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Improving feed suitability and bolstering the global upsurge in fish production is a strategic challenge for aquaculture. The utilization of plant and animal derived ingredients in aquafeed for achieving sustainable in finfish aquaculture is affected by various factors, including the presence of antinutritional factors, lowered nutrient bioavailability, indigestible particles and microbial contaminants. Applying fermentation to overcome these problems in aquafeed ingredients has received considerable attention in recent years as fermentation provides health‐promoting probiotic benefits to host organisms. Fermentation has also been shown in many studies to improve nutrient availability and bioavailability of feed, increased palatability and digestibility and eliminate anti‐nutritional compounds in dietary feed ingredients, making them more easily digestible which eventually improve growth and health performance of fish. Therefore, it is imperative to accelerate the use of fermented feedstuffs as aquafeed if sustainable aquaculture is to be achieved. This review reported the various methods of fermentation, characteristics of fermented feed ingredients, factors that are considered during fermentation and overall nutritional quality of fermented feed ingredients for aquaculture production. The role of fermented feed ingredients for various farmed species in terms of growth, feed utilization, gut microbiota composition, immunity and disease resistance in fish is thoroughly discussed. The possible drawbacks associated with the fermentation process are also discussed in the article. [ABSTRACT FROM AUTHOR]

The aims of this review are to describe the role of 'blue‐food production' (animals, plants and algae harvested from freshwater and marine environments) within a circular bioeconomy, discuss how such a framework can help the sustainability and resilience of aquaculture and to summarise key examples of novel nutrient sources that are emerging in the field of fed‐aquaculture species. Aquaculture now provides >50% of the global seafood supply, a share that is expected to increase to at least 60% within the next decade. Aquaculture is an important tool for reducing resource consumption in global protein production and increasing resilience to climate change and other global disruptions (i.e. pandemics, geo‐political instability). Importantly, blue foods also provide essential nutrition for a growing human population. Blue foods are helping to help the global goal of 'zero hunger' (United Nation's Sustainable Development Goal 2) while reducing the dependency on finite natural resources but further refinement and new solutions are needed to make the industry more 'circular' and sustainable, particularly with respect to sourcing raw materials for aquafeeds. This review describes the feed resources that are available or may be created within a circular bioeconomy framework, their role within the framework and in aquaculture and ultimately, how these resources contribute to de‐risking and establishing a resilient aquaculture production chain. [ABSTRACT FROM AUTHOR]

The flavour of aquatic animal products is distinct from terrestrial foods, facilitating a competitive marketing advantage. However, the flavour of aquatic animals can also be highly variable. Importantly, differences are reported in the flavour of animals from aquaculture and wild‐capture systems. These differences can erode consumer acceptance of aquaculture products and reduce financial returns to producers. Mild 'fish‐like', 'marine', 'crustacean‐like', 'seafood' and 'sweet' odours are desirable. However, overt 'fish‐like', 'fatty' and 'earthy' odours are quality deficits and cause products to become unpalatable. Odorous volatile compounds are responsible for eliciting these characteristic odours. In this literature review, the odorous volatile compounds of 96 aquatic animal samples are reported, revealing 291 different compounds. Generalist compounds that are integral to the odour of aquatic animals are presented in addition to 86 compounds that elicit key characteristic odours. The influence of these compounds on aquatic animal flavour is explored and the specific factors likely to affect their manipulation in aquaculture products are discussed. The culture environment and diet are critical factors affecting volatile profiles of aquatic animals and are the variables that can be controlled by aquaculture producers. The information presented in this review can underpin the development of innovative aquaculture strategies that prevent environmental exposure of aquatic animals to unpalatable volatile compounds and facilitate the development of aquaculture diets that optimise the volatile profile of edible tissues. [ABSTRACT FROM AUTHOR]

