| 1. |
- Mulokozi, Deogratias Pius, et al.
(författare)
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Rural aquaculture : Assessment of its contribution to household income and farmers' perception in selected districts, Tanzania
- 2020
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Ingår i: Aquaculture Economics & Management. - : Informa UK Limited. - 1365-7305 .- 1551-8663 .- 1365-7313. ; 24:4, s. 387-405
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Tidskriftsartikel (refereegranskat)abstract
- Rural fish farming is being promoted as a good source of protein and income diversification to fight poverty and inequality. However, its actual contribution to these rural households and local community at large is little known. Through interviews with 89 farmers' and 6 key informants, we examined the contribution of rural fish farming to local farmers' household income and investigate farmers' perceptions, opportunities, and constraints towards fish farming in six districts of Tanzania. Results indicated that fish farming contributed on average 13% to household incomes and that it explained 5% of the variation of the household income while 84% of the variation was due to non-fish sources. The majority (79%) of the farmers wanted to continue with fish farming, 9% planned to quit, and 12% had not decided whether to continue or not. Conclusively, much higher aquaculture contribution towards rural development could be obtained if appropriate measures are taken.
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| 2. |
- Lundh, Torbjörn, et al.
(författare)
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In search for protein sources: Evaluating an alternative to the traditional fish feed for Arctic charr (Salvelinus alpinus L.)
- 2018
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 486, s. 253-260
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Tidskriftsartikel (refereegranskat)abstract
- Traditional sources of protein in fish feed for salmonids, such as fishmeal, face sustainability problems. Therefore, ingredients not attractive for human consumption are increasingly being considered for the development of future feeds. However, it is uncertain how this alternative range of ingredients will affect fish growth, quality and consumer opinion. In this experimental study, we tested a new fish feed on Arctic charr, containing a protein mixture from the Baltic Sea and yeast, all ingredients unattractive for human consumption. This feed comprised of sprat (Sprattus sprattus) and herring (Clupea harengus), blue mussels (Mytilus edulis) and baker's yeast (Saccharomyces cerevisiae), in a ratio of three parts to the whole. Fish fed with this feed grew 11.5% less than the control group. The digestibility and microscopy analysis of the faeces suggested a lower digestibility of the test feed, presumably caused by the fish's inability to utilize the nutrients from the yeast cells. Consumers' perceptions of the final product were evaluated through a sensory evaluation, indicating no differences in scores of fillet quality between the two treatments. Potential implications of these results are discussed in context of feed composition, quality and other factors including species biology and season, which are relevant topics in the discussions on feed sustainability. Statement of relevance: Evaluating a feed mix unattractive for human consumption.
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| 3. |
- Vidakovic, Aleksandar, et al.
(författare)
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Evaluation of growth performance and intestinal barrier function in Arctic Charr (Salvelinus alpinus) fed yeast (Saccharomyces cerevisiae), fungi (Rhizopus oryzae) and blue mussel (Mytilus edulis)
- 2016
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Ingår i: Aquaculture Nutrition. - : Hindawi Limited. - 1353-5773 .- 1365-2095. ; 22:6, s. 1348-1360
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Tidskriftsartikel (refereegranskat)abstract
- Arctic charr (Salvelinus alpinus) were fed for 99 days on experimental diets with 40% of fish meal replaced, on a crude protein basis, with intact yeast (Saccharomyces cerevisiae) (ISC), extracted yeast (ESC), Rhizopus oryzae fungus (RHO) or de-shelled blue mussels (Mytilus edulis) (MYE). The fish were evaluated for growth performance, nutrient digestibility and fish intestinal function. Growth performance, retention of crude protein and sum of amino acids were not affected in fish fed diets ISC or MYE compared with those fed the reference (REF) diet. However, fish fed diet ISC displayed decreased digestibility of crude protein and indispensable amino acids and decreased intestinal barrier function compared with fish fed the REF diet. Fish fed diet ESC exhibited decreased growth performance and protein retention, but had comparable digestibility to fish fed the REF diet. Fish fed diets MYE and RHO showed similar performance in terms of growth, nutrient digestibility and intestinal barrier function. Overall, the results indicated that blue mussel and intact S. cerevisiae yeast are promising protein sources for Arctic charr.
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| 4. |
- Da, Chau Thi, et al.
(författare)
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Digestibility of dietary components and amino acids in plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings
- 2013
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Ingår i: Aquaculture Nutrition. - : Hindawi Limited. - 1353-5773 .- 1365-2095. ; 19, s. 619-628
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Tidskriftsartikel (refereegranskat)abstract
- The apparent digestibility (AD) of dietary components, energy and essential amino acids (EAA) of selected locally available plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings was studied. The AD of the test ingredients (ADi) differed (P < 0.05) and ranged from 66.2 to 89.6% for ADiDM, from 63.6 to 91.3% for ADiCP, from 65.4 to 85.3% for ADiOM and from 69.8 to 89.3% for ADiGE. The highest ADiDM, ADiOM and ADiGE in the test ingredients was obtained for broken rice, maize meal and soybean meal, while the lowest values were obtained for duckweed meal. Soybean meal and duckweed meal had the highest ADiCP, while there were no differences (P > 0.05) between the other test ingredients. The AD of total and individual EAA was higher in soybean meal, duckweed meal and broken rice than in the other test feed ingredients (P < 0.05). The lowest AD of individual EAA was found in maize meal, followed by cassava leaf meal and sweet potato leaf meal (P < 0.05). The low AD of individual plant feed ingredients may limit their potential to be used as replacement for fish meal in the feed.
