Effect of diet and sex-sorting on growth and gonad development in farmed South African abalone, Haliotis midae
- Authors: Ayres, Devin William Philip
- Date: 2014
- Subjects: Haliotis midae -- South Africa , Haliotis midae fisheries -- South Africa , Abalone culture -- South Africa , Abalones -- Physiology -- South Africa , Abalones -- South Africa -- Growth , Abalones -- Feeding and feeds -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5357 , http://hdl.handle.net/10962/d1010856 , Haliotis midae -- South Africa , Haliotis midae fisheries -- South Africa , Abalone culture -- South Africa , Abalones -- Physiology -- South Africa , Abalones -- South Africa -- Growth , Abalones -- Feeding and feeds -- South Africa
- Description: Abalone, Haliotis midae, farmers in South Africa that feed formulated diets reported a periodic drop in abalone growth during periods of increased gonad development. A large drop in abalone biomass was noticed after presumed spawning events. This study was aimed to determine the effect of diet and sex-sorting on gonad development in abalone. Experiments were conducted on a commercial abalone farm from July 2012 to the end of June 2013. Isonitrogenous and isoenergetic diets were formulated with two protein sources. A fishmeal and soybean meal (S-diet) diet and a fishmeal only (F-diet) diet were fed to abalone (50 - 70 g abalone⁻¹) over 12 months. Weight and length gain, gonad bulk index (GBI), visceral index (%) and meat mass index (%) were determined monthly and seasonally. A histological study on the female gonads was conducted. This study also included an experiment to test the effect of sex-sorting (70 - 80 g abalone⁻¹) on growth and body composition with treatments including males (M), females (F) and equal numbers of males and females (MF). Weight gain and length gain were faster in S-diet-fed abalone (RM-ANOVA, F ₍₁, ₁₆₎ = 7.77, p = 0.01; F ₍₁, ₆₉₎ = 49.9, p < 0.001, respectively). Gonad development was significantly affected by the inclusion of soybean meal with S-diet-fed abalone showing higher GBI-values than F-diet-fed abalone (RM-ANOVA, F ₍₁, ₃₃)= 16.22, p = 0.0003). Male abalone had higher GBI-values than females (RM-ANOVA, F ₍₁, ₃₃₎ = 39.87, p < 0.0001). There was no significant difference in average feed conversion ratio (FCR) between diets over time (RM-ANOVA, F ₍₁, ₂₁₎ = 0.008, p = 0.97). However, average FCR-values were significantly highest between November 2012 and March 2013, the presumed spawning season. The visceral mass (gut and gonad) as a proportion of whole mass (visceral index, %) was significantly higher in abalone fed the S-diet (RM-ANOVA; F ₍₁, ₆₉₎ = 68.06, p < 0.0001). There was no difference in meat mass index (%) between diets for both male and female abalone (RM-ANOVA; F ₍₇, ₂₄₈₎ = 0.80, p = 0.60; F ₍₇, ₂₄₁₎ = 1.7, p = 0.11,respectively). Meat mass index significantly decreased from September 2012 to February 2013 coinciding with the period of high GBI-values. The distribution of oocyte maturity stages differed between diets. The majority of oocytes within S-diet-fed abalone were fully mature stage 8 oocytes compared to a majority of stage 7 oocytes in F-diet-fed abalone. Histology corroborated peaks in GBI-values for abalone fed both diets. There was no significant difference in growth, GBI, visceral index (%) and meat mass index (%) between abalone sorted into monosex and mixed-sex populations. Thus, the presence of the opposite sex did not have an effect on growth and gonad mass in H. midae. The phytoestrogens daidzin, glycitin, genistin, daidzein, glycitein and genistein were present in soybean meal and only traceable amounts were found in the F-diet. This study provided evidence that soybean meal present in formulated feed affected growth and gonad development in H.midae. The difference in the distribution of the maturity stages of oocytes was affected by diet. Sex-sorting abalone into monosex and mixed-sex populations had no influence on weight and length gain and gonad development.
- Full Text:
- Date Issued: 2014
- Authors: Ayres, Devin William Philip
- Date: 2014
- Subjects: Haliotis midae -- South Africa , Haliotis midae fisheries -- South Africa , Abalone culture -- South Africa , Abalones -- Physiology -- South Africa , Abalones -- South Africa -- Growth , Abalones -- Feeding and feeds -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5357 , http://hdl.handle.net/10962/d1010856 , Haliotis midae -- South Africa , Haliotis midae fisheries -- South Africa , Abalone culture -- South Africa , Abalones -- Physiology -- South Africa , Abalones -- South Africa -- Growth , Abalones -- Feeding and feeds -- South Africa
- Description: Abalone, Haliotis midae, farmers in South Africa that feed formulated diets reported a periodic drop in abalone growth during periods of increased gonad development. A large drop in abalone biomass was noticed after presumed spawning events. This study was aimed to determine the effect of diet and sex-sorting on gonad development in abalone. Experiments were conducted on a commercial abalone farm from July 2012 to the end of June 2013. Isonitrogenous and isoenergetic diets were formulated with two protein sources. A fishmeal and soybean meal (S-diet) diet and a fishmeal only (F-diet) diet were fed to abalone (50 - 70 g abalone⁻¹) over 12 months. Weight and length gain, gonad bulk index (GBI), visceral index (%) and meat mass index (%) were determined monthly and seasonally. A histological study on the female gonads was conducted. This study also included an experiment to test the effect of sex-sorting (70 - 80 g abalone⁻¹) on growth and body composition with treatments including males (M), females (F) and equal numbers of males and females (MF). Weight gain and length gain were faster in S-diet-fed abalone (RM-ANOVA, F ₍₁, ₁₆₎ = 7.77, p = 0.01; F ₍₁, ₆₉₎ = 49.9, p < 0.001, respectively). Gonad development was significantly affected by the inclusion of soybean meal with S-diet-fed abalone showing higher GBI-values than F-diet-fed abalone (RM-ANOVA, F ₍₁, ₃₃)= 16.22, p = 0.0003). Male abalone had higher GBI-values than females (RM-ANOVA, F ₍₁, ₃₃₎ = 39.87, p < 0.0001). There was no significant difference in average feed conversion ratio (FCR) between diets over time (RM-ANOVA, F ₍₁, ₂₁₎ = 0.008, p = 0.97). However, average FCR-values were significantly highest between November 2012 and March 2013, the presumed spawning season. The visceral mass (gut and gonad) as a proportion of whole mass (visceral index, %) was significantly higher in abalone fed the S-diet (RM-ANOVA; F ₍₁, ₆₉₎ = 68.06, p < 0.0001). There was no difference in meat mass index (%) between diets for both male and female abalone (RM-ANOVA; F ₍₇, ₂₄₈₎ = 0.80, p = 0.60; F ₍₇, ₂₄₁₎ = 1.7, p = 0.11,respectively). Meat mass index significantly decreased from September 2012 to February 2013 coinciding with the period of high GBI-values. The distribution of oocyte maturity stages differed between diets. The majority of oocytes within S-diet-fed abalone were fully mature stage 8 oocytes compared to a majority of stage 7 oocytes in F-diet-fed abalone. Histology corroborated peaks in GBI-values for abalone fed both diets. There was no significant difference in growth, GBI, visceral index (%) and meat mass index (%) between abalone sorted into monosex and mixed-sex populations. Thus, the presence of the opposite sex did not have an effect on growth and gonad mass in H. midae. The phytoestrogens daidzin, glycitin, genistin, daidzein, glycitein and genistein were present in soybean meal and only traceable amounts were found in the F-diet. This study provided evidence that soybean meal present in formulated feed affected growth and gonad development in H.midae. The difference in the distribution of the maturity stages of oocytes was affected by diet. Sex-sorting abalone into monosex and mixed-sex populations had no influence on weight and length gain and gonad development.
- Full Text:
- Date Issued: 2014
The preparation of antigen for the generation of polyclonal antibodies against the capsid subunit, VP1, and the viral protease, 3Cpro, of Theiler's murine encephalomyelitis virus (TMEV)
- Authors: Moetlhoa, Boitumelo
- Date: 2014
- Subjects: Enteroviruses , Encephalomyelitis , Antigens
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4118 , http://hdl.handle.net/10962/d1013225
- Description: The Picornaviridae is a family of viruses of economic importance that have a major impact on human and animal health. Some of the major genera found in the Picornaviridae family are Enterovirus which includes Poliovirus (PV) and Human Rhinovirus (HRV), Cardiovirus which includes Theiler’s murine encephalomyelitis virus (TMEV) and Saffold virus (SAFV), Aphthovirus of which the Foot and Mouth disease virus (FMDV) is a member and Hepatovirus which includes Hepatitis A virus (HAV). Picornaviruses have a single stranded, positive sense RNA genome which is approximately 7.5-8.4 kb pairs in size. The picornavirus genome is translated into a large polyprotein and is proteolytically cleaved by viral proteases namely 2Apro, 3Cpro and 3CDpro into mature viral structural and non-structural polypeptides encoded by the P1, P2 and P3 domains. Picornaviruses utilise host cell machinery and cellular pathways for entry and uncoating, genome replication and capsid assembly. In our laboratory, we are studying the mechanisms by which TMEV interacts with host cell components and our recent research shows that molecular chaperones are required for a production infection. To follow up on this observation, the overall aim of this study was to prepare antigen for the generation of polyclonal antibodies against the TMEV VP1 and 3Cpro proteins. To this end, the TMEV VP1 and 3Cpro amino acid sequences were analysed to identify hydrophobic, hydrophilic and antigenic regions. Homology modelling was performed in order to predict linear B cell epitopes exposed on the surface of the protein structures. The full length coding sequences of VP1 and 3Cpro were selected for amplification by the PCR and cloning into pQE-80L for expression in a bacterial system. Time course induction studies of recombinant VP1 and 3Cpro showed that the proteins were maximally expressed at 6 hrs and 4 hrs respectively. Recombinant VP1 was solubilised using the detergent, Sarcosyl and purified by Nickel affinity chromatography under native conditions. Because recombinant VP1 co-purified with an unidentified protein, the pET expression system was used. Although no protein of the estimated size was observed by SDS-PAGE analysis in the time course induction study, Western analysis using anti-His6 (2) antibodies detected a signal of ~35 kDa. Solubility studies resulted in the presence of two protein bands in the insoluble fraction resolved between 35 and 40 kDa. Recombinant 3Cpro expressed in a bacterial system was predominantly present in the insoluble fraction. Treatment with Sarcosyl had no effect on the solubility of the recombinant protein and it was therefore purified under denaturing conditions using 8M urea. Following dialysis, 3Cpro was used for immunisation of rabbits. Crude anti-TMEV 3Cpro antibodies were able to detect as little as 107 ng of bacterially expressed antigen at a dilution of 1:100 000 by Western analysis. The presence of contaminating proteins was reduced using pre-cleared anti-TMEV 3Cpro antibodies. The antibodies were unable to detect virally expressed 3Cpro in BHK-21 cell lysate supernatant. In an attempt to determine whether TMEV 3Cpro is present in the insoluble fraction, anti-TMEV 3Cpro antibodies were tested using total protein prepared from infected and mock-infected cell lysates. Once again, no protein band the size of 3Cpro was detected. The antibodies were further tested for detection of 3Cpro in TMEV-infected cells by indirect immunofluorescence and confocal microscopy. A diffuse cytoplasmic and perinuclear distribution, as well as nuclear staining, was observed in infected BHK-21 cells. This staining pattern resembled that observed for the HRV, FMDV and EMCV 3Cpro in similar experiments. Further experiments are required to confirm specificity of these antibodies for virally-expressed 3Cpro by Western analysis and indirect immunofluorescence.
