With World Health Organization estimation of population increase to over 9 billion by 2050, malnutrition and food insecurity are predicated to be two of the main challenges facing the world in the future. Fish is a source of protein that can have a significant contribution for solving the global food crisis. Fish for human consumption is provided by both the aquaculture industry and the capture fisheries, however, the flat-lined production of seafood from capture fisheries means aquaculture production should double in number to provide enough protein by 2050. Culturing fish at higher densities is being used as a way to increase the global aquaculture production. Modern aquaculture intensified practices expose the fish to various stressors that can negatively impact their welfare. Good nutrition can improve the health status of aquacultured fish while accumulation of specific nutrient can add value to the fillet. In line with that, the studies described in this dissertation aimed to examine the vital role of fish in human health and evaluate strategies to improve the sustainable aquaculture production of fish using novel aquafeeds. This was completed by conducting a survey of the essential minerals and heavy metals of commercially available catfish, salmon, and tilapia fillets in the United States marketplace and three fish nutritional trials to evaluate the impacts of novel aquafeeds on production and health of fish and the food quality of their respective fillets. Selenium with the established health benefit for human and fish was the trace mineral of interest in this dissertation. This element is the main component of a group of selenium containing proteins called selenoproteins that are antioxidant and maintain oxidative homeostasis of fish and human. Additionally, selenium is an antagonist for many heavy metals such as mercury. The market study revealed that catfish, salmon and tilapia samples available in United States marketplace are good source of selenium, zinc and phosphorous. The concentration of heavy metals in all the samples were lower than safety standards. Nile tilapia (Oreochromis niloticus) and rainbow trout (Oncorhynchus mykiss), which are two economically important aquacultured fish, were used as animal models in the fish nutritional trials. Different forms of selenium supplemented to Nile tilapia diet. The form of Dietary Se form did not have any significant (p>0.05) effect on growth, and plasma and hepatic GPX activity of Nile tilapia. However, organic selenium supplement showed significantly (p<0.05) higher bioavailability and accumulated in the fillets at the significantly higher concentration. In the second fish trial selenoneine, a novel selenium containing compound, was supplemented at various concentrations to rainbow trout diet. Other than growth parameters multiple other health biomarkers (lysozyme, glutathione peroxidase, superoxide dismutase activities) were examined to determine whether selenoneine supplementation had a positive impact on fish health. Selenoneine enriched diet significantly(p<0.05) increased the weight gain, lysozyme and oxidative enzymes activities of rainbow trout. Lastly rainbow trout feed was supplemented with commercially available probiotic (Actisaf®), prebiotic (Safmmann®), and their mixture (synbiotic). These dietary supplements did not have any significant effect on fish production but led to a significant increase in activity of oxidative enzymes in plasma when compared to control diet. These results suggest that feed supplements used in this dissertation can be used to promote the fish health raised in recirculating aquaculture systems and support an economically and environmentally sustainable aquaculture. / PHD / Fish contributes significantly to human’s diet in terms of high quality, easily digestible animal protein that helps fight malnutrition and food insecurity. More than half of the fish for human consumption is produced by the aquaculture industry and the growth of the industry is very critical for meeting the future needs for protein. Other than production of high-quality protein the aquaculture industry has made a great contribution to people’s livelihood, poverty alleviation, income generation, employment and, trade globally. To continue contributing effectively to global food security aquaculture industry should overcome various obstacles such as disease and sustainable production of high-quality feed. In this dissertation, important roles of fish in human diet was examined by measuring the mineral composition of commercially available catfish, salmon and tilapia in the United States market place. Also diets of Nile tilapia and rainbow trout were supplemented with various forms of selenium, prebiotics, and/or probiotics which have positive effect on health of both human and fish. These supplementations led to production of valued-added fish fillets enriched in selenium and improved the fish growth and health.

