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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Effect of dietary replacement of fishmeal by insect meal on growth performance, blood profiles and economics of growing pigs in Kenya
Chia, Shaphan Y. ; Tanga, Chrysantus M. ; Osuga, Isaac M. ; Alaru, Alphonce O. ; Mwangi, David M. ; Githinji, Macdonald ; Subramanian, Sevgan ; Fiaboe, Komi K.M. ; Ekesi, Sunday ; Loon, Joop J.A. van; Dicke, Marcel - \ 2019
Animals 9 (2019)10. - ISSN 2076-2615
Alternative protein - Animal feeds - Blood parameters - Cost benefit analysis - Growing pigs - Insect larval meal - Return on investment

Pig production is one of the fastest growing livestock sectors. Development of this sector is hampered by rapidly increasing costs of fishmeal (FM), which is a common protein source in animal feeds. Here, we explored the potential of substituting FM with black soldier fly larval meal (BSFLM) on growth and blood parameters of pigs as well as economic aspects. At weaning, 40 hybrid pigs, i.e., crossbreeds of purebred Large White and Landrace were randomly assigned to five iso-nitrogenous and iso-energetic dietary treatments: Control (0% BSFLM and 100% FM (T0)), and FM replaced at 25% (T25), 50% (T50), 75% (T75) and 100% (T100) with BSFLM. Average daily feed intake (ADFI), average daily gain (ADG), body weight gain (BWG) and feed conversion ratio (FCR) were calculated for the whole trial. Hematological and serum biochemical parameters, the cost– benefit ratio (CBR) and return on investment (RoI) were evaluated. No significant effect of diet type was observed on feed intake and daily weight gain. Red or white blood cell indices did not differ among diets. Pigs fed T25, T75 and T100, had lower platelet counts compared to T0 and T50. Dietary inclusion of BSFLM did not affect blood total cholesterol, triglycerides, low-density lipoprotein and high-density lipoprotein. CBR and RoI were similar for the various diets. In conclusion, BSFLM is a suitable and cost-effective alternative to fishmeal in feed for growing pigs.

The nutritive value of black soldier fly larvae reared on common organic waste streams in Kenya
Shumo, Marwa ; Osuga, Isaac M. ; Khamis, Fathiya M. ; Tanga, Chrysantus M. ; Fiaboe, Komi K.M. ; Subramanian, Sevgan ; Ekesi, Sunday ; Huis, Arnold van; Borgemeister, Christian - \ 2019
Scientific Reports 9 (2019). - ISSN 2045-2322

In Africa, livestock production currently accounts for about 30% of the gross value of agricultural production. However, production is struggling to keep up with the demands of expanding human populations, the rise in urbanization and the associated shifts in diet habits. High costs of feed prevent the livestock sector from thriving and to meet the rising demand. Insects have been identified as potential alternatives to the conventionally used protein sources in livestock feed due to their rich nutrients content and the fact that they can be reared on organic side streams. Substrates derived from organic by-products are suitable for industrial large-scale production of insect meal. Thus, a holistic comparison of the nutritive value of Black Soldier Fly larvae (BSFL) reared on three different organic substrates, i.e. chicken manure (CM), brewers’ spent grain (SG) and kitchen waste (KW), was conducted. BSFL samples reared on every substrate were collected for chemical analysis after the feeding process. Five-hundred (500) neonatal BSFL were placed in 23 × 15 cm metallic trays on the respective substrates for a period of 3–4 weeks at 28 ± 2 °C and 65 ± 5% relative humidity. The larvae were harvested when the prepupal stage was reached using a 5 mm mesh size sieve. A sample of 200 grams prepupae was taken from each replicate and pooled for every substrate and then frozen at −20 °C for chemical analysis. Samples of BSFL and substrates were analyzed for dry matter (DM), crude protein (CP), ether extracts (EE), ash, acid detergent fibre (ADF), neutral detergent fibre (NDF), amino acids (AA), fatty acids (FA), vitamins, flavonoids, minerals and aflatoxins. The data were then subjected to analysis of variance (ANOVA) using general linear model procedure. BSFL differed in terms of nutrient composition depending on the organic substrates they were reared on. CP, EE, minerals, amino acids, ADF and NDF but not vitamins were affected by the different rearing substrates. BSFL fed on different substrates exhibited different accumulation patterns of minerals, with CM resulting in the largest turnover of minerals. Low concentrations of heavy metals (cadmium and lead) were detected in the BSFL, but no traces of aflatoxins were found. In conclusion, it is possible to take advantage of the readily available organic waste streams in Kenya to produce nutrient-rich BSFL-derived feed.

