Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Orsay virus infection reduces outcrossing behaviour of Caenorhabditis elegans males
    Sluijs, L. van; Liu, Jie ; Schrama, Mels ; Hamond, Sanne van; Vromans, Sophie ; Scholten, Marèl ; Žibrat, Nika ; Riksen, J.A.G. ; Sterken, M.G. ; Pijlman, G.P. ; Kammenga, J.E. - \ 2020
    Dietary non-starch polysaccharides influenced natural food web and fish production in semi-intensive pond culture of Nile tilapia
    Kabir, K.A. ; Verdegem, M.C.J. ; Verreth, J.A.J. ; Phillips, M.J. ; Schrama, J.W. - \ 2020
    Aquaculture 528 (2020). - ISSN 0044-8486
    ADC - Cellulose - Lignin - Pectin - Stable isotope

    Dietary non-starch polysaccharides (NSP) changes the nutrient digestibility and faecal characteristics in fish. This study assessed the effect of the type of dietary NSPs on fish production and the contribution of natural food to the total fish production in semi-intensively managed tilapia ponds. Twelve ponds, each divided into three equally-sized compartments, were assigned to test the effect of the type of dietary NSPs (i.e. “PecHem-Diet”, a diet with easily fermentable NSP, vs “LigCel-Diet”, a diet with slowly fermentable NSP). Fish were restrictively fed, based on the crude protein content of the feed. Three feeding levels (“no = 0”, “low = 9 g.kg-0.8.d−1” and “high= 18 g.kg-0.8.d-1”) nested in pond were analysed in a split plot design. Initial fish biomass was 3084 g.compartment−1 and the experiment lasted 56 days. With the “LigCel-Diet” biomass gain was higher (2599 vs 2192 g.compartment−1) and feed conversion ratio (FCR) was lower (1.4 vs 1.9; P < .001) than with the “PecHem-Diet”. Diet had no effect on fish survival and specific growth rate (SGR). For both diets, increasing feeding level increased (P < .001) biomass gain, fish survival, FCR and SGR. There was a significant interaction effect (P < .05) between diet and feeding level on FCR. Fish body composition was the same in both diets. With the “LigCel-Diet”, the apparent digestibility coefficient (ADC) was higher (P < .001) for crude protein, fat, phosphorus and calcium and lower (P < .05) for ash compared to the other diet. Neither feeding level nor the interaction between diet and feeding level influenced the apparent digestibility coefficient (ADC) of any nutrient. Diet composition did not alter the organic matter (OM) composition of the faeces. δ13C and δ15N from the stable isotope analysis revealed that N gain in fish originated from both feed and natural food of the pond. Natural food abundance in the pond increased over time for both diets. Chlorophyll-a was higher in the pond fed with “LigCel-Diet”. Fish gut content and calculated N gain indicated an enhanced contribution of natural food to fish growth in ponds fed with “LigCel-Diet”. In conclusion, the type of dietary NSP determines tilapia productivity in semi-intensive managed ponds by altering food web productivity.

    Effect of dietary non-protein energy source (starch vs. fat) on total bile acid pool size and composition of rainbow trout (Oncorhynchus mykiss)
    Staessen, T.W.O. ; Verdegem, M.C.J. ; Eding, E.H. ; Nederlof, M.A.J. ; Schrama, J.W. - \ 2020
    In: Wias Annual Conference 2020 WIAS - p. 82 - 82.
    Bile acids play a key role in digestion and absorption of dietary fat. Synthesis of primary bile acids occurs in the liver, by oxidation of cholesterol and conjugation with either taurine orglycine. Bile acids are actively secreted into bile and stored in the gallbladder. The majority of bile acids is actively reabsorbed within the ileum, after which it returns to the liver for reuse. Under homeostatic conditions, the total bile acid pool size and composition is maintained relatively constant, compensating faecal bile acid loss with de novo synthesis. The process described above is known as entero hepatic circulation of bile acids (EHC). Diet macro nutrient composition can affect both the rate of EHC and bile acid synthesis. The level of gallbladder contraction (i.e., rate of EHC) in response to a meal has been shown to affect the bile acid pool size and composition in humans, with a low-fat diet decreasing the rate of contraction and increasing the bile acid pool size. Furthermore, less secondary bile acids are produced in response to decreased EHC. Dietary fat level has also been shown to influence bile acid synthesis. Feeding a diet high in fat stimulated bile acid synthesis(CYP7A1), while a low-fat diet decreased bile acid synthesis in rats. Data on the effect of diet macro nutrient composition on bile acid pool size and composition of fish are lacking.Therefore, this study investigated in rainbow trout (Oncorhynchus mykiss) if the type of dietary non-protein energy source (starch vs. fat) influences the size and composition of the total bile acid pool. Two diets were formulated with similar digestible protein to digestible energy ratio, but differing in inclusion of either maize starch or rapeseed oil as the main non-protein source. Fish were fed to satiation for 44 days. Feed, feces and fish samples were analyzed for proximate composition and bile acid content. The fat diet resulted in a lower total bile acid pool size compared to the Starch diet. Diet (i.e., type of non-protein energy source) does affect total bile acid pool size of rainbow trout, but does not affect bile acid pool composition. The daily fecal bile acid losses in rainbow trout are 2.0 ± 0.3 % of the total body pool and are not affected by dietary non-protein energy source.
