The present study investigated effects of dietary inclusion of black soldier fly larvae (BSFL) (
) meal and paste on gut health, plasma biochemical parameters, immune response and skin mucus proteome ...in pre-smolt Atlantic salmon (
). The seven-week experiment consisted of seven experimental diets: a control diet based on fishmeal and plant protein (Control-1); three BSFL meal diets, substituting 6.25% (6.25IM), 12.5% (12.5IM) and 25% (25IM) of protein; two BSFL paste diets, substituting 3.7% (3.7IP) and 6.7% (6.7IP) of protein and an extra control diet with 0.88% of formic acid (Control-2). The 6.25IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, and reduced IgM in distal intestine. The fish fed 12.5IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, had a higher plasma lysozyme content compared to 6.25IM, and tend to increase phagocytic activity in head-kidney macrophages-like cells. On the other hand, 25IM diet improved distal intestine histology, but showed mild-moderate enterocyte steatosis in pyloric caeca, increased IFNγ and reduced IgM in distal intestine. In the case of BSFL paste diets, 3.7IP diet caused mild inflammatory changes in distal intestine, although it reduced enterocyte steatosis in pyloric caeca. The 6.7IP diet reduced enterocyte steatosis in pyloric caeca and improved distal intestine histology. Increasing level of BSFL meal in the diet linearly decreased plasma C-reactive protein, whereas increasing level of BSFL paste linearly increased plasma antioxidant capacity. Dietary inclusion of BSFL meal and paste had minor effects on the expression profile of proteins in skin mucus and no effects on immune markers in splenocytes. BSFL meal showed no negative effect on liver and muscle health as indicated by plasma alanine aminotranseferase, asparate aminotransferase and creatine kinase. The present study showed that replacing conventional protein sources with low to moderate levels of BSFL meal (6.25% and 12.5%) or paste (3.7% and 6.7%) reduced enterocyte steatosis in pyloric caeca, while replacing up to 25% with BSFL meal or 6.7% with paste improved distal intestine histology. Further, dietary inclusion of BSFL meal and paste had minor effects on skin mucus proteome and immune response in Atlantic salmon.
Yeasts are becoming popular as novel ingredients in fish feeds because of their potential to support better growth and concomitantly ensure good fish health. Here, three species of yeasts ...(Cyberlindnera jadinii, Blastobotrys adeninivorans and Wickerhamomyces anomalus), grown on wood sugars and hydrolysates of chicken were subjected to two down-stream processes, either direct heat-inactivation or autolysis, and the feed potential of the resulting yeast preparations was assessed through a feeding trial with Atlantic salmon fry. Histological examination of distal intestine based on widening of lamina propria, showed that autolyzed W. anomalus was effective in alleviating mild intestinal enteritis, while only limited effects were observed for other yeasts. Our results showed that the functionality of yeast in counteracting intestinal enteritis in Atlantic salmon was dependent on both the type of yeast and the down-stream processing method, and demonstrated that C. jadinii and W. anomalus have promising effects on gut health of Atlantic salmon.
Aquaculture feeds have changed dramatically from being largely based on fishmeal (FM) towards increased use of plant protein sources, which could impact the fish's immune response. In order to ...characterize immunomodulatory properties of novel functional ingredients, this study used four diets, one based on FM, a challenging diet with 40% soybean meal (SBM), and two diets containing 40% SBM with 5% of
yeast exposed to different down-stream processing conditions: heat-inactivated (ICJ) or autolysation (ACJ). The immunomodulatory effects of the diets were analyzed in the spleen of Atlantic salmon after 37 days of feeding, using a transcriptomic evaluation by RNA sequencing (RNA-seq) and the detection of specific immunological markers at the protein level through indirect Enzyme-linked Immunosorbent Assay (indirect ELISA). The results showed that SBM (compared to FM) induced a down-regulation of pathways related to ion binding and transport, along with an increase at the protein level of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). On the other hand, while ICJ (compared to FM-group) maintain the inflammatory response associated with SBM, with higher levels of TNFα and IFNγ, and with an upregulation of creatine kinase activity and phosphagen metabolic process, the inclusion of ACJ was able to modulate the response of Atlantic salmon compared to fish fed the SBM-diet by the activation of biological pathways related to endocytosis, Pattern recognition receptor (PPRs)-signal transduction and transporter activity. In addition, ACJ was also able to control the pro-inflammatory profile of SBM, increasing Interleukin 10 (IL-10) levels and decreasing TNFα production, triggering an immune response similar to that of fish fed an FM-based diet. Finally, we suggest that the spleen is a good candidate to characterize the immunomodulatory effects of functional ingredients in Atlantic salmon. Moreover, the inclusion of ACJ in fish diets, with the ability to control inflammatory processes, could be considered in the formulation of sustainable salmon feed.