Sea urchin gonads (roe) are a prized global sea food commodity, with growing demand driving the need for urchin roe enhancement aquaculture. Effective roe enhancement of urchins using formulated feeds require species‐specific optimization and an understanding of the interactions between key dietary components (e.g. protein, lipid, carbohydrate, energy and/or algal supplements). Here, we tested 18 formulated feeds on the sea urchin Heliocidaris erythrogramma, collected from barrens. The 18 iso‐energetic (~20 MJ/kg) feed combinations contained one of three protein levels (250, 375 or 500 g/kg), three lipid levels (73, 101 or 131 g/kg) combined with a single (45 g/kg Sargassum spp.) or multiple (45 g/kg Sargassum spp., 25 g/kg Solieria robusta, 25 g/kg Ulva lactuca) dried algal supplement. From two consecutive 12‐week enhancement trials, the most optimal feed type contained 375 g/kg protein, 73 g/kg lipid and a 45 g/kg algal supplement (Sargassum spp.) and produced gonad indices of 18.5 ± 0.4% (Trial 1) and 21.7 ± 1.2% (Trial 2). Across feed types, there was no significant difference in the proportion of marketable quality (A and B grade) roe produced (56%–85% Trial 1, 65%–85% Trial 2). We conclude that roe enhancement of H. erythrogramma collected from barrens is highly feasible. [ABSTRACT FROM AUTHOR]

A more efficient utilisation of marine-derived sources of dietary n -3 long-chain PUFA (n -3 LC PUFA) in cultured Atlantic salmon (Salmo salar L.) could be achieved by nutritional strategies that maximise endogenous n -3 LC PUFA synthesis. The objective of the present study was to quantify the extent of n -3 LC PUFA biosynthesis and the resultant effect on fillet nutritional quality in large fish. Four diets were manufactured, providing altered levels of dietary n -3 substrate, namely, 18 : 3 n -3, and end products, namely, 20 : 5 n -3 and 22 : 6 n -3. After 283 d of feeding, fish grew in excess of 3000 g and no differences in growth performance or biometrical parameters were recorded. An analysis of fatty acid composition and in vivo metabolism revealed that endogenous production of n -3 LC PUFA in fish fed a diet containing no added fish oil resulted in fillet levels of n -3 LC PUFA comparable with fish fed a diet with added fish oil. However, this result was not consistent among all treatments. Another major finding of this study was the presence of abundant dietary n -3 substrate, with the addition of dietary n -3 end product (i.e. fish oil) served to increase final fillet levels of n -3 LC PUFA. Specifically, preferential β -oxidation of dietary C18 n -3 PUFA resulted in conservation of n -3 LC PUFA from catabolism. Ultimately, this study highlights the potential for endogenous synthesis of n -3 LC PUFA to, partially, support a substantial reduction in the amount of dietary fish oil in diets for Atlantic salmon reared in seawater. [ABSTRACT FROM AUTHOR]

This study assessed the influence of diet composition on hyaline sphere (HS) development in auricularia larvae of the sandfish, Holothuria scabra , and the subsequent relationships between the presence and size of hyaline spheres and competency through settlement and early juvenile performance. Two-day old larvae were fed one of three commercially available micro-algae diets that varied in their nutrient compositions: (1) Isochrysis sp. (Haptophyceae); (2) Pavlova sp. (Haptophyceae); and (3) Thalassiosira weissflogii (Bacillariophyceae) or a ternary combination of the three. There were positive significant correlations between HS development in late auriculariae on days 10, 11, 12 and 13 post-fertilisation, and the proportion of competent doliolariae on day 15, post-settlement size (day 21) and post-settlement survival (day 25). The dietary components that most strongly influenced these relationships were carbohydrates and the n-3 polyunsaturated fatty acids arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Our result confirm the strong relationship between HS formation in late auriculariae of sandfish and subsequent larval competency through settlement. As such, the presence and size of HS is a reliable indicator of subsequent performance for sandfish. Given that HS development was influenced by the nutrients available to sandfish auriculariae, there is clear opportunity for development of more appropriate diets for hatchery culture of this species that will improve HS formation and larval performance supporting improved hatchery production. Statement of relevance Our results have confirmed that for sandfish larvae, the presence and size of HS at the end of the auricularia stage, is indeed a reliable indicator of subsequent performance. Our results have also confirmed that HS formation and size is significantly influenced by the nutrient composition of the auricularia diet, and that there are significant positive correlations between HS formation and dietary levels of carbohydrate, EPA:DHA and EPA:ARA ratios. This information provides a strong basis for development of more appropriate diets for sandfish larvae that will improve HS formation and larval performance during hatchery culture and in turn improve hatchery production of this species. [ABSTRACT FROM AUTHOR]

