspaat sub-dominant, terwyl spore van mika ook in beide skalie- en granietgronde gevind is. Granietgronde het betekenisvol hoër hoeveelhede growwe sand bevat, terwyl skaliegronde meer fyn sand bevat het. Hierdie verskille het ‘n effek op waterhouvermoë gehad en daartoe gelei dat waterinhoude oor die algemeen hoër was vir skaliegronde. Skaliegronde het groter hoeveelhede totale K bevat, maar granietgronde se vermoë om K vry te stel was hoër, omdat hulle ‘n hoër konsentrasie oplosbare K bevat het. Die Q/I parameters, potensiële buffervermoë vir K (PBCK) en ewewig aktiwiteitsverhouding vir K (ARK), is nie op ‘n konsekwente wyse deur geologiese verskille beïnvloed nie. Vir die Sauvignon blanc wingerde was kalium konsentrasies in blaarskywe (gemonster voor oes in 2007) hoër vir graniet- as vir skaliegronde. Kalium konsentrasies in die sap vanaf Cabernet Sauvignon (gemonster in 2007) het hoër geneig vir granietgronde. In 2008 het die kalium konsentrasies, vir beide kultivars, hoër geneig in sap vanaf skaliegronde. Gedurende dié seisoen het die pH van sap ook hoër geneig vir Sauvignon blanc vanaf skaliegronde, wat dus ooreenstem met die K inhoud van die sap. Stikstof konsentrasies was hoër in sap vanaf skaliegronde vir Cabernet Sauvignon (2007) en vir Sauvignon blanc (2008). In terme van die wingerde se waterstatus, het stokke op die granietgrond, by een van die lokaliteite, geneig om gedurende beide seisoene onder groter stremming te wees op graniet as op skaliegrond. In hierdie Sauvignon blanc en Cabernet Sauvignon wingerde, is K voedingstatus nie op ‘n konsekwente wyse deur geologie geaffekteer nie, maar gedurende sommige seisoene was daar wel duidelike tendense vir ‘n spesifieke kultivar. Omdat die stokke binne dieselfde blok op skalie- en graniet gronde geplant is, was grondvoorbereiding eenders vir die twee grondtipes terwyl besproeiingskedule, lowerbestuur en klimaatstoestande ook identies was. Daar is dus ‘n hoë waarskynlikheid dat al hierdie faktore daartoe kon bygedra het dat die effek van geologie op die K status van van gronde versluier is, veral die effek op die K inhoud van sap teen oestyd. Dit was duidelik dat seisoenale klimaatsverskile en bemestingspraktyke ’n groter effek as geologie op die voedingstatus van die wingerd gehad het.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / Biogenic amines are nitrogenous compounds of low molecular weight found in most fermented foods, including wine. These biologically produced amines are essential at low concentrations for normal metabolic and physiological functions in animals, plants and micro-organisms. However, biogenic amines can have adverse effects at high concentrations and pose a health risk for sensitive individuals. Symptoms include nausea, hot flushes, headaches, red rashes, respiratory distress and fluctuations in blood pressure. A number of countries have implemented upper limits for histamine in food and wine. This development has already started to threaten commercial export transactions and may become more serious in the near future, especially in the competitive wine industry of today. The most important biogenic amines in wine include histamine, tyramine, putrescine, cadaverine and phenylethylamine which are produced from the amino acids histidine, tyrosine, ornithine, lysine and phenylalanine respectively. Biogenic amines are mainly produced in wine by microbial decarboxylation of the corresponding precursor amino acid. It may be produced by yeast during alcoholic fermentation, by lactic acid bacteria during malolactic fermentation, or potentially by spoilage microbes such as acetic acid bacteria and Brettanomyces. However, lactic acid bacteria are widely accepted as the main causative agents. Inoculation with commercial malolactic fermentation starter cultures that do not possess the relevant decarboxylase genes may inhibit the growth and activity of decarboxylase positive indigenous bacteria and as such control the production of biogenic amines in wine. In this study it was shown that co-inoculation of malolactic starter cultures together with alcoholic fermentation could reduce the incidence of biogenic amines in wine compared to conventional inoculation protocols; presumably because undesirable activities were restrained at an earlier stage during co-inoculation. It was also indicated in this work that in some cases the effect of co-inoculation on biogenic amine reduction may only be visible after a period of ageing. The frequency of biogenic amine occurrence in wines aged for a short period was generally higher in the presence of fermentation lees than in its absence. This work also included a preliminary investigation into the contribution of commercial wine yeast starter cultures to biogenic amine production. Diamines and polyamines (putrescine, spermidine and cadaverine) were produced to variable extents by all yeasts with very little or no production of physiologically important biogenic amines (histamine, tyramine and phenylethylamine). Another objective of this study was to evaluate the influence of common winemaking practices on biogenic amine production under winemaking conditions. We have shown that biogenic amine production by lactic acid bacteria could be influenced, amongst others, by the presence of precursor amino acids in the grape must or wine, the time of contact between juice or wine and grape skins, the time of contact between wine and yeast lees, the presence of microbial nutrients, wine pH, sulphite and ethanol levels, the phenolic composition of the wine and the number of decarboxylase positive lactic acid bacteria present in the wine. Lately, the wine industry is under increasing pressure to increase measures to ensure food safety and security and to eliminate any compound, present even in trace amounts that could reduce the wholesomeness of the wine. The need arises for a rapid and inexpensive method for quality control. In this study we investigated the potential to use Fourier transform infrared spectroscopy to rapidly screen for the presence of elevated levels of biogenic amines. This presents a novel method for the detection and quantification of total biogenic amines in wines.