Aquaculture is one of the most resource‐efficient and sustainable ways to produce animal protein. The Food and Agriculture Organization predicts that cultivated aquatic species will provide around ...53% of the world's seafood supply by 2030. Further growth of intensive farmed aquatic species may be limited by a shortage of feed resources. The aquaculture sector therefore needs to intensify its search for alternative ingredients based on renewable natural resources. A significant increase in production will require an accelerated transition in technology and production systems, better use of natural available resources, development of high‐quality alternative feed resources and exploitation of available space. The present review discusses the urgent need to identify appropriate alternative ingredients for a sustainable future salmonid production. We describe and evaluate the most promising marine ingredients, including low‐trophic species (mesopelagic fish, zooplankton, polychaetes, macroalgae and crustaceans), novel microbial ingredients (bacteria, yeast and microalgae), insects (black soldier fly, yellow meal worm and crickets), animal by‐products (poultry meal, meat and bone meal, blood meal and hydrolysed feather meal) and by‐products from other commercial productions (trimmings and blood). Furthermore, we discuss the available volumes and need for new processing technologies and refining methods to ensure commercial production of nutritionally healthy ingredients. The essential production steps and considerations for future development of sustainable and safe seafood production are also discussed.
In this study, Candida utilis was included as alternative protein source in diets for Atlantic salmon (Salmo salar) parr and the effects on growth performance and distal intestinal (DI) health were ...assessed. The potential of C. utilis to counteract possible adverse effects of a high soybean meal (SBM) diet was additionally assessed by using graded levels of C. utilis in combination with a 40% SBM diet. Six experimental diets were formulated: Fishmeal control (FM); FM with 20% C. utilis (FM20CU); SBM-based diet containing 40% SBM (SBM); three SBM-based test diets, where wheat gluten and starch were substituted with increasing levels of C. utilis of 5%, 10% and 20% (SBM5CU, SBM10CU and SMB20CU, respectively). A total of 2700 Atlantic salmon parr with an average weight of 4.4 g were distributed into 18 tanks and the diets were fed in triplicates. The experiment lasted 28 days and sampling for histology and gene expression analysis was done at the end of the experiment.
The fish grew to an average weight of 14.8 g in 28 days. Fish fed FM20CU obtained a significantly higher specific growth rate (SGR) of 4.59 than the other dietary groups. While fish fed FM and FM20CU displayed normal morphology of the DI, fish fed SBM-based diets showed mild histological changes in the DI that can be related to classical SBM induced enteritis (SBMIE). These changes included reduced height of simple folds and decreased presence of supranuclear vacuoles. The severity of these changes was not altered with increasing levels of C. utilis in the SBM diet. The expression of four of the five selected genes analyzed in the DI were altered by 40% dietary SBM inclusion. Aquaporin 8ab demonstrated the clearest changes among dietary groups, showing down-regulation independent of dietary inclusion of C. utilis. The strong down-regulation of aquaporin has been observed before and may be an indicator for intestinal barrier dysfunction. In conclusion, adding C. utilis to diets for Atlantic salmon parr gave high growth performance without any obvious adverse effects on intestinal health, but were unable to counteract the mild histology changes seen in DI of the SBM fed fish.