The closed-cycle rearing of palinurid lobsters in commercially relevant quantities currently represents one of the most difficult challenges facing modern-day aquaculture. The length and complexity of the larval life cycle exacerbate the problem, comprising the major bottleneck to their successful aquaculture. The general consensus is that developments in the key research area of nutrition will provide the necessary breakthroughs to make the closed-cycle rearing of lobster a reality. Due to the cryptic nature of feeding preferences and complex larval morphology, a commercially formulated feed for their culture does currently not exist. Nevertheless, there has been a wealth of research conducted to elucidate many of the unknowns concerning larval nutritional requirements. This review presents a synthesis of this information, ranging from investigations of larval morphology and feeding behaviour, hatchery nutrition practices, the elucidation of wild prey items and the nutritional content of wild-caught larval species. Based on the information available, this review culminates with a 'best guess' formulation for a larval spiny lobster diet, taking aspects concerning both the physical and chemical attributes of formulation into consideration. It is concluded that larval spiny lobsters are likely comparatively low in relation to other larval species with respect to their quantitative dietary requirements. Ultimately, the overall success of the larval cycle appears to be dictated by the stockpiling of lipids to fuel an energy-demanding metamorphosis and a subsequent nonfeeding puerulus phase. These insights provide valuable direction for the formulation of nutritionally complete feeds to permit the closed-loop culture of spiny lobster species. [ABSTRACT FROM AUTHOR]

The implementation of alternative lipid sources for use in aquaculture is of considerable interest globally. However, the possible benefit of using stearidonic acid (SDA)-rich fish oil (FO) alternatives has led to scientific confusion. Two hundred and forty rainbow trout (Oncorhynchus mykiss) were fed 1 of 4 diets (3 replicate tanks/treatment) containing either FO, linseed oil (LO), echium oil, or mixed vegetable oil (72% LO, 23% sunflower oil, and 6% canola oil) as the dietan/ lipid source (16.5%) for 73 d to investigate the competition and long-chain PUFA (LC-PUFA) biosynthesis between the fatty acid Substrates &agr;-linolenic acid (ALA) and SDA. SDA was more efficiently bioconverted to LC-PUFA compared with ALA. However, when the dietary lipid sources were directly compared, the increased provision of CI 8 PUFA within the LO diet resulted in no significant differences in (n-3) LC-PUFA content compared with fish fed the other diets. This study therefore shows that, rather than the previously speculated substrate competition, the limiting process in the apparent in vivo (n-3) LC-PUFA biosynthesis appears to be substrate availability. Rainbow trout fed the SDA- and ALA-rich dietary lipid sources subsequently had similar significant reductions in (n-3) LC-PUFA compared with fish fed the FO diet, therefore providing no additional dietary benefit on (n-3) LC-PUFA concentrations [ABSTRACT FROM AUTHOR]