Thesis (MSc (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2002. / Pathogen devastation of food products has been the topic of extensive research efforts worldwide. Fungal infections are foremost amongst these pests, contributing not only to losses in product yield, but also significantly affecting the quality thereof. It is not surprising then that producers of these foodstuffs and their derived products continually strive towards the highest possible product quality. Therefore, it remains imperative that satisfactory methods are implemented to control these fungal pathogens. The current strategies are all hampered by drawbacks, and severe crop losses are still experienced. New technologies are being explored; one such technology is the genetic transformation of plant species. This method has enabled scientists to introduce foreign genes, with known functions and predictable outcomes, into plants. Genes identified to be involved in disease resistance have become the focus of numerous research efforts concerned with the improvement of the plant's innate defence response. This study aimed to enhance disease resistance to fungal pathogens by means of the genetic transformation of two genes previously shown to be involved in disease resistance. These genes encode polygalacturonase-inhibiting proteins (PGIPs) from Phaseolus vulgaris and resveratrol synthase from Vitis vinifera. PGIPs specifically inhibit the action of fungal polygalacturonases (PGs), which are enzymes responsible for the hydrolytic breakdown of plant cell walls. These enzymes were also found to be the first enzymes that are secreted by fungal pathogens during infection of the host plant. Additionally, PGIP-PG interaction results in the existence of molecules involved in the activation of plant defence responses. Resveratrol, the product of resveratrol synthase, exerts its antifungal action by destruction of the microbial cellular membranes. These mentioned genes were transformed alone, and in combination, into Nicotiana tabacum and the resultant transgenic lines were evaluated for enhanced disease resistance and for possible synergistic effects between the transgenes. Several independent transgenic lines were regenerated with genes integrated into the tobacco genome. Almost all the plants harbouring only pgip or vst1 genes also expressed these genes at a high frequency. Some non-expressing lines were identified from the transgenic plants that had integrated both genes, but several lines were obtained expressing both transgenes. Good correlations were observed between transgene product activity and enhanced resistance to the fungus Botrytis cinerea in an antifungal in planta assay. Lines showing the highest PGIP activity and resveratrollevels were more resistant to the pathogen, leading to disease resistance of up to 80% seven days after inoculation in comparison to an untransformed control. These lines maintained their strong inhibition, even three weeks post-inoculation, showing a complete halt in disease development and fungal growth. These results provide good indications of the efficacy of these transgenes in the upregulation of plant defence. However, the study will have to be expanded to include even more transgenic lines to elucidate the possible synergistic effects of these genes. In an additional pilot study, genes encoding for precursors and for the formation of resveratrol were introduced into the yeast Saccharomyces cerevisiae. The resultant recombinant yeast strains were evaluated for their ability to produce the phenolic substance, resveratrol. This compound has been implicated in beneficial aspects relating to human health, including positive effects on atherosclerosis and platelet aggregation as a direct result of its antioxidant and anti-inflammatory activities. Recombinant yeast strains were constructed that expressed genes coding for coenzyme A ligase and resveratrol synthase. These strains were shown to be able to produce the phenolic compound resveratrol from the precursors present in the yeast as well as from the products introduced with the transformation. The resveratrol was complexed with an added glucose moiety. These results are extremely positive, considering the possibility of manipulating wine yeasts to produce resveratrol during the wine fermentation, thereby adding to the health aspects of both red and white wine. This is the first report of the production of this compound by the introduction of genes necessary for its biosynthesis in a foreign host. This study has confirmed the importance of PGIPs and resveratrol in the effort to enhance disease resistance in plants through genetic transformation technology. It has also shown that the health benefits of resveratrol could be exploited more optimally in the wine industry, by producing wine yeasts with the ability to synthesise this important antioxidant.

