| 1. |
- Kiessling, Anders, et al.
(författare)
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Alternative protein sources for fish, not competing with the human food demand evaluated by traditional and novel approaches
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- At present, most alternative feed sources in fish is since long known in terrestrial animals. However, in a longer time frame this is questionable from a food security perspective, as these sources often are of human food quality. This is an argument rapidly growing in importance. Microbes, insects and products from other forms of extractive aquaculture are of major interest considering their growth potential, nutritional profile, probiotic qualities and ability to use simple resources as substrates. However, with a transition towards a circular economy, substrates that produce such feed ingredients will to a higher degree be based on waste and by-products. This development will demand novel approach in nutrition research in order to understand non-intuitive positive and negative effects in the fish gut biota, immune response, metabolism, welfare and product quality/safety. We will present our ongoing work, concerning physiological implications of alternative protein sources using in situ experimental technologies, such as cannulation and repeated tissue sampling. This work also combines advanced analytic methods of metabolomics and gut microbiota using amplicon next generation sequencing that targets 16S rDNA for bacterial identification. Data on post-prandial plasma AA profile, hematological parameters and erythrocyte indices will be presented together with data concerning the interaction between diet and stress in fish where fishmeal has been replaced by yeast up to 60%. Also, data concerning changes of the microbiota of fish given fungal mycelium-, yeast-, insect- (if ready) and mussel meal will be presented, including comparison between nutrient efficiency of feed given in clear or “green” water environments. Finally, experiments concerning yeast as biological barrier to prions, i.e. food safety, will be discussed. In all, an overall picture of one possible future development in fish nutrition will be painted with a focus on the use of novel feed stuffs in circular food production systems.
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| 2. |
- Nguyen, Huu Yen Nhi
(författare)
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Brewer’s yeast as a protein source in the diet of tilapia (Oreochromis niloticus) and freshwater prawns (Macrobrachium rosenbergii) reared in a clear water or biofloc environment
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigated the effects of dietary protein replacement of fishmeal or soybean meal with spent brewer’s yeast (SBY) in farmed tilapia and giant freshwater prawns. The effect of rearing tilapia and prawn in two different rearing systems, clear water recirculating aquaculture system (CW-RAS) and biofloc recirculating aquaculture system (Bio-RAS), were also investigated. The fish reared in Bio-RAS displayed higher growth, a higher protein efficiency ratio and a lower feed conversion rate than fish reared in CW-RAS. This difference between systems was not as apparent in the growth and protein efficiency ratio of freshwater prawns. In freshwater prawns, the survival rate was not affected by aquaculture water system nor by the replacement of fishmeal with SBY. The growth performance of prawns was not significantly different between any dietary treatments in Bio-RAS or CW-RAS. Significant differences were only found between brewer’s yeast replaced fishmeal at 60% in a CW-RAS and at 40% in Bio-RAS. Tilapia reared in CW-RAS with replacement of fishmeal with SBY showed a significantly (p<0.05) lower weight gain, daily weight and specific growth rate than fish in Bio-RAS when all diet groups per treatment was combined. However, at diet group level this difference was significant only in the 100% replacement group of CW-RAS when compared with the control in Bio-RAS. The protein requirement experiment showed that 27% and 31% crude protein can be used for tilapia in Bio-RAS and CW-RAS, respectively. The study demonstrated that tilapia reared in the Bio-RAS had a higher capacity to compensate for a reduction in dietary protein levels, as demonstrated by a higher growth rate than in fish reared in CWRAS. The apparent digestibility of crude protein by tilapia was high in diets with high crude protein, but there was no difference between the two rearing systems. SBY replace up to 100% of soybean meal without a significant reduction in tilapia growth. Tilapia exhibited the best performance when fed a diet where 30% soybean meal was replaced with SBY. This thesis concludes that SBY represents a sustainable, high-volume protein substitute for fishmeal and soybean meal in tilapia and giant freshwater prawn production and that the protein requirement of tilapia can be reduced if reared in a high-density microbial environment, i.e. a so-called Bio-RAS.