Four methods of seed (eggs, sac-fry, and fry) production for Rocky Mt. White hybrid® tilapia, (0. niloticus x O. aureus), were compared under green water conditions over a six month period in an environmentally controlled greenhouse at the Virginia Polytechnic Institute and State University's Aquaculture Research Laboratory. Twelve 3 m2 rectangular tanks were stocked with brood stock (mean wt. 680 g), at a sex ratio of 3 females to 1 male. Nine tanks were stocked at one of three densities (1, 2, and 4 females m-2), and seed was collected from females' mouths weekly. Three additional tanks were stocked at a density of 2 females m-2, and fry were collected from the edges of the tanks when seen. Seed production was among the highest seen for related studies. Average number of viable fry produced at I females m-2, 1660 fry female- I month-I, was significantly higher than the combined average production of densities 2 females m-2 (629 fry female- I month-I) and 4 females m-2 (695 fry female-1 month- 1) (p< 0.02). Even though there was no significant difference between viable fry production meter-2 (p>0.05), the highest density consistently produced more fry meter-2. No significant difference was observed in viable fry production between the two seed collection methods (Clutch removal- 629 fry female-1 month-I; Natural mouth-brooding- 520 fry female-1 month-I) (p>0.05). The effects of stocking density on growth and survival were evaluated by stocking 14-16 day old artificially incubated fry (25.5 ± .32 mg, 12.1 ± .04 mm), into 150 liter troughs at three densities (3, 6, and 12 fry liter-I) under green water conditions for 30 days. The mean monthly hatchery seed survival was 65.7 ± 2.3%, which varied largely depending on initial seed developmental stage. Significant differences were observed between mean weight, length, survival, and feed conversion ratios among the various fry stocking densities (p<O.05). The greatest growth was at a density of 3 fry liter 1 , while survival was not affected until a density of 12 fry liter-I. These results that to maximize fry production and reduce labor, a density of 4 females m-2 or higher be used under the natural mouth brooding seed collection method. They also suggest a fry density between 6 to 12 fry liter-1 should be used with periodic grading or sex reversal to reduce cannibalism and increase growth. / Master of Science

The purpose of this study is to modify an existing static analytical model developed for a Re-circulating Aquaculture Systems through incorporation of risk considerations to evaluate the economic viability of the system. In addition the objective of this analysis is to provide a well documented risk based analytical system so that individuals (investors/lenders) can use it to tailor the analysis to their own investment decisions—that is to collect the input data, run the model, and interpret the results. The Aquaculture Economic Cost Model (AECM) was developed by Dr. Charles Coale, Jr. and others from the department of Agricultural and Applied Economics at Virginia Tech. The AECM is a spreadsheet model that was developed to help re-circulating aquaculture producers make strategic business decisions. The model can be used by potential producers interested in investing in re-circulating aquaculture through development of a financial analysis that in turn will help them obtain funding for the enterprise. The model is also useful for current producers who want to isolate inefficient aspects of their operation. AECM model consists of three major sections which include the Data Entry, Calculations and Analysis. The first section requires that the producer conducts background research about their operation to ensure accurate calculation and analysis. The calculation section provides a great deal of information about the operation's finances, while the analysis section provides information about the operation's financial stability. While the AECM is a powerful model, it is based on single, usually mean, values for prices, costs, and input and output quantities. However, market, financial and production uncertainties result in fluctuating prices, costs and yields. An individual who is making management decisions for a re-circulating aquaculture system will be faced with some or all of these uncertainties. By adding simulation to the AECM model to account for these uncertainties individuals will be able to make better management decisions. Information of the varying likelihoods or probabilities of achieving profits will be of crucial interest to individuals who plan on entering into or modifying an existing aquaculture system. Risks associated with six variables were examined in this paper: feed cost, feed conversion, mortality rate, capital interest rate, final weight, and output price. Data for the Interest Rate and output price were obtained from the Federal Reserve System and NMFS website respectively. Expert opinion was the source of data for the other variables. After probability distributions were applied to the random variables to account for the uncertainty the model was simulated for ten thousand iterations to obtain expected returns for three years in advance that the model calculates an income statement. In addition to that, sensitivity analyses were carried out in order to inform the producer which factors are contributing the most to the profitability of the operation. In this way the producer will have a better idea as to which aspects of the operation to monitor closely and consider modifying. The analysis shows that the mean income for the three years will be negative and thus the business would be losing money. The simulated mean net incomes were: -$216,905, -$53,689, -$53,111 for year1 through year3 respectively. Sensitivity analysis confirmed that output price is by far the most significant input that makes the overall bottom line to fluctuate most. Output price was on top of the list for all the three years analyzed in this study. Feed cost and Feed conversion were the next most significant inputs. The other inputs were also significant in explaining the fluctuation of the bottom line; however both their regression and correlation coefficients were small. / Master of Science