Distant Non-Obvious Mutations Influence the Activity of a Hyperthermophilic Pyrococcusfuriosus Phosphoglucose Isomerase
Subramanian, Kalyanasundaram ; Mitusińska, Karolina ; Raedts, John ; Almourfi, Feras ; Joosten, Henk Jan ; Hendriks, Sjon ; Sedelnikova, Svetlana E. ; Kengen, Servé W.M. ; Hagen, Wilfred R. ; Góra, Artur ; Martins Dos Santos, Vitor A.P. ; Baker, Patrick J. ; Oost, John van der; Schaap, Peter J. - \ 2019
Biomolecules 9 (2019)6. - ISSN 2218-273X
Comulator - cupin phosphoglucose isomerase - Protein engineering - Pyrococcus furiosus - solvent access

The cupin-type phosphoglucose isomerase (PfPGI) from the hyperthermophilic archaeon Pyrococcus furiosus catalyzes the reversible isomerization of glucose-6-phosphate to fructose-6-phosphate. We investigated PfPGI using protein-engineering bioinformatics tools to select functionally-important residues based on correlated mutation analyses. A pair of amino acids in the periphery of PfPGI was found to be the dominant co-evolving mutation. The position of these selected residues was found to be non-obvious to conventional protein engineering methods. We designed a small smart library of variants by substituting the co-evolved pair and screened their biochemical activity, which revealed their functional relevance. Four mutants were further selected from the library for purification, measurement of their specific activity, crystal structure determination, and metal cofactor coordination analysis. Though the mutant structures and metal cofactor coordination were strikingly similar, variations in their activity correlated with their fine-tuned dynamics and solvent access regulation. Alternative, small smart libraries for enzyme optimization are suggested by our approach, which is able to identify non-obvious yet beneficial mutations.

Influence of temperature on selected life-history traits of black soldier fly (Hermetia illucens) reared on two common urban organic waste streams in Kenya
Shumo, Marwa ; Khamis, Fathiya M. ; Tanga, Chrysantus M. ; Fiaboe, Komi K.M. ; Subramanian, Sevgan ; Ekesi, Sunday ; Huis, Arnold Van ; Borgemeister, Christian - \ 2019
Animals 9 (2019)3. - ISSN 2076-2615
Black soldier fly (BSF) - Development - Fecundity - Growth - Longevity - Organic waste bioconversion - Rearing temperature

In sub-Saharan Africa, urban populations are projected to increase by 115% in the coming 15 years. In addition, economic growth and dietary shifts towards animal source foods have put high pressure and demand on agricultural production. The high ecological footprint of meat and dairy production, as well as high feed costs, prevent the livestock sector from meeting the increasing demand in a sustainable manner. Insects such as the black soldier fly (BSF) have been identified as potential alternatives to the conventionally used protein sources in livestock feed due to their rich nutrient content and the fact that they can be reared on organic side streams. Substrates derived from organic byproducts are suitable for industrial large-scale production of insect meal. Although efficient in waste management and in feed production, BSF larvae are very sensitive to the external environment such as temperature and rearing medium. Therefore, we studied the effect of temperature and substrate type, i.e., brewers’ spent grain (SG) and cow dung (CD), on the development and survival of BSF larvae. Both organic substrates were readily available in Nairobi, Kenya, the location of the experiments. In our experiment, 100 3–5-day-old BSF larvae were placed into containers that contained either SG or CD and further treated at temperatures of 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C. The duration of larval development was recorded, and the prepupae were removed, weighed, and placed individually in separate, labeled, 35-mL plastic cups filled with moist sawdust. After emergence, 10 2-day-old adults (5 males and 5 females) from every replica per substrate were transferred into a cage (40 × 40 × 40 cm) and allowed to mate for 24 h at their respective temperatures. The laid egg batches were collected and counted, and the adult flies’ longevity was recorded. The data were subjected to a two-way analysis of variance (ANOVA) using the general linear model procedure. BSF larvae reared on SG developed faster than those reared on CD; the former also favored higher temperatures for their larval development and emergence into adults. The optimum range was 25–30 °C. With increasing temperatures, the longevity of adult BSF decreased, while the fecundity of females increased. Thus, it is possible to take advantage of the readily available SG waste streams in the urban environments of Kenya to produce BSF larvae-derived livestock feed within a short duration of time and at relatively high temperatures.

