Bancroft's Theory and Practice of Histological Techniques

Essential fatty acid (EFA) requirements vary qualitatively and quantitatively with both species and during ontogeny of fish, with early developmental stages and broodstock being critical periods. Environment and/or trophic level are major factors, with freshwater/diadromous species generally requiring C18 polyunsaturated fatty acids (PUFA) whereas marine fish have a strict requirement for long-chain PUFA, eicosapentaenoic, docosahexaenoic and arachidonic acids. Other than marine fish larvae, defining precise quantitative or semi-quantitative EFA requirements in fish have received less attention in recent years. However, the changes to feed formulations being forced upon the aquaculture industry by the pressing need for sustainable development, namely the replacement of marine fish meal and oils with plant-derived products, have reintroduced EFA into the research agenda. It is particularly important to note that the physiological requirements of the fish to prevent deficiency pathologies and produce optimal growth may not parallel the requirements for maintaining nutritional quality. For instance, salmonids can be successfully cultured on vegetable oils devoid of long-chain n-3 PUFA but not without potentially compromising their health benefits to the human consumer. Solving this problem will require detailed knowledge of the biochemical and molecular basis of EFA requirements and metabolism.

Fatty acid requirements in ontogeny of marine and freshwater fish

Almost total replacement of fish meal by plant protein sources in the diet of a marine teleost, the European seabass, Dicentrarchus labrax

It is well known that healthy gut microbiota is essential to promote host health and well-being. The intestinal microbiota of endothermic animals as well as fish are classified as autochthonous or indigenous, when they are able to colonize the host's epithelial surface or are associated with the microvilli, or as allochthonous or transient (associated with digesta or are present in the lumen). Furthermore, the gut microbiota of aquatic animals is more fluidic than that of terrestrial vertebrates and is highly sensitive to dietary changes. In fish, it is demonstrated that [a] dietary form (live feeds or pelleted diets), [b] dietary lipid (lipid levels, lipid sources and polyunsaturated fatty acids), [c] protein sources (soybean meal, krill meal and other meal products), [d] functional glycomic ingredients (chitin and cellulose), [e] nutraceuticals (probiotics, prebiotics, synbiotics and immunostimulants), [f] antibiotics, [g] dietary iron and [h] chromic oxide affect the gut microbiota. Furthermore, some information is available on bacterial colonization of the gut enterocyte surface as a result of dietary manipulation which indicates that changes in indigenous microbial populations may have repercussion on secondary host–microbe interactions. The effect of dietary components on the gut microbiota is important to investigate, as the gastrointestinal tract has been suggested as one of the major routes of infection in fish. Possible interactions between dietary components and the protective microbiota colonizing the digestive tract are discussed.

https://biblio.ugent.be/publication/8517580/file/8525700.pdf

Effect of dietary components on the gut microbiota of aquatic animals. A never‐ending story?

The global farming of fish and shellfish has been the fastest growing food producing sector in the last few decades and has become an important industry in many countries. Fishmeal made from pelagic fish used to be the major dietary protein source in compounded feed for many important farmed species, but the limited amount available has resulted in massive research to identify alternative protein sources. The average levels of pelagic fishmeal in aquaculture feed have decreased substantially in the last decade and recent published results in the scientific literature show that it is possible to replace even more in diets both for carnivorous and herbivorous/omnivorous species. If the predicted low inclusion levels are reached in the next decade, there may be room for a relatively large increase in the total production of farmed fish and shellfish without any increased use of fishmeal.

/pdf/a-limited-supply-of-fishmeal-impact-on-future-increases-in-1mbtjj962o.pdf

Denis Coves

Papers

Almost total replacement of fish meal by plant protein sources in the diet of a marine teleost, the European seabass, Dicentrarchus labrax

Effect of chronic ammonia exposure on growth of European seabass (Dicentrarchus labrax) juveniles

Regulation of feed intake, growth, nutrient and energy utilisation in European sea bass (Dicentrarchus labrax) fed high fat diets

Effect of chronic exposure to ammonia on growth, food utilisation and metabolism of the European sea bass (Dicentrarchus labrax)

Self-feeding of European sea bass (Dicentrarchus labrax, L.) under laboratory and farming conditions using a string sensor