Assessment and mitigation of biosecurity risks associated with macroalgae inclusion in farmed abalone diets in South Africa
- Mwangudza, Petronilla Masika
- Authors: Mwangudza, Petronilla Masika
- Date: 2024-10-11
- Subjects: Biosecurity , Seaweed , Abalone culture South Africa , Abalones Feeding and feeds , Haliotis midae , High-throughput nucleotide sequencing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466748 , vital:76775 , DOI https://doi.org/10.21504/10962/466748
- Description: The provision of biosecure diets for use in intensive aquaculture conditions requires attention, to reduce the risk of introducing potential pathogens to the farmed stock. Such introductions could lead to infections and disease outbreaks. Despite the benefits associated with macroalgae inclusion in abalone diets, several microbial hazard cases have been reported in the animal feed and human food industries. This has necessitated the application of biosecurity measures on fresh macroalgae to reduce or eliminate potential hazards and the risks of pathogen transfer to abalone stock when used as a feed or feed supplement. The present thesis assessed the efficacy of different processing treatments, including heat, ultra-violet irradiation (UVC), different pH levels, salinity concentrations, and povo-iodine on the inactivation of potential macroalgaetransmitted abalone pathogens. The effect of the processed macroalgae on the growth, health and gut microbial composition of abalone were also explored and compared with abalone fed non-processed diets. The efficacy of the different processing treatments was initially assessed on pure cultures of the test pathogens, which included a bacterium (Vibrio anguillarum), an oomycete (Halioticida noduliformans) and the bacteriophage lambda. Data from the initial assessments were then used to select the most optimal treatments for further assessment on the test pathogens inoculated in a macroalgae matrix, to simulate a more natural scenario. The viability of the three test pathogens following exposure to different processing treatments was assessed using culture methods. The results indicated that a combination of three treatments; disinfection using povo-iodine solution (5000 mg/L) for 20 min, oven drying 40 ℃ for 8.0 h and UVC treatment for 10 min rendered all the test pathogens non-culturable. Growth trials were conducted to assess the effect of the biosecure macroalgae Ecklonia maxima, Ulva lacinulata and Gracilaria gracilis on the growth performance of the abalone Haliotis midae. The macroalgae were subjected to the combination of three biosecurity processing treatments and experimental diets were then formulated to incorporate the macroalgae that had been subjected to the biosecurity processing treatments as well as macroalgae that were not. Growth parameters of the abalone after a 150-day feeding trial were compared between the biosecure and non-bioseeure macroalgae dietary treatments. Overall, the lowest growth was observed in the abalone fed with the control diet (AbfeedTM S34R) compared to all the macroalgae diets. However, no significant differences in abalone weight and shell length were recorded between the dietary treatments after the 150-day growth trial with an overall mean final weight (} standard error) of 56.55 } 0.78 g and a mean final length of 66.26 } 0.344 mm (RM-ANOVA: F(18,63) = 0.706; p = 0.792; : F(18,63) = 0.941; p = 0.535 respectively). Similarly, the biosecurity process method (biosecure vs. non-biosecure) did not have an impact on abalone weights and shell length (p > 0.05). Moreover, specific growth rate, length gain and condition factor of abalone did not differ between the biosecure and nonbiosecure dietary treatments with overall means (}standard error) of 0.27 } 0.01 % bw/d, 1.79 } 0.07 mm/month and 1.13 } 0.01, respectively (p > 0.05). Dietary macroalgae are known to contribute to the gut microflora of abalone. To determine if the biosecure process influenced this community complex, a next generation sequencing (NGS) approach was used to identify and compare the bacterial communities in abalone that were fed diets containing macroalgae that had been subjected to biosecurity treatment and those that were not. The NGS approach was also used to determine the gut microbiome profile of the abalone fed with a formulated diet supplemented with fresh U. lacinulata and G. gracilis to assess the potential modulatory effect seaweeds and their associated microbiota may have on the gut microbiome of H. midae. The bacterial alpha diversity did not differ significantly across all the diets at family, genus and species levels (p > 0.05). No significant differences in the microbiome composition were detected indicating little or no dissimilarities of the bacterial communities between the diets for all the biosecure and non-biosecure macroalgae diets. A similar core microbiome was also observed in the digestive tracts of abalone fed with the biosecure and non-biosecure diets. It was concluded that the biosecure process did not influence the natural microbiota of abalone that were fed dietary ingredients that were subjected to the process. The findings of this research have contributed to understanding the production of biosecure macroalgae formulated diets without compromising their benefits to the growth and health of farmed abalone. The combined treatment used in this study can be applied in the macroalgae and the feed industry to produce biosecure feeds. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mwangudza, Petronilla Masika