- Full Text:
- Date Issued: 2014
- Authors: Moetlhoa, Boitumelo
- Date: 2014
- Subjects: Enteroviruses , Encephalomyelitis , Antigens
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4118 , http://hdl.handle.net/10962/d1013225
- Description: The Picornaviridae is a family of viruses of economic importance that have a major impact on human and animal health. Some of the major genera found in the Picornaviridae family are Enterovirus which includes Poliovirus (PV) and Human Rhinovirus (HRV), Cardiovirus which includes Theiler’s murine encephalomyelitis virus (TMEV) and Saffold virus (SAFV), Aphthovirus of which the Foot and Mouth disease virus (FMDV) is a member and Hepatovirus which includes Hepatitis A virus (HAV). Picornaviruses have a single stranded, positive sense RNA genome which is approximately 7.5-8.4 kb pairs in size. The picornavirus genome is translated into a large polyprotein and is proteolytically cleaved by viral proteases namely 2Apro, 3Cpro and 3CDpro into mature viral structural and non-structural polypeptides encoded by the P1, P2 and P3 domains. Picornaviruses utilise host cell machinery and cellular pathways for entry and uncoating, genome replication and capsid assembly. In our laboratory, we are studying the mechanisms by which TMEV interacts with host cell components and our recent research shows that molecular chaperones are required for a production infection. To follow up on this observation, the overall aim of this study was to prepare antigen for the generation of polyclonal antibodies against the TMEV VP1 and 3Cpro proteins. To this end, the TMEV VP1 and 3Cpro amino acid sequences were analysed to identify hydrophobic, hydrophilic and antigenic regions. Homology modelling was performed in order to predict linear B cell epitopes exposed on the surface of the protein structures. The full length coding sequences of VP1 and 3Cpro were selected for amplification by the PCR and cloning into pQE-80L for expression in a bacterial system. Time course induction studies of recombinant VP1 and 3Cpro showed that the proteins were maximally expressed at 6 hrs and 4 hrs respectively. Recombinant VP1 was solubilised using the detergent, Sarcosyl and purified by Nickel affinity chromatography under native conditions. Because recombinant VP1 co-purified with an unidentified protein, the pET expression system was used. Although no protein of the estimated size was observed by SDS-PAGE analysis in the time course induction study, Western analysis using anti-His6 (2) antibodies detected a signal of ~35 kDa. Solubility studies resulted in the presence of two protein bands in the insoluble fraction resolved between 35 and 40 kDa. Recombinant 3Cpro expressed in a bacterial system was predominantly present in the insoluble fraction. Treatment with Sarcosyl had no effect on the solubility of the recombinant protein and it was therefore purified under denaturing conditions using 8M urea. Following dialysis, 3Cpro was used for immunisation of rabbits. Crude anti-TMEV 3Cpro antibodies were able to detect as little as 107 ng of bacterially expressed antigen at a dilution of 1:100 000 by Western analysis. The presence of contaminating proteins was reduced using pre-cleared anti-TMEV 3Cpro antibodies. The antibodies were unable to detect virally expressed 3Cpro in BHK-21 cell lysate supernatant. In an attempt to determine whether TMEV 3Cpro is present in the insoluble fraction, anti-TMEV 3Cpro antibodies were tested using total protein prepared from infected and mock-infected cell lysates. Once again, no protein band the size of 3Cpro was detected. The antibodies were further tested for detection of 3Cpro in TMEV-infected cells by indirect immunofluorescence and confocal microscopy. A diffuse cytoplasmic and perinuclear distribution, as well as nuclear staining, was observed in infected BHK-21 cells. This staining pattern resembled that observed for the HRV, FMDV and EMCV 3Cpro in similar experiments. Further experiments are required to confirm specificity of these antibodies for virally-expressed 3Cpro by Western analysis and indirect immunofluorescence.
- Full Text:
- Date Issued: 2014
Web-based M-learning system for ad-hoc learning of mathematical concepts amongst first year students at the University of Namibia
- Authors: Ntinda, Maria Ndapewa
- Date: 2014
- Subjects: Mathematics -- Study and teaching (Higher) -- Namibia , Mathematics -- Technological innovations , Mobile communication systems in education , Teaching -- Aids and devices , Educational innovations , Open source software
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4701 , http://hdl.handle.net/10962/d1013174
- Description: In the last decade, there has been an increase in the number of web-enabled mobile devices, offering a new platform that can be targeted for the development of learning applications. Worldwide, developers have taken initiatives in developing mobile learning (M-learning) systems to provide students with access to learning materials regardless of time and location. The purpose of this study was to investigate whether it is viable for first year students enrolled at the University of Namibia (UNAM) to use mobile phones for ad-hoc learning of mathematical concepts. A system, EnjoyMath, aiming to assist students in preparing for tests, examinations, review contents and reinforce knowledge acquired during traditional classroom interactions was designed and implemented. The EnjoyMath system was designed and implemented through the use of the Human Centred Design (HCD) methodology. Two revolutions of the four-step process of the HCD cycle were completed in this study. Due to the distance between UNAM and Rhodes University (where the researcher was based), the researcher could not always work in close relation with the UNAM students. Students from the Extended Study Unit (ESU) at Rhodes University were therefore selected in the first iteration of the project due to their proximity to the researcher and their similar demographics to the first year UNAM students, while the UNAM students were targeted in the second iteration of the study. This thesis presents the outcome of the two pre-intervention studies of the first-year students' perceptions about M-learning conducted at Rhodes University and UNAM. The results of the pre-intervention studies showed that the students are enthusiastic about using an M-learning system, because it would allow them to put in more time to practice their skills whenever and wherever they are. Moreover, the thesis presents the different stages undertaken to develop the EnjoyMath system using Open Source Software (PHP and MySQL). The results of a user study (post-intervention) conducted with participants at UNAM, ascertained the participants' perception of the usability of the EnjoyMath system and are also presented in this thesis. The EnjoyMath system was perceived by the participants to be "passable"; hence an M-learning system could be used to compliment an E-learning system at UNAM.