Disease outbreaks have overwhelmed the aquaculture industry as a whole and have been catastrophic for many single operations. To minimize disease outbreaks, efforts are underway to enhance animal health and disease resistance to pathogens without the use of antibiotics. The overall purpose of this study was to explore a potential prophylactic, a novel antibody diet, for the bacterial pathogen, Aeromonas hydrophila, in tilapia. The tilapia were on an anti-interleukin-10 antibody diet as a neutralization of interleukin-10 (IL-10), an anti-inflammatory cytokine. The anti-inflammatory function of IL-10 has been shown to allow persistence of gastrointestinal pathogens. Tilapia were fed the novel diet and were challenged via bath immersion or oral gavage with A. hydrophila. Four trials of challenge studies were conducted. Clinical signs of the disease and survival were monitored post-challenge of the bacteria. Out of the 4 trials, one bath immersion trial showed significantly lower survival in the group fed the novel antibody diet (p=0.044) compared to the control fed group, after challenged with A. hydrophila. The other trials tested showed no significant differences in survival between diets. Among the survival percentages collected as a whole, it cannot be determined from in vivo results whether this anti-IL-10 diet is effective in preventing mortality from A. hydrophila in tilapia. Therefore, an in vitro study using an enzyme-linked immunosorbent assay (ELISA) was used to determine the neutralization capability of anti-IL-10 on IL-10 using tilapia splenocytes. Interferon-γ, a pro-inflammatory cytokine, was quantified in order to find a trend in expression of IL-10 in vitro in various tilapia cell treatments. The protocol for the ELISA study is under development being that the use of this antibody is novel and has never before been done in fish. / Master of Science in Life Sciences / Aquaculture is the fastest growing animal-production sector for food in the world. Health and safety issues are prevalent among aquatic animals during massive growth and production. Disease outbreaks within aquaculture facilities can cause losses worth billions of dollars. Antibiotics are currently in use in aquaculture as a therapeutant for treating disease. However, over time the use of antibiotics has brought up a new set of issues; antibiotic resistant bacteria/genes and transfer of these to the environment and to humans via consumption. A novel antibody feed, containing an antibody to interleukin-10, with potential as a preventative disease measure was used to study disease development after exposure with a bacterial pathogen. Thus, tilapia were exposed to the bacteria, Aeromonas hydrophila, and signs of disease and survival were monitored to see if the novel antibody feed would prevent disease onset. Further research is necessary on the antibody before confirming effectiveness on disease prevention.

Fler svenskar vill konsumera mer inhemskt producerad fisk. Scandinavian Aquasystems odlar och försöker introducera fisken tilapia på svenska marknaden. Tilapia är en fisk som precis börjat göra intåg i Europa men är stor runtomkring resten av världen. En smakprofil som berättar hur länge produkten är sensoriskt tjänlig kan vara av hjälp. Denna undersökning syftade till att skapa en sensorisk smakprofil för fisken tilapia och till att se hur smakprofilen förändrades vid lagring i vakuumförpackning. För att skapa smakprofilen användes metoden QDA. Resultatet gav många egenskapsord var av vissa kunde klassificeras som färskhetsrelaterade och vissa som förskämningsrelaterade. Det kunde även konstateras att färsk, odlad tilapia har en antydan av saftigare och mer mjäll textur. Vid lagring finns en möjlighet att tilapia får en intensivare smak av dy och metall, samt en intensivare doft av dy. / A large amount of Swedes has a desire to consume more nationally produced fish. Scandinavian Aquasystems produces and tries to introduce tilapia into the Swedish market. As a fish, tilapia has just begun making ways into Europe but is already a big commodity around the rest of the world. In addition, a sensory profile which tells how long the product remains sensorially suitable could be of help. This study aimed to create a sensory profile and to study its inherent effects of vacuum packaging over time. In creating the sensory profile, a QDA method was used. The study resulted in a variance of different attributes which of some could be categorized as either fresh related or spoilage related. It was found that fresh, farmed tilapia carried an indication of having a juicier and more tender texture. With storage there is chance of tilapia getting a more intense flavor of mud and metal, as well as a more intense odor of mud.

