This thesis describes a two-component study undertaken in smallholder dairy systems of Central Kenya. One component characterized delivery systems for tick and tick-borne disease (TTBD) technologies including treatment packages, tick control products and vaccines, while the second component evaluated the important factors in their utilization by farmers. A combination of two economic analytical tools was used for the characterisation component. The first, the structure-conduct-performance (SCP) framework, was used to evaluate the performance of marketing systems and compare it to a perfectly competitive model, and the second, the new institutional economics (NIE) framework, was used to analyse the role of transaction costs in the delivery of products and services and their access by farmers. A probit model was applied to identify the specific factors that farmers consider in their choices of animal health services. Recommendations were made for the optimal pathways to deliver East Coast fever vaccines to smallholder farmers. The study was conducted in three phases. The first phase involved a cross- sectional survey of 344 smallholder dairy farmers in the central highlands of Kenya, using a structured questionnaire. These farms were selected on a gradient of market access, with high, medium and low market access represented by Kiambu, Nakuru and Nyandarua districts, respectively. The second phase involved an exhaustive survey of all service providers delivering animal health services in the study areas. The third phase involved working backwards through the marketing chain to the distributors and suppliers of technologies, as well as interviewing key informants at policy and institutional levels. Delivery of TTBD products and services was found to be highly competitive, mostly carried out by paravets (35% of the total) and stores (33%), particularly in rural areas. Vets (18%) had a higher distribution in peri-urban areas, and their limited distribution in rural areas raised the transaction costs associated with rural farmers’ search and screening for high quality services. There were no formal regulatory bodies supervising the quality of the products and services being supplied to farmers and no state restrictions existed on the type of service providers selling tick control products. Although pyrethrines (pour-ons) were only permitted for tsetse control, they were freely being sold to farmers for tick control. A live vaccine, the infection and treatment method (ITM) for ECF immunization, was available in the country but its sale was restricted to a single site, the Kenya Coast. Thus, this vaccine was not available in the study areas. The study identified three key problems that require specific policy intervention: i) poor access of services and products by farmers, with an undefined role of paravets who are presently under-utilized, ii) information asymmetries among farmers and the need to enforce service quality control of products and services, iii) lack of voice among smallholder farmers with no leverage for compensations in cases where they receive poor or inappropriate services. Several transaction costs were identified as constraining the utilization of animal health services by farmers, and ranged from information, through negotiation to monitoring costs. Farmers considered the ethnicity and the service quality (as determined by past performance) of the nearest service provider as important in their choices, and the density of service providers over a given radius around each farm as well as travel time to a service provider were crucial determinants in farmer decision-making. Using a combination of economic and epidemiological approaches, the study assessed supply and demand issues associated with delivery pathways for ECF vaccines among smallholder farmers. The supply-side component involved evaluating transaction costs associated with two ECF vaccines; ITM and a sub-unit vaccine under development, and identifying the appropriate role of public and private sector in delivery. The main constraints associated with ECF vaccine delivery and requiring appropriate policies included high information asymmetries faced by farmers, lack of appropriate quality control and limited accessibility to products and services by farmers. On the demand side, ECF risk was found to vary with cattle production systems and agro-ecology. Potential demand for vaccines was found to be high in both Nyandarua and Nakuru districts and relatively low in Kiambu, where zero-grazing reduces risk substantially. The study recommends utilization of paravets for ECF vaccine delivery as an effective means of reducing transaction costs by increasing service penetration especially in rural areas where the density of veterinarians tends to be low. / Thesis (PhD (Veterinary Sciences))--University of Pretoria, 2002. / Veterinary Tropical Diseases / unrestricted