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| 3. |
- Nguyen, Huu Yen Nhi, et al.
(författare)
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Comparative evaluation of Brewer's yeast as a replacement for fishmeal in diets for tilapia (Oreochromis niloticus), reared in clear water or biofloc environments
- 2018
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 495, s. 654-660
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Tidskriftsartikel (refereegranskat)abstract
- Brewer's yeast as a replacement for fishmeal in the diet of tilapia (Oreochromis niloticus) was evaluated in a clear water and a biofloc environment. Triplicate groups, each of 20 juvenile tilapia (initial weight of 29 +/- 3.2 g), were randomly assigned to 24 conical 500-L tanks equipped with feed waste traps. Twelve of the tanks were in a recirculating aquaculture system (RAS) with clear water, with mechanical and biological filters and on average 15% daily replacement of water. The other 12 tanks were connected to four serial 10 m3 open biogenerator tanks that were initially fed with Bacillus subtilis and nutrients in order to achieve a C: N ratio of 10, supporting bacterial growth. In this biofloc system, only evaporated water was replaced. Four iso-nitrogenous (35%) and isoenergetic (19 MJ kg-1) diets were formulated to contain graded levels of brewer's yeast where 0%, 30%, 60% and 100% of fishmeal protein was replaced by yeast. Fish were reared for 3 months, with hand-feeding twice a day, achieving at least a fivefold increase in weight. At the end of the experiment, feed intake, protein intake, weight gain, daily weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, survival rate and body indices of tilapia were determined. In fish reared in clear water there was a lower weight gain, daily weight gain and specific growth rate with replacement of fishmeal, but significant only in the 100% replacement group. Despite nearly identical feed and protein intake in both environments, significantly higher growth was observed in fish kept in the biofloc environment, accompanied by significantly improved feed conversion ratio and protein efficiency and reduced mortality. A significant decrease in entero-somatic and intestinal index with increasing level of dietary brewer's yeast was observed, but only in the clear water environment. No significant effects or trends were noted in any other body index data, either for yeast inclusion rates or water environments. Based on this, we concluded that brewer's yeast represents a possible high-volume substitute for fishmeal in tilapia diets, especially if the fish are reared in a high-density microbial environment, i.e. a so-called biofloc environment.
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| 4. |
- Nguyen, Huu Yen Nhi, et al.
(författare)
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Growth and feed utilisation of Nile tilapia (Oreochromis niloticus) fed different protein levels in a clear-water or biofloc-RAS system
- 2021
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 536
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Tidskriftsartikel (refereegranskat)abstract
- A 9-week feeding experiment was conducted to evaluate different dietary protein levels in juvenile Nile tilapia reared in either a biofloc (Bio-RAS) or clear water recirculating aquaculture system (CW-RAS). The fish were fed four isoenergetic (19 MJ kg(-1)) diets with graded levels of a fixed mixture of three protein sources (animal, plant, and microbial origin) and containing 23, 27, 31 or 35% crude protein. Triplicate groups of 20 juvenile tilapia (initial weight: 39.1 +/- 2.5 g) were randomly assigned to 24 identical conical 500-L tanks equipped with feed waste traps. Twelve of the tanks were supplied with clear water purified by a mechanical and biological filter, denoted CW-RAS, and on average 15% daily replacement of water. The other 12 tanks were supplied with a biofloc suspension, maintained by a bioreactor system, denoted Bio-RAS, where the mechanical and biological filters were replaced with four serial 10 m(3) open bioreactor tanks. In this later system only evaporated water was replaced. The bioreactor tanks were initially inoculated with Bacillus subtilis, and nutrients were supplied to achieve a C: N ratio of 10, supporting heterotrophic bacterial growth. Feed and protein intake, weight gain, specific growth rate, protein efficiency of fish in all treatments, and biomass of micro components in the bioreactor tanks, as well as apparent digestibility of dietary components, were determined at end of the experiment. Growth, feed intake and protein efficiency, especially if retention of the floc was included, was overall higher in the Bio-RAS than in the CW-RAS system. Feed conversion was influenced both by protein level and by the availability of biofloc, with a general lower value in the Bio-RAS and fish given higher protein containing diets. Apparent digestibility of total protein did not vary with the rearing system but was higher with higher dietary levels of crude protein. No significant effect was found for mortality or body index, except for hepato-somatic index and intestinal quotient index, with the latter being significantly higher in the fish given access to biofloc. In all fish given access to biofloc, given all other factors being equal, displayed higher and more feed efficient growth than fish kept in clear water with only access to fabricated diets. Our results tally with other studies using biofloc tank technology and reports from more commercial settings indicating that our data is valid also at a more general level.