Firstly, a cell line derived from the liver of tilapia, Hepa-T1, was used as a model and exposed to two sub-lethal concentrations of waterborne copper for 96 h. The proteins expressed in Hepa T1 were investigated by differential protein profiling using two-dimensional gel electrophoresis (2-DE). It was found that Cu2+ (120 microM and 300 microM) caused differential expression of 93 different proteins, 18 of which were further verified by real-time quantitative polymerase chain reaction (PCR) analysis. Following analysis with ingenuity pathway software, several proteins were found to be involved in lipid metabolism, tissue connective development and cell cycle control, thus indicating that copper toxicity affects these cellular functions. / Fourthly, to further reveal the mechanism of copper tolerance and sensitivity in tilapia and zebrafish, two important copper transporters (ATP7A & B) and metallothionein (MT) were chosen for studying. Until now, a full length of ATP7A and partial length of ATP7B were obtained in tilapia. Then a real time quantitative PCR was conducted to study the different regulations of these three genes in tilapia and zebrafish. It was found that Cu2+ could induce more MT and ATP7A & B in tilapia than zebrafish both in vivo and in vitro. These results help us to understand that the copper tolerance of tilapia is possibly due to higher expression level of both copper transporters and MT. / Last but not least, I also compared the toxicity and biomarker gene expression in zebrafish exposed to Cu2O nanoparticle (NP) and CuCl2, respectively. It was found that the toxicity of CuCl2 is much higher than that of Cu2O NP. Then seven genes, including MT, ATP7A & B, copper transporter 1 (Ctr1), metal regulatory transcription factor 1 (MTF1), glutathione sulfur transferase (GST), Cu/Zn superoxide dismutase (Cu/Zn SOD), were chosen for studying. It was found that both Cu2O NP and CuCl 2 up-regulated the mRNA levels of MT, Cu/Zn SOD, and Ctr1, ATP7A & 7B, but down-regulated the mRNA levels of GST. Interestingly, the inductions of MT, Ctr1, ATP7A & B in the Cu2O NP exposure groups were much higher than that of CuCl2 exposure groups in vivo . Furthermore, as determined by using Ctr1, ATP7A and ATP7B gene expression, the no observable effect levels (NOELs) of CuCl2 and nano-Cu2O were 11 ppb and 50 ppb, whereas the lowest observable effect levels (LOELs) of CuCl2 and nano-Cu2O were 43 ppb and 125 ppb. (Abstract shortened by UMI.) / Secondly, the high copper contents in the liver of the tilapia make this fish a suitable model for the study of copper binding proteins. Liver was dissected from tilapia injected with Cu2+ and cytosolic fractions were separated by using Superdex 75 column chromatography followed with atomic absorption spectrometry. Fractions containing copper-binding proteins were found in two major peaks, analyzed using differential proteomic approaches, and loaded on a Cu chelating ion-immobilized affinity column (Cu-IMAC). Of the 113 differentially expressed proteins in these two peaks, some well-characterized copper binding proteins were found, including copper transporter ATP7A, cytochrome c oxidase, metallothionein, collagen, catalase, and vitellogenin. These proteins are mainly involved in endocrine disruption, mitochondria dysfunction, ion competition, lipid metabolism, copper transfer, and cytoskeleton disruption. In addition, a more concrete image about copper transportation pathway was hypothesized according to the function of the novel copper binding proteins identified. / The aims of this study are to identify some novel copper binding proteins and proteins related to Cu2+ toxicity or detoxification mechanisms in the tilapia (Oreochromis niloticus) and the zebrafish (Danio rerio) using a proteomic approach, and to reveal the mechanism of copper tolerance and copper sensitivity by comparing the different biochemical responses to copper exposures between the two model species. / Thirdly, zebrafish liver cell line (ZFL) was also used as a model to study the mechanism of copper toxicity. After processing similar experimental procedures of previous Hepa T1 experiment, 72 different proteins were identified to be regulated by Cu2+ (100 microM and 200 microM). More than 50 % of these proteins were also found differentially expressed in the tilapia. The results suggested that the toxicity mechanism between zebrafish and tilapia was generally conserved. Although, in ZFL, the regulation of several proteins, related to ROS effect, mitochondrion copper transportation, and stress response, was quite different from that in tilapia. / Chen, Dongshi. / Adviser: Chun Ung Ming. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 173-190). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

