/pdf/thoughts-for-the-future-of-aquaculture-nutrition-realigning-3d25mhzike.pdf

Thoughts for the Future of Aquaculture Nutrition: Realigning Perspectives to Reflect Contemporary Issues Related to Judicious Use of Marine Resources in Aquafeeds

Aquaculture is the fastest growing animal food production industry, now producing 50% of all food fish. However, aquaculture feeds remain dependent on fishmeal derived from capture fisheries, which must be reduced for continued sustainable growth. Purple phototrophic bacteria (PPB) efficiently yield biomass from wastewater with high product homogeneity, a relatively high protein fraction, and potential added value as an ingredient for fish feeds. Here we test bulk replacement of fishmeal with PPB microbial biomass in diets for Asian sea bass (Lates calcarifer), a high value carnivorous fish with high protein to energy requirement. Mixed culture PPB were grown in a novel 1 m3 attached photo-biofilm process using synthetic and real wastewater. Four experimental diets were formulated to commercial specifications but with the fishmeal substituted (0%, 33%, 66%, and 100%) with the synthetic grown PPB biomass and fed to a cohort of 540 juvenile fish divided amongst 12 tanks over 47 days. Weight and standard length were taken from individual fish at 18, 28, and 47d. No significant difference in survival was observed due to diet or other factors (94–100%). There was a negative correlation between PPB inclusion level and final weight (p = 5.94 × 10−5) with diet accounting for 4.1% of the variance over the trial (general linear model, R2 = 0.96, p = 1 × 10−6). Feed conversion ratio was also significantly influenced by diet (p = 6 × 10−7) with this factor accounting for 89% of variance. Specifically, feed conversion ratio (FCR) rose to 1.5 for the 100% replacement diet during the last sample period, approximately 1.0 for the partial replacement, and 0.8 for the nil replacement diet. However, this study demonstrates that bulk replacement of fishmeal by PPB is feasible, and commercially viable at 33% and 66% replacement.

Mixed culture purple phototrophic bacteria is an effective fishmeal replacement in aquaculture.

A variety of strategies can be used to assess the nutritional quality of ingredients; however, the choice of strategies used can have a strong impact on the interpretation of that information. A landmark review paper published over a decade ago has been considered the benchmark approach by which to structure research assessing the quality of ingredients (Glencross, Booth, & Allan, 2007). In that review, a series of five steps (and the order in which they should be done) to develop a comprehensive data set on which to base judgements about ingredient quality were proposed; 1. Characterization, 2. Palatability, 3. Digestibility, 4. Utilization and 5. Functionality (processability). Once these five steps had been achieved, a formulator could make the judicious choice as to whether to use, and with what constraints to impose, any ingredient that they were presented with. Without any one of these steps, the risk exposure substantially increased as the formulator needed to make assumptions, and this significantly increased the risk of a feed failing in one or more specifications (Glencross et al., 2019). Typically, many studies in this domain have skipped many of these early steps and gone straight to the assessment of utilization (step 4). However, in doing so, many of these studies have ended up with erroneous outcomes and/ or misleading assessments of the ingredients that they are testing, not Received: 28 February 2020 | Revised: 29 May 2020 | Accepted: 15 June 2020 DOI: 10.1111/anu.13138

/pdf/a-feed-is-still-only-as-good-as-its-ingredients-an-update-on-46ny4ta598.pdf

A feed is still only as good as its ingredients: An update on the nutritional research strategies for the optimal evaluation of ingredients for aquaculture feeds