    Quantifying methionine requirement of African catfish (clarias gariepinus) using a plant-based diet
    Elesho, Folasade ; Verreth, J.A.J. ; Sutter, D.A.H. ; Kröckel, S. ; Schrama, J.W. - \ 2020
    In: Wias Annual Conference 2020 WIAS - p. 65 - 65.
    The increasingly use of plant ingredients to replace high cost fishmeal has motivated fish nutritionist to investigate the amino acid (AA) profile and their individual requirements in commonly cultured species. Problems associated with the use of plant ingredients include the presence of anti-nutritional factors and AA deficiencies. Methionine is the first limiting AA in most leguminous plants. It is a sulphur-containing essential amino acid that is required for the synthesis of cysteine in animal and humans. Methionine is an initiation codon required during protein synthesis for protein formation. Inclusion levels of methionine below the requirements may cause growth reduction and decrease feed efficiency in fish. Therefore,adequate supply of methionine is essential in fish diets. Methionine requirements have been determined for several fish species, however, no reliable information is currently available for African catfish (Clarias gariepinus). Therefore, a 7-week experiment was conducted to estimate the dietary methionine requirement of juvenile African catfish (initial weight78 g), reared in a recirculation aquaculture system. A low-methionine (plant-based) dietwas formulated using soy protein concentrate and faba beans as intact protein. Based onthe methionine requirements for other species, which was obtained from literature, 7 diets were formulated, which all had the same basal composition but supplemented with different amount of crystalline DL-methionine: 0, 0.12, 0.24, 0.36, 0.48, 0.60, and 0.84%. Fish werefed restrictively twice a day at 90% satiation. Apparent digestibility coefficient (ADC) ofnutrients were measured by using settling tanks connected to the outlet of the aquaria in which African catfish were housed. The body composition of the fish were analysed both at the start and end of the experiment to determine the amino acid deposition, energy and nitrogen balance. At the end of the experiment, fish were weighed to determine the final body weight. Broken-line regression analysis was used to determine the quantitative methionine requirement by estimating the break-point for retained nitrogen and growth.The break point of the growth response curve occurred at 6.01 g methionine /kg diet. The reported methionine requirement value in this study can be used to formulate least cost -diets using plants ingredients for production of African catfish.
    Digestible energy versus net energy approaches in feed evaluation for rainbow trout
    Groot, R. ; Lyons, Philip ; Schrama, J.W. - \ 2020
    In: Wias Annual Conference 2020. - WIAS - p. 40 - 40.
