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- Nutrition, quality and performance in marine fish larvaePublication . Conceição, L. E. C.; Alves-Martins, D.; Engrola, S.; Gavaia, Paulo J.; Richard, Nadège; Aragão, C.O cultivo de larvas de peixes marinhos é caracterizado por altas mortalidades e por problemas de qualidade, nomeadamente malformações esqueléticas. A solução de parte destes problemas passa por uma melhor compreensão dos requisitos nutricionais. Este trabalho pretende fazer uma revisão de trabalhos recentes que demonstram como os aminoácidos, os ácidos gordos e a vitamina K, mas também o regime alimentar, podem influenciar a qualidade e a performance das larvas de peixes marinhos.
- Plant‐based diets fed to juvenile meagre Argyrosomus regius with low methionine and taurine supplementation led to an overall reduction in fish performance and to an increase in muscle fibre recruitmentPublication . Saavedra, Margarida; Pereira, Teresa G.; Barata, Marisa; Aragão, Cláudia; Requeijo, Bárbara; Conceição, Luís E.C.; Pousão‐Ferreira, PedroMethionine and taurine are amino acids (AA) that are usually deficient when fish meal is replaced by plant proteins. In this study, three diets were tested in juvenile meagre (initial weight: 13.4 g) for 8 weeks. The D1 diet had 0.2% methionine and 1% taurine supplementation; the D2 and D3 diets had 0.6% methionine and 1% and 2% taurine supplementation, respectively. The results showed that meagre fed the D1 diet had lower specific growth rate (2.2 to 2.5), lower feed efficiency (0.9 to 1.2) and higher food conversion rate (FCR, 1.1 to 0.8) as well as a lower activity of the alanine aminotransferase (ALAT) enzyme. Furthermore, a higher recruitment of muscle fibres (46% compared to 36%) as well as a higher fibre density was observed (1019 compared to 870 fibres mm(-2)). This study shows that meagre requires a sufficient quantity of methionine in plant-based diets to avoid a reduction in fish performance. Furthermore, taurine supplementation in the D1 diet was not able to mitigate the effects of methionine deficiency. A higher taurine supplementation did not improve meagre performance.
- Novel methodologies in marine fish larval nutritionPublication . Conceição, L. E. C.; Aragão, C.; Richard, Nadège; Engrola, S.; Gavaia, Paulo J.; Mira, Sara; Dias, J.Major gaps in knowledge on fish larval nutritional requirements still remain. Small larval size, and difficulties in acceptance of inert microdiets, makes progress slow and cumbersome. This lack of knowledge in fish larval nutritional requirements is one of the causes of high mortalities and quality problems commonly observed in marine larviculture. In recent years, several novel methodologies have contributed to significant progress in fish larval nutrition. Others are emerging and are likely to bring further insight into larval nutritional physiology and requirements. This paper reviews a range of new tools and some examples of their present use, as well as potential future applications in the study of fish larvae nutrition. Tube-feeding and incorporation into Artemia of 14C-amino acids and lipids allowed studying Artemia intake, digestion and absorption and utilisation of these nutrients. Diet selection by fish larvae has been studied with diets containing different natural stable isotope signatures or diets where different rare metal oxides were added. Mechanistic modelling has been used as a tool to integrate existing knowledge and reveal gaps, and also to better understand results obtained in tracer studies. Population genomics may assist in assessing genotype effects on nutritional requirements, by using progeny testing in fish reared in the same tanks, and also in identifying QTLs for larval stages. Functional genomics and proteomics enable the study of gene and protein expression under various dietary conditions, and thereby identify the metabolic pathways which are affected by a given nutrient. Promising results were obtained using the metabolic programming concept in early life to facilitate utilisation of certain nutrients at later stages. All together, these methodologies have made decisive contributions, and are expected to do even more in the near future, to build a knowledge basis for development of optimised diets and feeding regimes for different species of larval fish.