Marine tropical carnivorous (MTC) fish are less tolerant to high dietary lipid compared with cold and temperate climate fish However, insufficient n‐3 long‐chain (≥C 20 ) polyunsaturated fatty acids (LC‐PUFA) compromises MTC fish health and growth which requires attention when choosing lipid sources in aquafeed formulations Fish oil (FO) has been the major lipid source for feeding key MTC fish We estimated that more than 200 thousand tonnes of FO were used to feed farmed MTC fish in 2016, representing nearly 25% of global FO production Nevertheless, recent increases in FO prices and demand, and the foreseen inability of wild fisheries to produce sufficient FO in the future, have created a need for cheaper and more sustainable alternatives Meta‐analysis showed that feeding vegetable oils (VO) to MTC fish can slightly reduce their growth, with a marked decrease in n‐3 LC‐PUFA content in the fish tissues corresponding with the increased replacement of FO and fishmeal in the diet Rendered terrestrial animal fat or modulating the bioconversion of n‐3 LC‐PUFA precursors in VO can be utilised further in MTC fish nutrition with more research recommended on these approaches Oils and oil‐rich meals from non‐food marine organisms are rich in n‐3 LC‐PUFA and represent an underutilised alternative to FO for tropical aquaculture With oils rich in n‐3 LC‐PUFA produced from transgenic plants presently gaining regulatory approvals and becoming available as a renewable alternative to FO, aquaculture in the tropics and around the globe is ready to leap into a new phase of sustainable expansion

Sustainable alternatives to dietary fish oil in tropical fish aquaculture

/pdf/replacement-of-fish-oil-with-vegetable-oil-blends-in-feeds-dk7v2myld4.pdf

Replacement of fish oil with vegetable oil blends in feeds for greater amberjack (Seriola dumerili) juveniles: Effect on growth performance, feed efficiency, tissue fatty acid composition and flesh nutritional value

https://dspace.stir.ac.uk/bitstream/1893/23755/1/Glencross%20et%20al%202016%20-%20Fishmeal%20and%20Fishoil%20Replacement%20-%20FPV.pdf

An evaluation of the complete replacement of both fishmeal and fish oil in diets for juvenile Asian seabass, Lates calcarifer

The evolution of sex determination (SD) mechanisms in teleost fishes is amazingly dynamic, as reflected by the variety of different master sex-determining genes identified, even sometimes among closely related species. Pangasiids are a group of economically important catfishes in many South-Asian countries, but little is known about their sex determination system. Here, we generated novel genomic resources for 12 Pangasiid species and provided a first characterization of their SD system. Based on an Oxford Nanopore long-read chromosome-scale high quality genome assembly of the striped catfish Pangasianodon hypophthalmus, we identified a duplication of the anti-Müllerian hormone receptor type II gene (amhr2), which was further characterized as being sex-linked in males and expressed only in testicular samples. These first results point to a male-specific duplication on the Y chromosome (amhr2by) of the autosomal amhr2a. Sequence annotation revealed that the P. hypophthalmus Amhr2by is truncated in its N-terminal domain, lacking the cysteine-rich extracellular part of the receptor that is crucial for ligand binding, suggesting a potential route for its neofunctionalization. Short-read genome sequencing and reference-guided assembly of 11 additional Pangasiid species, along with sex-linkage studies, revealed that this truncated amhr2by duplication is also conserved as a male-specific gene in many Pangasiids. Reconstructions of the amhr2 phylogeny suggested that amhr2by arose from an ancient duplication / insertion event at the root of the Siluroidei radiation that is dated around 100 million years ago. Altogether these results bring multiple lines of evidence supporting that amhr2by is an ancient and conserved master sex-determining gene in Pangasiid catfishes, a finding that highlights the recurrent usage of the transforming growth factor β pathway in teleost sex determination and brings another empirical case towards the understanding of the dynamics or stability of sex determination systems.

/pdf/an-ancient-truncated-duplication-of-the-anti-mullerian-34p4h07o.pdf

An ancient truncated duplication of the anti-Mullerian hormone receptor type 2 gene is a potential conserved master sex determinant in the Pangasiidae catfish family

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An evaluation of the complete replacement of both fishmeal and fish oil in diets for juvenile Asian seabass, Lates calcarifer

An ancient truncated duplication of the anti-Mullerian hormone receptor type 2 gene is a potential conserved master sex determinant in the Pangasiidae catfish family