Sustainable alternatives to fish meal and fish oil in fish nutrition: Effects on growth, tissue fatty acid composition and lipid metabolism

Traditionally, fish meal (FM) and fish oil (FO) have been used extensively in aquafeeds, mainly due to their excellent nutritional properties. However, various reasons dictate the use of sustainable alternatives and the reduction of the dependence on these commodities in fish feeds. Hence, the aim of the present thesis was to investigate the effects of the replacement of FM and FO with two vegetable oils (VO) and an oilseed meal on the growth performance, feed utilization, nutrient and fatty acids (FA) digestibility and tissue FA composition and metabolism in three commercially important European fish species. Specifically, in Experiment I crude palm oil (PO) was used to replace FO in diets for rainbow trout. In Experiments II and III FO was replaced with rapeseed oil (RO) in diets for Atlantic salmon at various dietary protein/lipid levels aiming also at further reductions of FM by using low protein (high lipid) diet formulations. In Experiments II and III the fish were reared at low and high water temperatures, respectively, in order to elucidate, also, the potential effects of temperature. Lastly, the effects of the replacement of FM with full fat soya meal (FFS) in Atlantic cod were investigated in Experiment IV. The results of the present thesis showed no negative effects on growth performance and feed utilization in rainbow trout when FO was replaced with PO. The dietary inclusion of RO improved the growth of Atlantic salmon, possibly, due to changes in the nutrient and FA digestibilities and FA catabolism while, the growth and feed utilization were unaffected by the dietary protein/lipid level. However, the growth of Atlantic cod was affected negatively by the replacement of FM with FFS. The proximate composition of the fish whole body was in most cases unaffected by dietary treatments. The changes in dietary formulations affected the dietary FA compositions and resulted in significant changes in the fish tissue FA compositions. It was clearly shown that the fish tissue total lipid FA composition reflects the FA composition of the diet, although specific FA were selectively utilized or retained in the tissues by the fish. These may have serious implications not only for fish metabolism and growth but also for the quality of the final product, especially in terms of possible reductions of n-3 HUFA.Vasileios Karalazos was supported by a studentship award from the Greek Scholarship Foundation (IKY), Greece

The compositional and metabolic responses of gilthead seabream (Sparus aurata) to a gradient of dietary fish oil and associated n-3 long-chain PUFA content

The authors express their gratitude to the technical team at the BioMar Feed Trial Unit, Hirtshals, in particular, Svend Jørgen Steenfeldt for expert care of the experimental subjects, for training and supervision provided by laboratory staff at Nutrition Analytical Services and Molecular Biology at the Institute of Aquaculture, University of Stirling, UK. S. J. S. H’s. PhD was co-funded by BioMar and the Marine Alliance for Science and Technology Scotland. BioMar provided the experimental feeds, trial facilities and fish, and covered travel expenses. V. K. and J. T. designed and executed the nutritional trial and all authors contributed to planning the analyses. V. K., J. T. and S. J. S. H. carried out the sampling. O. M., D. R. T and S. A. M. M. supervised the lead author. M. B. B. provided training in molecular biology to S. J. S. H. who carried out all analytical procedures. S. J. S. H. analysed all of the data and prepared the manuscript. Subsequently the manuscript was shared between all authors who made amendments, contributions and recommendations. The authors declare that there are no conflicts of interestPeer reviewedPublisher PD

Influence of the dietary protein: lipid ratio and fish oil substitution on fatty acid composition and metabolism of Atlantic salmon (Salmo salar) reared at high water temperatures