Characterization of Male-Produced Aggregation Pheromone of the Bean Flower Thrips Megalurothrips sjostedti (Thysanoptera: Thripidae)
Niassy, Saliou ; Tamiru, Amanuel ; Hamilton, James G.C. ; Kirk, William D.J. ; Mumm, R. ; Sims, Cassie ; Kogel, W.J. de; Ekesi, Sunday ; Maniania, N.K. ; Bandi, Krishnakumari ; Mitchell, Fraser ; Subramanian, Sevgan - \ 2019
Journal of Chemical Ecology 45 (2019). - ISSN 0098-0331 - p. 348 - 355.
Aggregation of the bean flower thrips, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), has been observed on cowpea, Vigna unguiculata (L.) Walp. To understand the mechanism underpinning this behavior, we studied
the responses of M. sjostedti to headspace volatiles from conspecifics in a four-arm olfactometer. Both male and female M. sjostedti were attracted to male, but not to female odor. Gas chromatography/mass spectrometry (GC/
MS) analyses revealed the presence of two distinct compounds in male M. sjostedti headspace, namely (R)-lavandulyl 3-methylbutanoate (major compound) and (R)-lavandulol (minor compound); by contrast, both compounds were only present in trace amounts in female headspace collections. A behavioral assay using synthetic compounds showed that male M. sjostedti was attracted to both (R)-lavandulyl 3-methylbutanoate and (R)-lavandulol, while females responded only to (R)-lavandulyl 3-methylbutanoate. This is the first report of a male-produced aggregation pheromone in the genus Megalurothrips. The bean flower thrips is the primary pest of cowpea, which is widely grown in sub-Saharan Africa. The attraction of male and female M. sjostedti to these compounds offers an opportunity to develop ecologically sustainable management methods for M. sjostedti in Africa.
Muscle growth mechanisms in response to isoenergetic changes in dietary non-protein energy source at low and high protein levels in juvenile rainbow trout
Alami-Durante, Hélène ; Cluzeaud, Marianne ; Bazin, Didier ; Schrama, Johan W. ; Saravanan, Subramanian ; Geurden, Inge - \ 2019
Comparative Biochemistry and Physiology. A, Molecular and Integrative Physiology 230 (2019). - ISSN 1095-6433 - p. 91 - 99.
This study investigates muscle growth mechanisms in juvenile rainbow trout in response to isoenergetic changes in dietary non-protein energy (NPE) source (F, fat vs. C, carbohydrates) at two levels of digestible protein to digestible energy (DP/DE) ratio. Fish (initial weight 32.4 g) were fed four diets having similar DE levels (~18 kJ g−1) with a high (HP/E~26 mg kJ−1) vs. low (LP/E~14 mg kJ−1) DP/DE ratio using F or C as major NPE source (7 week-experiment). The lowering of dietary DP/DE ratio increased myoblast determination protein 1a (myod1a) and decreased myostatin 1b (mstn1b) and cathepsin D (ctsd) muscle mRNA levels. The isoenergetic change in dietary NPE from F to C decreased myod1a and proliferative cell nuclear antigen (pcna) muscle mRNA levels. An interaction between DP/DE ratio and NPE source was observed in muscle transcript levels of myogenic factor 6 (mrf4/myf6), fast myosin heavy chain (fmhc) and fast myosin light chain 2 (fmlc2). White muscle total cross-sectional area decreased at low dietary DP/DE ratio and also when NPE source changed from F to C, linked i) to a decreased total number of white muscle fibres, indicating that low dietary DP/DE restricted muscle hyperplasia and that dietary carbohydrate were less efficiently used than fat to sustain muscle hyperplasia, and ii) to decreased percentage of large muscle fibres, indicating limited fibre hypertrophy. Not only the DP level or the DP/DE ratio, but also the isoenergetic change in dietary NPE source (fat vs carbohydrates) thus appears as a potent regulator of muscle hyperplasia and hypertrophy.
Effects of dietary protein level and non-protein energy source on muscle growth mechanisms in rainbow trout (Oncorhynchus mykiss) juveniles
Alami-Durante, H. ; Cluzeaud, M. ; Bazin, D. ; Schrama, J.W. ; Subramanian, S. ; Geurden, Inge - \ 2018
- 1 p.
Modulating D-amino acid oxidase (DAAO) substrate specificity through facilitated solvent access
Subramanian, Kalyanasundaram ; Góra, Artur ; Spruijt, Ruud ; Mitusińska, Karolina ; Suarez-Diez, Maria ; Martins Dos Santos, Vitor ; Schaap, Peter J. - \ 2018
PLoS ONE 13 (2018)6. - ISSN 1932-6203