- Full Text:
- Date Issued: 2014
- Authors: Ntinda, Maria Ndapewa
- Date: 2014
- Subjects: Mathematics -- Study and teaching (Higher) -- Namibia , Mathematics -- Technological innovations , Mobile communication systems in education , Teaching -- Aids and devices , Educational innovations , Open source software
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4701 , http://hdl.handle.net/10962/d1013174
- Description: In the last decade, there has been an increase in the number of web-enabled mobile devices, offering a new platform that can be targeted for the development of learning applications. Worldwide, developers have taken initiatives in developing mobile learning (M-learning) systems to provide students with access to learning materials regardless of time and location. The purpose of this study was to investigate whether it is viable for first year students enrolled at the University of Namibia (UNAM) to use mobile phones for ad-hoc learning of mathematical concepts. A system, EnjoyMath, aiming to assist students in preparing for tests, examinations, review contents and reinforce knowledge acquired during traditional classroom interactions was designed and implemented. The EnjoyMath system was designed and implemented through the use of the Human Centred Design (HCD) methodology. Two revolutions of the four-step process of the HCD cycle were completed in this study. Due to the distance between UNAM and Rhodes University (where the researcher was based), the researcher could not always work in close relation with the UNAM students. Students from the Extended Study Unit (ESU) at Rhodes University were therefore selected in the first iteration of the project due to their proximity to the researcher and their similar demographics to the first year UNAM students, while the UNAM students were targeted in the second iteration of the study. This thesis presents the outcome of the two pre-intervention studies of the first-year students' perceptions about M-learning conducted at Rhodes University and UNAM. The results of the pre-intervention studies showed that the students are enthusiastic about using an M-learning system, because it would allow them to put in more time to practice their skills whenever and wherever they are. Moreover, the thesis presents the different stages undertaken to develop the EnjoyMath system using Open Source Software (PHP and MySQL). The results of a user study (post-intervention) conducted with participants at UNAM, ascertained the participants' perception of the usability of the EnjoyMath system and are also presented in this thesis. The EnjoyMath system was perceived by the participants to be "passable"; hence an M-learning system could be used to compliment an E-learning system at UNAM.
- Full Text:
- Date Issued: 2014
The geological framework and depositional environments of the coal-bearing Karoo strata in the Central Kalahari Karoo Basin, Botswana
- Authors: Segwabe, Tebogo
- Date: 2009
- Subjects: Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4955 , http://hdl.handle.net/10962/d1005567 , Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Description: The investigation of the geological history (i.e., stratigraphy and sedimentology) and the dynamics of coal depositional environments, in particular, the forces responsible for changes in the accommodation space (e.g., subsidence vs. sedimentation rates) in the Permian coal-bearing Karoo strata in the Central Kalahari Karoo Basin (Botswana) revealed new details about the depositional processes and environments. Detailed review of the temporal and spatial stratigraphic variation of the coal-bearing Ecca Group successions via the analysis of facies changes based on core descriptions, gamma logs, field observations and palaeo-current measurements, lead to the identification of two main informal stratigraphic units, namely the Basal and Upper Units. The Basal Unit is characterised by an upward-coarsening succession, and it is interpreted as a product of a progradational deltaic setting (i.e., regressive deltaic cycle). This is followed by five sequences of fining-upward successions of sandstones and siltstones in the Upper Unit, interpreted as deposits of distributary channels (the basal arenaceous member) capped by finer argillaceous sequences of the deltaic floodplains (the upper coal-bearing member). The Upper Unit thus is interpreted as a delta plain facies association which was formed during transgressive phases when conditions for coal-quality peat accumulation (e.g., high water table) were present and the available accommodation space was partly controlled by tectonic uplift (repeated?) at basin margins. Limited palaeo-current analysis indicates deposition by channels flowing from the east, south-east and north-east. The lack of good quality exposures hampers the reconstruction of the plan form of the channel patterns. However, the little available evidence indicates a high-energy fluvio-deltaic system with irregular discharge and a high proportion of bedload sediments. Coal-seam thickness in the upper coal-bearing member reflect the complex control of the geological processes associated with and following peat formation, such as differential compaction of the underlying lithology, and the erosive or protective nature of the immediately overlying lithology.
- Full Text:
- Date Issued: 2009
- Authors: Segwabe, Tebogo
- Date: 2009
- Subjects: Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4955 , http://hdl.handle.net/10962/d1005567 , Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Description: The investigation of the geological history (i.e., stratigraphy and sedimentology) and the dynamics of coal depositional environments, in particular, the forces responsible for changes in the accommodation space (e.g., subsidence vs. sedimentation rates) in the Permian coal-bearing Karoo strata in the Central Kalahari Karoo Basin (Botswana) revealed new details about the depositional processes and environments. Detailed review of the temporal and spatial stratigraphic variation of the coal-bearing Ecca Group successions via the analysis of facies changes based on core descriptions, gamma logs, field observations and palaeo-current measurements, lead to the identification of two main informal stratigraphic units, namely the Basal and Upper Units. The Basal Unit is characterised by an upward-coarsening succession, and it is interpreted as a product of a progradational deltaic setting (i.e., regressive deltaic cycle). This is followed by five sequences of fining-upward successions of sandstones and siltstones in the Upper Unit, interpreted as deposits of distributary channels (the basal arenaceous member) capped by finer argillaceous sequences of the deltaic floodplains (the upper coal-bearing member). The Upper Unit thus is interpreted as a delta plain facies association which was formed during transgressive phases when conditions for coal-quality peat accumulation (e.g., high water table) were present and the available accommodation space was partly controlled by tectonic uplift (repeated?) at basin margins. Limited palaeo-current analysis indicates deposition by channels flowing from the east, south-east and north-east. The lack of good quality exposures hampers the reconstruction of the plan form of the channel patterns. However, the little available evidence indicates a high-energy fluvio-deltaic system with irregular discharge and a high proportion of bedload sediments. Coal-seam thickness in the upper coal-bearing member reflect the complex control of the geological processes associated with and following peat formation, such as differential compaction of the underlying lithology, and the erosive or protective nature of the immediately overlying lithology.