- Date: 2024-10-11
- Subjects: Biosecurity , Seaweed , Abalone culture South Africa , Abalones Feeding and feeds , Haliotis midae , High-throughput nucleotide sequencing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466748 , vital:76775 , DOI https://doi.org/10.21504/10962/466748
- Description: The provision of biosecure diets for use in intensive aquaculture conditions requires attention, to reduce the risk of introducing potential pathogens to the farmed stock. Such introductions could lead to infections and disease outbreaks. Despite the benefits associated with macroalgae inclusion in abalone diets, several microbial hazard cases have been reported in the animal feed and human food industries. This has necessitated the application of biosecurity measures on fresh macroalgae to reduce or eliminate potential hazards and the risks of pathogen transfer to abalone stock when used as a feed or feed supplement. The present thesis assessed the efficacy of different processing treatments, including heat, ultra-violet irradiation (UVC), different pH levels, salinity concentrations, and povo-iodine on the inactivation of potential macroalgaetransmitted abalone pathogens. The effect of the processed macroalgae on the growth, health and gut microbial composition of abalone were also explored and compared with abalone fed non-processed diets. The efficacy of the different processing treatments was initially assessed on pure cultures of the test pathogens, which included a bacterium (Vibrio anguillarum), an oomycete (Halioticida noduliformans) and the bacteriophage lambda. Data from the initial assessments were then used to select the most optimal treatments for further assessment on the test pathogens inoculated in a macroalgae matrix, to simulate a more natural scenario. The viability of the three test pathogens following exposure to different processing treatments was assessed using culture methods. The results indicated that a combination of three treatments; disinfection using povo-iodine solution (5000 mg/L) for 20 min, oven drying 40 ℃ for 8.0 h and UVC treatment for 10 min rendered all the test pathogens non-culturable. Growth trials were conducted to assess the effect of the biosecure macroalgae Ecklonia maxima, Ulva lacinulata and Gracilaria gracilis on the growth performance of the abalone Haliotis midae. The macroalgae were subjected to the combination of three biosecurity processing treatments and experimental diets were then formulated to incorporate the macroalgae that had been subjected to the biosecurity processing treatments as well as macroalgae that were not. Growth parameters of the abalone after a 150-day feeding trial were compared between the biosecure and non-bioseeure macroalgae dietary treatments. Overall, the lowest growth was observed in the abalone fed with the control diet (AbfeedTM S34R) compared to all the macroalgae diets. However, no significant differences in abalone weight and shell length were recorded between the dietary treatments after the 150-day growth trial with an overall mean final weight (} standard error) of 56.55 } 0.78 g and a mean final length of 66.26 } 0.344 mm (RM-ANOVA: F(18,63) = 0.706; p = 0.792; : F(18,63) = 0.941; p = 0.535 respectively). Similarly, the biosecurity process method (biosecure vs. non-biosecure) did not have an impact on abalone weights and shell length (p > 0.05). Moreover, specific growth rate, length gain and condition factor of abalone did not differ between the biosecure and nonbiosecure dietary treatments with overall means (}standard error) of 0.27 } 0.01 % bw/d, 1.79 } 0.07 mm/month and 1.13 } 0.01, respectively (p > 0.05). Dietary macroalgae are known to contribute to the gut microflora of abalone. To determine if the biosecure process influenced this community complex, a next generation sequencing (NGS) approach was used to identify and compare the bacterial communities in abalone that were fed diets containing macroalgae that had been subjected to biosecurity treatment and those that were not. The NGS approach was also used to determine the gut microbiome profile of the abalone fed with a formulated diet supplemented