D-amino acid oxidase (DAAO) degrades D-amino acids to produce α-ketoacids, hydrogen peroxide and ammonia. DAAO has often been investigated and engineered for industrial and clinical applications. We combined information from literature with a detailed analysis of the structure to engineer mammalian DAAOs. The structural analysis was complemented with molecular dynamics simulations to characterize solvent accessibility and product release mechanisms. We identified non-obvious residues located on the loops on the border between the active site and the secondary binding pocket essential for pig and human DAAO substrate specificity and activity. We engineered DAAOs by mutating such critical residues and characterised the biochemical activity of the resulting variants. The results highlight the importance of the selected residues in modulating substrate specificity, product egress and enzyme activity, suggesting further steps of DAAO re-engineering towards desired clinical and industrial applications.

Effects of waste stream combinations from brewing industry on performance of black soldier fly, Hermetia illucens (Diptera: Stratiomyidae)
Chia, Shaphan Y. ; Tanga, Chrysantus M. ; Osuga, Isaac M. ; Mohamed, Samira A. ; Khamis, Fathiya M. ; Salifu, Daisy ; Sevgan, Subramanian ; Fiaboe, Komi K.M. ; Niassy, Saliou ; Loon, Joop J.A. van; Dicke, Marcel ; Ekesi, Sunday - \ 2018
PeerJ 2018 (2018)11. - ISSN 2167-8359
Agro-industrial by-products - Hermetia illucens - Mass rearing - Net energy - Protein quality - Quality control parameters

Background: In recent years, there has been a rapidly growing demand for readily accessible substrates for mass production of Black Soldier Fly, Hermetia illucens Linnaeus. Beer production results in various by-products that typically end up in uncontrolled dumpsites constituting pollution problems, which merits urgent attention. The present study investigated whether the 12 formulated diets composed of brewers’ spent grains (BSGs), brewers’ yeast and cane molasses can serve as substrate for H. illucens production. Methods: Four different BSGs were selected and formulated into 12 diets, aiming at varying protein and net energy levels. The diets were offered to newly hatched (∼1 h old) H. illucens larvae and the influence on developmental duration, survival, wet weight, pre-oviposition time, fecundity, and longevity were compared. Results: Developmental duration of the larvae (16–21 days) and pre-pupae (8–11 days) differed significantly across the different diets. The developmental duration of the pupae (8.7–9.1 days) was not affected by diet. The larval (86–99.2%), pre-pupal (71–95%), and pupal (65–91%) survival rates varied significantly between flies reared on the different diets. The pre-oviposition time was similar for flies provided with water (7–11 days) and 10% sugar solution (8–14 days) or across the different diets. The mean fecundity per female ranged from 324–787 eggs and did not differ between females provided with water or sugar solution. However, the number of eggs laid per female varied significantly across the different diets when provided with water. The longevity of starved H. illucens adults was significantly lower (5 days) compared to those provided with water (11–14 days) or sugar solution (14–15 days). Discussion: The implications of these findings as part of a quality control procedure for commercial production of high-quality H. illucens larvae as an alternative protein ingredient in livestock and aquaculture feed are discussed.

Threshold temperatures and thermal requirements of black soldier fly Hermetia illucens : Implications for mass production
Chia, Shaphan Yong ; Tanga, Chrysantus Mbi ; Khamis, Fathiya M. ; Mohamed, Samira A. ; Salifu, Daisy ; Sevgan, Subramanian ; Fiaboe, Komi K.M. ; Niassy, Saliou ; Loon, Joop J.A. van; Dicke, Marcel ; Ekesi, Sunday - \ 2018
PLoS ONE 13 (2018)11. - ISSN 1932-6203

