Thesis (D. Miss.)--Trinity International University, 1999. / Abstract. Includes bibliographical references (leaves 223-229).

Thesis (Ph.D.)--Brown University, 2008. / Vita. Advisor : Andrew D. Foster. Includes bibliographical references (leaves 86-91).

Doctoral thesis. / Format: PDF. Bibl.

Master's thesis. / Format: PDF. Bibl.

Bachelor's thesis. / Format: PDF. Bibl.

Master's thesis. / Format: PDF. Bibl.

Master's thesis. / Format: PDF. Bibl.

Master's thesis. / Format: PDF. Bibl.

The nutritional suitability of some Bangladeshi oilseed by-products (mustard, Brassica juncea; linseed, Linum usitatissimum; sesame, Sesamum indicum) as fish meal substitutes in carp diets was investigated. These protein sources were shown to cause depressed growth and feed efficiency when substituting 25% or more of the fish meal protein in semi-purified diets. However, the use of these oilseed meals in combination was found to be more effective than that of single sources. Supplementation of plant protein diets with crystalline EAA improved their nutritive value. Growth performance was better in fish fed diets supplemented with all deficient EAA than in fish fed diets supplemented with the first limiting EAA. Nutrient digestibility studies with these plant proteins suggested reasonable agreement between apparent protein digestibility (APD) and average apparent amino acid digestibility (AAAD). APD and AAAD values ranged from 78.9% to 85% and 82.4% to 85.8% respectively. Both aqueous and enzyme treatments were effective in reducing (49% and 57% respectively) the anti-nutritional factors (e. g. allyl isothiocyanate) in mustard oilcake. In linseed and sesame meals heat treatment was the most effective (reducing phytic acid levels by 72% and 74% respectively). Use of detoxified meals in diets improved growth performance and food utilization compared to untreated meals. Dietary phytic acid in the presence of increased levels of calcium and magnesium significantly (p < 0.05) depressed growth, food utilization and mineral bioavailability (especially Ca and Zn) in carp. Carp were shown to be tolerant of a dietary glucosinolate (allyl isothiocyante) level of 0.4 mg glucosinolate/g diet without inhibiting growth performance or adverse effects on fish health. However, fish fed diets containing higher levels of mustard oilcake or allyl isothiocyanate showed abnormal changes in thyroid tissues. The results of this study are discussed in relation to previously published research on fish and other monogastric animals.

Ricefield based fish seed production (RBFSP) in irrigated spring (boro) ricefields after initial introductions by external promoters has spread among farmers in parts of Northwest Bangladesh. This approach to producing juvenile fish, rather than by specialised geographically clustered hatchery and nursery enterprises, has been recognised as a strategy for decentralised production that makes large high quality seed available locally and supports food fish production. RBFSP has been promoted by the international NGO CARE as part of a process to improve rice-based livelihoods of farming households using a farmer field school (FFS) approach in two consecutive projects between 1993 and 2005. The approach is technically simple and is based on the stocking of common carp (Cyprinus carpio) eggs and Nile tilapia (Oreochromis niloticus) broodfish in ricefields. As a new approach to farmer level fish seed production, its livelihood impacts on the farming households as well as associated actors; its adoption, adaptation and rejection process in farming households; and its cost-effectives for dissemination at farmer level were not well understood. This thesis mainly applies the concept of the sustainable livelihood approach (SLA) using tools and processes of the growing family of participatory research. A systems approach was used to ensure that the key stakeholders including households, community and extension organizations were included. The study was initiated with a well-being analysis of community households to identify poorer households before exploring impacts of RBFSP on poorer producing households (RF) compared to non-producing (NRF) households based on one-off and longitudinal surveys. Livelihoods impacts on other actors linked directly and indirectly with RBFSP were also investigated. The adoption process of RBFSP at the household level and the cost-effectiveness of its promotion were assessed. Impact studies at the household level showed that RF households were significantly larger and had lower levels of formal education than NRF. Adoption of RBFSP had improved practical skills and hence substantially improved human capital in RF households. RF households tended to have more of their ricefish plots located adjacent to their households. Poor and intermediate adopters had smaller riceplots than better-off households but higher seed production efficiencies (poor-315.1 kg fingerlings/ha; intermediate-419.1 kg fingerlings/ha) than better-off households (294.6 kg fingerlings/ha). In addition to direct consumption of large fingerlings, RF households restocked them for further growth in their household ponds in doing so increasing yields by 60%. Fish consumption increased substantially in RF households based on their own production reducing their dependency on purchase from markets. The year round longitudinal survey revealed that activities for RBFSP were compatible with their existing rice-based agriculture activities for household members including men, women and children. The relatively limited income from fingerling production improved cash flow in the low income months. Consumption of large size fingerlings from ricefields provided nutrient dense food in the ‘hungry gap’ months when supplies of wild fish were poor, smoothing consumption. Apart from RF households, RBFSP extended its livelihoods impacts to a wide range of actors in and around the seed producing community. Poor fry traders were found to be key actors in the spread and support of RBFSP. On average fry traders supplied fingerlings to 35 foodfish producers within a mean distance of 5 Km from producing households in a community where RBFSP was well established. The end users (foodfish producers) included households with their own ponds, ponds with multiple ownership and larger waterbodies leased by small groups. Locally available RFBSP juveniles were attractive to each of these groups, supplementing hatchery derived seed. A large number of complex socio-cultural and technical factors were related to household level adoption of RBFSP. The major factors included use of cash generated to prevent distress sales of rice; lack of requirement to use pesticide in ricefields; meeting the household consumption demand; capacity to restock fingerlings in ponds; lack of any negative effects on rice production; increased non-stocked fish production in riceplots; simplicity of the technology; ease of fish harvest from riceplots; increased ability to gift fingerlings/foodfish to relatives and neighbours; more efficient use of both riceplot and irrigation pumps. The most important reasons for households not attempting or quickly rejecting RBFSP were labour conflicts with other activities. However, lost access to the riceplots through changes in tenure was the most common cause of late rejection by households who had practiced RBFSP for several years after withdrawal of CARE support. Location of fish seed producing plots close to the homesteads facilitated household women to contribute to seed production activities through feeding and looking after fish. Women were able to decide and control resources generated from fingerling sales as well as choosing to gift fingerlings to their relatives. Informal transfer of fingerlings in this way stimulated spread of RBFSP. Decentralised fish seed production was promoted through FFS very cost effectively. The introduction of an improved strain of Nile tilapia (GIFT) broodfish greatly enhanced the returns from decentralised seed production based on common carp alone. High levels of secondary adoption improved benefits from promoting RBFSP. The major benefit derived from the improved returns to food fish farmers using locally produced seed. Higher levels of net present value (NPV) and benefit cost ratio (BCR) were achieved based on promotion of mixed-sex tilapia in RBFSP than mono-sex tilapia produced in a large scale central hatchery. Cost-effectiveness in terms of multiplier development impacts on ramification of secondary adopters and, income of fry traders and foodfish producers, RBFSP also showed better performance than a mono-sex tilapia hatchery.