Thesis (MScAgric (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Necrotrophic fungi infect many economically important crop plants. This results in great losses in the agricultural sector world-wide. Understanding the nature by which plants respond to pathogens is imperative for genetically enhancing disease resistance in plants. Research tools have significantly contributed to our understanding of how the plant responds to pathogen attack, identifying an array of defence mechanisms used by plants upon attack. Many fungal pathogens secrete endopolygalacturonases (endoPGs) when infecting plants. These hydrolytic enzymes are inhibited by polygalacturonase-inhibiting proteins (PGIPs) associated with plant cell walls. PGIPs are well characterised and their current known functions are all linked to endoPG inhibition and the subsequent upregulation of plant defence pathways. Work on grapevine PGIPs have shown that apart from being efficient antifungal proteins, leading to protection of the plant against Botrytis cinerea when overexpressed, PGIPs might also have additional functions linked to cell wall strengthening. This working hypothesis formed the motivation of this study where a cinnamyl alcohol dehydrogenase (CAD) (1.1.1.195) gene was targeted for functional analysis in tobacco (Nicotiana tabacum). Some previous work and genetic resources obtained is relevant to this study, specifically previously characterized transgenic tobacco lines overexpressing the Vitis vinifera pgip1 (Vvpgip1) gene. These lines have confirmed PGIP-specific resistance phenotypes against B. cinerea, as well as increased levels of CAD transcripts in healthy plants. Moreover, preliminary evaluations indicated increased lignin levels as well as differential expression of several other cell wall genes in these overexpressing lines (in the absence of infections). In this study we generated a transgenic tobacco population, overexpressing the native CAD14 gene, via Agrobacterium transformations. The transgene was overexpressed with the Cauliflower Mosaic Virus promoter (CaMV 35Sp). The CAD transgenic population was analyzed for transgene integration and expression and showed active transcription, even from leaves that normally don’t express CAD to high levels. These lines, together with the untransformed control, and a representative transgenic VvPGIP1 tobacco line previously characterized with elevated expression of CAD were used for all further analyses, specifically CAD activity assays of stems and leaves, as well as whole plant infections with B. cinerea. CAD enzyme activity assays were performed on healthy uninfected plant lines, without inducing native CAD expression or resistance phenotypes (i.e. without Botrytis infection). CAD activity was detected in leaves and stems, but a statistically sound separation between the CAD population and the untransformed control was only observed in the stems. The CAD assays also confirmed previous results that indicated that CAD transcription was upregulated in the PGIP line in the absence of infection. Overall, in all plant lines the stems exhibited 10-fold higher levels of CAD activity than the leaves, but the transgenic VvPGIP1 line showed a further 2-3-fold increase in CAD activity in the stems, when compared to the untransformed control and the majority of the CAD overexpressing lines. Disease assessment by whole plant infections with B. cinerea of the CAD transgenic plants revealed reduced disease susceptibility towards this pathogen. A reduction in disease susceptibility of 20 – 40% (based on lesion sizes) was observed for a homologous group of transgenic lines that was statistically clearly separated from the untransformed control plants following infection with Botrytis over an 11-day-period. The VvPGIP1 transgenic line displayed the strongest resistance phenotype, with reduction in susceptibility of 47%. The reduction in plant tissue maceration and lesion expansion was most pronounced in the VvPGIP1 line compared to the CAD transgenic plants, while the CAD transgenic plants showed more reduction than the untransformed control. In combination, the data confirms that CAD upregulation could lead to resistance phenotypes. Relating this data back to the previously observed upregulation of CAD in the VvPGIP1-overexpressing lines, the findings from this study corroborates that increased CAD activity contributes to the observed resistance phenotypes, possibility by strengthening the cell wall. In conclusion, this study yielded a characterized transgenic population overexpressing the CAD14 gene; this overexpression contributed to increased RNA transcription compared to the untransformed control plant, increased CAD activity (most notably in the stems) and a disease resistance phenotype against Botrytis. These findings corroborates the current working hypothesis in our group that PGIPs might have a role in preparing the plant cell for attack by contributing to specific cell wall changes. The exact mechanisms are still currently unknown and under investigation. The transgenic lines generated in this study will be invaluable in the subsequent analyses where these various phenotypes will be subjected to profiling and accurate cell wall analyses. / AFRIKAANSE OPSOMMING: Nekrotrofiese swamme infekteer en beskadig verskeie ekonomies belangrike gewasse. Dit lei wêreldwyd tot groot verliese vir die