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| 5. |
- Da, Chau Thi, et al.
(författare)
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Evaluation of local feed resources as alternatives to fish meal in terms of growth performance, feed utilisation and biological indices of striped catfish (Pangasianodon hypophthalmus) fingerlings
- 2012
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 364-365, s. 150-156
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Tidskriftsartikel (refereegranskat)abstract
- A 16-week feeding experiment was conducted to evaluate growth performance, feed utilisation and body indices of striped catfish (Pangasianodon hypophthalmus) fed diets where fish meal protein was replaced with protein from local feed resources. The reference diet contained fish meal as the main crude protein (CP) source, whilst in the six test diets 20 to 100% of the fish meal CP was replaced with CP from local ingredients (soybean meal, cassava leaf meal, sweet potato leaf meal, groundnut cake, golden apple snail meal and shrimp head meal). Final body weight (BW) and total weight gain (WG) were lowest for the cassava leaf meal diet (P < 0.05), whilst there were no differences in BW and WG between the other diets. Final BW, WG and daily weight gain were numerically highest for the shrimp head meal diet. Fish survival rate, feed intake, feed utilisation and fish fillet proportion did not differ between the reference diet and the test diets (P > 0.05). The viscera-somatic, hepato-somatic, kidney and intra-peritoneal fat indices differed between treatments (P < 0.05). The results suggest that fish meal protein in feed for striped catfish fingerlings can be replaced with protein from locally available plant and animal ingredients without compromising growth performance, feed utilisation and carcass traits.
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| 6. |
- Huyben, David, et al.
(författare)
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Dietary live yeast and increased water temperature influence the gut microbiota of rainbow trout
- 2018
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 124, s. 1377-1392
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Tidskriftsartikel (refereegranskat)abstract
- Aims: The objective was to determine the effects of dietary substitution of fishmeal (FM) with live yeast and increasing water temperature on the diversity and composition of gut microbiota in rainbow trout.Methods and Results: Fish were fed either FM or yeast (Saccharomyces cerevisiae) and reared in water temperatures of either 11 degrees C (cold) or 18 degrees C (warm) for 6 weeks. Luminal content and mucosa were collected from the distal gut and the load, diversity and species abundance of yeast and bacteria were analysed using agar plating, MALDI-TOF and rRNA gene amplicon sequencing. Yeast in the gut of fish fed FM were represented by S. cerevisiae, Rhodotorula spp. and Debaryomyces hansenii, while fish fed yeast contained 4-5 log higher CFU per g of yeast that were entirely represented by S. cerevisiae. For gut bacteria, sequencing of 16S rRNA gene amplicons using Illumina MiSeq showed lower bacterial diversity and abundance of lactic acid bacteria, especially Lactobacillus, in fish reared in warm rather than cold water. Fish fed yeast had similar bacterial diversity and lower abundance of Leuconostocaceae and Photobacterium compared with fish fed FM.Conclusions: Feeding live yeast mainly increased yeast load in the gut, while increased water temperature significantly altered the gut microbiota of rainbow trout in terms of bacterial diversity and abundance.Significance and Impact of the Study: Live yeast can replace 40% of FM without disrupting bacteria communities in the gut of rainbow trout, while increased water temperature due to seasonal fluctuations and/or climate change may result in a gut dysbiosis that may jeopardize the health of farmed fish.
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| 7. |
- Huyben, David, et al.