Feedlot cattle are subjected to numerous stresses that impede on their growth performance and carcass quality. Stress also depletes the animal body with its nutrients subsequently leading to deficiencies. The aim of this study was to investigate the effect of selenium (Se) and chromium (Cr) on stress and subsequently on growth performance, carcass characteristics including meat colour and liver tissue minerals. It is thought that Se, as anti-oxidant and Cr effectiveness in glucose metabolism might be effective on these production parameters. Four experiments were conducted for that purpose. The first experiment consisted in the assessment of the response of animals to dietary supplement of 0.3 mg.kg –1 DM Se and 0.3 mg.kg –1 DM Cr in a 3x4 factorial design. Seventy-two steers were allocated to 12 pens of six animals each. The results showed no statistical difference in blood cortisol levels on day 0 (d 0). On d 04, cortisol concentrations were lower than on d 0 (P≤0.05) except for treatment “Se X Cr combination” (SEL/CHR). On d 42, the values were high again except for SEL/CHR that had very low cortisol values (P≤0.05). The plots of blood glucose concentrations were almost similar to those of blood cortisol. There was no carry-over effect of alleviation of stress on performance. It was suggested that the animal type used was not appropriate for feedlot. The carcass characteristics were not statistically different. Meat pH measurements were similar but the differences between pH taken on slaughter day (pH 1) and 24 hours later were different (P≤0.05) for CHR and SEL/CR. This suggests that Cr because of its effect on glycogen storage is more effective in maintaining an appropriate meat pH fall and subsequently a longer meat shelf life. The liver tissue mineral status of the animals was normal. However, supplemental Se increased significantly (P≤0.05) the liver tissue Ca, Mg, Co and Mn while Cr decreased the concentrations of Ca, Mg and Co. Selenium was positively correlated to Cu and P while Cr was negatively correlated to Co. There was no relationship between liver tissue mineral and production parameters. The second trial dealt with the meat colour. Twenty-four prime rib samples were randomly collected from the animals described in Experiment-1 in a 2x3x4 factorial design (two samples per pen). Samples were treated as described by Buys et al. (2000). The readings of metmyoglobin as an indication of meat discoloration were not different between treatments. However, the ratio of metmyoglobin over the rest of meat components showed that supplemental chromium (CHR) had a lower value (P≤0.05). Chromium might have permitted a better glucose utilisation and glycogen storage in muscle of live animal. This might have maintained an adequate drop in meat pH subsequently lowering the lipid peroxidation and preventing the accumulation of metmyoglobin. The third trial was aimed to verify the findings of Experiment-1 and to compare the effect of Cr sulphate to that of high-Cr yeast and their interactions with Se. Seventy-two weaner calves were allocated to six pens of 12 animals each. Cortisol and glucose concentrations were similar on d 0. On d 04 treatments SEL and Cr sulphate (ICH) had low values (P≤0.05) while on d 42, combined Se and organic Cr (SOC) tended to have low values. These results and those from Experiment-1 showed that Se is efficient in the alleviation of stress in the adaptation days on feed while combined Se and Cr treatments are more efficient in the production phase. The organic Cr is not more effective than Cr sulphate in alleviation of stress. The combination “Se and inorganic Cr” (SIC) had higher ADG and better P-FCR (P≤0.05) and it tended to have better carcass characteristics. Mineral concentrations were normal and similar. As seen in Experiment-1, treatment SEL highly (P≤0.01) increased liver Ca concentration. Chromium and most other mineral concentrations were not affected by supplemental Cr. Overall, organic Cr was not superior to Cr sulphate. Previous experiments indicated that combining Se to Cr might give better results. The fourth trial aimed to find the best combination. Thirty-six weaner steers were allocated to six pens of six animals each. There was no difference in cortisol levels but a tendency (P=0.1) was noted on d 47 with combined “sodium selenite x Cr sulphate” (ISIC) and “high-Se yeast x Cr sulphate” (OSIC) having low values. Blood