A factorial, two-way, experimental design was used for this 10-week nutritional trial, aiming to elucidate the interactive effects of decreasing dietary protein:lipid level and substitution of fish oil (FO) with rapeseed oil (RO) on tissue fatty acid (FA) composition and metabolism of large Atlantic salmon (Salmo salar L.) reared at high water temperatures (sub-optimal, summer temperatures: 11·6 C). The six experimental diets were isoenergetic and formulated to include either FO or RO (60% of the added oil) at three dietary protein:lipid levels, specifically (1) 350 g/kg protein and 350 g/kg lipid, (2) 330 g/kg protein and 360 g/kg lipid, (3) 290 g/kg protein and 380 g/kg lipid. Final weight, specific growth rate and thermal growth coefficient were positively affected by the dietary RO inclusion at the expense of FO, while no significant effects were seen on growth due to the decreasing protein level. The oil source had a significant effect on muscle and liver FA composition. However, the changes in muscle and liver FA indicate selective utilisation or retention of individual FA and moderate reductions in tissue EPA and DHA. Pyloric caeca phospholipid FA composition was significantly affected by the two factors and, in some cases, significant interactions were also revealed. Liver and red muscle b-oxidation capacities were significantly increased due to RO inclusion, while an interactive effect of protein level and oil source was shown for white muscle b-oxidation capacity. The results could explain, at least partially, the better performance that was shown for the RO groups and the enhanced protein-sparing effect

Occurrence and potential transfer of mycotoxins in gilthead sea bream and Atlantic salmon by use of novel alternative feed ingredients

Plant ingredients and processed animal proteins (PAP) are suitable alternative feedstuffs for fish feeds in aquaculture practice, although their use can introduce contaminants that are not previously associated with marine salmon and gilthead sea bream farming. Mycotoxins are well known natural contaminants in plant feed material, although they also could be present on PAPs after fungi growth during storage. The present study surveyed commercially available plant ingredients (19) and PAP (19) for a wide range of mycotoxins (18) according to the EU regulations. PAP showed only minor levels of ochratoxin A and fumonisin B1 and the mycotoxin carry-over from feeds to fillets of farmed Atlantic salmon and gilthead sea bream (two main species of European aquaculture) was performed with plant ingredient based diets. Deoxynivalenol was the most prevalent mycotoxin in wheat, wheat gluten and corn gluten cereals with levels ranging from 17 to 814 and μg kg−1, followed by fumonisins in corn products (range 11.1–4901 μg kg−1 for fumonisin B1 + B2 + B3). Overall mycotoxin levels in fish feeds reflected the feed ingredient composition and the level of contaminant in each feed ingredient. In all cases the studied ingredients and feeds showed levels of mycotoxins below maximum residue limits established by the Commission Recommendation 2006/576/EC. Following these guidelines no mycotoxin carry-over was found from feeds to edible fillets of salmonids and a typically marine fish, such as gilthead sea bream. As far we know, this is the first report of mycotoxin surveillance in farmed fish species.EU Seventh Framework Programme by ARRAINA Project, 288925. project SAFE-PAP, Research Council Research and Development Project National Institute of Nutrition and Seafood Research (NIFES, Norway), 227387. Generalitat Valenciana, PROMETEO II/2014/023 PROMETEO II/2014/085 ISIC/2012/01

Inorganic, organic, and encapsulated minerals in vegetable meal based diets for Sparus aurata (Linnaeus, 1758)

Substituting fishmeal (FM) with vegetable meal (VM) can markedly affect the mineral composition of feeds, and may require additional mineral supplementation. Their bioavailability and optimal supplementation levels depend also on the form of delivery of minerals. The aim of the study was to determine the effect of different delivery forms of three major trace elements (Zn, Mn and Se) in a marine teleost. Gilthead sea bream juveniles of 22.5 g were fed a VM-based diet for 12 weeks that was either not supplemented with these minerals or supplemented with inorganic, organic, or encapsulated inorganic forms of minerals in triplicate and compared to a FM-based diet. Our results showed that mineral delivery form significantly affected the biochemical composition and morphology of posterior vertebrae. Supplementation of VM-based diets with inorganic forms of the target minerals significantly promoted growth, increased the vertebral weight and content of ash and Zn, enhanced bone mineralization and affected the vertebral shape. Conversely, encapsulation of inorganic minerals reduced fish growth and vertebral mineral content, whereas supplementation of organic minerals, enhanced bone osteogenesis by upregulating bone morphogenetic protein 2 (bmp2) gene and produced vertebrae with a larger length in relation to height. Furthermore, organic mineral forms of delivery downregulated the expression of oxidative stress related genes, such as Cu/Zn superoxide dismutase (Cu/Zn sod) and glutathione peroxidase 1 (gpx-1), suggesting thus that dietary minerals supplemented in the organic form could be reasonably considered more effective than the inorganic and encapsulated forms of supply