Efforts to recycle organic wastes using black soldier fly (BSF) Hermetia illucens into high-nutrient biomass that constitutes a sustainable fat (biodiesel) and high-quality protein ingredient in animal feeds have recently gained momentum worldwide. However, there is little information on the most suitable rearing conditions for growth, development and survivorship of these flies, which is a prerequisite for mass production technologies. We evaluated the physiological requirements for growth and reproduction of H. illucens on two diets [spent grains supplemented with brewers' yeast (D1) and un-supplemented (D2)]. Development rates at nine constant temperatures (10-42°C) were fitted to temperature-dependent linear and non-linear day-degree models. Thereafter, life history table parameters were determined within a range of favourable temperatures. The thermal maximum (TM) estimates for larval, pre-pupal and pupal development using non-linear model ranged between 37.2 ± 0.3 and 44.0 ± 2.3°C. The non-linear and linear day-degree model estimations of lower developmental temperature threshold for larvae were 11.7 ± 0.9 and 12.3 ± 1.4°C for D1, and 10.4 ± 1.7 and 11.7 ± 3.0°C for D2, respectively. The estimated thermal constant of immature life stages development of BSF was higher for the larval stage (250±25 DD for D1 and 333±51 for D2) than the other stages evaluated. Final larval wet weight was higher on D1 compared to D2. The population growth rate was most favourable at 30-degree celsius (°C) with higher intrinsic rate of natural increase (rm = 0.127 for D1 and 0.122 for D2) and shorter doubling time (5.5 days for D1 and 5.7 days for D2) compared to the other temperatures. These results are valuable for the optimization of commercial mass rearing procedures of BSF under various environmental conditions and prediction of population dynamics patterns using computer simulation models.

On jet instability modes of a subsonic Hartmann whistle
Varadharajan, Ramanathan ; Kamin, Manu ; Ganesh, Subramanian ; Mathew, Joseph - \ 2018
Sadhana 43 (2018)9. - ISSN 0256-2499
Hartmann whistle - jet-instability mode - large-eddy simulation - subsonic flow

Numerical experiments to understand the resonant acoustic response of a subsonic jet impinging on the mouth of a tube, known as the Hartmann whistle configuration, were performed as large-eddy simulations. The tube length was chosen so that its fundamental duct mode, for one end closed and one end open, would match the dominant mode in the exciting jet. When the tube mouth was placed in the path of a regular stream of vortex rings, formed by the instability of the jet’s bounding shear layer, a strong resonant, tonal response (whistling) was obtained. At three diameters from the jet, OASPL was 150–160 dB. A tube with a thicker lip generated a louder response. When the tube was held closer to the nozzle exit, the impinging unsteady shear layer could not provoke any significant resonance. The simulations reveal that the tonal response of a Hartmann whistle operating in subsonic mode is significant.

Active aggregation among sexes in bean flower thrips (Megalurothrips sjostedti) on cowpea (Vigna unguiculata)
Niassy, Saliou ; Ekesi, Sunday ; Maniania, N.K. ; Orindi, Benedict ; Moritz, G.B. ; Kogel, W.J. de; Subramanian, Sevgan - \ 2016
Entomologia Experimentalis et Applicata 158 (2016)1. - ISSN 0013-8703 - p. 17 - 24.
Aggregation behaviour - Dispersion index - Fabaceae - Grain legumes - Semiochemical - Thripidae - Thysanoptera

Male sexual aggregations are a common territorial, mating-related or resource-based, behaviour observed in diverse organisms, including insects such as thrips. The influence of factors such as plant substrate, time of day, and geographic location on aggregation of thrips is uncertain, therefore we monitored the dispersion of male and female bean flower thrips (BFT), Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), on cowpea, Vigna unguiculata (L.) Walp. (Fabaceae), over three cowpea growth stages and across three cowpea-growing areas of Kenya. Our results indicated that for all the crop growth stages, the density of BFTs varied over the time of day, with higher densities at 10:00, 13:00, and 16:00 hours than at 07:00 hours. Thrips densities did not differ among blocks at the budding stage, but they did at peak flowering and podding stages. Dispersion indices suggested that both male and female BFTs were aggregated. Active male aggregation occurred only on green plant parts and it varied across blocks, crop stages, and locations. Similarly, active female aggregation was observed in peak flowering and podding stages. Such active aggregation indicates a semiochemical or behaviour-mediated aggregation. Identification of such a semiochemical may offer new opportunities for refining monitoring and management strategies for BFT on cowpea, the most important grain legume in sub-Saharan Africa.

Spatial separation of semiochemical Lurem-TR and entomopathogenic fungi to enhance their compatibility and infectivity in an autoinoculation system for thrips management
Mfuti, D.K. ; Subramanian, S. ; Tol, R.W.H.M. van; Wiegers, G.L. ; Kogel, W.J. de; Niassy, S. ; Plessis, H. du; Ekesi, S. ; Maniania, N.K. - \ 2016
Pest Management Science 72 (2016)1. - ISSN 1526-498X - p. 131 - 139.