In recent times, diminishing freshwater resources, due to the rapidly increasing drain of urban, industrial and agricultural activities in combination with the impact of climate change, has led to an urgent need to manage marine and brackish water environments more efficiently. Therefore the diversification of aquacultural practices, either by the introduction of new candidate species or by the adaptation of culture methods for existing species, is vital at a time when innovation and adaptability of the aquaculture industry is fundamental in order to maintain its sustainability. The Nile tilapia (Oreochromis niloticus, Linnaeus, 1758), which has now been spread well beyond its natural range, dominates tilapia aquaculture because of its adaptability and fast growth rate. Although not considered to be amongst the most salt tolerant of the cultured tilapia species, the Nile tilapia still offers considerable potential for culture in low-salinity water. An increase in knowledge of the limits and basis of salinity tolerance of Nile tilapia during the sensitive early life stages and the ability to predict responses of critical life-history stages to environmental change could prove invaluable in improving larval rearing techniques and extend the scope of this globally important fish species. The capability of early life stages of the Nile tilapia to withstand variations in salinity is due to their ability to osmoregulate, therefore the ontogeny of osmoregulation in the Nile tilapia was studied from spawning to yolk-sac absorption after exposure to different experimental conditions ranging from freshwater to 25 ppt. Eggs were able to withstand elevated rearing salinities up to 20 ppt, but transfer to 25 ppt induced 100% mortality by 48 h post-fertilisation. At all stages embryos and larvae hyper-regulated at lower salinities and hypo-regulated at higher salinities, relative to the salinity of the external media. Osmoregulatory capacity increased during development and from 2 days post-hatch onwards remained constant until yolk-sac absorption. Adjustments to larval osmolality, following abrupt transfer from freshwater to experimental salinities (12.5 and 20 ppt), appeared to follow a pattern of crisis and regulation, with whole-body osmolality for larvae stabilising at c. 48 h post-transfer for all treatments, regardless of age at time of transfer. Age at transfer to experimental salinities (7.5 – 20 ppt) had a significant positive effect on larval ability to osmoregulate; larvae transferred at 8 dph maintained a more constant range of whole body osmolality over the experimental salinities tested than larvae at hatch. Concomitantly, survival following transfer to experimental salinities increased with age. There was a significant effect (GLM; p < 0.05) of salinity of incubation and rearing media on the incidence of gross larval malformation that was seen to decline over the developmental period studied. It is well established that salinity exerts a strong influence on development and growth in early life stages of fishes therefore the effects of varying low salinities (0 - 25 ppt) on hatchability, survival, growth and energetic parameters were examined in the Nile tilapia during early life stages. Salinity up to 20 ppt was tolerable, although reduced hatching rates at 15 and 20 ppt suggest that these salinites may be less than optimal. Optimum timing of transfer of eggs from freshwater to elevated salinities was 3-4 h post-fertilisation, following manual stripping and fertilisation of eggs, however increasing incubation salinity lengthened the time taken to hatch. Salinity was related to dry body weight, with