Influence of the dietary protein:lipid ratio and fish oil substitution on fatty acid composition and metabolism of Atlantic salmon (Salmo salar) reared at high water temperatures

Abstract A factorial, two-way, experimental design was used for this 10-week nutritional trial, aiming to elucidate the interactive effects of decreasing dietary protein:lipid level and substitution of fish oil (FO) with rapeseed oil (RO) on tissue fatty acid (FA) composition and metabolism of large Atlantic salmon (Salmo salar L.) reared at high water temperatures (sub-optimal, summer temperatures: 11·68C). The six experimental diets were isoenergetic and formulated to include either FO or RO (60 % of the added oil) at three dietary protein:lipid levels, specifically (1) 350 g/kg protein and 350 g/kg lipid, (2) 330 g/kg protein and 360 g/kg lipid, (3) 290 g/kg protein and 380 g/kg lipid. Final weight, specific growth rate and thermal growth coefficient were positively affected by the dietary RO inclusion at the expense of FO, while no significant effects were seen on growth due to the decreasing protein level. The oil source had a significant effect on muscle and liver FA composition. However, the changes in muscle and liver FA indicate selective utilisation or retention of individual FA and moderate reductions in tissue EPA and DHA. Pyloric caeca phospholipid FA composition was significantly affected by the two factors and, in some cases, significant interactions were also revealed. Liver and red muscle b-oxidation capacities were significantly increased due to RO inclusion, while an interactive effect of protein level and oil source was shown for white muscle b-oxidation capacity. The results could explain, at least partially, the better performance that was shown for the RO groups and the enhanced protein-sparing effect

Comprehensive strategy for pesticide residue analysis through the production cycle of gilthead sea bream and Atlantic salmon

Plant ingredients and processed animal proteins are alternative feedstuffs for fish feeds in aquaculture. However, their use can introduce contaminants like pesticides that are not previously associated with marine Atlantic salmon and gilthead sea bream farming. This study covers the screening of around 800 pesticides by gas chromatography (GC) and liquid chromatography (LC) coupled to high resolution time-of-flight mass spectrometry in matrices throughout the entire marine food production chain. Prior to analysis of real-world samples, the screening methodology was validated for 252 pesticides to establish the screening detection limit. This was 0.01 mg kg−1 for 113 pesticides (45%), 0.05 mg kg−1 for 73 pesticides (29%) and >0.05 mg kg−1 for 66 pesticides (26%). After that, a quantitative methodology based on GC coupled to tandem mass spectrometry with atmospheric pressure chemical ionization source (GC-APCI-MS/MS) was optimized for the pesticides found in the screening. Although several polar pesticides, of which pirimiphos methyl and chlorpyriphos-methyl were most dominant, were found in plant material and feeds based on these ingredients, none of them were observed in fillets of Atlantic salmon and gilthead sea bream fed on these feeds.This work has been developed within the framework of the Research Unit of Marine Ecotoxicology (IATS (CSIC)-IUPA (UJI)

Dietary butyrate helps to restore the intestinal status of a marine teleost (Sparus aurata) fed extreme diets low in fish meal and fish oil