Abstract: Recommendations to endorse the sustainability of wild fish stock utilisation, supporting the health of marine ecosystems, are clashing with those to increase omega-3 fatty acids (n−3 LC-PUFA) consumption and promoting human health. The objective of this study was to evaluate the role of salmonid aquaculture as a user or supplier of n−3 LC-PUFA, as a means of understanding the potential of the sector in conserving or depleting wild fisheries. A case-study feeding trial was implemented on rainbow trout up to commercial size, in which fish were fed a fish oil- or a linseed oil-diet. Harvested fish were analysed for fatty acid composition and difference and liking using consumers. The n−3 LC-PUFA input/n−3 LC-PUFA output ratio was computed. Consumers showed no preference, but were able to distinguish between samples. The fatty acids of the fillets were significantly modified by the diets. On the input side, for the production of 100g of fish fillet, it was necessary to use 8.6g of n−3 LC-PUFA to produce an output of 1.9g of n−3 LC-PUFA in the fish oil-fed fish; in contrast it was only necessary to use 270mg of n−3 LC-PUFA to produce 560mg of these fatty acids in the linseed oil-fed fish. It was showed that the substitution of fish oil with linseed oil in aquafeed is an easily implemented tool to transform salmonids farming from a consumer into a net producer of health promoting n−3 LC-PUFA and accomplish its role in conserving wild fisheries in the future. [ABSTRACT FROM AUTHOR]

Abstract: With the salmonid industry currently exploiting the vast majority of globally available fish oil, there is the need to optimise fish oil utilisation by increasing its efficiency in terms of transferring the health-promoting long chain omega-3 fatty acids (n−3 LC-PUFA) into farmed fish flesh. The aim of this study was to evaluate if dietary fatty acid deposition is affected by the time of feeding, and hence identify possible innovative feeding strategies towards more efficient use of dietary fish oil. Over a period of 12weeks, three diets with different lipid sources, canola oil (CO), fish oil (FO) or a 50/50 blend of the two oils (Mix), were alternated daily and fed to rainbow trout (Oncorhynchus mykiss). Six treatments were administered to fish, reference treatment (REF, continuously fed FO), control treatment (CT, continuously fed Mix), am canola oil ration (amCOR), pm canola oil ration (pmCOR), am canola oil satiation (amCOS) and pm canola oil satiation (pmCOS). Fish received either the CO diet in the am or pm feeds and received the FO diet at the opposite time. A significant increase in growth and feed consumption was noted in the pmCOS treatment. Fillet fatty acid profile was modified by associated feeding schedules and was generally reflective of dietary fatty acid profile. No significant increases in n−3 LC-PUFA deposition were observed. However, both linoleic acid (18:2n−6) and α-linolenic acid (18:3n−3) contents were significantly higher in pmCOR compared to amCOR and CT. The results of the present study suggest the existence of cyclical circadian patterns in fatty acid deposition in rainbow trout. [Copyright &y& Elsevier]

Abstract: The replacement of fish oil with vegetable based oils is a strategy which is increasingly being adopted by the aquafeed industry as an essential component to reduce the reliance on a limited supply of a natural resource, which in turn also provides cost benefits. The aim of the present investigation was to evaluate the lipid and fatty acid digestibility of a mix blend vegetable oil in juvenile Murray cod; an emerging species of increasing interest in the Australian aquaculture sector. Five semi purified experimental diets were formulated with 17% lipid originating from fish oil (FO) which was substituted in 25% increments by blended vegetable oil (VO), formulated using olive oil (12%), palm oil (43%) and linseed oil (45%) to match the major fatty acid classes of the FO. Significant differences between the dietary treatments with regard to the lipid and individual fatty acid digestibility were recorded. This study clearly demonstrated that in Murray cod fatty acid digestibility decreases with chain length, and inversely increases relative to the degree of unsaturation. The combination of chain length, degree of unsaturation and the melting point of individual fatty acids resulted in the digestibility of PUFA>MUFA>SFA and short chain>longer chain fatty acids. Therefore, the inclusion of a mixed blend vegetable oil resulted in significantly reduced lipid digestibility in juvenile Murray cod. [Copyright &y& Elsevier]

