A comparison between marine and terrestrial invertebrate meals for mirror carp (Cyprinus carpio ) diets: Impact on growth, haematology and health

Invertebrate meals (e.g. polychaetes and insects) present novel and sustainable high-quality nutrient sources for use in fish feed formulations. To test this innovative source, an eleven-week feeding trial was conducted evaluating the effects of replacing the fishmeal (FM) component as an example of a superior protein source (FM CTRL) with ragworm meal (RW, Nereis virens) and/or silkworm pupae (SWP, Bombyx mori) in mirror carp (Cyprinus carpio) diets. Three experimental diets with partial replacement of FM (diets: RW + FM, SWP + FM and RW + SWP + FM) were formulated. All diets were formulated to be iso-nitrogenous, iso-lipidic and iso-energetic. Growth performance and feed utilization indices were assessed, and the feeding trial concluded with the analysis of haematological parameters to provide an indication of carp physiological and health status. Mean weight gain was greatest in mirror carp fed RW + FM (60.83 fish−1 day−1; P < 0.05 vs. all other diets) followed by SWP + FM (40.62 g fish−1 day−1; P < 0.05 vs. all other diets). The least weight gain was achieved in fish fed FM + SWP + RW+ and FM CTRL (34.34 and 33.96 g fish−1 day−1, respectively; not significantly different from each other). Fish fed on RW + FM diet had significantly lower plasma ammonia concentrations than any other dietary groups (P = 0.04). Mirror carp fed on SWP + FM diet (111.52 units mL−1) were observed to have a marked enhancement in alternative complement activity than FM CTRL (79.21 units mL−1, P = 0.041). Both ragworm and silkworm pupae meal present attractive sustainable functional feed component in carp diets, with benefits on enhancing growth performance and specific physiological parameters

The potential of a solid-state fermentation supplement to augment white lupin (Lupinus albus) meal incorporation in diets for farmed common carp (Cyprinus carpio)

A 10-week feeding trial was conducted to evaluate the effects of partially substituting soya protein concentrate (SPC), with white lupin (Lupinus albus) meal in carp (Cyprinus carpio) diets. This study further investigated the dietary inclusion of a solid-state fermentation (SSF) product of Aspergillus niger in tandem with SPC replacement. Six experimental diets were produced to be isonitrogenous (42%), isolipdic (8%) and isoenergetic (19 MJ kg−1). Four diets were formulated to have 12.5 and 25% substitution of SPC using lupin meal, and with and without a supplement of 0.1% of SSF. An additional two diets were designed to serve as a basal reference with no SPC replacement, but one supplemented with 0.1% SSF inclusion. The results of this study showed that SPC can be replaced with up to 25% white lupin meal in carp diets, without reduction of growth performance, feed utilisation, body composition, gut integrity or health. The addition of SSF to the test diets enhanced growth performance (specific growth rate, P < 0.05) and nutrient utilisation (e.g. feed conversion ratio and protein efficiency ratio, P < 0.05)

Dietary supplementation of autolysed yeast enhances growth, liver functionality and intestinal morphology in African catfish

A feeding trial was conducted to evaluate the potential of dietary supplementation of autolysed brewer's yeast (AY) on African catfish. The catfish (22.5 ± 1.15 g/fish, 20 fish 33 L/tank) were fed with either of diets (390 g/kg crude protein, 140 g/kg lipid) supplemented with 0, 3, 6 or 10 g/kg AY (n = 3). After 49 days of feeding, the final body weight and metabolic growth rate of the catfish fed 3 g/kg AY (3‐AY) diet were higher than those fed the control diet (p .05) in intestinal perimeter ratio. However, an elevated (p < .05) abundance of goblet cells and intraepithelial leucocytes were found in the intestine of catfish fed 3, 6 and 10 g/kg AY diets, with the highest level of abundance recorded in the mid‐intestine of the catfish fed 3‐AY diet. The results suggest that dietary 3 g/kg autolysed brewer's yeast supplementation improves growth performance of African catfish without deleterious effect on liver functionality and gut morphology