The effect of spatial separation of the semiochemical Lurem-TR, which has been found to inhibit conidia of entomopathogenic fungi when put together, on the persistence of conidia of Metarhizium brunneum and M. anisopliae was evaluated in the greenhouse and field in order to develop an autodissemination strategy for the management of Megalurothrips sjostedti on cowpea crop. Influence of spatial separation of the semiochemical on thrips attraction and conidial acquisition by thrips from the autoinoculation device was also investigated in the field.
Persistence of conidia of M. brunneum and M. anisopliae increased with distance of separation of Lurem-TR. Direct exposure of fungus without separation from Lurem-TR recorded the lowest conidial germination as compared with the other treatments. Attraction of thrips to the device also varied significantly according to distance between device and semiochemical, with a higher number of thrips attracted when Lurem-TR was placed in a container below the device and at 10 cm distance. There was no significant difference in conidial acquisition between spatial separation treatments of conidia and Lurem-TR. Attraction of other insect pests to the device did not significantly vary between treatments. Positive correlations were found between conidial acquisition and thrips attraction.
This study suggests that spatial separation of fungal conidia from Lurem-TR in an autoinoculation device could provide a low-cost strategy for effective management of thrips in grain legume cropping systems.

Temporal, Affective, and Embodied Characteristics of Taste Experiences: A Framework for Design
Obrist, M. ; Comber, R. ; Subramanian, S. ; Piqueras Fiszman, B. ; Velasco, C. ; Spence, C. - \ 2014
In: Proceedings of the SIGCHI Conference on Human Factors in Computing Systems. - - p. 2853 - 2862.
We present rich descriptions of taste experience through an analysis of the diachronic and synchronic experiences of each of the five basic taste qualities: sweet, sour, salt, bitter, and umami. Our findings, based on a combination of user experience evaluation techniques highlight three main themes: temporality, affective reactions, and embodiment. We present the taste characteristics as a framework for design and discuss each taste in order to elucidate the design qualities of individual taste experiences. These findings add a semantic understanding of taste experiences, their temporality enhanced through descriptions of the affective reactions and embodiment that the five basic tastes elicit. These findings are discussed on the basis of established psychological and behavioral phenomena, highlighting the potential for taste-enhanced design.
Community Well-Being in Biocultural Landscapes : Are We Living Well?
Verschuuren, B. ; Subramanian, S.M. ; Hiemstra, W. - \ 2014
Bourton-on-Dunsmore : Practical Action Publishing Ltd - ISBN 9781853398377 - 168
There is a growing recognition that living well must go beyond economic and material plenty to encompass social and spiritual well-being. But what do we understand by these wider aspects of well-being? Community Well-being in Biocultural Landscapes provides an introduction to the concept of human well-being as it relates to international rural development and conservation policy and practice. It demonstrates that well-being is understood and managed in a variety of ways in different cultures but also across the geographical scales at which decision-making processes take place, from the local, to regional, national and international scales. This book shows how community well-being can be measured using indicators chosen by local people to reflect the worldviews of their culture. It provides a unifying approach that is flexible enough to be used by conservation and rural development workers.This book is important reading for the staff of international aid and conservation agencies, for students of international development and those exploring concepts of well-being.
Feed intake and oxygen consumption in fish
Subramanian, S. - \ 2013
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Johan Schrama; S.J. Kaushik; I. Geurden. - Wageningen : Wageningen UR - ISBN 9789461737571 - 163
vissen - voeropname - zuurstofconsumptie - energieopname - voer - samenstelling - energiemetabolisme - macronutriënten - visvoeding - visteelt - aquacultuur - voedingsfysiologie - fishes - feed intake - oxygen consumption - energy intake - feeds - composition - energy metabolism - macronutrients - fish feeding - fish culture - aquaculture - nutrition physiology