with fresh U. lacinulata and G. gracilis to assess the potential modulatory effect seaweeds and their associated microbiota may have on the gut microbiome of H. midae. The bacterial alpha diversity did not differ significantly across all the diets at family, genus and species levels (p > 0.05). No significant differences in the microbiome composition were detected indicating little or no dissimilarities of the bacterial communities between the diets for all the biosecure and non-biosecure macroalgae diets. A similar core microbiome was also observed in the digestive tracts of abalone fed with the biosecure and non-biosecure diets. It was concluded that the biosecure process did not influence the natural microbiota of abalone that were fed dietary ingredients that were subjected to the process. The findings of this research have contributed to understanding the production of biosecure macroalgae formulated diets without compromising their benefits to the growth and health of farmed abalone. The combined treatment used in this study can be applied in the macroalgae and the feed industry to produce biosecure feeds. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Quantifying feed intake and feeding intensity using two experimental conditions and the effect of different feeding strategies on the production parameters of farmed South African abalone, haliotis midae
- Authors: Wortley, Ross Michael
- Date: 2023-03-29
- Subjects: Mariculture South Africa , Abalone culture , Abalones Growth , Abalones Feeding and feeds , Feed conversion ratio , Haliotis midae
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:71932
- Description: As abalone are slow-growing animals there is a high investment of capital, running costs and labour in commercial abalone farming. Revenue needs to be maximised by achieving fast growth rates. A foremost driver of abalone growth is feed intake and feeding intensity of the abalone as well as the feeding regimen a farm utilises. While feed intake is well-documented in H. midae, there is a paucity of information regarding this aspect in abalone above 70 g and the relationship between feeding intensity, feed conversion rate (FCR) and daily growth rate needs to be documented. Similarly, there are a limited number of studies dealing with the effects of different pellet types of the same formulation, that differ only in shape and size, on feed intake and production in H. midae. This study made use of both a controlled laboratory experiment and commercial-scale farm experiment with the aim of testing whether feed intake information produced under laboratory conditions can provide good estimates of feed intake under farming conditions, which can further be implemented into feeding strategies on abalone farms. This study quantified daily feed intake (F) in 10 – 20 g, 100 – 110 g and 150 – 160 g abalone weight classes using two different pellet types and determined the relationship between the duration of feed availability and feed intake under laboratory conditions. The effect of three different pellet type strategies (fed daily: a leaf-only strategy = L d-1, a short-pellet only strategy = SP d-1, and a strategy that used both = B d-1) on abalone production parameters under farming conditions such as growth rate, feed conversion ratio (FCR), feeding intensity (FI) and weight variation of 30 – 40 g H. midae was also investigated. A commercial-scale farm study was designed to test the effect of four commercially relevant feeding regimens (three size-specific regimens and one commercially practiced feeding method) on the growth, FCR, feeding intensity and weight variation of these three abalone weight classes while taking into account an economic model to assess the profitability of each feeding regimen. Daily feed intake as a percentage of body mass (% BM d-1) was a function of abalone weight class between the 10 – 20 g and two larger weight classes 100 – 110 g and 150 – 160 g p < 0.0001), however feed intake was not different between the 100 – 110 g and 150 – 160 g weight classes. Pellet type did not affect feed intake in all abalone weight classes (p = 0.15). Feed intake (F) was positively linearly correlated with duration of feed availability (h) in the 10 – 20 g weight class (r2 = 0.76, p <0.00001) and logarithmically correlated in the 100 – 110 g (r2 = 0.25, p < 0.02) and 150 – 160 g (r2 = 0.52, p < 0.0001) weight classes (10 – 20 g abalone-1: 3 F (% BM) = 0.02(h) + 0.1976, 100 – 110 g abalone-1: F (% BM) = log10(h)*0.17 + 0.17, 150 – 160 g abalone-1: F (% BM) = log10(h)*0.36 + 0.07). There was no significant difference in monthly average abalone weight, daily growth rate (G), FCR and feeding intensity between each pellet type strategy (G: p = 0.60, FCR: p = 0.62, FI: p = 0.54 ). However, abalone grew well over the 112-day growth period with average abalone weight increasing