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Rainbow trout were fed diets containing either fish meal and fish oil (FM-FO) (control) or diets in which 40% of the fishmeal was substituted with a mixture of ingredients grown organically including plant protein concentrate (PP) in combination with either fish oil (FO) as lipid source, or one of the following organic plant oils; rapeseed (RO), linseed/flaxseed (LO), grape seed (GO), or sunflower (SO). The impact of these substitutions was investigated by measuring fish muscle fatty acid profile as well as oxidative and color stability of the fillet during 14 days ice storage. The inclusion of plant protein concentrate did not affect the fatty acid profile significantly but resulted in a slightly improved oxidative stability of the fish fillets as compared to the control diet. The fatty acid profile of the oil used was in general well reflected in the fish muscle fatty acid profile. Fish fed PP-RO were the most oxidatively stable during ice storage but the omega-3 fatty acid content was reduced by 40% compared to fish fed the FM-FO control diet. Replacing FO by LO was not suitable as it induced oxidation and the fillet contained 40-50% less of long chain omega-3 fatty acids. Practical applications: Replacing marine ingredient by organic plant ones in the diet of rainbow trout is feasible but it impacts the fish fatty acid profile of the fish muscle and its oxidative stability. Plant protein improved the oxidative stability of the fillet during ice storage. Moreover, replacement of fish oil with more saturated plant oils in the diet of trout lead to an increased oxidative stability of the fillet, but at the same time reduced the level of omega-3 fatty acids in the fish muscle. Linseed oil resulted in a more favorable omega-3 content (ALA) than the other plant oils but resulted in highly unstable fish muscle with respect to oxidation. Substitution of fish ingredients in the fish diet significantly influenced the nutritional value of the fish fillet, as it resulted in significant less EPA and DHA in the muscle. [ABSTRACT FROM AUTHOR]

Larval size heterogeneity is known to induce cannibalism, and procedures to avoid larval size differences are consequently implemented already during egg incubation and hatching. We investigated the relation between larval development variability, size heterogeneity and cannibalism in pikeperch. Larvae were sorted into five groups according to the time of hatching during a 65-h period. The larvae with different times of hatch were then reared separately or together during an 18-day period. Late hatched larvae were longer ( P=0.003) and had less yolk remaining ( P<0.001) than early hatched individuals at the time of hatching. However, on 11 days post fertilization, the late-hatching larvae tended to have larger yolk reserves than earlier hatched individuals ( P=0.07). Furthermore, the next day, a lower proportion in the late fraction had switched to exogenous feeding ( P=0.024). That larvae with a late hatching time developed slower suggests a positive relationship between the hatching time and the embryonic developmental rate. However, differences in the length and available yolk reserves at hatching between larval fractions with different hatching times suggest that hatching is not strictly associated with a specific developmental stage, and that factors other than the development rate of the embryo are involved in the timing of hatching. [ABSTRACT FROM AUTHOR]

Extruded feeds are widely used for major aquatic animal production, particularly for finfish. However, the transition from fresh/frozen to extruded/pelleted feeds remains a major obstacle to progressing sustainable farming of European lobster (Homarus gammarus). The aim of the present study was to investigate the effects of using extruded feeds with different protein levels and lipid/carbohydrate ratios on growth, feed utilisation, nucleic acid derived indices (sRD) and digestive enzymatic activity of H. gammarus juveniles. Six extruded feeds were formulated to contain two protein levels (400 and 500 g/kg), with three lipid/carbohydrate ratios (LOW – 1:3; MEDium – 1:2; HIGH – 1:1). The extruded feeds were tested against Antarctic krill (Euphausia superba) used as control (CTRL). Overall, the CTRL and 500MED feed supported the highest growth and nutritional condition estimated by means of sRD, while the poorest results were observed for the 400HIGH and 400MED groups. The FCR was significantly lower in the CTRL than all extruded feeds, among which the most efficient, i.e., lower FCR, was the 500MED. The highest activity of trypsin and amylase in lobsters fed the 400MED and 400HIGH feeds points to the activation of a mechanism to maximise nutrients assimilation. The highest lipase activity observed for the 500LOW and 500MED groups indicates a higher capacity to metabolise and store lipids. Overall, the results suggest that the 500MED feed (500 g/kg protein, 237 g/kg carbohydrates and 119 g/kg lipids) is a suitable extruded feed candidate to replace Antarctic krill, commonly used to grow lobster juveniles. [ABSTRACT FROM AUTHOR]