In fish, the voluntary feed intake is influenced by dietary, environmental and/or physiological factors. It is well known that under hypoxia the concentration of oxygen in the water (DO) determines the feed intake of fish. However at non-limiting water DO levels (normoxia), several other mechanisms might play a role in feed intake regulation. Under hypoxia feed intake and oxygen consumption are interrelated. In this thesis we proposed the ‘oxystatic’ concept of feed intake regulation, which states that even at normoxia and in the absence of other constraints, the long term (weeks) voluntary feed intake of fish can be constrained by a set-point value of oxygen consumption. Dietary macronutrient composition affects the ‘dietary oxygen demand’ (i.e., amount of O2 consumed per unit of feed). This oxystatic concept implies that fish fed to satiation with diets differing in ‘dietary oxygen demand’ (mg O2/ g or kJ feed) will have a different digestible energy intake but a similar oxygen consumption. The validity of the oxystatic concept was assessed in two species, Nile tilapia and rainbow trout. These fish were fed diets which had large contrasts in nutrient composition (i.e., protein to energy ratio; type of the non-protein energy source (starch vs. fat); amino acid composition) in order to create contrasts in dietary oxygen demand. In all conducted studies with both species, the digestible energy intake was affected by the diet composition. However, in some studies oxygen consumption was similar and in others it differed between the diets, which respectively supports and contradicts the oxystatic concept. In all studies with both species, the digestible energy intake of tilapia and trout was negatively related to dietary oxygen demand and positively related to efficiency of oxygen utilization for energy retention. Furthermore it was observed in tilapia that the within-day variation in feed intake was affected by dietary macronutrient composition. The variation in within-day feed intake was related to pre-feeding oxygen levels. Based on the combined results, it is suggested that even at normoxia voluntary feed intake in fish is limited/determined by oxygen consumption and/or the oxidative metabolism. Overall, the oxystatic concept appears to be valid for certain conditions, but its generic application remains questionable. Yet, the oxystatic concept enables the combination of dietary, environmental and fish factors into one concept. Further it provides a conceptual insight for better understanding of feed intake regulation in fish.