glucose values were not different. Blood cortisol concentrations were positively correlated to glucose on d 47. Selenium and Cr did not significantly affect the overall growth efficiency of the steers but during the adaptation period, the controls and OSIC treatments had better ADG and PFCR. Treatments ISIC and “sodium selenite x organic Cr” (ISOC) had similar live weight whilst treatment OSIC had higher live weight than “organic Se x organic Cr” OSOC. The combined organic forms were better than the inorganic ones. The carcass parameters were not affected. However, ISIC tend to have higher carcass mass than ISOC; similarly, OSIC tended to perform better than OSOC. Higher liver tissue Se and Cr were due to supplemental Se and Cr (P≤0.05). Treatment ISIC had the highest liver Se levels (P≤0.05) in this experiment and in Experiment-3. Selenium did not interact with other elements. In contrast, Cr was negatively correlated to Fe and Mn and positively to Mg. Chromium tends to be negatively correlated to other minerals. Precautions might be recommended when feeding excessive Cr because Cr does not augment the liver concentration of other minerals (Chang et al., 1992; Anderson et al., 1997). / Thesis (PhD)--University of Pretoria, 2001. / Production Animal Studies / unrestricted

Bovine Respiratory disease (BRD) accounts for the highest proportion of morbidities and mortalities in feedlot cattle. Since both clinical and subclinical disease is known to affect growth performance, it is clear that both should be accounted for in estimating the overall effect of BRD on performance in feedlot cattle. To our knowledge there have been no studies estimating the true impact of BRD on the economy of the South African feedlot industry, including both the direct costs of treatment, labour and mortalities and the hidden costs of lower gains due to BRD. This was an observational study, utilising predominantly routinely collected data from two commercial cattle feedlots. Assessment of the effect of treatment for BRD on outcome variables (performance parameters and prevalence of lesions) took the form of a prospective cohort study. Assessment of the effect of lung lesions at slaughter on performance took the form of a cross-sectional study, in which the presence of lung lesions and performance parameters were recorded at slaughter. Assessment of the overall effect of BRD on performance was then done using a combined case definition (treatment for BRD and/or lung lesions present at slaughter). Slaughter data for 2036 animals were available for the final analysis. Mean average daily gain (ADG) for all animals was 1.504 kg for the period from processing to slaughter. Average days on feed (DOF) was 136 days. Peak incidence of respiratory disease in the feedlots occurred on Day 18 after arrival. A total of 22.7% of animals were treated for clinical respiratory disease. No mortalities occurred due to BRD during this period. A total of 42.8% of animals had lung lesions present at slaughter. Of animals never treated for respiratory disease, 38.5% had lung lesions at slaughter. Of animals that had lung lesions at slaughter, 69.5% had never been treated for respiratory disease. Using the combined case definition, the estimated incidence of BRD during this study was 52%. It was found that pulling for BRD was associated with an overall decrease in ADG of 19 g for the whole period in the feedlot. The presence of lung lesions (bronchopneumonia and/or adhesions/pleuritis) at slaughter was associated with a decrease in ADG of 27 g for the whole feeding period. The occurrence of BRD (using the combined case definition) was associated with a decrease in ADG of 28 g for the period from processing to slaughter. This translated into a hidden cost of R14.93 per animal in the feedlot. This was nearly equal to the direct variable cost/animal entering the feedlot of R15.40. The total loss due to BRD was estimated to be R30.30 per animal entering the feedlot with an estimated cost of about R40m per year to the South African feedlot industry. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2004. / Production Animal Studies / unrestricted