larvae in salinities greater than 15 ppt displaying, at hatch, a significantly (GLM: p < 0.05) lower body weight but containing greater yolk reserves than those in freshwater or lower salinities. Survival at yolk-sac absorption displayed a significant (GLM; p < 0.05) inverse relationship with increasing salinity and mortalities were particularly heavy in the higher salinities of 15, 20 and 25 ppt. Mortalities occurred primarily during early yolk-sac development yet stabilised from 5 dph onwards. Salinity had a negative effect on yolk absorption efficiency (YAE). Salinity-related differences in oxygen consumption rates were not detectable until 3 days post-hatch; oxygen consumption rates of larvae in freshwater between days 3 – 6 post-hatch were always significantly higher (GLM p < 0.05) than those in 7.5, 15, 20 and 25 ppt, however, on day 9 post-hatch this pattern was reversed and freshwater larvae had a significantly lower QO2 than those in elevated salinities. Salinity had a significant inverse effect on larval standard length, with elevated salinities producing shorter larvae from hatch until 6 dph, after which time there was no significant differences between treatments. Salinity had a significant effect on whole larval dry weight, with heavier larvae in elevated salinities throughout the yolk-sac period (GLM; p < 0.05). The ability of the Nile tilapia to withstand elevated salinity during early life stages is due to morphological and ultrastructural modifications of extrabranchial mitochondria-rich cells (MRCs) that confer an osmoregulatory capacity before the development of the adult osmoregulatory system. A clearly defined temporal staging of the appearance of these adaptive mechanisms, conferring ability to cope with varying environmental conditions during early development, was evident. Ontogenetic changes in MRC location, 2-dimensional surface area, density and general morphological changes were investigated in larvae incubated and reared in freshwater and brackish water (15 ppt) from hatch until yolk-sac absorption using Na+/K+-ATPase immunohistochemistry with a combination of microscope techniques. The pattern of MRC distribution was seen to change during development under both treatments, with cell density decreasing significantly on the body from hatch to 7 days post-hatch, but appearing on the inner opercular area at 3 days post-hatch and increasing significantly (GLM; p < 0.05) thereafter. Mitochondria-rich cells were always significantly (GLM; p < 0.05) denser in freshwater than in brackish water maintained larvae. In both freshwater and brackish water, MRCs located on the outer operculum and tail showed a marked increase in size with age, however, cells located on the abdominal epithelium of the yolk-sac and the inner operculum showed a significant decrease in size (GLM; p < 0.05) over time. Mitochondria-rich cells from brackish water maintained larvae from 1 day post-hatch onwards were always significantly larger (GLM; p < 0.05) than those maintained in freshwater. Preliminary scanning electron microscopy studies revealed structural differences in chloride cell morphology that varied according to environmental conditions. Mitochondria-rich cell morphology and function are intricately related and the plasticity or adaptive response of this cell to environmental changes is vital in preserving physiological homeostasis and contributes to fishes’ ability to inhabit diverse environments. Yolk-sac larvae were transferred from freshwater at 3 days post-hatch to 12.5 and 20 ppt and sampled at 24 and 48 h post-transfer. The use of scanning electron microscopy allowed a quantification of MRC, based on the appearance and surface area of their apical crypts, resulting in a reclassification of ‘sub-types’ i.e. Type I or absorptive, degenerating form (surface area range 5.2 – 19.6 μm2), Type II or active absorptive form (surface area range 1.1 – 15.7 μm2), Type III or differentiating form (surface area range 0.08 – 4.6 μm2) and Type IV or active secreting form (surface area range 4.1 – 11.7 μm2). In addition, the crypts of mucous cells were discriminated from those of MRCs based on the presence of globular extensions and similarly quantified.