- Changes in plasma amino acid levels in a euryhaline fish exposed to different environmental salinitiesPublication . Aragão, C.; Costas, B.; Vargas-Chacoff, L.; Ruiz-Jarabo, I.; Dinis, Maria Teresa; Mancera, J. M.; Conceição, L. E. C.Previous studies have shown that Senegalese sole is partially euryhaline in the juvenile phase, being able to adapt to a wide range of salinities in a short-time period, due to changes at the osmoregulatory and metabolic level. This study aimed to assess the effects of acclimation of sole to a wide range of salinities, with a special emphasis on the role of plasma amino acids during this process. Sole juveniles were acclimated for 2 weeks to different salinities: 5, 15, 25, 38, and 55 g L−1. Plasma levels of cortisol, glucose, osmolality, and free amino acids were assessed at the end. Changes in plasma levels of cortisol, glucose, and amino acids indicate that fish reared at 5 and 55 g L−1 were facing extra energy costs. Amino acids seem to play an important role during salinity acclimation, either as energy sources or as important osmolytes for cell volume regulation.
- Can dietary aromatic amino acid supplementation be beneficial during fish metamorphosis?Publication . Pinto, W.; Rodrigues, V.; Dinis, Maria Teresa; Aragão, C.Aromatic amino acids (AA, phenylalanine and tyrosine) are the precursors of thyroid hormones, which regulate metamorphosis in all vertebrates. In fish, this is a critical developmental stage where physiological requirements for aromatic AA may increase. Therefore, it is possible that dietary aromatic AA supplementation may be beneficial to accomplish a successful transition from larvae to the juvenile stage. This work aimed to assess the effect of dietary aromatic AA supplementation on tyrosine metabolism in species with an accentuated (Senegalese sole, Solea senegalensis) and a less marked (gilthead seabream, Sparus aurata) metamorphosis. For this purpose, either species were fed Artemia and subsequently received or not an aromatic AA supplement through tube-feeding, together with a L-[U-14C] tyrosine marker, throughout metamorphosis. Tyrosine was elected as a tracer since the metabolic fate of this aromatic AA is directly linked to the production of thyroid hormones and metamorphosis. Results showed that dietary phenylalanine supplementation did not increase tyrosine retention in Senegalese sole larvae during metamorphosis, suggesting that this species may not be able to biosynthesise tyrosine from phenylalanine at a sufficient rate to supply its physiological requirements until after metamorphosis. Furthermore, dietary tyrosine supplementation effectively increased tyrosine availability in Senegalese sole body fluids at metamorphosis, most likely for coping with metamorphosis-related processes, such as production of thyroid hormones. Therefore, dietary tyrosine supplementation may be beneficial for Senegalese sole during metamorphosis. On the other hand, results indicated that gilthead seabream larvae do not seem to require an additional supply of aromatic AA during metamorphosis, probably because the physiological requirements for tyrosine do not increase during this developmental stage. The different results observed for Senegalese sole and gilthead seabream are probably related to the complexity of metamorphosis that each species undergoes and to the needs for production of thyroid hormones, which seems to affect aromatic AA requirements during this critical stage of development. These findings may be important for physiologists, fish nutritionists and for the flatfish aquaculture industry.
- Dietary nitrogen and fish welfarePublication . Conceição, L. E. C.; Aragão, C.; Dias, J.; Costas, B.; Terova, G.; Martins, C.; Tort, L.Little research has been done in optimizing the nitrogenous fraction of the fish diets in order to minimize welfare problems. The purpose of this review is to give an overview on how amino acid (AA) metabolism may be affected when fish are under stress and the possible effects on fish welfare when sub-optimal dietary nitrogen formulations are used to feed fish. In addition, it intends to evaluate the current possibilities, and future prospects, of using improved dietary nitrogen formulations to help fish coping with predictable stressful periods. Both metabolomic and genomic evidence show that stressful husbandry conditions affect AA metabolism in fish and may bring an increase in the requirement of indispensable AA. Supplementation in arginine and leucine, but also eventually in lysine, methionine, threonine and glutamine, may have an important role in enhancing the innate immune system. Tryptophan, as precursor for serotonin, modulates aggressive behaviour and feed intake in fish. Bioactive peptides may bring important advances in immunocompetence, disease control and other aspects of welfare of cultured fish. Fishmeal replacement may reduce immune competence, and the full nutritional potential of plant-protein ingredients is attained only after the removal or inactivation of some antinutritional factors. This review shows that AA metabolism is affected when fish are under stress, and this together with sub-optimal dietary nitrogen formulations may affect fish welfare. Furthermore, improved dietary nitrogen formulations may help fish coping with predictable stressful events.