The objectives of the study were to compare the efficacy of six intramammary dry-cow antibiotic preparations for curing existing IMI and for preventing the introduction of new IMI during the dry period. The effect of factors such as parity, milk yield, udder depth, teat canal integrity, number of infected quarters per cow, quarter-site infections and somatic cell count at drying off on cure-rates and new IMI as well as the length of the dry period and rainfall during the dry period were examined. The possible influence of treatment on the SCC during the subsequent lactation was also examined. Prior to the study a herd survey was performed to determine the basic udder health status of the trial herd. Cows due for drying off were clinically evaluated for enrollment and randomly allocated to receive one of the six dry-cow intramammary products under investigation. The six products that were studied were Nafpenzal DC (procaine benzylpenicillin, nafcillin and dihydrostreptomycin), Rilexine 500 DC (cephalexin and neomycin sulphate), Orbenin Extra DC (cloxacillin), Cepravin Dry Cow (cephalonium), Bovaclox DC (cloxacillin and ampicillin) and Dispolac Dry Cow (procaine benzylpenicillin and dihydrostreptomycin). Quarter milk samples were collected at drying off, (prior to treatment), and 1 to 6 days after calving for determination of the SSC and presence of micro-organisms in the milk. Cows were closely observed during the dry period and udders were clinically examined on a weekly basis and post-calving till udder oedema disappeared. Data from 162 cows and 648 quarters are summarized. The following were determined · Prevalence of pathogens at drying off and post-calving · Overall cure-rate and new intramammary infection rate. · Comparative efficacy of dry-cow treatment on cure-rate and prevention of new IMI. · Effect of parity, milk yield at drying off, udder depth, teat canal integrity, SCC, quarter-site infection, number of infected quarters at drying off, length of the dry period and rainfall during the dry period. · Effect of treatment on three SCC post calving during the subsequent lactation. Clinical mastitis developed in two quarters of two cows (1,03%) during the dry period which was less than described in literature, and they were removed from the trial. The prevalence of pathogens at drying off was 29,78%, of which 7,87% and 21,91% were due to major and minor pathogens respectively. The prevalence of pathogens post-calving was 22,22%, a net reduction of 7,56%, of which 4,47% and 17,75% were due to major and minor pathogens respectively. The overall cure-rate was 83,94% for quarters and varied between 72,3% and 93,9% for the various products. The overall difference in the percentage of cases cured, compared to the different micro-organisms, was found to be only marginally significant (p<0,057). High cure- rates were observed for STA, SAG and non-agalactiae pathogenic streptococci compared to studies previously done, while lower cure-rates than described were observed with CNS. Antimicrobial products used in this trial differed substantially in their efficacy to cure Gram-positive IMI. Cure rates for Cepravin Dry Cow was 93,9%, Orbenin Extra DC 91,5%, Rilexine 500 DC 85,7%, Nafpenzal DC 79,2%, Bovaclox DC 75,0% and Dispolac Dry Cow 72,4%. Interestingly, but not of any significance, was an observation that the two products with the highest overall cure-rates both contained only one antimicrobial agent compared to the other 4 products which were combinations of two or more antimicrobials. There was no significant association between parity, milk yield, teat canal integrity, number of infected quarters per cow, quarter-site infections at drying off, length of the dry period and rainfall during the dry period and the cure-rate. However, there was a significant association between udder depth (p<0,0056) and SCC (p<0,005) at drying off and cure-rate. The cure-rate was significantly less in cows with udder depth scores of 1 and 2 or SCC of more than 750 000 cells per ml milk at drying off. The overall rate of new IMI during the dry period was 17,44%. The new intramammary infection rate for quarters which received dry-cow treatment varied between 13,4% and 24,1% for the different products. The majority (70,8%) of new IMI were caused by CNS during the dry period. Almost all (96,6%) major pathogens isolated post-calving were new IMI, while 74,1% of minor pathogens were new IMI. Antimicrobial products differed in their efficacy in preventing new IMI during the dry period. The percentages of new IMI observed in cows treated with the six products were: 13,2% for Cepravin Dry Cow, 16,3% for Rilexine 500 DC, 16,7% for Dispolac Dry Cow, 17,3% for Bovaclox DC, 21,4% for Nafpenzal DC and 25,9% for Orbenin Extra DC. The probability of quarters developing new IMI during the dry period was significantly increased when cows were dried off with milk yields higher than 18kg (p<0,0037) or had low udder depth (scores of 1 or 2) (p<0,0003). Higher parity cows (p<0,005) and those that had a teat canal score of 4 (p<0,039) and above at drying off were also at an increased risk for new IMI. Marginally significantly (p<0,06) more IMI were contracted on the left side of the udder than the right side of the udder and cows at drying off and cows with dry periods longer than 80 days had marginally (p<0,06) more new IMI during the dry period. A positive correlation was found between low SCC (<250 000 cell per ml milk) and number of infected quarters per cow and parity (less than 3 lactations) at drying off. There was no significant association between the SCC at drying off and new IMI during the dry period. Significantly fewer new IMI (p<0,05) were observed when no rain fell during the dry period, compared to cows that experienced rain during their dry period. A comparison between the six antibiotic intramammary dry-cow products in relation to their efficacy in curing existing IMI and preventing new IMI showed qualitative differences between them, ranked as follows: Dispolac Dry Cow was the most effective and Orbenin Extra dry the least effective in preventing new IMI with major pathogens and Cepravin Dry Cow was to most and Nafpenzal DC the least effective in preventing new IMI with minor pathogens. Cepravin Dry cow was the most effective in the overall prevention of new IMIduring the dry period. Due to the random selection of cows the percentage of IMI differed for each product at the start of the trial. To compensate for this initial variation, percentage point improvement from drying off until calving was calculated for each antimicrobial product, taking both the cure-rates and new IMI into account. The efficacy of antimicrobial products during the dry period differed substantially when percentage point improvements were utilised: from an increase in IMI post-calving of 11,73% with Nafpenzal DC to a decrease of more than 50% in IMI at calving with both Cepravin Dry Cow and Rilexine 500 DC. Cows dried off with Rilexine 500 DC had a significantly lower SCC for the first two months post-calving than those dried off with the other five products in this trial. It is concluded that a substantial difference in efficacy exists between antimicrobial intramammary dry-cow products in their ability to cure and prevent new IMI during the dry period. Dry cow therapy should form part of a holistic approach towards the dry period, which also includes cow factors, dry-cow management, micro-organisms and the environment of the dry cow. Cow factors (milk yields, udder depth, parity, TCS and quarter-site infections) mainly have an influence on new IMI but a few cow factors (udder depth and SCC) are associated with the cure-rate of IMI. Management and rainfall during the dry period mainly affected new IMI rather than the cure-rate of existing IMI. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2004. / Production Animal Studies / unrestricted

This study was motivated by the desire to make a difference in the world. A better understanding of how ancient peoples perceived the phenomenon of war, and how these perceptions were shaped by social values, can hold great value for contemporary peace processes. A large number of Old Testament passages can further be illuminated through a study of this nature. The problem can be summarised by the following question: ● Why did the ancient person positively regard war as an inevitable cultural phenomenon, while the contemporary Western person negatively regards war as an anomaly? The hypotheses are as follows: ● the social values of respectively the Western and the ancient world can explain why there is a discrepancy between their respective perceptions about war; ● a study of Joshua 23 can verify the results attained above. The purpose of this essay is: ● to determine whether the social values of respectively the Western and the ancient world can explain why there is a discrepancy between their respective perceptions about war; ● to determine whether a study of Joshua 23 can verify the results attained above. Chapter 1 introduces the study. Chapter 2 examines the difference between Western and ancient perceptions of war regarding the following social values: honour and shame, group-orientation, limited goods, purity. A synchronic exegesis of Joshua 23 follows in Chapter 3. During the course of this exegesis, the results of Chapter 2 will both illuminate and be verified by Joshua 23. Chapter 4 presents the interested student with guidelines for further study on this subject. The aim of this study is to promote peace in 2004 by illuminating Joshua 23. / Dissertation (MA (Ancient Languages and Culture Studies))--University of Pretoria, 2004. / Ancient Languages / unrestricted