Voluntary Feed Intake in Rainbow Trout Is Regulated by Diet-Induced Differences in Oxygen Use
Subramanian, S. ; Geurden, I. ; Figueiredo-Silva, A.C. ; Kaushik, S.J. ; Verreth, J.A.J. ; Schrama, J.W. - \ 2013
The Journal of Nutrition 143 (2013)6. - ISSN 0022-3166 - p. 781 - 787.
tilapia oreochromis-niloticus - oncorhynchus-mykiss - food-intake - digestible energy - nile tilapia - induced thermogenesis - lipid level - dicentrarchus-labrax - growth-performance - self-feeders
This study investigated the hypothesis that the voluntary feed intake in fish is regulated by diet-induced differences in oxygen use. Four diets were prepared with a similar digestible protein:digestible energy ratio (18 mg/kJ), but which differed in the composition of nonprotein energy source. This replacement of fat (F) by starch (S) was intended to create a diet-induced difference in oxygen use (per unit of feed): diets F30-S70, F50-S50, F65-S35, and F80-S20 with digestible fat providing 28, 49, 65, and 81% of the nonprotein digestible energy (NPDE), respectively. Each diet was fed to satiation to triplicate groups of 20 rainbow trout for 6 wk. As expected, diet-induced oxygen use decreased linearly (R(2) = 0.89; P <0.001) with increasing NPDE as fat. The digestible and metabolizable energy intakes of trout slightly increased with increasing NPDE as fat (i.e., decreasing starch content) (R(2) = 0.30, P = 0.08; and R(2) = 0.34, P = 0.05, respectively). Oxygen consumption of trout fed to satiation declined with increasing dietary NPDE as fat (R(2) = 0.48; P = 0.01). The inverse relation between digestible energy intake of trout and the diet-induced oxygen use (R(2) = 0.33; P = 0.05) suggests a possible role of diet-induced oxygen use in feed intake regulation as shown by the replacement of dietary fat by starch.
Dietary electrolyte balance affects the nutrient digestibility and maintenance energy expenditure of Nile tilapia
Subramanian, S. ; Geurden, I. ; Orozco, Z.G.A. ; Kaushik, S.J. ; Verreth, J.A.J. ; Schrama, J.W. - \ 2013
The British journal of nutrition 110 (2013). - ISSN 0007-1145 - p. 1948 - 1957.
acid-base-balance - cation-anion difference - water rainbow-trout - juvenile african catfish - clarias-gariepinus burchell - fresh-water - alkaline tide - oreochromis-niloticus - gastrointestinal-tract - oncorhynchus-mykiss
Acid–base disturbances caused by environmental factors and physiological events including feeding have been well documented in several fish species, but little is known about the impact of dietary electrolyte balance (dEB). In the present study, we investigated the effect of feeding diets differing in dEB ( - 100, 200, 500 or 800 mEq/kg diet) on the growth, nutrient digestibility and energy balance of Nile tilapia. After 5 weeks on the test diet, the growth of the fish was linearly affected by the dEB levels (P<0·001), with the lowest growth being observed in the fish fed the 800 dEB diet. The apparent digestibility coefficient (ADC) of fat was unaffected by dEB, whereas the ADC of DM and protein were curvilinearly related to the dEB levels, being lowest and highest in the 200 and 800 dEB diets, respectively. Stomach chyme pH at 3 h after feeding was linearly related to the dEB levels (P<0·05). At the same time, blood pH of the heart (P<0·05) and caudal vein (P<0·01) was curvilinearly related to the dEB levels, suggesting the influence of dEB on postprandial metabolic alkalosis. Consequently, maintenance energy expenditure (MEm) was curvilinearly related to the dEB levels (P<0·001), being 54 % higher in the 800 dEB group (88 kJ/kg0·8 per d) than in the 200 dEB group (57 kJ/kg0·8 per d). These results suggest that varying dEB levels in a diet have both positive and negative effects on fish. On the one hand, they improve nutrient digestibility; on the other hand, they challenge the acid–base homeostasis (pH) of fish, causing an increase in MEm, and thereby reduce the energy required for growth.
Oxygen Consumption Constrains Food Intake in Fish Fed Diets Varying in Essential Amino Acid Composition
Subramanian, S. ; Geurden, I. ; Figueiredo-Silva, A.C. ; Nusantoro, S. ; Kaushik, S.J. ; Verreth, J.A.J. ; Schrama, J.W. - \ 2013
PLoS ONE 8 (2013)8. - ISSN 1932-6203 - 7 p.
trout oncorhynchus-mykiss - european sea bass - rainbow-trout - dissolved-oxygen - nile tilapia - feed-intake - oreochromis-niloticus - salmo-gairdneri - self-selection - protein
Compromisation of food intake when confronted with diets deficient in essential amino acids is a common response of fish and other animals, but the underlying physiological factors are poorly understood. We hypothesize that oxygen consumption of fish is a possible physiological factor constraining food intake. To verify, we assessed the food intake and oxygen consumption of rainbow trout fed to satiation with diets which differed in essential amino acid (methionine and lysine) compositions: a balanced vs. an imbalanced amino acid diet. Both diets were tested at two water oxygen levels: hypoxia vs. normoxia. Trout consumed 29% less food under hypoxia compared to normoxia (p0.05). This difference in food intake between diets under normoxia together with the identical oxygen consumption supports the hypothesis that food intake in fish can be constrained by a set-point value of oxygen consumption, as seen here on a six-week time scale.
A comparative study of the metabolic response in rainbow trout and Nile tilapia to changes in dietary macronutrient composition
Figueiredo-Silva, A.C. ; Subramanian, S. ; Schrama, J.W. ; Panserat, S. ; Kaushik, S.J. ; Geurden, I. - \ 2013
The British journal of nutrition 109 (2013)5. - ISSN 0007-1145 - p. 816 - 826.
x oreochromis-aureus - european sea-bass - oncorhynchus-mykiss - body-composition - lipid level - hepatic lipogenesis - growth-performance - enzyme-activities - glucose-6-phosphatase expression - glucose-metabolism
Metabolic mechanisms underlying the divergent response of rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus) to changes in dietary macronutrient composition were assessed. Fish were fed one of four isoenergetic diets having a digestible protein-to-digestible energy (DP:DE) ratio above or below the optimal DP:DE ratio for both species. At each DP:DE ratio, fat was substituted by an isoenergetic amount of digestible starch as the non-protein energy source (NPE). Dietary DP:DE ratio did not affect growth and only slightly lowered protein gains in tilapia. In rainbow trout fed diets with low DP:DE ratios, particularly with starch as the major NPE source, growth and protein utilisation were highly reduced, underlining the importance of NPE source in this species. We also observed species-specific responses of enzymes involved in amino acid catabolism, lipogenesis and gluconeogenesis to dietary factors. Amino acid transdeamination enzyme activities were reduced by a low dietary DP:DE ratio in both species and in tilapia also by the substitution of fat by starch as the NPE source. Such decreased amino acid catabolism at high starch intakes, however, did not lead to improved protein retention. Our data further suggest that a combination of increased lipogenic and decreased gluconeogenic enzyme activities accounts for the better use of carbohydrates and to the improved glycaemia control in tilapia compared with rainbow tront fed starch-enriched diets with low DP:DE ratio.
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