- Full Text:
- Date Issued: 2009
Investigations into the nutritional requirements of juvenile dusky kob, Argyrosomus japonicus (Pisces sciaendae), under ambient culture conditions
- Authors: Daniel, Simon James
- Date: 2004
- Subjects: Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5197 , http://hdl.handle.net/10962/d1002602 , Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Description: The effect of dietary protein, protein and energy ratios, fish meal replacement by Soya bean meal and feeding frequency was investigated on the growth, feed efficiency and body composition, of juvenile dusky kob, Argyrosomus japonicus. The effect of dietary protein levels was investigated by comparing isocaloric diets containing 35, 40, 45 and 55% protein. Dietary protein inclusion level significantly affected specific growth rates, feed efficiency and body composition (in terms of fat deposition) and results show that a minimum of 45% and maximum of 52.3% dietary protein is optimal. The protein and energy requirements were investigated by comparing three protein levels (35,40 and 45%) with three lipid levels (6, 9 and 12%) in a 3x3 factorial design. A diet 45% protein and 9% lipid, with a P: E ratio of29 mglkJ and DE of 15.5 kJ/g resulted in an optimal specific growth rate (1.6± 0.2), feed efficiency (FCR= 1.7±0.44; PER= 1.36) and body composition for A. japonicus. To investigate the effect of partial fish meal replacement by Soya bean meal (SBM) in the diet, 20-50% of the protein from fish meal was substituted by protein from SBM, and were compared with a control diet containing only fish meal. No significant differences in the specific growth rates, feed efficiencies and the body composition were recorded for the fish fed the control diet and for fish fed the 20 and 30% SBM treatments. Results show that up to 30% of the protein from fish meal can be replaced with protein from SBM in the diet of this species. The effect of feeding frequency and gut evacuation time was investigated by comparing four feeding frequencies. Fish were fed to satiation either once, twice, three or four times a day. Feed intake was significantly affected by feeding frequency and fish fed 2, 3 and 4 meals a day ate significantly more food (p< 0.05) than the fish fed one meal a day. No significant differences (p> 0.05) in the specific growth rates, feed efficiencies and body composition were recorded for fish fed 2, 3 and 4 times a day. Feed intake was used to calculate an optimal daily ration and feeding two meals a day resulted in an optimal daily ration of 4% BW/day. A gut evacuation time of 7.25 hours indicates that fish fed twice a day probably had sufficient time to digest their food and evacuate their guts, resulting in the same daily feed intake as fish given 3 and 4 meals a day. Results conclude that under the present experimental conditions, a minimum daily ration of 4% BW/day, fed twice a day (in the morning and evening) is required for optimal growth (SGR= 1.33± 0.1), feed efficiency (FCR= 1.96± 0.4; PER= 1.44± 0.2) and body composition in juvenile dusky kob.
- Full Text:
- Date Issued: 2004
- Authors: Daniel, Simon James
- Date: 2004
- Subjects: Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5197 , http://hdl.handle.net/10962/d1002602 , Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Description: The effect of dietary protein, protein and energy ratios, fish meal replacement by Soya bean meal and feeding frequency was investigated on the growth, feed efficiency and body composition, of juvenile dusky kob, Argyrosomus japonicus. The effect of dietary protein levels was investigated by comparing isocaloric diets containing 35, 40, 45 and 55% protein. Dietary protein inclusion level significantly affected specific growth rates, feed efficiency and body composition (in terms of fat deposition) and results show that a minimum of 45% and maximum of 52.3% dietary protein is optimal. The protein and energy requirements were investigated by comparing three protein levels (35,40 and 45%) with three lipid levels (6, 9 and 12%) in a 3x3 factorial design. A diet 45% protein and 9% lipid, with a P: E ratio of29 mglkJ and DE of 15.5 kJ/g resulted in an optimal specific growth rate (1.6± 0.2), feed efficiency (FCR= 1.7±0.44; PER= 1.36) and body composition for A. japonicus. To investigate the effect of partial fish meal replacement by Soya bean meal (SBM) in the diet, 20-50% of the protein from fish meal was substituted by protein from SBM, and were compared with a control diet containing only fish meal. No significant differences in the specific growth rates, feed efficiencies and the body composition were recorded for the fish fed the control diet and for fish fed the 20 and 30% SBM treatments. Results show that up to 30% of the protein from fish meal can be replaced with protein from SBM in the diet of this species. The effect of feeding frequency and gut evacuation time was investigated by comparing four feeding frequencies. Fish were fed to satiation either once, twice, three or four times a day. Feed intake was significantly affected by feeding frequency and fish fed 2, 3 and 4 meals a day ate significantly more food (p< 0.05) than the fish fed one meal a day. No significant differences (p> 0.05) in the specific growth rates, feed efficiencies and body composition were recorded for fish fed 2, 3 and 4 times a day. Feed intake was used to calculate an optimal daily ration and feeding two meals a day resulted in an optimal daily ration of 4% BW/day. A gut evacuation time of 7.25 hours indicates that fish fed twice a day probably had sufficient time to digest their food and evacuate their guts, resulting in the same daily feed intake as fish given 3 and 4 meals a day. Results conclude that under the present experimental conditions, a minimum daily ration of 4% BW/day, fed twice a day (in the morning and evening) is required for optimal growth (SGR= 1.33± 0.1), feed efficiency (FCR= 1.96± 0.4; PER= 1.44± 0.2) and body composition in juvenile dusky kob.