Rural subsistence farming practices are the primary agricultural activity in northeastern KwaZulu-Natal, South Africa. Cattle in this area have long been affected by tsetse-borne trypanosome infections. The causative organism, Trypanosoma brucei brucei was first identified by Bruce in the late 1800’s. Approximately 120000 cattle fall within a tsetse (Glossina austeni and Glossina brevipalpis) belt common to Mozambique and South Africa. Between 1991 and 1994 cattle in this area were treated with homidium bromide, and dipped with cyhalothrin, in an attempt to control trypanosomosis. No control measures have been implemented since 1994, however, and trypanosomosis re-emerged as a threat to animal health. In order to determine the optimum control measure available, a longitudinal incidence study was conducted to evaluate three possible control options. Four sentinel herds were selected from populations exposed to similar trypanosome challenges. The baseline trypanosome incidence rate was determined for each herd, after which each herd was subjected to a different trypanosome control measure. Two of the herds were subjected to topical pyrethroid treatment (Cyfluthrin pour-on and Flumethrin plunge-dip) as vector-control measures, one herd was treated 6 weekly with an injectable trypanocidal drug (isometamidium hydrochloride), and one herd served as an untreated control group. Monthly incidence rates were determined using the ‘dark-ground buffy smear technique’. The monthly incidence rates were standardized in order to account for variation in trypanosomosis challenge between the 4 herds. The standardized rates were then compared and the impact of the control strategies was quantified using the Area Under The Curve method. The cost efficacy of each control strategy was evaluated based on a partial budget system. Both the cyfluthrin pour-on and the injectable trypanocide were cost effective and had a dramatic trypanosomosis control effect with the pour-on having the greater impact/ control. The flumethrin plunge-dip displayed moderate trypanosomosis control properties, but proved not to be cost effective. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2004. / Production Animal Studies / unrestricted

The addition of prostatic fluid to intravaginally inseminated frozen-thawed semen resulted in an increase in pregnancy rate in bitches when compared with frozen-thawed semen inseminated on its own (Nöthling and Volkmann, 1993). However, the volume and viscosity of the inseminates varied greatly, which may have caused the improvement in fertility. Sperm TALP is a sperm-friendly fluid used extensively inin vitro processes. It was modified to exclude albumin to avoid any potentially beneficial effect. Twenty-eight young, healthy German shepherd bitches were inseminated with frozen-thawed semen to which either prostatic fluid (Group P) or albumin-free TALP (Group T) was added to provide an insemination volume of 7 ml. All bitches were inseminated daily from the onset of the appearance of shrunken angular folds on vaginoscopic evaluation until the day prior to diestrus as confirmed by cytological evaluation. Approximately 50 million progressively motile sperm was used per insemination. The semen was inseminated intravaginally after the addition of the appropriate fluid. Bitches were spayed 3 weeks after the onset of dioestrus and the number of conceptuses and corpora lutea counted. The non-resorbed conceptuses were taken as the litter size. The number of corpora lutea did not differ between the groups (n=25, P=0.496). The pregnancy rate between the groups did not differ. Among pregnant bitches, Group P (n=13) had significantly higher litter sizes than Group T (n=12) (P = 0.036). For the 13 bitches that received prostatic fluid, there were 139 corpora lutea and 80 conceptuses whereas, for the 12 bitches that received albumin-free TALP, there were 117 corpora lutea and 44 conceptuses (Chi-squared, P=0.002). Prostatic fluid has a positive influence on the fertility of frozen-thawed sperm more than by merely increasing the volume or decreasing the viscosity of the inseminate. The exact mechanism of its influence remains unknown. / Dissertation (MMedVet (Gyn))--University of Pretoria, 2002. / Production Animal Studies / unrestricted