Macroalgae as a sustainable aquafeed ingredient

Macroalgae, commonly known as seaweed, offer a novel and added‐value dietary ingredient in formulated diets for fish. Production of biomass can be achieved without reliance on expensive arable land, as seaweed may be collected from coastal regions or farmed. There are three taxonomic groups represented by the term ‘macroalgae’: Rhodophyta (red), Chlorophyta (green) and Phaeophyta (brown). Like terrestrial plants, nutritional content in macroalgae can vary greatly amongst species, genera, divisions, seasons and locations. Aside from their basic nutritional value, seaweeds contain a number of pigments, defensive and storage compounds, and secondary metabolites that could have beneficial effects on farmed fish. This review appraises the beneficial qualities of these macroalgae compounds and their potential for exploitation in commercial finfish feeds. The current knowledge of the effects of macroalgae inclusion in finfish diets is also addressed. From these >50 fish feeding studies that were analysed, enhancing trends in fish growth, physiology, stress resistance, immune system and fillet muscle quality were reported. However, only a small fraction of algal species have so far been investigated as potential components in finfish diets, and furthermore, this review has identified a number of knowledge gaps that current research has yet to address. To conclude, an appraisal is made of the possible technologies employed to exploit seaweeds to an industrial level through stabilising the algal meal, enhancing the digestibility and functional food properties

Temporal changes in the gut microbiota in farmed Atlantic cod (Gadus morhua) outweigh the response to diet supplementation with macroalgae

Background: Aquaculture successfully meets global food demands for many fish species. However, aquaculture production of Atlantic cod (Gadus morhua) is just 2.5% of total market production. For cod farming to be a viable economic venture specific challenges on how to increase growth, health and farming productivity need to be addressed. Feed ingredients play a key role here. Macroalgae (seaweeds) have been suggested as a functional feed supplement with both health and economic benefits for terrestrial farmed animals and fish. The impact of such dietary supplements to cod gut integrity and microbiota, which contribute to overall fish robustness is unknown. The objective of this study was to supplement the diet of juvenile Atlantic cod with macroalgae and determine the impacts on fish condition and growth, gut morphology and hindgut microbiota composition (16S rRNA amplicon sequencing). Fish were fed one of three diets: control (no macroalgal inclusion), 10% inclusion of either egg wrack (Ascophyllum nodosum) or sea lettuce (Ulva rigida) macroalgae in a 12-week trial. Results: The results demonstrated there was no significant difference in fish condition, gut morphology or hindgut microbiota between the U. rigida supplemented fish group and the control group at any time-point. This trend was not observed with the A. nodosum treatment. Fish within this group were further categorised as either ‘Normal’ or ‘Lower Growth’. ‘Lower Growth’ individuals found the diet unpalatable resulting in reduced weight and condition factor combined with an altered gut morphology and microbiome relative to the other treatments. Excluding this group, our results show that the hindgut microbiota was largely driven by temporal pressures with the microbial communities becoming more similar over time irrespective of dietary treatment. The core microbiome at the final time-point consisted of the orders Vibrionales (Vibrio and Photobacterium), Bacteroidales (Bacteroidetes and Macellibacteroides) and Clostridiales (Lachnoclostridium). Conclusions: Our study indicates that U. rigida macroalgae can be supplemented at 10% inclusion levels in the diet of juvenile farmed Atlantic cod without any impact on fish condition or hindgut microbial community structure. We also conclude that 10% dietary inclusion of A. nodosum is not a suitable feed supplement in a farmed cod diet

The utilisation of European processed animal proteins as safe, sustainable and circular ingredients for global aquafeeds

The global increase in seafood demand has resulted in significant growth in aquaculture production in a wide range of aquatic species. Consequently, this has led to an industry-wide need to find sustainable feed ingredients that would meet the nutritional requirements used in aquafeeds. The associated dependency on plant by-products as the major alternatives has brought concerns to aquaculture through associated carbon footprint, increase deforestation and arable land use to meet the demands of plant proteins and oils, and the constraining effects of plant by-products has on farmed aquatic animal growth and health. Animal by-products (ABPs) are produced as a direct consequence of terrestrial animal production and the associated meat processing industries. The link between feeding meat and bone meal (MBM) and bovine spongiform encephalopathy (BSE) outbreak in Europe during the 1980s resulted in a ban of its use animal feeds. This led to a radical overhaul of the rendering industry, including the use of only low-risk ABP and the development of rendering processes to reduce the risk of prions that causes BSE to enter the food chain. The resulting processed animal proteins (PAPs) are considered safe to be used in farmed animal feeds. This review examines how ABP production has changed due to the BSE outbreak, leading to the current commercially available PAP products for aquafeed use. We evaluated how these products can be effectively used as viable protein sources in aquaculture and examine their limitations and the potential advancements that could lead to a more circular food production system

Barriers in European spiny lobster ( Palinurus elephas ) aquaculture: What we know so far?