A considerable body of literature exists concerning the use of marine-derived raw materials in aquaculture feed formulations and the resulting modifications of the health promoting qualities of farmed fish. However, these investigations and reports are fundamentally limited to fatty acids and little is known regarding the other nutritional characteristics of cultured fish and seafood products. This knowledge gap, often coupled with inaccurate or incomplete media reports, generates consumer confusion and mistrust in relation to farmed fish quality. The aim of the present study was therefore to characterise not only the fatty acid composition, but also the resulting protein, amino acid and micronutrient composition of rainbow trout fed diets containing fish oil or vegetable oils. To achieve this, triplicate groups of rainbow trout ( Oncorhynchus mykiss ) were subjected to two distinct vegetable oil- based diets (one rich in alpha-linolenic acid, 18:3n-3, ALA and the other rich in linoleic acid, 18:2n-6, LNA) and a traditional n-3 long chain polyunsaturated fatty acid (LC-PUFA) rich, fish oil-based diet over a 126 day period. Growth performance and feed utilisation parameters as well as tissue fatty acid composition, amino acid composition, vitamin, mineral and trace element concentration in fish fillets were subsequently assessed. Expectedly, major differences were evident between treatments in relation to fatty acid composition, where for the most part fillet composition reflected that of the diet. Notably, no differences were observed regarding fillet amino acid composition, as was also the case for the vast majority of vitamins, minerals and trace elements. Therefore, with the exception of the fatty acid profile and vitamin A concentration, other beneficial nutritional qualities of fish are fundamentally maintained and unaffected when alternative oil sources are implemented in aquaculture feed formulations, maintaining cultured rainbow trout a nutritious and nourishing product for human consumption. [ABSTRACT FROM AUTHOR]

In the effort to increase the commercial value of urchin gonads produced via roe enhancement aquaculture, a variety of formulated feeds have been tested to increase gonad production and improve colour and taste. The addition of dried algal supplements to formulated feeds can further enhance gonad quality, but the level of improvement is highly variable and algae or urchin species dependent. Here we test whether the inclusion of three types of dried algal supplements (Sargassum fallax , Ecklonia radiata, and Durvillea potatorum) added to a pellet-based formulated aquaculture feed could further enhance the colour, taste and gonad quality in the temperate urchin Heliocidaris erythrogramma during two 12 wk. gonad enhancement periods, April to June, and July to September. All feed types resulted in urchins with gonad indices (GIs) of commercially acceptable quantities (Apr-Jun: GI = 14.6%, Jul-Sep: GI = 14.9%). The proportion of marketable gonads (A + B grades) was significantly higher during the Jul-Sep (87.9 ± 3%, mean ± SE) compared to the Apr-Jun (76.6 ± 3%, mean ± SE) enhancement period, however, algal supplement type did not improve gonad colour, taste, or the proportion of marketable gonads when compared to the control feed. We conclude that additional algal supplements may fail to further improve roe quality if the base formulated feed used to roe enhance is already of a standard that produces a sufficient proportion (>70%) of marketable roe. • This research investigates using locally sourced algal supplements in formulated feeds to improve gonad quality and taste. • Greater than 70% high quality roe was achievable in all treatment groups regardless of algal supplement type. • Best gonad quality was produced during a winter-spring enhancement period. • The findings indicate a 4.5% algal supplement is sufficient in formulated feeds for the urchin H. erythrogramma. [ABSTRACT FROM AUTHOR]