The objective of this research project was to evaluate the clinical effect of Dimethyl sulphoxide in the symptomatic treatment of sheep suffering from heartwater caused by lichia ruminantiumforrmerly Cowdria ruminantium). 32 Merino crossbred sheep were used of which, 16 were infected with heartwater and 16 were control animals. Of the 16 sheep infected with heartwater, 8 were treated with a 10% solution of DMSO in polyionic fluid at the dose rate of 1g/kg twice daily for three consecutive days. Treatment was initiated two days after the onset of clinical disease. Eight of the control sheep were treated with DMSO following the same protocol. The remaining 8 infected and 8 not infected sheep were given similar volumes of polyionic fluid as placebo treatment. Arterial and venous blood samples for blood gas, haematocrit and total plasma protein measurement were collected daily from 5 days before, to 7 days following the onset of clinical disease. Gross pathological findings and cytological confirmation of the disease were recorded for the 16 infected sheep. The infected sheep treated with DMSO were able to maintain pulmonary gas exchange, had reduced pleural effusion and plasma protein loss compared to the untreated infected sheep that became hypoxic, developed severe pleural effusion and plasma protein loss. However, the infected sheep treated with DMSO developed a mild uncompensated metabolic acidosis. Non-infected sheep treated with DMSO showed reduced appetite while non-infected untreated sheep remained normal. The reduction in pleural effusion, maintenance of gaseous exchange and plasma protein levels, as a result of the use of DMSO in the symptomatic treatment of sheep suffering from heartwater, are considered beneficial. / Dissertation (MMedVet (Med))--University of Pretoria, 2002. / Production Animal Studies / unrestricted

The South African agricultural sector has experienced a long history of state intervention. In the past decade, the marketing of agricultural products has been transformed from a highly regulated to an essentially free dispensation. South African agriculture is now exposed to an uncertain environment that is influenced by the dynamic changes in the world economy. The dynamic environment in which producers of agricultural products operate urges the need to understand the production and consumption patterns of the products that they produce. South Africa does not have a modelling system in place that can simulate the impact of economic policies and exogenous changes on commodity markets. The general objective of this dissertation is to analyse the structure of the South African wheat market using economic theory and econometric modelling techniques. The specific objectives are to make baseline projections regarding the supply and use of wheat in South Africa and to analyse the impacts of various policy alternatives on the wheat sector for the period 2002 to 2008. The convenient and efficient methodology developed by the Food and Agricultural Policy Research Institute (FAPRI) for conducting policy analysis research, is particularly pertinent to this study and hence underpins the approach used for modelling the market and policy alternatives for the South African wheat sector. Ordinary Least Squares (OLS) is used to estimate single equations, which are collapsed into one system and estimated simultaneously using the Two-Stage-Least-Squares (2SLS) modelling technique. After the validation of the model’s performance, it is used to make baseline projections for the South African wheat sector during the period 2002 to 2008. In order to establish a baseline, a number of assumptions are made, relating to agricultural policies, the macroeconomic environment, and weather conditions. In the final part of this study, the constructed model is used to simulate the impacts of changes in policies, world markets and the production environment on domestic prices as well as levels of demand and supply. Three scenarios are analysed, the elimination of the import tariff for wheat, a twelve percent depreciation in the exchange rate, and the convergence of the elimination of the import tariff and the 12% depreciation in the exchange rate. Although the model developed in this dissertation is for a South African specific case study and therefore, contributes significantly to the understanding of the South African wheat market, it also highlights a number of shortcomings in the structure, relevance and applicability of such models, that need to be considered and addressed. The first of which is that the model structure is based on the level of knowledge, understanding, and perception that the modeller has of the sector; therefore, the basic structure of the model could be bias. The second is that this particular model was not developed with the necessary interaction between the different commodity and livestock sectors and that this model should ideally be integrated into a larger model, incorporating a larger number of commodities and policy variables. Lastly, it is important to take the nature of the good being modelled into consideration by asking whether or not the relevant product is a homogenous good. Ideally, a model of this nature would include a supply and demand function for each type of wheat that could then be estimated as a single system of equations. / Dissertation (MSc (Agric))--University of Pretoria, 2002. / Agricultural Economics, Extension and Rural Development / unrestricted