Dietary phosphorus (P) levels affect the excretion of orthophosphate (PO 4 -P) from fish. Since most recirculating aquaculture systems (RAS) do not specifically remove PO 4 -P within the recirculating loop, dietary P levels may influence PO 4 -P concentrations in RAS water. A feeding trial was performed in freshwater RAS, aiming to determine the relationship between dietary P levels and PO 4 -P accumulation in RAS water, and to examine potential effects of dietary P levels on microbial activity and abundance in RAS water given that P is an essential mineral for all microorganisms. Three diets with 1.49% (HiP), 1.20% (MeP), and 0.89% (LoP) total P, respectively, were each fed to triplicate pilot-scale RAS with juvenile rainbow trout (Oncorhynchus mykiss) for five weeks, applying a daily feed loading of 1.67 kg feed/m3 make-up water. Digestible dietary P levels correlated significantly with the PO 4 -P concentrations in RAS water at the end of the trial, while no similar correlations with microbial abundance or activity were observed. Nitrate-N concentrations measured by the end of the trial matched predicted equilibrium concentrations. In contrast, measured PO 4 -P concentrations were approximately 40 – 50% lower than predicted regardless of diets, suggesting that PO 4 -P was likely utilized by RAS microbes. We therefore speculate whether lowering dietary P levels could become an effective tool for microbial management in RAS. • Significant correlation between dietary P levels and PO 4 -P accumulation in RAS. • Dietary P did not affect other physicochemical water quality. • Difference between predicted and recovered PO 4 -P indicates microbial uptake. [ABSTRACT FROM AUTHOR]

Selective Catalytic Reduction (SCR) systems are one of the leading techniques used in the after treatment systems of the diesel engines for the abatement of nitrogen oxides (NOx) emissions. Ammonia is used as reducing agent in the catalyst which is supplied in the mixing chamber in the form of Urea Water Solution (UWS - 32.5% urea solution) spray. After evaporation of water, urea droplets undergo a series of secondary reactions eventually leading to the formation of solid deposits on the walls of the system. This not only hinders the deNOx efficiency but also interferes with the overall after treatment system by creating back pressure. Therefore, a deep understanding of the factors and mechanisms of spray–wall interaction is a basic requirement to prevent any undesired decomposition phenomena that could lead to failure of the whole system. In the present paper, droplet diameter distributions are analyzed pre and post impingement events on a hot mixer plate surface, both experimentally and numerically. The work was performed using a commercial six-hole pressure driven injector in a test section of heated cross flow wind tunnel. Phase Doppler Anemometry (PDA) was used to measure the droplet kinetics prior and after the wall impingement on the mixer plate. Based on the data, numerical simulation was setup using a commercial CFD code, AVL FIRE and droplet characteristics as well as thermal response of the mixer plate analyzed against the experimental data. • Experimental study of spray impingement under hot flow conditions. • The cross flow velocity determines the spray–wall heat transfer. • 3D simulation can accurately predict pre impingement diameter distributions. • Wall film mass requires an accurate selection of specific heat scaling factor. • Spray initialization criteria is of vital importance in numerical simulations involving spray impingement. [ABSTRACT FROM AUTHOR]