landbousektor. Dit is noodsaaklik om te verstaan hoe plante reageer teenoor patogene, sodat die siekteweerstand van plante verbeter kan word. Navorsingshulpbronne het beduidend bygedra tot die kennis van plantreaksies tydens patogeniese aanvalle, en het sodoende ‘n reeks van weerstandmeganismes, wat die plant inspan tydens ‘n aanval, geïdentifiseer. Verskeie patogeniese swamme skei endopoligalakturonases (endoPGs) af tydens plantinfeksie. Hierdie hidrolitiese ensieme word geïnhibeer deur poligalakturonase-inhiberende proteïene (PGIPs) wat met die plantselwand geassosieerd is. PGIPs is goed gekarakteriseerd en al hulle huidiglik bekende funksies is gekoppel aan endoPG inhibisie en die daaropvolgende opregulering van plant weerstandspaaie. Navorsing op wingerd PGIPs het gewys dat, afgesien van die feit dat PGIPs goeie antifungiese proteïene is wat lei tot beskerming van die plant teen Botrytis cinerea wanneer dit ooruitgedruk word, PGIPs ook moontlik addisionele funksies verrig wat verwant is aan selwandversterking. Hierdie werkshipotese vorm die motivering vir hierdie studie waarin ‘n sinnamiel alkohol dehidrogenase (SAD) (1.1.1.195) geen geteiken is vir funksionele analise in tabak (Nicotiana tabacum). Vorige navorsing en genetiese hulpbronne daardeur verkry is belangrik vir hierdie studie, spesifiek die gekarakteriseerde transgeniese tabaklyne wat die Vitis vinifera pgip1 (Vvpgip1) geen ooruitdruk. Hierdie lyne besit bevestigde PGIP-spesifieke weerstandsfenotipes teen B. cinerea, sowel as hoër vlakke van SAD transkripte in gesonde plante. Voorlopige analises het ook aangedui dat hierdie ooruitdrukkende lyne hoër lignien vlakke het, asook differensiële uitdrukking van verskeie ander selwandgene (in die afwesigheid van infeksie). In hierdie studie is ‘n transgeniese tabakpopulasie gegenereer wat die natuurlike tabak SAD14 geen ooruitdruk, deur middel van Agrobacterium transformasie. Die transgeen is ooruitgedruk deur die Blomkool Mosaïek Virus promoter (CaMV 35Sp). Die SAD transgeniese populasie is geanaliseer vir transgeen integrasie en uitdrukking en het aktiewe transkriptering getoon, selfs in blare waar daar normaalweg nie hoë vlakke van SAD uitgedruk word nie. Hierdie lyne, die ongetransformeerde wilde-tipe kontrole sowel as ’n verteenwoordigende transgeniese VvPGIP1 tabaklyn wat vooraf gekarakteriseerd was met hoë SAD uitdrukking, is gebruik vir alle verdere analises, spesifiek SAD aktiwiteitstoetse in stingels en blare, asook heelplantinfeksies met B. cinerea. Aktiwiteitsanalises van die SAD ensiem is gedoen op gesonde ongeinfekteerde plantlyne, sonder om natuurlike tabak SAD uitdrukking of weerstandsfenotipes te induseer (dus sonder Botrytis infeksie). SAD aktiwiteit is waargeneem in beide die blare en stingels, maar ‘n statisties betekenisvolle skeiding is slegs gevind tussen die SAD populasie en die ongetransformeerde kontrole in die stingels. Die SAD toetse het ook vorige resultate bevestig wat aangedui het dat SAD transkripsie opgereguleer word in die PGIP lyn in die afwesigheid van infeksie. Die stingels het oor die algemeen ‘n 10-voudige vermeerdering in SAD aktiwiteitsvlakke getoon in vergelyking met die blare, maar die transgeniese VvPGIP1 lyn het ‘n verdere 2-3-voudige verhoging in SAD aktiwiteit gehad in die stingels ,in vergelyking met die ongetransformeerde kontrole en die meerderheid van die SADooruitdrukkende lyne. Siekteweerstand ondersoeke deur middel van heelplantinfeksies met B. cinerea van die SAD transgeniese plante, het verminderde vatbaarheid aangedui ten opsigte van hierdie patogeen. ‘n Afname in siekte-vatbaarheid van 20 – 40% (gebaseer op wondgroottes) is waargeneem vir ‘n homoloë groep transgeniese lyne wat statisties betekenisvol geskei kon word van die ongetransformeerde kontrole plante na infeksie met Botrytis in ‘n infeksietoets wat 11 dae geduur het. Die VvPGIP1 transgeniese lyn het die mees weerstandbiedende fenotipe gehad, met ‘n afname in siekte-vatbaarheid van 47%. Die afname in plantweefselafbreking en wondgrootte was die duidelikste in die VvPGIP1 lyn in vergelyking met die SAD transgeniese plante, terwyl die SAD transgeniese plante ‘n groter afname aangedui het as die ongetransformeerde kontrole. In kombinasie het die data bevestig dat SAD opregulasie kan lei tot weerstandbiedende fenotipes. Hierdie data, in vergelyking met die vorige bevinding van opregulasie van SAD in die VvPGIP1-ooruitdrukkende lyne, bevestig dat hoër SAD aktiwiteit bydra tot die waargenome weerstandbiedende fenotipes, moontlik deur versterking van die plantselwand. Ter afsluiting, hierdie studie het ‘n gekarakteriseerde transgeniese populasie wat die SAD14 geen ooruitdruk gelewer; hierdie ooruitdrukking het bygedra tot hoër RNA transkripsie in vergelyking met die kontrole, verhoogde SAD aktiwiteit (veral in die stingels) en siekteweerstandbiedende fenotipes teenoor Botrytis. Hierdie bevindinge ondersteun die huidige werkshipotese in ons groep dat PGIPs moontlik ‘n rol speel in die voorbereiding van die plantsel teen infeksie deur spesifieke selwandveranderinge te veroorsaak. Die spesifieke meganismes is steeds onbekend en word verder ondersoek. Die transgeniese lyne wat tydens hierdie studie gegenereer is, sal baie belangrik wees in opvolgende analises waar hierdie verskillende fenotipes gebruik kan word om die profiel van selwandkomponente, maar ook die akkurate selwandsamestelling te bestudeer.