Palinurids, also known as spiny lobsters, are high-value seafood, which is economically important for many European and Asian seafood trades. However, the reduction of wild European spiny lobster populations produces a need for developing alternative renewable strategies to meet current and future demands. Aquaculture of spiny lobsters has the potential to become of major economic importance in the coming years with growing markets in Asia, Europe, and America, with Palinurus elephas being a promising candidate species for use in the commercial culture and stock enhancement of natural fisheries. This is due to its shorter larval periods and rapid growth to the critical puerulus stage compared with other spiny lobster species. While we have a basic understanding of the lifecycle and biology of P. elephas, much of this is based on work undertaken on similar species globally. There are many gaps in our knowledge that need to be addressed to make its aquaculture viable with appropriate feeds being an immediate issue as well as many other husbandry-related factors. Previous studies act as a platform providing a baseline for further research and highlighting constraints. Developments in the use of P. elephas are promising due to realistically bridgeable knowledge gaps, the likelihood of producing sustainable food and the high commercial value of spiny lobsters. This review identifies our present state of knowledge and outlines the scope for further research and necessary technological developments to make it a viable contribution towards crustacean aquaculture in Europe

Delivering a nutritionally enhanced tilapia fillet using a pre‐harvest phase omega‐3 thraustochytrids protist enriched diet

Nile tilapia (Oreochromis niloticus) offers an affordable food source to many low-income consumers. However, farmed tilapia has drawn much criticism over the low omega-3 (n-3) and high omega-6 (n-6) lipid levels. Subsequently, it has been questioned whether it is truly healthy food. This study fed tilapia with a specialized “finishing” diet with the inclusion of commercial Thraustochytrids protist biomass and oil before the harvestable fish size. The fish are fed with two different dietary regimes over 6 weeks. One is a commercially available tilapia feed used as a reference. The second diet is composed of an exclusive oil source from Thraustochytrids protist (HI-n3). The results show that HI- n3 has significantly increased the fillet n-3 content by 400% in comparison to commercial diet (COM) after Week 6 of feeding. Specifically, docosahexaenoic acid (DHA, n-3) content is the attributing fatty acid for the n-3 increase. This is particularly evident when DHA is expressed as a percentage of total lipid content. The n-3:n-6 ratio increased in tilapia fed with the HI-n3 diet attributed to the DHA accumulation. The investigation shows that it is possible to favorably “lipid tailor” tilapia before harvest. Practical applications: The practical application of this technique is to enrich farmed tilapia with a high dietary omega-3 (n-3) Thraustochytrids protist oil source for a short-term period before harvesting. It is an objective that the fillet product would be more functional in its nutritional content by supplying more than just high-quality protein for consumers. This would have paramount implications for low-income consumers, where high n-3 oil foods are not readily available or affordable (e.g., landlocked nations). Furthermore, tilapia is widely consumed in China and Southeast Asian countries but is also promoted as a high nutritional value food source in the western hemisphere. This investigation advocates the ability to change the image of this fish species by a simple dietary manipulation. In an era of elevated intake of omega 6 (n-6) fatty acids food sources, n-3 rich fish is a vital balance to counter this negative trend in human health

Drivers of ecological assembly in the hindgut of Atlantic Cod fed a macroalgal supplemented diet

It is difficult to disentangle the many variables (e.g. internal or external cues and random events) that shape the microbiota in the gastrointestinal tract of any living species. Ecological assembly processes applied to microbial communities can elucidate these drivers. In our study, farmed Atlantic cod (Gadus morhua) were fed a diet of 10% macroalgae supplement (Ulva rigida [ULVA] or Ascophyllum nodosum [ASCO] or a non-supplemented control diet [CTRL]) over 12 weeks. We determined the influence of ecological assembly processes using a suite of null-modelling tools. We observed dissimilarity in the abundance of common OTUs over time, which was driven by deterministic assembly. The CTRL samples showed selection as a critical assembly process. While dispersal limitation was a driver of the gut microbiome for fish fed the macroalgae supplemented diet at Week 12 (i.e., ASCO and ULVA). Fish from the ASCO grouping diverged into ASCO_N (normal) and ASCO_LG (lower growth), where ASCO_LG individuals found the diet unpalatable. The recruitment of new taxa overtime was altered in the ASCO_LG fish, with the gut microbiome showing phylogenetic underdispersion (nepotistic species recruitment). Finally, the gut microbiome (CTRL and ULVA) showed increasing robustness to taxonomic disturbance over time and lower functional redundancy. This study advances our understanding of the ecological assembly and succession in the hindgut of juvenile Atlantic cod across dietary treatments. Understanding the processes driving ecological assembly in the gut microbiome, in fish research specifically, could allow us to manipulate the microbiome for improved health or resilience to disease for improved aquaculture welfare and production