Fish are the main source of long-chain polyunsaturated fatty acids (LC-PUFA, >C 18) for human consumption. In general, it has been widely observed that the fatty acid (FA) profiles of farmed fish are reflective of the diet. However, the degree of tissue FA "distortion" based on incorporation of different dietary FA into fish tissues varies greatly depending on FA type, fish species and environmental factors. In terms of fish FA composition, this variation has not been comprehensively reviewed, raising the question: "Are fish what they eat?". To date, this remains unanswered in detail. To this end, the present review quantitatively summarized the 'diet-fish' FA relationship via an analysis of FA composition in diets and fish tissues from 290 articles published between 1998 and 2018. Comparison of this relationship among different fish species, tissue types or individual FA was summarized. Furthermore, the influence of environmental factors such as temperature and salinity, as well as of experimental conditions such as fish size and trophic level, feeding duration, and dietary lipid level on this relationship are discussed herein. Moreover, as a means of restoring LC-PUFA in fish, an emphasis was paid to the fish oil finishing strategy after long-term feeding with alternative lipid sources. It is envisaged that the present review will be beneficial in providing a more comprehensive understanding of the fundamental relationship between the FA composition in diets, and subsequently, in the farmed fish. Such information is integral to maintaining the quality of farmed fish fillets from the perspective of FA composition. • The 'diet-fish' FA relationship was systematically reviewed. • The 'diet-fish' FA relationship was analyzed by quantitative approaches. • Factors influencing the 'diet-fish' FA relationship were analyzed and discussed. • An emphasis was paid to the fish oil finishing strategy in fish farming. • Dietary FA incorporation in fish tissues is affected by many non-dietary factors. [ABSTRACT FROM AUTHOR]

This study investigated the effects of different dissolved carbon dioxide (CO 2) concentrations (400, 700, and 1000 ppm) on the growth and vertebral column formation of hybrid tiger grouper × giant grouper (TG × GG) in their advanced larval stage under controlled laboratory conditions for 12 weeks. Growth parameters, including specific growth rate (SGR), survival rate, food consumption (FC), and food conversion rate (FCR), were calculated at the end of the experiment. Vertebral column formation was analysed using X-radiography and osteology methods. The results showed that all growth parameters were significantly affected by CO 2 concentration, with the best performances observed under 400 ppm CO2. The highest statistically significant (p < 0.05) SGR, survival rate, and FC were observed under 400 ppm CO 2 , whereas the lowest was observed under 1000 ppm CO2. The lowest FCR (0.40, p < 0.05) was observed in 400 ppm CO 2 and the highest was observed at 1000 ppm CO 2 (0.59, p < 0.05). Furthermore, larvae without vertebral column malformations were observed in 400 ppm CO 2 , while larvae with small angles of kyphosis were observed in 700 ppm CO 2 , and larvae with kyphosis, lordosis, and vertebral compression were observed in 1000 ppm CO 2. Only six spine measurements out of 31 obtained under different CO 2 concentrations were significantly different (p < 0.05). Overall, the results suggest that CO 2 concentration plays a crucial role in the growth and vertebral column formation of TG × GG in their advanced larval stage. The optimal CO 2 concentration for the aquaculture of TG × GG in their advanced larval stage was found to be 400 ppm or lower. This study highlights the importance of maintaining optimal CO 2 concentrations to enhance the growth and health of fish in aquaculture systems. • Ocean acidification harms marine hybrid larvae - tiger grouper × giant grouper (TG × GG). • 1000 ppm CO 2 results in poor growth, weight, survival, and food conversion. • Deformities in vertebral columns at 1000 ppm CO 2 ; normal at 400 ppm CO 2. • Study offers direction for further research on marine larvae in high CO 2 conditions. [ABSTRACT FROM AUTHOR]