Thesis (MSc(Agric)) -- Stellenbosch University, 1966. / INLEIDING: Die ontstaan van kooperasiewese kan teruggevoer word na die jaar 1844 toe 28 wewers van Rochdale in Engeland 'n suksesvolle koöperatiewe verbruikswinkel geloods het. Die sogenaamde Rochdale-pioniers word veral onthou vanweë die feit dat hulle die beginsels van koöperasiewese duidelik geformuleer het. In Suid-Afrika speel landboukoöperasie vandag 'n belangrike rol in die bemarking van landbouprodukte, die verskaffing van boerderybenodighede en die lewering van dienste aan boere. Koöperasies is, veral in die beginjare, meesal gestig met die doel om gebreke in die bemarking en verwerking van landbouprodukte te oorbrug. In Suid-Afrika het koöperasiewese ontwikkel sedert die twintigste eeu toe 'n Ier, Mnr. P.J. Hannon na die land gebring is om te dien as superintendent van landboukoöperasies. Vandaar het dit ontwikkel tot feitlik al die sektore van die landboubedryf in Suid-Afrika.

Thesis (PhD(Agric) (Agriculture))--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The concept of social welfare maximisation directs strategic decision-making within a milieu of integrated planning problems. This study applies the aforementioned statement to decision-making regarding the long-term allocation of bulk-water resources in the Berg Water Management Area of South Africa. Public goods, such as bulk water supply infrastructure, is vulnerable to failures in market and government allocation strategies because both fields are subjected to unaccounted costs and benefits. This implies a measurement problem for the quantification of the total cost/benefit of management options and result in decision-making with incomplete information. Legitimate decision-making depends on reliable and accurate information, and the measurement problem, therefore, poses an obstacle to better social welfare maximisation. A need has been identified to broaden the decision-making context in the Berg Water Management Area to promote the accommodation of unaccounted for costs and benefits in water resource allocation decision-making. This study engaged this need by expanding the temporal and spatial dimensions of the decision-making context. Accordingly, improved indecision-making information and decision-support processes is needed. Spatial expansions manifested in physical expansions of the decision-making boundaries that led to expansions in representation in the decision-making process. Temporal expansions manifested in the consideration of different sequences of bulk supply schemes over time instead of a selection of schemes at the same time. The study incorporated components of economic valuation theory, multi-criteria decision analysis, a public survey and a modified Delphi expert panel technique to account for the increased decisionmaking information load. The approach was applied in the Western Cape province of South Africa and specifically focused on a choice problem regarding different long-term bulk-water resource management options for the area. Two surveys were completed to accommodate these expansions. The first focused on public preference in water allocation management and the second survey utilized a modified Delphi technique. Questions regarding the extend of public participation in long-term water resource allocation decision-making came to the fore and the applicability of economic theory to accommodate public preference as a regulatory instrument, was questioned. A willingness to pay for “greener” water was observed and may be used to motivate a paradigm shift from management’s perspective to consider, without fear of harming their own political position, “greener” water supply options more seriously even if these options imply higher direct costs.