Mycoplasma control in any poultry company requires an integrated approach involving diligent biosecurity, animal husbandry and disease surveillance. Mycoplasma gallisepticum (MG) infection is very costly to the broiler industry as it predisposes birds to a variety of primary and secondary respiratory diseases thus reducing production efficiency and profitability. Since the primary disease is rather insidious, relatively difficult to confirm (especially in vaccinated flocks), prone to becoming quiescent and vertically transmitted, control measures must begin at the breeder level and involve conscientious flock surveillance. While disease eradication is the best approach to MG control the economic pressures of modern broiler production often preclude such drastic measures. Vaccination programmes are often introduced to reduce the economic impact of the disease in breeder flocks and to minimize, or hopefully prevent vertical transmission. To prevent vertical transmission and lateral spread of field strain MG infection, early diagnosis is critical. Flock testing needs to be done every 2-4 weeks (depending on prevailing risk), on 90 birds (for an average flock of 7 000 birds) to satisfy statistical requirements for the detection of a 5% infection-rate with 99% confidence. The RSPA test provides an inexpensive, reliable and rapid means of evaluating the serological response to ts-11 strain vaccination during the rearing phase. A floor pen trial confirmed that, three to ten weeks after ts-11 vaccination at 10 weeks of age, the RSPA test reactor rate is between 30% and 60%. PCR was used to confirm the absence of field challenge. A retrospective analysis of 4 years of RSPA test data from broiler breeder flocks immunized with the live ts-11 strain MG vaccine indicated that traditional RSPA test monitoring protocols were unreliable as a means of differentiating ts-11 vaccination from field strain MG infection. Non-infected (PCR negative) vaccinated flocks reached sero-positive agglutination rates of 100% making the differentiation of vaccine response and field infection impossible during the lay cycle. RSPA monitoring of broiler breeders during the pullet rearing stage (0-20 weeks) was in contrast still very effective. While previously reported trials indicated that the introduction and subsequent serological monitoring of in-contact non-vaccinated sentinels may enhance the efficacy of the RSPA monitoring procedure this trial indicated that it does not. The ts-11 strain MG spread to in-contact sentinels so rapidly under field conditions that the serum agglutination pattern of these birds mimics that of the vaccinated pullets. The potential for ts-11 strain MG to spread from bird to bird is a reality and even spread from pen to pen (within the same house) may be possible if biosecurity is inadequate. The decision to vaccinate should include consideration as to the consequence of ts-11 strain MG spread to surrounding susceptible flocks. The use of molecular diagnostic techniques on pooled tracheal swabs taken from representative flock birds is a potentially cost effective and reliable means of differentiating ts-11 vaccine strain from field strain MG. PCR amplification of DNA from tracheal swab samples and strain identification based on amplicon size was shown to be a reliable and sensitive means of detecting ts-11 strain following vaccination. The proprietary PCR primer used in this trial was specifically designed to identify the ts-11 strain by amplifying a 229 bp fragment that is characteristic and distinguishable from all other MG field strain isolates based on amplicon size. This technique provides the opportunity to differentiate field strain infection from vaccine strain MG, provided strain specific PCR primers are available. It is recommended that the RSPA assay is used to differentiate effective vaccination from field exposure during pullet rearing and PCR assay is used to monitor broiler breeder flocks for MG challenge during the laying cycle and confirm that point-of-lay broiler breeder pullets are free of field strain MG infection. Where possible flocks with a confirmed field strain challenge should be eliminated and all hatching eggs removed from the hatchery and destroyed. / Dissertation (MMedVet (Altil.))--University of Pretoria, 2004. / Production Animal Studies / unrestricted