- Full Text:
- Date Issued: 2004
Perspectives on inter-professional collaboration : mediation
- Authors: Tatchell, Dolores
- Date: 2000
- Subjects: Divorce mediation -- South Africa , Custody of children-- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:707 , http://hdl.handle.net/10962/d1006519 , Divorce mediation -- South Africa , Custody of children-- South Africa
- Description: This research is based on the continuous search for alternatives in dealing with custody and access of minor children in divorcing families. In spite of the Mediation in Certain Divorce Matters Act, 1987, providing for mediation, it did not lead to the widespread implementation of mediation as an alternative form of dispute resolution in divorce matters. The family advocate as provided for in the Act, serves to protect the interest of minor children in disputes. However, custody evaluation is still used to determine the custody of minor children. Custody evaluation comprises an in depth study and assessment of the structure and functioning of the family made by a social worker and written up in the form of an evaluative report which is then submitted to the family advocate. It occurred to the researcher that there had to be better ways of dealing with custody disputes and consequently the damage done by the parents who fight over their children without any regard for the children’s feelings. It was considered an option to find out from the professionals directly involved with divorce and custody disputes why they have not considered alternatives, such as mediation, to resolve the disputes arising out of a divorce. Semi-structured interviews were conducted with five social workers and five attorneys to gain their perspectives on mediation, how the two professions could cooperate to assist divorcing couples and how inter-professional collaboration could be used to promote the use of mediation in East London. The family advocate was identified as a key role player. The possibility of mandatory mediation was raised with recommendations that it be considered. The co-mediation model was raised to enhance inter-professional collaboration. Social workers see their role as mediating custody issues where the attorneys see their role as mediating division of property and assets. Both professions recognize that they have their own unique contribution to make. Both social workers and attorneys have been found to be willing to collaborate with each other to make a mediation service available to divorcing couples
- Full Text:
- Date Issued: 2000
- Authors: Tatchell, Dolores
- Date: 2000
- Subjects: Divorce mediation -- South Africa , Custody of children-- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:707 , http://hdl.handle.net/10962/d1006519 , Divorce mediation -- South Africa , Custody of children-- South Africa
- Description: This research is based on the continuous search for alternatives in dealing with custody and access of minor children in divorcing families. In spite of the Mediation in Certain Divorce Matters Act, 1987, providing for mediation, it did not lead to the widespread implementation of mediation as an alternative form of dispute resolution in divorce matters. The family advocate as provided for in the Act, serves to protect the interest of minor children in disputes. However, custody evaluation is still used to determine the custody of minor children. Custody evaluation comprises an in depth study and assessment of the structure and functioning of the family made by a social worker and written up in the form of an evaluative report which is then submitted to the family advocate. It occurred to the researcher that there had to be better ways of dealing with custody disputes and consequently the damage done by the parents who fight over their children without any regard for the children’s feelings. It was considered an option to find out from the professionals directly involved with divorce and custody disputes why they have not considered alternatives, such as mediation, to resolve the disputes arising out of a divorce. Semi-structured interviews were conducted with five social workers and five attorneys to gain their perspectives on mediation, how the two professions could cooperate to assist divorcing couples and how inter-professional collaboration could be used to promote the use of mediation in East London. The family advocate was identified as a key role player. The possibility of mandatory mediation was raised with recommendations that it be considered. The co-mediation model was raised to enhance inter-professional collaboration. Social workers see their role as mediating custody issues where the attorneys see their role as mediating division of property and assets. Both professions recognize that they have their own unique contribution to make. Both social workers and attorneys have been found to be willing to collaborate with each other to make a mediation service available to divorcing couples
- Full Text:
- Date Issued: 2000
Studies on captive rearing of spotted grunter, pommadasys commersonnii (Pisces : Haemulidae) under ambient conditions
- Authors: Bacela, Ntobeko
- Date: 1999
- Subjects: Grunts (Fishes)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5322 , http://hdl.handle.net/10962/d1005167 , Grunts (Fishes)
- Description: The effects of stocking density, size grading, feeding frequency and ambient temperature on the growth performance and size variation of spotted grunter, Pomadasys commersonnii were investigated. The time that would be required to rear the species to market size was modelled. An area where maximum growth rate could be achieved under ambient temperature conditions, and therefore the location of a commercial farm within the distribution range of spotted grunter along the coast of South Africa, was predicted. The growth performance of spotted grunter was not significantly affected by stocking density. Growth performance seemed to improve with increasing stocking density. Competitive behaviour was absent among fish in the various stocking densities. Growth in terms of fork length and body weight was not significantly different between stocking densities. The highest specific growth rate, best food consumption, food conversion ratio and protein efficiency ratio of the fish were recorded at a density of 6.4 kg/m³, whereas the best condition factor was recorded at a density of 3.8 kg/m³. The lack of significant difference in many of the growth parameters between the various stocking densities suggest that juvenile spotted grunter could be reared at densities higher than 6.4 kg/m³. Further investigations are needed to determine the optimal initial stocking density of juvenile spotted grunter under ambient temperature and photoperiod conditions. Replacing the largest fish with average sized fish did not have a significant effect on the specific growth rate and competitive behaviour based on the relationship between the coefficient of variation and average size. Feeding frequency had a sIgnificant effect on food consumption, food conversion and protein efficiency ratio, and not on size increase, specific growth rate and condition factor. Its effect on competitive behaviour could not be conclusively explained. The best food conversion ratio recorded when feeding once a day showed that although the fish consumed a limited amount of food, they utilised the food that was fed most effectively. It is suggested that the fish be fed three times a day. The survival of juvenile spotted grunter was 95.6 % when feeding three times a day compared to 90 and 90.2 % when feeding once and five times a day, respectively. Fluctuating ambient temperature had a dramatic effect on specific growth rate and food consumption of spotted grunter. Growth modelling showed that the fish could be reared to a market size of 550 g (270 mm FL) in 19 months under ambient temperature conditions (23.2°C) at Richard's Bay. The optimal predicted rearing period of 19 months is approximately seven months less than that calculated for fish in the wild, and can possibly, be reduced further by feeding a balanced diet. The overall food consumption (on a dry weight basis) in the three size classes ranged from 0.15 ± 0.16 to 0.38 ± 0.35 % body weight per day. Food conversion ratio improved with increasing fish size. This relationship was attributed to diet quality and more specifically, the protein : energy ratio. As a result, fish in the large size class had the best overall protein efficiency ratio. Maximum specific growth rates of1.5, 0.84 and 0.74 % body weight per day were recorded from the small, medium and large size classes in the peak of summer with average daily temperature ranging from 21 to 22°C. Positive slopes in the coefficient of variation against fish size in the large size class indicated the presence of competitive behaviour which was attributed to the onset of adolescence. The information from this study can be used for pilot production of spotted grunter. Further research should be undertaken to investigate captive reproduction of the species.