162 leaves printed on single pages, preliminary pages i- vii and numbered pages 1-152. Includes bibliography and abbreviations. / Digitized at 600 dpi grayscale to pdf format (OCR), using a Bizhub 250 Konica Minolta Scanner. / Thesis (PhD(Agric))--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Maize, forage sorghum, lucerne, oats, barley and triticale are the most common silage crops in South Africa, while tropical grasses like Eragrostis curvula and Digitaria eriantha are ensiled to a lesser extent. The aim of this study was to determine the effect of adding a lactic acid bacterial inoculant to E. curvula, D. eriantha, lucerne, forage sorghum, maize and oat silage. The effect of the addition of a lactic acid bacterial inoculant when ensiling E. curvula on the fermentation dynamics during ensiling and the aerobic stability of the silage was determined. The addition of the lactic acid bacterial inoculant to E. curvula at ensiling resulted in a more rapid lowering in pH and improved preservation. Inoculated silage had a higher lactic acid content, less protein breakdown and a lower butyric acid content compared to that of the control silage. Both silages were stable when exposed to air for five days. Digitaria eriantha was ensiled, with or without the addition of a lactic acid bacterial inoculant containing Lactobacillus plantarum. Streptococcus faecium and Pediococcus acidilactici together with the enzymes, cellulase, hemicellulase and amylase. The addition of the inoculant resulted in a more rapid drop in pH, a higher level of lactic acid, an increase in the number of lactic acid bacteria, less protein breakdown and lower numbers of enterobacteria, clostridial spores, yeast and mould compared to the control silage. Digitaria eriantha hay, control and inoculated silage diets were fed to 24 Merino rams (n = 8 per treatment) to determine intake and digestibility. The intake of diets consisting of 90.9% D. eriantha hay, control silage or inoculated silage, differed significantly (p<0.05) at 1395, 1540 and 1848 g DM/day, respectively. The in vivo organic matter digestibility (glkg) of D. eriantha hay, untreated silage and inoculated silage diets was 561, 546, 574, respectively. The addition of the bacterial inoculant when ensiling D.eriantha resulted in better preservation, improved aerobic stability, as well as a higher in vivo organic matter digestibility and intake of D. eriantha silage. The addition of an inoculant or molasses to lucerne (Medicago sativa), ensiled in laboratory silos was investigated. The addition of the additives resulted in an increased preservation rate as indicated by a more rapid lowering of pH, a faster rate of lactic acid production and less protein breakdown compared to control silage. The inoculant was more effective than the molasses in improving the rate of preservation. The aerobic stability of lucerne silage was not affected by inoculation or the addition of molasses. The addition of an inoculant to wilted big bale lucerne silage was studied. The inoculant improved silage quality as indicated by a lower pH, higher lactic acid content, lower ammonia nitrogen content and lower level of butyric acid in inoculated silage compared to the control lucerne silage. The composition of big round bale lucerne silage differed markedly from that of lucerne ensiled in laboratory silos as the former had a higher pH, ammonia nitrogen, butyric acid and acetic acid content and a lower lactic content. Whole crop forage sorghum cultivar FS2 was harvested at the late bloom (20.7% DM) and soft dough (28.9% DM) stages of maturity and ensiled in laboratory silos with the addition of commercial silage inoculants. At both stages of maturity the inoculants caused a more rapid rate of pH decline and a higher amount of lactic acid production. All the silages were well preserved. Silages of the sorghum ensiled at the late bloom stage with all treatments were stable after 5 days of aerobic exposure, whereas sorghum ensiled at the soft dough stage with the addition of the inoculants deteriorated upon aerobic exposure. It is concluded that addition of lactic acid bacterial inoculants to mature sorghum at ensiling might impair the aerobic stability of the silage. The yield, nutritional value and production potential of silage made from twenty one maize hybrids was compared. It was concluded that maize hybrids did differ in metabolizable energy content, rate of digestion, predicted intake and predicted milk production potential. The content of NDF and ADF did not differ between the maize hybrids used in this study and could therefore not be used to predict nutritional value or production potential. Maize was harvested at the hard dough stage and ensiled with or without the addition of a lactic acid bacterial inoculant in laboratory silos and in 210 litre drums. The adding of the inoculant to maize at ensiling did not result in a more rapid drop in pH and higher levels of lactic acid. The intake and growth of South African Mutton Merino lambs fed inoculated and untreated maize silage