There is a constant need to find feed additives that improve health and nutrition of farmed fish and lessen the intestinal inflammation induced by plant-based ingredients. The objective of this study was to evaluate the effects of adding an organic acid salt to alleviate some of the detrimental effects of extreme plant-ingredient substitution of fish meal (FM) and fish oil (FO) in gilthead sea bream diet. Three experiments were conducted. In a first trial (T1), the best dose (0.4%) of sodium butyrate (BP-70 ®NOREL) was chosen after a short (9-weeks) feeding period. In a second longer trial (T2) (8 months), four diets were used: a control diet containing 25% FM (T2-D1) and three experimental diets containing 5% FM (T2-D2, T2-D3, T2-D4). FO was the only added oil in D1, while a blend of plant oils replaced 58% and 84% of FO in T2-D2, and T2-D3 and T2-D4, respectively. The latter was supplemented with 0.4% BP-70. In a third trial (T3), two groups of fish were fed for 12 and 38 months with D1, D3 and D4 diets of T2. The effects of dietary changes were studied using histochemical, immunohistochemical, molecular and electrophysiological tools. The extreme diet (T2-D3) modified significantly the transcriptomic profile, especially at the anterior intestine, up-regulating the expression of inflammatory markers, in coincidence with a higher presence of granulocytes and lymphocytes in the submucosa, and changing genes involved in antioxidant defences, epithelial permeability and mucus production. Trans-epithelial electrical resistance (Rt) was also decreased (T3-D3). Most of these modifications were returned to control values with the addition of BP-70. None of the experimental diets modified the staining pattern of PCNA, FABP2 or ALPI. These results further confirm the potential of this additive to improve or reverse the detrimental effects of extreme fish diet formulations

The effect of organic and conventional production methods on sea bream growth, health and body composition: A field experiment

This study aimed to develop a better understanding of organic sea bream aquaculture production in Greece, in particular its consequences for fish growth, health and body composition, and to propose and update standards for sustainable organic sea bream farming. Gilthead sea bream were kept in sea cages at densities of 4 kg m–3 (organic) and 15 kg m–3(conventional), and were fed organically produced feed (45% crude protein, 14% fat) or conventional feed (46% crude protein, 17% fat). The amino acid profile of the conventional diet, particularly the lysine content, which is one of most important dietary amino acids for sea bream, appeared to be unsatisfactory. “Organic” sea bream stored less fat content in their white muscle than the conventional sea bream. The liver lipid content was lower and the hepatosomatic index was higher for the organic sea bream. The microbiological analysis showed that both Enterobacteriaceae and Escherichia coli on the skin were below the enumeration detection limit in both the organic and conventional sea bream. Total viable counts on the skin and muscle of both the organically and conventionally cultured sea bream were approximately 3 log cfu g–1, which is well below the acceptable limit (7 log cfu g–1) for marine species. The results showed that the combination of a low stocking density and feed with a different ingredient composition but similar nutritional value resulted in similar growth rates and nutrient profiles of the final product. Further research on nutrition is required to provide information on setting the appropriate standards for organic sea bream aquaculture to ensure that the final product is in line with the consumers’ preferences

Selection for growth is associated in gilthead sea bream (Sparus aurata) with diet flexibility, changes in growth patterns and higher intestine plasticity

Farmed gilthead sea bream (Sparus aurata) is able to grow efficiently with new feed formulations based on plant ingredients. Here, two experimental diets with standard and high inclusion levels of plant ingredients were formulated to assess the suited use of plant-based diets in fish with different growth genetic backgrounds. To pursue this issue, a long-term feeding trial (12-months) was conducted with fish (17 g initial body weight) of 16 families coming from the broodstock of PROGENSA project, that were grown communally in the IATS-CSIC experimental facilities. All fish in the study (2545) were PIT-tagged, and their pedigree was re-constructed with 96% success by using a SMsa1 multiplex of 11 microsatellites, which revealed the main parents contributions of 5 females and 6 males. Each diet was randomly assigned to replicate 3000 L tanks, gathering each replicate a similar family composition through all the feeding trial. Data on growth performance highlighted a strong ge- netic effect on growth trajectories, associated with enhanced growth during winter in fish selected for faster growth. No main dietary effects were found on growth rates or condition factor, and regression-correlation analyses of growth rates across families on both diets suggest that genome by diet interaction was weak, while genetic variation accounted for most of the growth phenotypic variation. Hepatosomatic index (HSI) and me- senteric fat index (MSI) of five families, covering the growth variability of the population, were regulated nu- tritionally and genetically, but without statistically significant genome by diet interactions. Fish from faster growing families showed shorter intestines after being fed the control diet, but this phenotype was masked by the enriched plant-based diet. Collectively, the results demonstrate that selection for faster growth is associated in gilthead sea bream with different growth trajectories and a high diet flexibility and intestine plasticity.Versión del editor2,04