•Dietary Candida utilis yeast gave high growth performance and normal intestinal health in Atlantic salmon parr.•Intestinal histology and gene expression in salmon parr fed high soybean meal diets were similar to that of saltwater adapted salmon.•Dietary inclusion of C. utilis did not support normal morphology in distal intestine when combined with 40% soybean meal.
The aim of this study was to investigate how diets containing partially deshelled or whole krill meals affected growth, digestibility of main nutrients, faecal excretion of minerals, fluoride ...accumulation, and organ indices and health parameters in Atlantic salmon (
Salmo salar). Three extruded diets were fed for 100
days to salmon with an average weight of 550
g, distributed into 9 tanks equipped with flow through sea water. The dietary treatments comprised a control diet based on high-quality fish meal (FM) and two experimental diets where the FM was substituted with either partially deshelled krill meal (PDKM) or whole krill meal (WKM). Shell removal reduced the chitin content from 28 to 8
g
kg
−1 dry matter (DM), while fluoride was only reduced from 940 to 631
mg
kg
−1 DM.
Growth rate for fish fed WKM was significantly lower than for salmon fed control diet whereas the PDKM diet did not appear to alter growth during the first feeding period. Digestibility of lipid tended to be higher for PDKM and lower for WKM compared to the FM control. No significant difference was seen for digestibility of nitrogen, but fish fed the FM diet had higher digestibility of threonine, serine, glutamine, histidine and lysine compared to fish fed the WKM diet. No major differences in plasma were seen for triacylglycerols, free fatty acids, glucose, total protein, albumin, globulin, urea, and total bilirubin. Trypsin activities in the pyloric and mid intestine were lower in fish fed the WKM diet compared to FM. Bile acid concentration in the pyloric intestine were significantly lower in fish fed the WKM diet compared to FM and PDKM. Fish fed both diets containing krill meal had signs of mild to moderate nephrosis. To conclude, PDKM could successfully replace FM as a sole protein source for Atlantic salmon, whereas the WKM slightly reduced growth rate compared to the FM and the PDKM diet.
Yeast is a microbial feed ingredient that can be produced from non-food biomasses. Brown seaweed contains high levels of complex carbohydrates that are not digested to any extent by monogastric ...animals but can be used as carbon sources for yeast production. The objective of this study was to investigate how minerals originating from brown macroalgae (Saccharina latissima) are incorporated in Cyberlindnera jadinii yeast and to assess the bioavailability of these different minerals as well as their accumulation into different organs of Atlantic salmon. The yeast C. jadinii was produced on a seaweed hydrolysate mixed with a sugar-rich wood hydrolysate in a 9:1 volume ratio and fed to Atlantic salmon (Salmo salar) in two different experiments: a digestibility experiment with 30% dietary inclusion of yeast and a retention experiment with increasing inclusion of yeast (5, 10, and 20%). Seaweed minerals such as zinc (Zn), copper (Cu), iodine (I), manganese (Mn), and cobalt (Co) were incorporated to a high degree in the yeast. The apparent fecal excretion of minerals was similar in both experiments, in general, with low excretion of, I, bromine (Br), and arsenic (As) (ranging from 18.0% to 63.5%) and high excretion of iron (Fe), Cu, Mn, aluminum (Al), cadmium (Cd) and lead (Pb) (ranging from 56.9% to <100%), despite the different fish size and fecal sampling method. High levels of Cu, I, Br, and Co in the yeast resulted in a linear decrease (p < 0.05) in retention of these minerals in salmon fed increasing levels of yeast. Despite increasing amounts of these minerals in the feed, whole-body levels of Cu and Mn remained stable, whereas whole-body levels of Co, somewhat unexpectedly, decreased with increased dietary yeast inclusion. The Cd from the yeast had low bioavailability but was concentrated more in the kidney (0.038 mg kg−1) and liver (0.025 mg kg−1) than in muscle (0.0009 mg kg−1). The given Cd level in fish strengthens the indication that it is safe to feed salmon with up to 20% inclusion of seaweed yeast without exceeding the maximum limit for Cd of 0.05 mg kg−1 w.w. in fish meat. The level and retention (p < 0.05) of As were lower in the yeast compared to fishmeal. The high level of iodine in S. latissima (3900 mg kg−1) was partly transferred to the yeast, and salmon fed increasing levels of yeast displayed a linear increase in whole-body I content (p < 0.05). There is, however, a need for a growth experiment with larger fish to draw any firm conclusions regarding food safety. Overall, this study shows that yeast grown on hydrolyzed seaweed can be a suitable mineral source for Atlantic salmon, especially when diets are low in fishmeal.