    Currently, a digestible energy (DE) approach is used in fish feed evaluation which assumes a constant utilisation of digestible energy for growth (kgDE). However, carbohydrates in rainbow trout (Oncorhynchus mykiss) feeds are, compared to protein and fat, not only considered to be lower in digestibility, but also to be utilised to a lesser extent for retained energy and thus growth. A lower utilisation of carbohydrates would thus suggest an over prediction of kgDE at higher dietary carbohydrate levels and an inaccuracy in the DE approach.Recently it has been proposed to use a net energy (NE) approach in feed evaluation for fish, which considers differences in the utilisation of the different digestible macronutrients (digestible protein, fat, carbohydrates). This study aimed to examine if a NE approach can increase the prediction precision of growth performance compared to a DE approach in feed evaluation for rainbow trout. Therefore, a feeding trial with feeds having different DElevels and with a wide contrast in macronutrient composition which reflect those found in practical rainbow trout diets was done. Eight different diets were formulated to include two protein levels (40 and 50%) and four different fat levels (14, 19, 25, 30%) coinciding in a wide range in carbohydrate levels (8-35%). NE was calculated both using linear efficiencies of digestible macronutrients (NElin=15.1×dCP+35.0×dFat+12.1×dCarb) and with a curvilinear effect of carbohydrates included (NEcurv=13.5×dCP+33.0×dFat+34.0×dCarb–3.64×(d-Carb)2) (NE as kJ/kg0.8 BW per d and dCP, dFat and dCarb as g/kg0.8 BW per d) (Schramaet al 2018). The results of the current study showed that growth was significantly (P < 0.5) linearly related to DE and NElin intake within each protein level, which suggested a constant efficiency of digestible carbohydrates even at the relatively high dietary carbohydrate levels used in this study. NElin showed the best prediction of growth (R2=0.94 compared toR2=0.93 for DE intake and R2=0.91 for NEcurv intake), which also showed that a NE approach with linear efficiencies of digestible macro nutrients can increase the prediction of growth performance in feed evaluation for rainbow trout. A NE approach, which assumed the utilisation of carbohydrates to be curvilinearly related to carbohydrate intake did not lead to an increased prediction of growth performance as compared to DE in the current study.
    The role of fisheries and aquaculture in a circular food system
    Hal, O. van; Boer, I.J.M. de; Ziegler, Friederike ; Schrama, J.W. ; Kuiper, Kiki ; Zanten, H.H.E. van - \ 2020
    In: WIAS Annual Conference 2020. - WIAS - p. 46 - 46.
    Recent studies show that animals fed solely with low-opportunity-cost feeds (LCF), products currently considered unsuitable or undesired for human consumption, can contribute significantly to human nutrient supply. So far, studies on the role of animals in such a circular food system focussed on livestock, while fish can make a valuable contribution through their supply of animal-source food (ASF) rich in essential ω-3 fatty acids (ω-3EFA). Here we assessed the potential contribution of capture fisheries and aquaculture (i.e. farmed salmon and tilapia) to a circular food system, using the EU-28 as a case study. The contribution of fisheries was assessed through multiple sustainable fisheries scenarios. The contribution of aquaculture was determined by the availability of LCF and their competitive advantage in upcycling them compared to livestock. Such advantages are the supply of ω-3EFA in fish,a high feed efficiency and legality to feed processed animal proteins banned as livestock feed. Aquaculture’s contribution was assessed with an optimisation model that allocates LCF available in the EU to that combination of animals that maximises human digestible protein (HDP) supply, given that human population requirements regarding vitamin B12and ω-3EFA are met. Results show that in the proposed circular food system, fish consumption(20 g/cap/d), aquaculture production (2.8 million tonne fish meat) and food supply from EU fisheries (4.5 g/cap/d) are higher than currently in the EU. Fish provided all ω-3EFA,of which 55% through farmed salmon, which depended on fisheries for ω-3EFA containing feed. Overcoming this dependency on fisheries for ω-3EFA is essential for nutrition security.While aquaculture is essential to ω-3EFA supply and able to upcycle animal based LCF,livestock, especially dairy cattle, is more efficient at protein provision. Under the abundant protein supply in the EU, however, the ability to supply essential nutrients that can only be derived from ASF (e.g. ω-3EFA) is more valuable and should be prioritised. Fish, therefore,belongs to balanced diets with respect for our planet, which requires a combination of livestock and fish production systems, that use available LCF efficiently.
    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – 16S data set
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - few-foods diet - biomarker - 16S metagenomics
    Metagenomic 16S amplicon sequencing data for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done during screening (t0), before the FFD (t1) and after 5 weeks of FFD (t2).