diets was determined. The average daily gain of lambs fed a diet consisting of either 60% control or inoculated maize silage over a growth period of 60 days was 239 ± 26 and 255 ± 44 g/day, respectively. Although the laboratory study showed very little effect of adding a lactic acid bacterial inoculant to maize at ensiling, lambs tended to consume more of the inoculated silage. In the second study the effect of the addition of a lactic acid bacterial inoculant with an enzyme to maize at ensiling on the fermentation dynamics during ensiling, aerobic stability of the silage, the intake, milk production and milk composition of Jersey cows fed maize silage diets was determined. The inoculant did not result in a more rapid lowering of the pH or a more rapid lactic acid production compared to untreated maize silage made in laboratory silos. Both the control and inoculated maize silages were well preserved. The addition of the inoculant to maize at ensiling improved the palatability, intake and the aerobic stability of maize silage compared to the untreated control maize silage. Milk production, milk composition, live weight and condition score of Jersey cows was not significantly affected by the addition of the inoculant to maize silage. The effect of the addition of an enzyme containing lactic acid bacterial inoculant to big bale oat (Avena sativa, cv Cederberg) silage on silage composition, silage intake, milk production and milk composition of Jersey cows was determined. The crop was cut at the bloom stage, wilted and ensiled in big round bales. The inoculant, Sil-All, was applied during the baling process on half of the bales. Silages were fed to Jersey cows in an intake and milk production study. Both the control and inoculated oat silages were well preserved. The inoculated oat silage had a lower level of butyric acid than the control oat silage. Cows fed the inoculated oat silage produced more (P=O.05) milk (17.7 kg/day) than cows fed the control oat silage (16.7 kg/day). The addition of a lactic acid bacterial inoculant to big bale oat silage improved silage composition and animal performance. This study clearly showed that the composition of silages made in bunker silos under commercial farm conditions differ largely from that of silages made in small scale laboratory silos. When the effect of silage additives on aerobic stability of silage is determined the evaluation should include studies on large scale bunker silages. Evaluation of silage additives should include intake and animal production studies. / AFRIKAANSE OPSOMMING: Mielies, voersorghum, lusem, hawer, gars en korog word algemeen as kuilvoer gewasse benut terwyl tropiese grasse soos Eragrostis curvula en Digitaria eriantha tot 'n mindere mate ingekuil word. Die doel van hierdie studie was om die invloed van 'n melksuurbakterieseinokulant op E. curvula-, D. eriantha-, lusem-, voersorghum-, mielie- en hawerkuilvoer te bepaal. Die invloed van 'n melksuurbakteriese-inokulant op die fermentasiedinamika en die aerobiese stabiliteit van E. curvula-kuilvoer is bepaal. Die toediening van die melksuurbakterieseinokulant tot E. curvula tydens inkuiling het 'n vinniger tempo van pH daling en beter preservering tot gevolg gehad in vergelyking met kontrole kuilvoer. Inokulant behandelde kuilvoer het 'n hoer melksuurinhoud, minder protei'en afbraak en 'n laer bottersuurinhoud as kontrole kuilvoer gehad. Beide kuilvoere was stabiel tydens blootstelling aan lug vir vyf dae. Digitaria eriantha is ingekuil met ofsonder die toediening van 'n melksuurbakteriese-inokulant wat Lactobacillus plantarum. Streptococcus faecium en Pediococcus acidilactici sowel as die ensieme, sellulase, hemisellulase and amilase bevat het. Die inokulant het 'n vinniger tempo van pH-daling, hoer vlakke van melksuur en melksuurbakterie, minder protei'en afbraak en laer getalle van enterobakterie, klostridiale spore, giste and swamme in vergelyking met die kontrole tot gevolg gehad. Digitaria eriantha hooi, kontrole kuilvoer en gei'nokuleerde kuilvoer diete is aan 24 Merino ramme (n = 8 per behandeling) gevoer vir bepaling van inname en verteerbaarheid. Die inname van diete wat uit 90.9% D. eriantha hooi, kontrole kuilvoer of gei'nokuleerde kuilvoer bestaan het, het betekenisvol (p<0.05) verskil en was 1395, 1540 en 1848 gDM/dag, respektiewelik. Die in vivo organiesemateriaal verteerbaarheid (gIkg) vanD. eriantha hooi, kontrole kuilvoer en geYnokuleerde kuilvoer was 561, 546, 574, respektiewelik. Die toediening van die bakteriese-inokulant tydens inkuiling vanD. eriantha het beter preservering, verbeterde aerobiese stabiliteit asook 'n hoer in vivo organiesemateriaal verteerbaarheid van D. eriantha kuilvoer tot gevolg gehad. Die effek van toediening van 'n melksuurbakteriese-inokulant en van molasse tot lusem (Medicago sativa) ingekuil in laboratoriumsilos is ondersoek. Die inokulant toediening en molasse toediening het die tempo van preservering versnel, die pH het vinniger gedaal, melksuur is teen 'n hoer tempo geproduseer en minder proteYen afbraak het plaasgevind