- Full Text:
- Date Issued: 1999
- Authors: Bacela, Ntobeko
- Date: 1999
- Subjects: Grunts (Fishes)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5322 , http://hdl.handle.net/10962/d1005167 , Grunts (Fishes)
- Description: The effects of stocking density, size grading, feeding frequency and ambient temperature on the growth performance and size variation of spotted grunter, Pomadasys commersonnii were investigated. The time that would be required to rear the species to market size was modelled. An area where maximum growth rate could be achieved under ambient temperature conditions, and therefore the location of a commercial farm within the distribution range of spotted grunter along the coast of South Africa, was predicted. The growth performance of spotted grunter was not significantly affected by stocking density. Growth performance seemed to improve with increasing stocking density. Competitive behaviour was absent among fish in the various stocking densities. Growth in terms of fork length and body weight was not significantly different between stocking densities. The highest specific growth rate, best food consumption, food conversion ratio and protein efficiency ratio of the fish were recorded at a density of 6.4 kg/m³, whereas the best condition factor was recorded at a density of 3.8 kg/m³. The lack of significant difference in many of the growth parameters between the various stocking densities suggest that juvenile spotted grunter could be reared at densities higher than 6.4 kg/m³. Further investigations are needed to determine the optimal initial stocking density of juvenile spotted grunter under ambient temperature and photoperiod conditions. Replacing the largest fish with average sized fish did not have a significant effect on the specific growth rate and competitive behaviour based on the relationship between the coefficient of variation and average size. Feeding frequency had a sIgnificant effect on food consumption, food conversion and protein efficiency ratio, and not on size increase, specific growth rate and condition factor. Its effect on competitive behaviour could not be conclusively explained. The best food conversion ratio recorded when feeding once a day showed that although the fish consumed a limited amount of food, they utilised the food that was fed most effectively. It is suggested that the fish be fed three times a day. The survival of juvenile spotted grunter was 95.6 % when feeding three times a day compared to 90 and 90.2 % when feeding once and five times a day, respectively. Fluctuating ambient temperature had a dramatic effect on specific growth rate and food consumption of spotted grunter. Growth modelling showed that the fish could be reared to a market size of 550 g (270 mm FL) in 19 months under ambient temperature conditions (23.2°C) at Richard's Bay. The optimal predicted rearing period of 19 months is approximately seven months less than that calculated for fish in the wild, and can possibly, be reduced further by feeding a balanced diet. The overall food consumption (on a dry weight basis) in the three size classes ranged from 0.15 ± 0.16 to 0.38 ± 0.35 % body weight per day. Food conversion ratio improved with increasing fish size. This relationship was attributed to diet quality and more specifically, the protein : energy ratio. As a result, fish in the large size class had the best overall protein efficiency ratio. Maximum specific growth rates of1.5, 0.84 and 0.74 % body weight per day were recorded from the small, medium and large size classes in the peak of summer with average daily temperature ranging from 21 to 22°C. Positive slopes in the coefficient of variation against fish size in the large size class indicated the presence of competitive behaviour which was attributed to the onset of adolescence. The information from this study can be used for pilot production of spotted grunter. Further research should be undertaken to investigate captive reproduction of the species.
- Full Text:
- Date Issued: 1999
Facies mapping of the Vaal Reef placer as an aid to remnant pillar extraction and stope width optimisation
- Authors: O'Donovan, Anthony Gareth
- Date: 1992
- Subjects: Facies (Geology) -- South Africa -- Vaal Reef placer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4947 , http://hdl.handle.net/10962/d1005559 , Facies (Geology) -- South Africa -- Vaal Reef placer
- Description: The Vaal Reef placer is situated on the unconformable junction of the Strathmore and Stilfontein formations of the Johannesburg Subgroup. Within the South Division of the Vaal Reefs Exploration and Mining company lease, the Vaal Reef Placer is shown to be composed of several different units. Each unit exhibits its own specific characteristics and trend direction which can be used to establish distinct "Reef packages". These packages can be mapped in such a way as to provide a preliminary lithofacies map for the Vaal Reef Placer. The delineation of such geologically homogenous zones, and the development of a suitable depositional model, can be utilised in several ways. The characteristics of a particular zone are shown to influence the control of stoping width, evaluation of remnant pillars and the geostatistical methodology of evaluating current and future ore reserve blocks.
- Full Text:
- Date Issued: 1992
- Authors: O'Donovan, Anthony Gareth
- Date: 1992
- Subjects: Facies (Geology) -- South Africa -- Vaal Reef placer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4947 , http://hdl.handle.net/10962/d1005559 , Facies (Geology) -- South Africa -- Vaal Reef placer
- Description: The Vaal Reef placer is situated on the unconformable junction of the Strathmore and Stilfontein formations of the Johannesburg Subgroup. Within the South Division of the Vaal Reefs Exploration and Mining company lease, the Vaal Reef Placer is shown to be composed of several different units. Each unit exhibits its own specific characteristics and trend direction which can be used to establish distinct "Reef packages". These packages can be mapped in such a way as to provide a preliminary lithofacies map for the Vaal Reef Placer. The delineation of such geologically homogenous zones, and the development of a suitable depositional model, can be utilised in several ways. The characteristics of a particular zone are shown to influence the control of stoping width, evaluation of remnant pillars and the geostatistical methodology of evaluating current and future ore reserve blocks.