    The effect of dietary non-starch polysaccharide level and bile acid supplementation on fat digestibility and the bile acid balance in rainbow trout (Oncorhynchus mykiss)
    Staessen, T.W.O. ; Verdegem, M.C.J. ; Weththasinghe, P. ; Schrama, J.W. - \ 2020
    Aquaculture 523 (2020). - ISSN 0044-8486
    Apparent nutrient digestibility - Feeding level - Non-starch polysaccharide - Oncorhynchus mykiss - Taurocholic acid

    This study investigated in rainbow trout (Oncorhynchus mykiss) if dietary bile acid supplementation is effective in restoring hampered fat digestibility related to conditions that enhance fecal bile acid loss (i.e., high dietary non-starch polysaccharide (NSP) level and high feeding level). Four diets were formulated according to a two-by-two factorial design. A Low- and High-NSP level (0 vs. 160 g kg-1 inclusion of a NSP-rich ingredient mixture) and two bile acid supplementation levels (0 vs. 2 g kg-1 inclusion of sodium taurocholate) were tested. A contrast in feeding level (i.e., feed intake) was created by subsequently feeding fish restrictively (1.1% BW d-1) for four weeks and to satiation for three weeks. The apparent digestibility coefficient (ADC) of all nutrients was affected by feeding period (i.e., restricted vs. satiation feeding), but the effect was dependent on diet composition with the ADC decline between feeding periods being larger for the High-NSP diets. The ADC of all macronutrients decreased alongside dietary NSP level, but this decrease was much more pronounced for fat compared to starch and protein, especially during satiation feeding (6.7%). This large drop in fat ADC during satiation feeding of NSP-rich diets occurred alongside enhanced fecal bile acid loss and correlated with a negative bile acid balance. The correlation between the bile acid balance and fat ADC found during satiation feeding of diets without bile acid supplementation was not present in fish fed diets with bile acid supplementation. In contrast to fat ADC, the ADC of protein and starch were independent from bile acid supplementation. In conclusion, dietary bile acid supplementation is an effective way to remediate decreased fat ADC related to enhanced fecal bile acid loss in rainbow trout, but is not effective in improving protein and starch ADC.

    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – lncRNA data set
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - few-foods diet - biomarker - lncRNA - coding RNA
    Long non-coding RNA and coding RNA sequencing data for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done before the FFD (t1) and after 5 weeks of FFD (t2).
    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – smallRNA data set
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - few-foods diet - biomarker - IncRNA - coding RNA
    Small RNA sequencing data for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done before the FFD (t1) and after 5 weeks of FFD (t2).
    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – Metagenomics data set
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - few-foods diet - biomarker - metagenomics
    Metagenomics sequencing data for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done before the FFD (t1) and after 5 weeks of FFD (t2).
    Effect of dietary carbohydrate to lipid ratio on performance of Nile tilapia and enhancement of natural food in pond aquaculture
    Kabir, Kazi A. ; Verdegem, Marc C.J. ; Verreth, Johan A.J. ; Phillips, Michael J. ; Schrama, Johan W. - \ 2020
    Aquaculture Research 51 (2020)5. - ISSN 1355-557X - p. 1942 - 1954.
    CHO - LIP ratio - natural food - non-protein energy - pond

    This study tested the effect of two diets differing in carbohydrate to lipid (CHO:LIP) ratio (4.7 vs. 19.5 g/g) on the contribution of natural food and the total fish production in tilapia ponds. Eight ponds, each divided into three equally sized compartments, were assigned to one of the two diets, which differed in CHO:LIP ratio but had the same digestible protein to digestible energy (DP:DE) ratio (15.5 and 15.6 g/MJ). Ponds were fed equal amounts of crude protein. Three feeding levels (no, low and high) were nested in each pond in a split plot design. Average body weight of fish at stocking was 90 g, and the duration of the experiment was 42 days. Increasing the CHO:LIP ratio had no impact on tilapia production. However, the feeding level influenced both biomass gain, specific growth rate and survival. The apparent digestibility coefficient (ADC) for fat and carbohydrate was influenced by dietary CHO:LIP ratio but ADC for energy was unaffected. Proximate analysis of fish body composition showed no effect of diet except for levels of ash. Diet had no effect on the organic matter composition of the faeces, and the contribution of natural food to fish nitrogen gain. Therefore, we postulate that changing the dietary non-protein energy source from lipid to carbohydrate does not have any impact on tilapia culture in semi-intensive ponds.

    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – Metabolomics data
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - few-foods diet - biomarker - metabolomics
    Small-molecule profiling data for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done before the FFD (t1) and after 5 weeks of FFD (t2).
    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – MultiplexELISA data
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - few-foods diet - biomarker - immunology - metabolism - hormones
    Multiplex ELISA data of immune, metabolism and hormone related molecules for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done before the FFD (t1) and after 5 weeks of FFD (t2).
    Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) – Behaviour scores
    Stobernack, Tim ; Frankena, Klaas ; Rodrigues Pereira, Rob ; Schrama, Rosan P.H. ; Baarlen, Peter van; Kleerebezem, Michiel ; Pelsser, Lidy ; Hontelez, Saartje - \ 2020
    Wageningen University & Research
    ADHD - ODD - few-foods diet - biomarker
    Symptom scores of ADHD and ODD for 79 children included in the Biomarker Research in ADHD: the Impact of Nutrition (BRAIN) study, an open-label trial during which children with ADHD followed a few-foods diet (FFD). Sampling was done before the FFD (t1) and after 5 weeks of FFD (t2).
    Carbohydrate utilisation by tilapia: a meta-analytical approach
    Maas, Roel M. ; Verdegem, Marc C.J. ; Wiegertjes, Geert F. ; Schrama, Johan W. - \ 2020
    Reviews in Aquaculture (2020). - ISSN 1753-5123
    digestibility - meta-analysis - non-starch polysaccharides - Oreochromis niloticus - starch

    Currently, studies reporting the digestibility of carbohydrates, starch and especially non-starch polysaccharides (NSP) in fish are scarce. Carbohydrate digestibility in the diet is largely dependent upon carbohydrate composition (starch vs. NSP). NSP are often considered to be indigestible and thus of no nutritional value. The present study reviews carbohydrates in fish feed, distinguishing between total carbohydrate, starch and NSP. Besides a qualitative approach, a meta-analysis was performed, compiling available data from digestibility studies on tilapia. Our meta-analysis confirms the negative effect of NSP on performance (FCR) and nutrient digestibility (crude protein, fat and energy). However, an average NSP digestibility of 24.3% was calculated in 95 cases. Out of these 95 cases, 88% of them showed a positive NSP digestibility. NSP digestibility was shown to contribute to energy digestibility. The digestion of NSP in fish is associated with fermentation in the gut, producing beneficial volatile fatty acids that are rapidly absorbed by the colonic lumen. Therefore, in diet formulation, digestibility and thus energy originating from NSP should be taken into consideration because NSP contribute to the energy needs of fish, here tilapia. Besides being an energy source, specific types of NSP may have immune-modulating and prebiotic effects and may be increasingly added to fish feed as modulators of fish health. We suggest that NSP is potentially (partly) digested by a wide range of fish species, especially by warm-water species with a long gut adapted to feeding on plant matter, as these factors favour gut fermentation.

    The effect of dietary protein source (fishmeal vs. plant protein) and non-starch polysaccharide level on fat digestibility and faecal bile acid loss in rainbow trout (Oncorhynchus mykiss)
    Staessen, Thomas W.O. ; Verdegem, Marc C.J. ; Koletsi, Paraskevi ; Schrama, Johan W. - \ 2020
    Aquaculture Research 51 (2020)3. - ISSN 1355-557X - p. 1170 - 1181.
    bile acids - cholesterol - fat digestibility - non-starch polysaccharides - Oncorhynchus mykiss - taurine

    This study investigated in rainbow trout (Oncorhynchus mykiss) if diet composition and feeding level affect faecal bile acid loss, and whether this reflects on the apparent digestibility coefficient (ADC) of fat. Six diets were formulated with either fishmeal or plant protein as main protein source. This created a contrast in the supply of bile acids, the bile acid precursor cholesterol, taurine and the taurine precursors (methionine + cysteine) involved in bile acid conjugation. For both protein sources, three diets were formulated with increasing inclusion of a non-starch polysaccharide (NSP)-rich ingredient mixture (0.0, 82.0 and 164.2 g/kg diet). This aimed at enhancing faecal bile acid loss. Fish were fed both restrictively (1.2% BW/day) and to satiation. A similar fat ADC was found when substituting fishmeal with a plant protein mixture, suggesting that the lower content of bile acids, cholesterol, taurine, methionine and cysteine in the plant-based diets did not limit fat digestion. Faecal bile acid loss increased alongside dietary NSP level, however, only during satiation feeding and most strongly for fish fed the fishmeal-based diets. Enhanced faecal bile acid loss was not caused by NSP-bile acid binding/entrapment, but by an increase in faeces production. During satiation feeding, fat ADC negatively correlated with faecal bile acid loss. From this it is concluded that bile acid availability/synthesis can become limiting for fat digestion in rainbow trout under conditions that enhance faecal bile acid loss (i.e. dietary NSP level and feeding level).