in vergelyking met die kontrole kuilvoer. Die tempo van preservering is meer effektief deur toediening van die inokulant verhoog as deur die toediening van molasse. Die aerobiese stabiliteit van lusernkuilvoer is nie beYnvloed deur die toediening van inokulant ofmolasse nie. Die effek van die toediening van 'n melksuurbakteriese-inokulant tot groot rondebaal lusernkuilvoer is ondersoek. Die inokulant het die kwaliteit van die kuilvoer verbeter en het 'n laer pH, hoer melksuur, laer ammoniak stikstofen laer bottersuurinhoud in rondebaallusernkuilvoer tot gevolg gehad in vergelyking met kontrole kuilvoer. Groot rondebaallusernkuilvoer het grootliks verskil van lusernkuilvoer wat in laboratoriumsilos ingekuil is. Die rondebaal kuilvoer het 'n hoer pH, hoer ammoniak-stikstof-, bottersuur- en asynsuurinhoud en 'n laer melksuurinhoud gehad as laboratorium lusernkuilvoer. Voersorghum kultivar FS2 is op die laat blom (20.7% DM) en op die sagte deeg (28.9% DM) stadium met die byvoeging van melksuurbakteriese-inokulante ingekuil in laboratoriumsilos. Toediening van beide inokulante tot sorghum hetop beide die inkuilstadiums gelei tot 'n vinniger tempo van pHdaling en meer melksuurproduksie. Aile kuilvoere insluitend die kontrole kuilvoer was goed gepreserveer. Kontrole sowel geYnokuleerde sorghumkuilvoer ingekuil op die laat blomstadium was stabiel tydens aerobiese blootstelling vir 5 dae. Sorghumkuilvoer ingekuil op die sagtedeegstadium met die byvoeging van inokulante was onstabiel tydens aerobiese blootstelling. Die toediening van melksuurbakteriese-inokulante tot sorghum wat op die sagtedeegstadium ingekuil word kan aerobiese stabiliteit van die kuilvoer grootliks benadeel. Die opbrengs, voedingswaarde en produksiepotensiaal van kuilvoer gemaak van 21 mielie hibriede is vergelyk. Verskille in metaboliseerbare energie inhoud, tempo van vertering, voorspelde inname en voorspelde melkproduksie het tussen mielie hibriede voorgekom. Die neutraalbestandevesel- en suurbestandeveselinhoud het nie verskil tussen hibriede nie en derhalwe kon dit nie gebruik word om voedingswaarde ofproduksiepotensiaal te beraam rue. Mielies is op die hardedeegstadium met of sonder die toediening van 'n melksuurbakterieseinokulant in laboratoriumsilos en 210 liter dromme ingekui!. Die toediening van die inokulant het geen invloed op tempo van pH-daling ofproduksie van melksuur gehad nie. Die inname en groei van SA Vleismerino lammers wat 'n dieet bestaande uit 60% kontrole of inokulant behandelde mieliekuilvoer ontvang het, is bepaa!. Die gemiddelde daaglikse toename van lammers was 239 ± 26 and 255 ± 44 g/dag vir die kontrole en inokulant mieliekuilvoer dieet respektiewelik. Alhoewel die laboratoriumstudie weinig verskille tussen die kontrole en die geYnokuleerde mieliekuilvoer getoon het, het lammers geneig om meer van die geYnokuleerde mieliekuilvoer in te neem. In die tweede studie met mieliekuilvoer is die effek van toediening van 'n melksuurbakteriese-inokulant met ensieme, op die ferrnentasiedinamika tydens inkuiling, die aerobiese stabiliteit van mieliekuilvoer asook die inname, melkproduksie en melksamestelling van Jersey koeie bepaa!. Die inokulant het nie die tempo van pH daling en produksie van melksuurverhoog nie en beide kontrole en geYnokuleerde mieliekuilvoerwas goed gepreserveer. Die toediening van die inokulant tot mieliekuilvoer het die smaaklikheid, inname en die aerobiese stabiliteit van mieliekuilvoer verhoog in vergeiyking met kontrole mieliekuilvoer. Melkproduksie, melksamestelling, liggaamsmassa en kondisiepunt van Jersey koeie is nie betekenisvol beYnvloed deur die toediening van die inokulant tot mieliekuilvoer nie. Die effek van die toediening van 'n ensiem bevattende melksuurbakteriese-inokulant tot groot rondebaal hawer (Avena sativa, cv Cederberg) kuilvoer op die samestelling van kuilvoer, kuilvoerinname, melkproduksie en melksamestelling van Jersey koeie is bepaa!. Die gewas is gesny op die blomstadium, verwelk en as rondebaalkuilvoer gepreserveer. Die inokulant, Sil-All, is tydens die baalproses toegedien op die helfte van die bale. Kuilvoere is aan Jersey koeie gevoer in 'n inname en melkproduksiestudie. Beide die kontrole en geYnokuleerde hawerkuilvoer was goed gepreserveer. Die bottersuurinhoud van geYnokuleerde hawerkuilvoer was laer as die van die kontrole hawerkuilvoer. Koeie wat geYnokuleerde hawerkuilvoer gevoer is het meer (P=0.05) melk (17.7 kg/dag) geproduseer as koeie wat kontrole hawerkuilvoer ontvang het (16.7 kg/dag). Die toediening van 'n melksuurbakteriese-inokulant het kuilvoer kwaliteit en diereproduksie verbeter. Hierdie studie wys duidelike verskille uit tussen kuilvoer wat in bunkersilos onder kommersiele toestande ingekuil is, en kuilvoer wat in laboratoriumsilos gemaak is. Wanneer die effek van kuilvoerbymiddels op die aerobiese stabiliteit van kuilvoer bepaal word behoort finale evaluasie gedoen te word op kuilvoer gemaak in bunkersilos soos onder plaastoestande plaasvind. Evaluasie van kuilvoerbymiddels behoort inname en diereproduksiestudies in te sluit.