Lack of affordable feeds is one of the major constraints facing small-scale fish farmers in Tanzania. This study evaluated the suitability of moringa leaf meal (MLM), cassava leaf meal (CLM) and cassava root meal (CRM) as novel ingredients in Nile tilapia, Oreochromis niloticus diets. Each of the ingredients was processed in an attempt to remove the most significant antinutritional factor. A series of five experiments was conducted in a recirculation system using juvenile O. niloticus. The fish were fed isonitrogenous (30g 100g-1), isolipidic (10g 100g-1) and isoenergetic (18 kJ g-1) diets containing graded levels of the processed ingredients to their apparent appetite but not exceeding 10% of their body weight for a period of 8 weeks. Processing led to the removal of 0.3% of saponin from MLM and 60% and 90% of hydrogen cyanide from CLM and CRM respectively. The contents of other inherent antinutritional factors such as phenols, tannins and phytic acid were little affected. Processed MLM, CLM and CRM had 31.1/29.0/1.5g 100g-1 of crude protein, 5.9/10.2/2.4g 100g-1 of crude fibre and 20.1/19.7/15.8k Jg-1 of gross energy. The content of sulphur amino acids was higher in CLM (0.47%) than in MLM (0.23%). Digestibe protein and digestible energy was higher in MLM (25.71g 100g-1/15.44kJ g-1) than in CLM (12.71g 100-1/9.16kJ g-1). CRM had a digestible energy content of 13.5kJ g-1. Inclusion of either of the leaf meals, even at the lowest level of 15g 100g-1 of total dietary protein, led to a significant reduction in feed intake, growth and feed utilisation. Liver and small intestine did not show any histopathological changes which could be linked to dietary treatment. Conversely, cassava root meal could replace up to 75% of wheat meal in the diet without significantly affecting performance. The performance of leaf meals was marginally improved by a combination of blending and feeding stimulants, whereby a blend containing 1 part MLM and 2 parts CLM could provide up to 20g 100g-1 of dietary protein without significantly reducing performance. Biological and economic performance of practical diets containing 30-50g 100g-1 of dietary protein from moringa and cassava blends (LMB) with feeding stimulants was significantly lower than a fishmeal-meal based diet (FM) but comparable to a soybean meal-based diet (SBM). The suitability of MLM and CLM as novel protein sources in O. niloticus diets will depend on 1) improving reduction/removal of inherent antinutritional factors in MLM and CLM as well as improving digestibility of CLM. On the other hand, the suitability of CRM as a carbohydrate energy source will depend on the availability of cost effective protein sources due to its low protein content.

Body colouration in tilapia is an important trait affecting consumer preference. In the Nile tilapia (Oreochromis niloticus), there are three colour variants which are normal (wild type), red and blond. In some countries, the red variant is important and reaches higher prices in the market. However, one major problem regarding red tilapia culture is their body colouration which is often associated with blotching (mainly black but also red) which is undesirable for the consumer. The overall aim of this work was to expand knowledge on various aspects of body colouration in Nile tilapia using genetic approaches. The results of this research are presented as four different manuscripts. The manuscripts (here referred as Papers) have either been published (Paper IV) or are to be submitted (Paper I, II and III) in relevant peer reviewed journals. Paper I and II investigated the inheritance of black blotching and other body colour components of the red body colour. Specifically, Paper I consisted of two preliminary trials (Trial 1 and 2), to look at the ontogeny of black blotching and body colour components over a period of six months. Trial 1 investigated the effect of tank background colour (light vs dark) on black blotching and other body colour components and was carried out using a fully inbred (all female) clonal red line. Trial 2 was carried out using mixed sex fish and was aimed to investigate the association of black blotching with the sex of the fish. The results from this study were used to guide the experiment described in Paper II. Sixteen red sires with various levels of black and red blotching were crossed to clonal females and the inheritance of blotching and other body colour components were investigated using parent-offspring regressions. The results showed no significant heritability for black blotching and body redness, but a significant correlation for body redness and black blotching was found in female offspring at one sampling point suggesting that attempts to increase body redness may increase black blotching, as had been hypothesized. Paper III was divided into two parts. The first objective was to map the blond locus onto the tilapia linkage map and the second was to investigate the interaction of the blond and red genes on black blotching using the blond-linked markers to distinguish different blond genotypes in heterozygous red fish (i.e. RrBlbl or Rrblbl). In the blond fish, the formation of melanin is almost blocked via much reduced melanophores and this feature may be able to help reducing the black blotching in red tilapia. Two intraspecific families (O. niloticus) and one interspecific family (O. aureus and O. niloticus) were used as mapping families and the blond locus was located in LG5. Four out of eight markers were successfully used to assess the interaction of blond on red blotched fish. The blond gene did not significantly reduce the area of blotching but did reduce the saturation (paler blotching) and enhanced the redness of body colour in the Rrblbl fish compared to the RrBlbl group. Finally, Paper IV aimed to find out the effect of male colouration on reproductive success in Nile tilapia. A choice of one wild type male and one red male was presented to red or wild type females and these fish were allowed to spawn under semi-natural spawning conditions. Eggs were collected from the female’s mouth after spawning and paternity was assessed using microsatellite genotyping and phenotype scoring. No significant departures from equal mating success were observed between the red and wild type males, however there was a significant difference between the red and wild type females in the frequency of secondary paternal contribution to egg batches. The results suggest that mating success of wild type and red tilapia is approximately equal. The results from this research help to broaden our knowledge and understanding on the aspects of body colouration in Nile tilapia and provide fundamental information for further research.