- Full Text:
- Date Issued: 1992
The distribution patterns and community structure of the Tsitsikamma rocky littoral ichthyofauna
- Authors: Burger, Lynton Francois
- Date: 1991
- Subjects: Fishes -- South Africa -- Geographical distribution , Tripterygiidae -- South Africa -- Geographical distribution , Littoral plants -- South Africa -- Tsitsikamma , Littoral plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5260 , http://hdl.handle.net/10962/d1005104 , Fishes -- South Africa -- Geographical distribution , Tripterygiidae -- South Africa -- Geographical distribution , Littoral plants -- South Africa -- Tsitsikamma , Littoral plants
- Description: The results of a community survey of the rocky intertidal and subtidal reef ichthyofauna of the Tsitsikamma National Park and adjacent areas are presented. An updated species checklist is given, comprising 116 species of 46 families, including a new genus and species of Tripterygiid. Single species are shown to dominate, in terms of numbers, both the cryptic and subtidal components for all the areas sampled down the vertical profile. Species richness, evenness and diversity are found to increase with depth for both the cryptic and suprabenthic components. A community level feeding study shows an increase in trophic specialisation with depth and food availability is found to be an important factor delimiting littoral fish vertical distribution. The nursery function of the Tsitsikamma rocky littoral area is assessed and it is shown that shallow littoral areas as a whole are more important than intertidal pools alone in functioning as nurseries. The results of the study are found to fit into the existing trend of an increase in species richness and diversity, from west to east, along the South African coast. A significant difference is shown between the observed frequencies of species on exploited reefs outside the Park and unexploited reefs inside the Park. The density of the key reef predator Petrus rupestris is shown to be nine times more abundant on deep reef inside the park compared to deep reef outside the park (0.0045 fish/m² and 0.0005 fish/m² respectively) and a paucity of larger individuals of this species on exploited reefs is noted. Marked differences in the relative abundance of other species between exploited and unexploited reefs are evident and it is hypothesised that community disruption has occurred on exploited reefs, either directly or indirectly because of the removal of P. rupestris. These results are discussed in the context of marine reserves as a conservation strategy and a recommendation is made to extend the 5.6km seaward boundary of the Tsitsikamma National Park westwards to include the large concentration of presently exploited rocky reefs between the Blaaukrans river mouth and Natures Valley.
- Full Text:
- Date Issued: 1991
- Authors: Burger, Lynton Francois
- Date: 1991
- Subjects: Fishes -- South Africa -- Geographical distribution , Tripterygiidae -- South Africa -- Geographical distribution , Littoral plants -- South Africa -- Tsitsikamma , Littoral plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5260 , http://hdl.handle.net/10962/d1005104 , Fishes -- South Africa -- Geographical distribution , Tripterygiidae -- South Africa -- Geographical distribution , Littoral plants -- South Africa -- Tsitsikamma , Littoral plants
- Description: The results of a community survey of the rocky intertidal and subtidal reef ichthyofauna of the Tsitsikamma National Park and adjacent areas are presented. An updated species checklist is given, comprising 116 species of 46 families, including a new genus and species of Tripterygiid. Single species are shown to dominate, in terms of numbers, both the cryptic and subtidal components for all the areas sampled down the vertical profile. Species richness, evenness and diversity are found to increase with depth for both the cryptic and suprabenthic components. A community level feeding study shows an increase in trophic specialisation with depth and food availability is found to be an important factor delimiting littoral fish vertical distribution. The nursery function of the Tsitsikamma rocky littoral area is assessed and it is shown that shallow littoral areas as a whole are more important than intertidal pools alone in functioning as nurseries. The results of the study are found to fit into the existing trend of an increase in species richness and diversity, from west to east, along the South African coast. A significant difference is shown between the observed frequencies of species on exploited reefs outside the Park and unexploited reefs inside the Park. The density of the key reef predator Petrus rupestris is shown to be nine times more abundant on deep reef inside the park compared to deep reef outside the park (0.0045 fish/m² and 0.0005 fish/m² respectively) and a paucity of larger individuals of this species on exploited reefs is noted. Marked differences in the relative abundance of other species between exploited and unexploited reefs are evident and it is hypothesised that community disruption has occurred on exploited reefs, either directly or indirectly because of the removal of P. rupestris. These results are discussed in the context of marine reserves as a conservation strategy and a recommendation is made to extend the 5.6km seaward boundary of the Tsitsikamma National Park westwards to include the large concentration of presently exploited rocky reefs between the Blaaukrans river mouth and Natures Valley.
- Full Text:
- Date Issued: 1991
Studies on the metabolism of SKF 525 A|
- Authors: Barber, Peter John
- Date: 1978 , 2013-10-14
- Subjects: Drugs -- Metabolism , Cytochrome P-450
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3835 , http://hdl.handle.net/10962/d1007591 , Drugs -- Metabolism , Cytochrome P-450
- Description: Spectrophotometric studies have been carried out to determine the pH dependence of binding of SKF 525 A, Brietal sodium and carbon monoxide to cytochrome P-450. The optimal pH for metabolic conversion of SKF 525 A has been investigated and this agent and its major metabolite, SKF 8742 A, have been metabolised in vitro by swine and rat hepatic microsomes. A suitable gas liquid chromatography assay has been developed and used to analyse metabolic production. The effects of carbon monoxide, dithiothreitol, n-octylamine and of induction of cytochrome P-450 by phenobarbital on metabolism of SKF 525 A and SKF 8742 A have been investigated. Attempts have been made to synthesise SKF 525 AN-oxide. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1978
- Authors: Barber, Peter John
- Date: 1978 , 2013-10-14
- Subjects: Drugs -- Metabolism , Cytochrome P-450
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3835 , http://hdl.handle.net/10962/d1007591 , Drugs -- Metabolism , Cytochrome P-450
- Description: Spectrophotometric studies have been carried out to determine the pH dependence of binding of SKF 525 A, Brietal sodium and carbon monoxide to cytochrome P-450. The optimal pH for metabolic conversion of SKF 525 A has been investigated and this agent and its major metabolite, SKF 8742 A, have been metabolised in vitro by swine and rat hepatic microsomes. A suitable gas liquid chromatography assay has been developed and used to analyse metabolic production. The effects of carbon monoxide, dithiothreitol, n-octylamine and of induction of cytochrome P-450 by phenobarbital on metabolism of SKF 525 A and SKF 8742 A have been investigated. Attempts have been made to synthesise SKF 525 AN-oxide. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1978
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