Phyllosoma of the tropical spiny rock lobster, Panulirus ornatus , possess a rudimentary digestive system with a limited capacity to digest large protein molecules. As such, to foster the successful aquaculture of this species, research into dietary requirements should place a focus on feed ingredients aligned with digestive capacity. Thus, the aim of the present study was to assess the effects of two protein pre-digestion treatments: acid denaturation and enzyme hydrolysis, on a regular fishmeal ingredient in a novel formulated diet for early–mid stage P . ornatus phyllosoma (Stages III–VIII). Three iso -nitrogenous, iso -lipidic and iso -energetic diets were formulated with 100% of protein originating from intact fishmeal (IFM), acid-denatured fishmeal (DFM) or enzyme hydrolysed fishmeal (HFM) and fed to early–mid stage phyllosoma for a period of 35-days. Growth performance metrics were all significantly higher in phyllosoma receiving the HFM treatment compared to the DFM and IFM treatments. Phyllosoma fed the HFM diet also had the most advanced development stages, with a significantly greater proportion of individuals reaching Stage VII (2). No significant differences were detectable in either the protein-bound or FAA composition of phyllosoma across all treatments, suggesting that the superior growth performance of the HFM fed phyllosoma was the result of an increased abundance of intermediate, shorter chain dietary peptides. The present study suggests that enzyme hydrolysed fishmeal is a superior protein ingredient for artificial diets and most closely resembles the requisite dietary protein format for P . ornatus phyllosoma. [ABSTRACT FROM AUTHOR]

Elucidation of the key nutritional requirements for complete larval development of the tropical spiny rock lobster, Panulirus ornatus , presents a major challenge for the development of robust commercial aquaculture for this crustacean. As a foundation study in this area, the chemical composition of early–mid stage P. ornatus phyllosoma (Stages I–VI) receiving a novel formulated diet was analysed immediately prior and post-ecdysis to provide insight into the crude nutritional trends during the larval development cycle. From the onset of moulting, cyclical patterns were evident in the proximate composition of phyllosoma, resulting in substantial restructuring between the pre- and post-moult stages of the moult cycle. Proportions of protein, lipid and ash were high at the premoult stage, reflecting growth and nutrient accumulation over the intermoult period, and reduced at the post-moult stage, reflecting the large uptake of water to facilitate subsequent growth. Polar lipid was the dominant lipid class, accounting for > 90% of the total lipid content. Conversely, triacylglycerol concentrations were low (< 5%), despite being the principal lipid class available in the formulated diet. Likewise, despite receiving high concentrations of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) (9.2 and 7.6% of the dietary lipid source, respectively), levels of these fatty acids were comparatively low in phyllosoma (3.4 and 4.7%, respectively). In contrast, there is selective deposition of these fatty acids in wild caught phyllosoma. This finding suggests a poor assimilation of triacylglycerols by captive larvae and highlights the importance of future investigations into alternative sources of EPA and DHA. Ultimately, this study provides insight into the nutritional requirements of phyllosoma, providing valuable knowledge on diet formulation for commercially viable hatchery production of spiny rock lobsters. [ABSTRACT FROM AUTHOR]

Aquafeed manufacturers are increasingly interested in ensuring consistently high-quality products, while relying heavily on poultry offal meal (POM), which is inevitably variable. This study examined the chemical composition of 22 different commercially and experimentally produced POM to determine which chemical variables best predict in vivo protein digestibility in Atlantic salmon (Salmo salar) and to evaluate which production variable, rendering temperature or raw material freshness, has a greater impact on digestibility. The chemical composition of commercially and experimentally produced POM was extremely variable. Significant relationships were found between in vivo dietary protein digestibility and D-glutamic acid (R2 = 0.64) and D-aspartic acid (R2 = 0.62). Rendering temperature and raw material freshness had significant effects on D-amino acids and biogenic amines. D-glutamic and D-aspartic acids may provide rapid-assessment indication of POM quality, as these D-amino acids were linked to protein digestibility and affected by the production variables. This study supports the well-held notion that POM is subject to significant variability and addresses the specific chemical characterisation of POM and the production conditions which impact nutrient digestibility in Atlantic salmon. These results prove beneficial to aquafeed manufactures aiming to ensure consistency and high nutritional quality in protein sources for aquafeed. • The chemical composition of poultry offal meals was extremely variable. • Digestibility correlated with D-glutamic acid and D-aspartic acid. • Rendering temperature and freshness affected D-amino acids and biogenic amines. • D-glu and D-asp may be rapid-assessment quality indicators of poultry meal. [ABSTRACT FROM AUTHOR]