Made available in DSpace on 2014-06-11T19:30:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-01-09Bitstream added on 2014-06-13T20:00:49Z : No. of bitstreams: 1 goncalves_gs_dr_jabo.pdf: 366406 bytes, checksum: 9292447bc252b06884ce3fe7463073d6 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Esse estudo teve como objetivo determinar a digestibilidade de ingredientes utilizados em formulações de rações para a aqüicultura, a melhor relação proteína digestível / lisina digestível, e por meio do conceito de proteína ideal a exigência em proteína e energia digestível para juvenis de tilápia do Nilo. Os resultados estão apresentados em capítulos, redigidos na forma artigos científicos para publicação em periódicos especializados. Foi possível observar diferenças em relação aos valores digestíveis dos nutrientes e aminoácidos, e verificar que os valores de coeficientes de digestibilidade aparente da proteína não refletem o coeficiente de digestibilidade aparente dos aminoácidos para alguns alimentos. Com relação à determinação da exigência em proteína e lisina em rações para juvenis de tilápia do Nilo (11,0 a 98,0g), o nível de 26% PD não diferiu do nível de 32,0% PD em relação a ganho em peso, sendo estes superiores ao tratamento com 22,0% PD. As diferentes relações proteína digestível (PD) / lisina digestível demonstram que o aminoácido lisina, ainda que, em níveis elevados de inclusão não foi suficiente para a melhora do desempenho produtivo da tilápia do Nilo, quando utilizado em dietas com baixo valor protéico. Entretanto, a suplementação de 7,5% de lisina em relação à proteína digestível (PD) em rações com níveis acima de 26% PD promoveu melhores respostas de desempenho produtivo para a espécie. A determinação da melhor relação proteína digestível / lisina digestível possibilitou a determinação posterior da melhor relação proteína digestível / energia digestível em rações formuladas com base no conceito de proteína ideal. Os resultados demonstram que a energia digestível das rações não influencia o desempenho dos peixes, uma vez que, as rações foram formuladas com base em energia... / The utilization of energetic and protein feeds, highly digestible as well, becomes more and more necessary due to the quality of formulated rations, zootecnic response and relationship with the environment. Apparent digestibility coefficient (ADC) of dry matter, protein, energy, phosphorus, and amino acids of corn starch, corn, wheat, rice, soybean, and cottonseed meal, corn gluten and fish meal were determined for Nile tilapia. ADC was determined using a reference ration based on albumin, gelatin and corn starch, indicator with the inert chromium III oxide (Cr2O3). Each test ration was made up of 70% of reference ration and 30% of the diet being evaluated. Feces were collected in groups of 5 replicates for each treatment. ADC values for protein and average ADC of amino acids were as follows: corn 89.76 and 96.43%, rice meal 95.88 and 92.26%, wheat meal 93.54 and 84.41%, fish meal 82.59 and 86.36%, corn gluten 89.82 and 87.98%, soybean meal 94.13 and 91.93%, cotton meal 87.10 and 77.47%, respectively. The results reported in this study suggest that ADC of protein might not be a very reliable indicator of ADC values of amino acids, even more so for wheat meal, corn, and cotton meal. Among protein feeds, soybean meal was found to have the highest ADC for protein and amino acids, while corn was the energetic feed with the highest ADC (86.15%) for energy.