In this study, experimental investigations on a Phase Change Material (PCM) based thermal energy storage system (TES) were carried out. The TES system was designed and tested as a first step of developing a potential TES product which can be integrated with commercially available ventilation system (VEX308) to provide cold intake air for space cooling applications. The system consisted of wedge-shaped air flow regions before and after an array of Compact Storage Module (CSM) plates filled with PCM and arranged vertically with air gaps between the plates. Two design configurations of the TES system were investigated based on air gap size between PCM plates (1.5 mm and 3 mm) in order to compare them for pressure loss through the system and thermal performance of the PCM storage. Investigations were done at two air flow rates of 400 m 3 / h and 800 m 3 / h which were within the working range of VEX308 for fixed air inlet temperatures of 27 °C and 13 °C for heating and cooling cycles of the PCM storage, respectively. The temperatures ranges were chosen to investigate the application of the TES system during summer season in Denmark. Parameters investigated were: pressure loss through the TES system, pressure distribution from top to bottom in the TES system before and after the PCM stack, temperature distribution in the TES system from top to bottom, and melting and solidification rates of the PCM. Results showed that pressure drop through the system, for both configurations, was well within the desired limits (< 180 Pa) for a successful integration of the TES system with VEX308. Temperature distribution was relatively fair from top to bottom of the PCM stack indicating an adequate inlet manifold design. The 1.5 mm gap configuration (55 CSM plates and 110 kg PCM) showed faster heating and cooling rates at both flow rates as compared to 3 mm system (50 CSM plates and 100 kg PCM). Both systems showed almost same system efficiency (78.3%) for the utilization of the PCM. The 1.5 mm system provided approximately 8.7% more energy storage potential than the 3 mm system because of the presence of 10 kg of extra PCM. [ABSTRACT FROM AUTHOR]

Different vegetable oils have been investigated as potential substitutes of fish oil in aquaculture feed and several of them have proven to be successful in terms of fish growth rates, survival rates, biometric indices or feeding efficiency, even when used as the only oils in the feed. However, final fish product composition (fish whole body or fish fillet) usually reflects feed composition, and fish products from fish fed with only vegetable oils usually show a deficiency in long chain polyunsaturated fatty acids (PUFAs). The welfare and health consequences for the fish of these alterations of the fatty acid profile are not well known. In the current study, three experimental diets using supercritically defatted fish meal as well as rapeseed oil as a 100% replacement of fish oil, and differing in essential fatty acid (eicosapentaneoid acid - EPA, docosahexaenoic acid - DHA) supplementation, were tested in rainbow trout, Oncorhynchus mykiss. The growth performance, feed conversion ratio and digestive enzyme profiles were evaluated. Further, stress-and infection-challenge experiments were performed to assess the robustness of the fish against stress and disease. The trout fry fed the experimental diets showed a different fatty acid profile than fish fed a commercial diet, with lower EPA and DHA levels but higher linolenic acid (18:3n-3) and oleic acid (18:1n-9) levels. No significant effects were found in growth performance, feed conversion ratio or digestive enzymatic activity among diets. The fish stress responsiveness (brain and plasma stress marker response) to acute and repeated stressors was in general also similar irrespective of the diet. Infection trials, however, showed a differential ability of the fish to survive upon a controlled infection with the bacterium Flavobacterium psychrophilum. Fish fed with the experimental diets displayed higher mortalities than fish fed a commercial trout fry diet. The current results highlight the need of further research on nutritional requirements to optimize the disease resilience in farmed fish. These results also demonstrate that the adaptation of the fish to new formulated feed (in this case associated to plant oil ingredients) should not be assessed solely based on the growth performance of the fish. Other aquaculture relevant welfare indicators, as disease or stress resilience, should be part of a more complete assessment of feed adequacy for fish farming purposes. • Total dietary replacement of fish oil by rapeseed oil was tested on rainbow trout. • Effects of essential fatty acid supplementation (EPA and DHA) were also assessed. • Oil replacement or fatty acid supplementation did not affect early growth performance. • Survival upon an infection trial was compromised with the substituted diets. • Results demonstrate the need of a wide approach when testing innovative diets in fish. [ABSTRACT FROM AUTHOR]