(författare)
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Post-prandial changes of unstressed and stressed dorsal aorta cannulated rainbow trout (Oncorhynchus mykiss) fed yeasts
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Introduction Feeding experiments can demonstrate long-term effects of test diets on fish growth and feed digestibility, however, they cannot determine short-term effects on nutrient uptake and stress response. Blood sampling during feeding experiments requires sedation and handling that can stress and affect blood parameters of fish (Djordjevic et al., 2011). Dorsal aorta (DA) cannulation of fish allows for serial blood sampling without inflicting stress. Single cell proteins, such as yeasts, are an ideal feed alternative to plant and fish meals as they do not compete as food for humans. In addition, yeasts, such as Saccharomyces cerevisiae, contain beta-glucans in their cell walls that can induce an immunostimulant effect on fish that increases disease resistance (Siwicki et al., 1994). The objective of this study was to determine the post-prandial changes of unstressed and stressed DA cannulated rainbow trout fed two different yeast diets. Materials and methods Rainbow trout were DA cannulated according to Kiessling et al (1995) with modifications. Briefly, fish were sedated with 1mg L-1 metomidate, anesthetised with 80mg L-1 tricaine methane sulfonate (MS222) and then placed in a recirculating surgery bath of 60mg L-1 MS222. Lidocain was used as a local anaesthetic at the incision sites where 180 polyethylene (PE) tubing was inserted in the snout of the fish and 90 PE tubing was inserted into the DA via guide wire. The 1m long cannula was injected with heparinised saline and sealed and the fish was given 3-5 days to recover while being fed a commercial diet. In total, 15 cannulated fish that weighed 849 ± 199g (±SD) were fed three iso-nitrogenous diets: fish meal control (FM), 60% replacement of fish meal with S. cerevisiae (YS) and 60% replacement with a 70:30 mix of W. anomalus and S. cerevisiae (YW). Fish were fed at 1% body weight (BW) via automated feeders with collectors in 200L tanks equipped with individual water flow (15C), shadow and light. For the diet test, 5 random fish were fed each diet for 1 week and then fed a different diet for weeks 2 and 3 (cross over design). For the stress test, fish were fed for a 4th week and then stressed via netting for 1min after feeding. Blood samples of 0.35mL were taken at 0 (before feeding), 3, 6, 12 and 24 hours on day 7 of every week. Blood was analysed for sodium, potassium, glucose, pH, PCO2, TCO2, HCO3, base excess and hemoglobin using an i-STAT analyser and haematocrit and leucocrit were measured after centrifugation. Red blood cells (RBC) were diluted and counted in a Burker chamber. Results Fish consumed diets at a rate of 0.83 ± 0.22% BW over 4 weeks. Samples from fish that consumed less than 0.20% BW were excluded from analyses. There were no mortalities, but 5 fish were replaced due to non-functioning cannulas. For the diet test, YS and YW diets were both significantly different (P<0.05) than FM diet for sodium, potassium, pH, TCO2, HCO3 and base excess. Hemaglobin of diet YW was different from diet FM. For the stress test, no significant differences existed between diets. In comparison, only glucose (YS and YW diets) and potassium (YW diet) were significantly different between diet and stress tests, although hematocrit and hemaglobin significantly increased and pH and blood gases significantly decreased after stress (i.e. 0 to 3 hr). Discussion and conclusion This study is one of the first to analyse blood samples from DA cannulated rainbow trout that voluntarily consumed feed after surgery. In the diet test, differences in blood potassium and sodium between diets are likely due to feed composition as yeast diets contained higher levels of potassium and lower levels of sodium compared to the FM diet. Increased levels of pH and blood gases in the yeast diets may be due to an immunostimulant effect from yeast beta-glucans (Siwicki et al., 1994), but more research is needed. In the stress test, increased levels of haematocrit, haemoglobin and glucose as well as reduced pH and blood gases have been previously reported as a result of increased catecholamine release and ventilation to cope with stress (Djordjevic et al., 2011). In conclusion, replacing fish meal with yeasts can significantly impact blood parameters of rainbow trout, however, yeasts diets had no significant effect on acute stress response. References Djordjevic B., T. Kristensen, Ø. Øverli, B. Rosseland, and A. Kiessling. 2011. Effect of nutritional status and sampling intensity on recovery after dorsal aorta cannulation in free-swimming Atlantic salmon. Fish Physiology and Biochemistry 38: 259-272. Kiessling A., B. Dosanjh, D. Higgs, G. Deacon, and N. Rowshandeli. 1995. Dorsal aorta cannulation: a method to monitor changes in blood levels of astaxanthin in voluntarily feeding Atlantic salmon. Aquaculture Nutrition 1(1): 43-50. Siwicki A., D. Anderson, and G. Rumsey. 1994. Dietary intake of immunostimulants by rainbow trout affects non-specific immunity and protection against furunculosis. Veterinary lmmunology and lmmunopathology 41: 125-139.
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| 8. |
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| 9. |
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| 10. |
- Mmanda, Francis Pius, et al.
(författare)
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Fish farming in Tanzania : the availability and nutritive value of local feed ingredients
- 2020
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Ingår i: Journal of Applied Aquaculture. - : Informa UK Limited. - 1045-4438 .- 1545-0805. ; 32:4, s. 341-360
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Tidskriftsartikel (refereegranskat)abstract
- An investigative field survey was performed to gather baseline data on locally available feed ingredients and fish farming practices in different regions of Tanzania. More than 80% of respondents relied on locally available feed ingredients as a major feed supplement for their cultured fish, with maize bran being the most commonly used feed ingredient in all regions. Crude protein content in most analyzed local feed ingredients was medium-high, while crude fat content was high in some animal and agricultural by-products, and medium-low in other ingredients. Most respondents were males and the majority of fish farms were owned by individuals. Earthen pond was the most common fish farming system in all regions except Dar es Salaam. Semi-intensively mixed-sex tilapia monoculture was the dominating fish farming practice. The results of the survey presented provide a good platform for future development of culture systems and feeding strategies for tilapia in Tanzania.
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