significantly between each monthly sample time (pooled pellet type strategy: Huynh-Feldt correction; p < 0.00001). Furthermore, abalone fed the leaf-only pellet type strategy (L d-1) fell into higher weight classes after a 112-day growth period (Z test: 50 – 70 g: 72%) which was 16.1 % higher compared to the SP d-1 and B d-1 strategies. Daily growth rate (r2 = 0.34, p < 0.01) and FCR (r2 = 0.42, p < 0.004) was negatively correlated and FCR was positively correlated with daily feeding intensity, respectively (G = - 2.59 (FI) + 1.526, FCR = 8.8082 (FI) – 2.7108). Feeding regimen affected the production parameters of three abalone weight classes. The method practiced on the farm resulted in the best growth in the 10 – 20 g abalone weight class. The farm feeding method resulted in slower yet more efficient growth rates (lowest FCR values) in the abalone weight classes, 100 – 110 g and 150 – 160 g abalone- 1. However, size-specific feeding regimens resulted in the fastest growth rates but resulted in higher FCR values (less efficient). The relationship between feeding intensity, daily growth rate and FCR all showed that an increase in feeding intensity results in increased daily growth rates and FCR values. The economic model suggests that the higher FCR values associated with size-specific regimens, which have higher associated costs to producing abalone, were greatly outweighed by the growth attained by the abalone in the 100 – 110 g and 150 – 160 g weight classes. The size-specific regimens generated a higher potential monetary value of abalone after a 112-day period, which would consequently result in higher income for abalone farms. For abalone ranging from 100 – 110 and 150 – 160 grams, the economic model suggested that in a quarterly grading schedule (112 days) that abalone be fed the size specific daily rations, which is a function of body mass, at 0.35 % BM d-1 and 0.352 % BM d-1, respectively. The two experimental conditions used in this study produced feed intake and production parameter information that is beneficial to South African abalone farmers. The small-scale laboratory study produced information on feed intake that can be used as reference values as to what abalone in these weight classes can consume on a daily basis. The laboratory study can provide estimates of feed intake under farming conditions but should only be used as minimum 4 values when determining size-specific feeding regimens. To maximise abalone growth, farmers should utilise size-specific feeding regimens for abalone above 30 g. Daily growth rate and FCR can be predicted as a function of the abalone’s feeding intensity. Further studies are needed to determine the effects of abalone weight class on production parameters when testing different pellet types as well as an exploration into behavioural studies focusing on diet preferences. Additionally, future studies need to take into consideration abalone above the weight of 100 g with additional focus of research on behavioural, genetic and environmental aspects on abalone feed intake. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Wortley, Ross Michael
- Date: 2023-03-29
- Subjects: Mariculture South Africa , Abalone culture , Abalones Growth , Abalones Feeding and feeds , Feed conversion ratio , Haliotis midae
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:71932
- Description: As abalone are slow-growing animals there is a high investment of capital, running costs and labour in commercial abalone farming. Revenue needs to be maximised by achieving fast growth rates. A foremost driver of abalone growth is feed intake and feeding intensity of the abalone as well as the feeding regimen a farm utilises. While feed intake is well-documented in H. midae, there is a paucity of information regarding this aspect in abalone above 70 g and the relationship between feeding intensity, feed conversion rate (FCR) and daily growth rate needs to be documented. Similarly, there are a limited number of studies dealing with the effects of different pellet types of the same formulation, that differ only in shape and size, on feed intake and production in H. midae. This study made use of both a controlled laboratory experiment and commercial-scale farm experiment with the aim of testing whether feed intake information produced under laboratory conditions can provide good estimates of feed intake under farming conditions, which can further be implemented into feeding strategies on abalone farms. This study quantified daily feed intake (F) in 10 – 20 g, 100 – 110 g and 150 – 160 g abalone weight classes using two different pellet types and determined the relationship between the duration of feed availability and feed intake under laboratory conditions. The effect of three different pellet type strategies (fed daily: a leaf-only strategy = L d-1, a short-pellet only