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| 5. |
- Nguyen, Huu Yen Nhi, et al.
(författare)
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Spent brewer's yeast as a replacement for fishmeal in diets for giant freshwater prawn (Macrobrachium rosenbergii), reared in either clear water or a biofloc environment
- 2019
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Ingår i: Aquaculture Nutrition. - : Hindawi Limited. - 1353-5773 .- 1365-2095. ; 25, s. 970-979
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Tidskriftsartikel (refereegranskat)abstract
- A 90-day feeding experiment was conducted in order to test spent brewer's yeast as a replacement for fishmeal in diets for giant freshwater prawn (Macrobrachium rosenbergii) reared in either a recirculating aquaculture system (RAS) or a biofloc system. Triplicate groups, each of 20 prawn (6.7 +/- 0.03 g), were randomly assigned to 24 identical tanks. Twelve tanks were connected to the RAS, and the other 12 tanks were connected to the biofloc system which were initially supplemented with Bacillus subtilis, molasses and blood meal to achieve a C:N ratio of 20:1. Four iso-nitrogenous (350 g/kg) and iso-energetic (19 MJ/kg) diets where 0%, 20%, 40% and 60% of fishmeal protein was replaced by spent brewer's yeast. Neither growth nor survival was affected (p > 0.05) by increasing levels of brewer's yeast. The exception, being fish given 60% replacement with brewer's yeast, reared in biofloc, which displayed a higher (p < 0.05) growth than fish given 40% replacement, reared in clear water. The feed conversion ratio of prawn reared in the biofloc environment was lower than in the clear water. We concluded that spent brewer's yeast represents a possible 60% substitute for fishmeal in giant freshwater prawn diets, especially for prawn reared in a biofloc environment.
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| 6. |
- Ström Hallenberg, Gunilla, et al.
(författare)
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Antibiotic Use by Small-Scale Farmers for Freshwater Aquaculture in the Upper Mekong Delta, Vietnam
- 2019
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Ingår i: Journal of Aquatic Animal Health. - : Wiley. - 0899-7659 .- 1548-8667. ; 31, s. 290-298
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Tidskriftsartikel (refereegranskat)abstract
- This study describes antibiotic use by small-scale freshwater aquaculture farmers in the upper Mekong Delta in southwestern Vietnam and the knowledge and practices surrounding the cause and prevention of aquaculture disease in that region. Forty five farmers were included in the study, of which 19 (42%) cultivated tilapia Oreochromis spp., 13 (29%) Striped Catfish Pangasianodon hypophthalmus and 13 (29%) giant river prawns Macrobrachium rosenbergii. Antibiotics were used by farmers of tilapia and Striped Catfish (84% and 69% of farmers, respectively), but not by any of the prawn farmers. Most farmers (72%) used antibiotics for around 3 d when treating diseases, depending on the farmers' economic means and whether the fish recovered, as judged by the farmer. If farmers perceived that the antibiotic treatment had failed, the most common response was to change to another type of antibiotic. Some farmers also used antibiotics in the absence of clinical symptoms as a preventive measure. In the absence of rapid, cost-effective diagnostics, the likelihood for the incorrect use of antibiotics is high, which has implications for antibiotic resistance. Moreover, the sequential use of different antibiotics following therapeutic failure is a risk factor for the emergence of resistance. All farmers that were surveyed were aware of the risks associated with antibiotic use. This may lead to successful intervention toward reduced antibiotic use in freshwater fish farming in Vietnam.
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