Yeast produced from lignocellulosic biomass has the potential to serve as a high-quality protein source with health benefits, especially during critical stages of the Atlantic salmon life cycle, such ...as during seawater transfer (SWT). In this study, we evaluated the effect of adding 25% Candida utilis yeast to salmon feed on growth performance and overall health by using morphometry, immunohistochemistry, cytokine enzyme-linked immunosorbent assays (ELISA) and gene expression analysis during and after SWT. There were four dietary treatments: 1) control diet in freshwater (FW) and seawater (SW) (Control); 2) control diet in FW and a yeast-based diet in SW (Control/Yeast); 3) yeast-based diet in FW and SW (Yeast); 4) yeast-based diet in FW and a control diet in SW (Yeast/Control). Our results showed that fish fed the yeast diet throughout the FW and SW period achieved higher feed intake and higher growth rate than fish fed the control diet. Morphometric and immunochemical analyses of the distal intestine (DI) revealed decreased length and number of CD3 labeled cells in the simple folds of fish fed control diet, while no changes were observed in fish fed the yeast diet. Furthermore, yeast significantly decreased the secretion of IFNγ, TNFα, IL-1β, IL-8, and modulated the gene expression of aquaporin 8 (aqp8ab), superoxide dismutase (sod1) and major histocompatibility complex 1 (mhc1) in DI, suggesting reduced inflammatory processes in yeast fed fish. These findings indicate that Candida utilis yeast is a promising alternative protein source with functional properties in diets for smolting Atlantic salmon before and after SWT.
•Yeast successfully modified immunosuppressive responses and histological parameters related to seawater acclimation.•Yeast decreased secretion of cytokines in distal intestine as well as decreased the expression of its genes.•Fish fed yeast had better growth performance and feeding behaviour in fresh- and post seawater transfer.
Sustainability concerns associated with protein sources and currently used fishmeal and plant‐based meal have necessitated the quests for novel sustainable ingredients for use in aquafeeds. Yeasts ...have been proposed as sustainable ingredients particularly because of their potential to valorise non‐food lignocellulosic biomass into valuable protein resources. Prior to now, extensive studies exist on the role of yeast cell wall components in modulating health responses of fish. However, research on its use as a major protein source in fish diets is still in its infancy. The current review collates, synthesises and discusses the prospects of five major yeast species as future protein ingredients with respect to their nutritional adequacy in fish. Nutritional quality of Saccharomyces cerevisiae, Cyberlindnera jadinii, Kluyveromyces marxianus, Blastobotrys adeninivorans and Wickerhamomyces anomalus and their use as replacement for fishmeal and soy protein in the diets of Atlantic salmon and rainbow trout are discussed based on three protein quality indices: chemical score, essential amino acid index and ideal protein concept based on the first limiting amino acids, methionine. The crude protein contents of yeast (40–55%) are lower than that of fishmeal, but comparable with soya bean meal. Compared to fishmeal, the different yeast species have favourable amino acid profiles, except for methionine, lysine, arginine and phenylalanine which are the frequently limiting essential amino acids in Atlantic salmon and rainbow trout. This review also presents future area of research and emphasise the need for large‐scale production of yeast at competitive price to constitute a feasible replacement for fishmeal and soy protein in aquaculture.
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