strategy = SP d-1, and a strategy that used both = B d-1) on abalone production parameters under farming conditions such as growth rate, feed conversion ratio (FCR), feeding intensity (FI) and weight variation of 30 – 40 g H. midae was also investigated. A commercial-scale farm study was designed to test the effect of four commercially relevant feeding regimens (three size-specific regimens and one commercially practiced feeding method) on the growth, FCR, feeding intensity and weight variation of these three abalone weight classes while taking into account an economic model to assess the profitability of each feeding regimen. Daily feed intake as a percentage of body mass (% BM d-1) was a function of abalone weight class between the 10 – 20 g and two larger weight classes 100 – 110 g and 150 – 160 g p < 0.0001), however feed intake was not different between the 100 – 110 g and 150 – 160 g weight classes. Pellet type did not affect feed intake in all abalone weight classes (p = 0.15). Feed intake (F) was positively linearly correlated with duration of feed availability (h) in the 10 – 20 g weight class (r2 = 0.76, p <0.00001) and logarithmically correlated in the 100 – 110 g (r2 = 0.25, p < 0.02) and 150 – 160 g (r2 = 0.52, p < 0.0001) weight classes (10 – 20 g abalone-1: 3 F (% BM) = 0.02(h) + 0.1976, 100 – 110 g abalone-1: F (% BM) = log10(h)*0.17 + 0.17, 150 – 160 g abalone-1: F (% BM) = log10(h)*0.36 + 0.07). There was no significant difference in monthly average abalone weight, daily growth rate (G), FCR and feeding intensity between each pellet type strategy (G: p = 0.60, FCR: p = 0.62, FI: p = 0.54 ). However, abalone grew well over the 112-day growth period with average abalone weight increasing significantly between each monthly sample time (pooled pellet type strategy: Huynh-Feldt correction; p < 0.00001). Furthermore, abalone fed the leaf-only pellet type strategy (L d-1) fell into higher weight classes after a 112-day growth period (Z test: 50 – 70 g: 72%) which was 16.1 % higher compared to the SP d-1 and B d-1 strategies. Daily growth rate (r2 = 0.34, p < 0.01) and FCR (r2 = 0.42, p < 0.004) was negatively correlated and FCR was positively correlated with daily feeding intensity, respectively (G = - 2.59 (FI) + 1.526, FCR = 8.8082 (FI) – 2.7108). Feeding regimen affected the production parameters of three abalone weight classes. The method practiced on the farm resulted in the best growth in the 10 – 20 g abalone weight class. The farm feeding method resulted in slower yet more efficient growth rates (lowest FCR values) in the abalone weight classes, 100 – 110 g and 150 – 160 g abalone- 1. However, size-specific feeding regimens resulted in the fastest growth rates but resulted in higher FCR values (less efficient). The relationship between feeding intensity, daily growth rate and FCR all showed that an increase in feeding intensity results in increased daily growth rates and FCR values. The economic model suggests that the higher FCR values associated with size-specific regimens, which have higher associated costs to producing abalone, were greatly outweighed by the growth attained by the abalone in the 100 – 110 g and 150 – 160 g weight classes. The size-specific regimens generated a higher potential monetary value of abalone after a 112-day period, which would consequently result in higher income for abalone farms. For abalone ranging from 100 – 110 and 150 – 160 grams, the economic model suggested that in a quarterly grading schedule (112 days) that abalone be fed the size specific daily rations, which is a function of body mass, at 0.35 % BM d-1 and 0.352 % BM d-1, respectively. The two experimental conditions used in this study produced feed intake and production parameter information that is beneficial to South African abalone farmers. The small-scale laboratory study produced information on feed intake that can be used as reference values as to what abalone in these weight classes can consume on a daily basis. The laboratory study can provide estimates of feed intake under farming conditions but should only be used as minimum 4 values when determining size-specific feeding regimens. To maximise abalone growth, farmers should utilise size-specific feeding regimens for abalone above 30 g. Daily growth rate and FCR can be predicted as a function of the abalone’s feeding intensity. Further studies are needed to determine the effects of abalone weight class on production parameters when testing different pellet types as well as an exploration into behavioural studies focusing on diet preferences. Additionally, future studies need to take into consideration abalone above the weight of 100 g with additional focus of research on behavioural, genetic and environmental aspects on abalone feed intake. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
- «
- ‹
- 1
- ›
- »