- Recent advances in nutrition of fish larval | Avanços recentes em nutrição de larvas de peixesPublication . Conceição, L. E. C.; Aragão, C.; Richard, Nadège; Engrola, S.; Gavaia, Paulo J.; Mira, Sara; Dias, J.Os requisitos nutricionais de larvas de peixes são ainda mal compreendidos, o que leva a altas mortalidades e problemas de qualidade no seu cultivo. Este trabalho pretende fazer uma revisão de novas metodologias de investigação, tais como estudos com marcadores, genómica populacional, programação nutricional, génomica e proteómica funcionais, e fornecer ainda alguns exemplos das utilizações presentes e perspectivas futuras em estudos de nutrição de larvas de peixes.
- Alternative proteins for fish diets: implications beyond growthPublication . Aragão, Cláudia; Gonçalves, Ana Teresa; Costas, Benjamín; Azeredo, Rita; Xavier, Maria João; Engrola, SofiaAquaculture has been challenged to find alternative ingredients to develop innovative feed formulations that foster a sustainable future growth. Given the most recent trends in fish feed formulation on the use of alternative protein sources to decrease the dependency of fishmeal, it is fundamental to evaluate the implications of this new paradigm for fish health and welfare. This work intends to comprehensively review the impacts of alternative and novel dietary protein sources on fish gut microbiota and health, stress and immune responses, disease resistance, and antioxidant capacity. The research results indicate that alternative protein sources, such as terrestrial plant proteins, rendered animal by-products, insect meals, micro- and macroalgae, and single cell proteins (e.g., yeasts), may negatively impact gut microbiota and health, thus affecting immune and stress responses. Nevertheless, some of the novel protein sources, such as insects and algae meals, have functional properties and may exert an immunostimulatory activity. Further research on the effects of novel protein sources, beyond growth, is clearly needed. The information gathered here is of utmost importance, in order to develop innovative diets that guarantee the production of healthy fish with high quality standards and optimised welfare conditions, thus contributing to a sustainable growth of the aquaculture industry.
- Different environmental temperatures affect amino acid metabolism in the eurytherm teleost Senegalese sole (Solea senegalensis Kaup, 1858) as indicated by changes in plasma metabolitesPublication . Costas, B.; Aragão, C.; Ruiz-Jarabo, I.; Vargas-Chacoff, L.; Arjona, F. J.; Mancera, J. M.; Dinis, Maria Teresa; Conceição, L. E. C.Senegalese sole (Solea senegalensis) is a eurytherm teleost that under natural conditions can be exposed to annual water temperature fluctuations between 12 and 26C. This study assessed the effects of temperature on sole metabolic status, in particular in what concerns plasma free amino acid changes during thermal acclimation.
- Optimizing diets to decrease environmental impact of Nile tilapia (Oreochromis niloticus) productionPublication . Teodósio, Rita; Engrola, Sofia; Colen, R.; Masagounder, Karthik; Aragão, CláudiaAquaculture is one of the most thriving animal production sectors, and Nile tilapia (Oreochromis niloticus) farming represents 8% of total finfish culture. However, the industry sustainability depends on the development of cost‐effective and environmental friendly feeds. This study aimed to reduce dietary protein levels in diets for juvenile tilapia and to minimize diet environmental impact while maximizing biological efficiency. A growth trial was performed using five isoenergetic plant protein‐based diets with decreasing levels of crude protein: 360, 340, 320, 300 and 280 g/kg diet (D360, D340, D320, D300 and D280, respectively). Dietary protein utilization was assessed by metabolic trials using a radiolabelled amino acid mixture. Tilapia in all treatments showed similar growth performance and feed intake. Feed conversion ratio was significantly higher in fish fed the D280 than the D360 diet, while no differences were found for other treatments. Protein retention was significantly higher in tilapia fed the D300 than the D360 diet. Amino acid catabolism increased in fish fed the D360 diet, though without significant differences in muscle amino acid retention. This study demonstrates that dietary protein levels can be reduced to 300 g/kg diet without hindering tilapia growth and feed conversion ratio, while reducing environmental nitrogen losses.