    The effect of dietary protein to energy ratio and stocking densities on fish production, food web enhancement and economic benefit of gift Nile tilapia aquaculture in ponds
    Kabir, K.A. ; Verdegem, M.C.J. ; Schrama, J.W. ; Verreth, J.A.J. ; Phillips, Michael J. - \ 2019
    In: Book of abstracts of the 12th Asian Fisheries & Aquaculture Forum (AFAF). - - p. 315 - 315.
    In non-lined ponds, natural food complements dietary P/E. We assessed the effect of lowering dietary PIE ratio with an increasing stocking density on performance of tilapia, food web enhancement and impact on pond nutrients. The experiment was conducted in a 2x2x2 factorial design: diet (CP:CE ratio 19 vs. 14 g.MJ-1); feeding level; and stocking density (2 vs 3 m-2) in 40 farmers' ponds. Biomass gain increased with a decreasing dietary PIE ratio and increasing stocking density). A negative accumulation of N and P in pond water was noticed for low stocking density ponds. Nitrogen gain in fish was higher for low P/E diet and also influenced by feed per square meter. At low P/E diet, the contribution of natural food to fish production was higher than for the high P/E diet. Net profit increased by lowering the dietary P/E ratio of the diet (2070 vs 1072 US$ ha-1 83 day-1).
    Effect of stocking density on the survival rate and grow-out of blue swimming crab (Portunus pelagicus) in brackish water ponds
    Wisnu Ariyati, Restiana ; Rejeki, Sri ; Bosma, R.H. ; Schrama, J.W. - \ 2019
    In: Book of abstracts of the 12th Asian Fisheries & Aquaculture Forum (AFAF). - - p. 76 - 76.
    Crabs only contribute a small percentage to Indonesia's total exports of aquaticproducts. Due to the growing popularity of the Blue swimming crab (Portunuspelagicus ), fishery catches of this species have increased since the early 1950s.This increased fishing pressure has led to a decline in the P. pelagicus population in Southeast Asian countries such as Thailand, Philippines, Vietnam and Indonesia. As a result, fishermen hardly catch large crab, and market also juveniles. Juvenile crabs are usually sold at lower prices; therefore, fattening small crab to market size may have a future. Furthermore, fattening to marketable size for an acceptable cost and effort might also reduce the fishing pressure. This study aimed to determine the optimal stocking density of Blue swimming crab for rearing in cages in shallow brackish water ponds. The research was conducted at Tambakbulusan village, Demak, Central Java, Indonesia. In a pond with 0.5 meter water depth we suspended 20 cages of 2.5 x 2 meter, for a Randomized Block Design of 4 stocking densities (2, 3, 4, and 5 individual's m-2) in five replications. Sea weed was added as shelter. The initial average size of these crabs was 5+1.6 cm in carapace length and 20+1.5 g in body weight. The crabs were fed trash-fish twice a day at a total dosage of 5 % of body weight; the quantity was adjusted bi-weekly after measuring and weighing all individuals. The effect of stocking density on the growth was not significantly different (P>0.05) but the survival rate was (P<0.05). Lowest densities (2 individual's m-2) resulted in highest survival rate (50 %). Research is needed oncauses and solutions for mortality as survival seems to be the most limiting factor for a feasible grow-out farming of Blue swimming crab.
    The effect of dietary protein to energy ratio and stocking densities on fish production, food web enhancement and economic benefit of gift Nile tilapia aquaculture in ponds
    Kabir, Kazi ; Verdegem, Marc ; Schrama, Johan ; Verreth, Johan ; Phillips, Michael J. - \ 2019
    In non-lined ponds, natural food complements dietary P/E. We assessed the effect of lowering dietary PIE ratio with an increasing stocking density on performance of tilapia, food web enhancement and impact on pond nutrients. The experiment was conducted in a 2x2x2 factorial design: diet (CP:CE ratio 19 vs. 14 g.MJ-1); feeding level; and stocking density (2 vs 3 m-2) in 40 farmers' ponds. Biomass gain increased with a decreasing dietary PIE ratio and increasing stocking density). A negative accumulation of N and P in pond water was noticed for low stocking density ponds. Nitrogen gain in fish was higher for low P/E diet and also influenced by feed per square meter. At low P/E diet, the contribution of natural food to fish production was higher than for the high P/E diet. Net profit increased by lowering the dietary P/E ratio of the diet (2070 vs 1072 US$ ha-1 83 day-1).
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