Dietary cholesterol supplementation to a plant-based diet for Atlantic salmon
ABSTRACT: The study evaluated effects of dietary cholesterol (1.5%) in Atlantic salmon fed a plant based diet for 77 days. Cholesterol supplementation did not affect growth or organ weights of Atlantic salmon, but promoted induction of cholesterol and plant sterol efflux in the intestine, whereas sterol uptake was suppressed. Microarray analyses in the liver indicated decreased cholesterol biosynthesis and enhanced conversion to bile acids. The marked effect of cholesterol on bile acid synthesis suggests that dietary cholesterol can be used to stimulate bile acid synthesis in fish. The study clearly demonstrated how Atlantic salmon adjusted metabolic functions in response to the dietary load of cholesterol, and has expanded our understanding of sterol metabolism and turnover that adds to the knowledge of these processes in fish. Atlantic salmon received feeds based on plant ingredients with (CH) and without (K) supplementation of cholesterol. Liver samples were collected after 77 days. Five individuals from each group were analyzed with microarrays, pooled liver sample of salmon fed with commerical fish meal based feed was used as a reference.
Project description:A study was conducted to determine if different levels of vegetable and fish oils can alter antiviral responses of salmon macrophage-like cells (MLCs). Atlantic salmon were fed diets containing 7.38% (FO7) or 5.09% (FO5) fish oil. These diets were designed to be relatively low in EPA+DHA (i.e. FO7: 1.41% and FO5: 1%), but near the requirement level, resulting in no significant change in salmon growth. After a 16-week feeding trial, macrophages isolated from fish in these dietary groups were stimulated by a viral mimic (dsRNA: pIC) or PBS (control) for 24 h. A 44K microarray experiment identified the diet-responsive transcripts between dietary treatments and pIC-responsive transcripts within each group. Overall design: Atlantic salmon were fed for 16 weeks with the FO7 or FO5 diet (4 tanks per diet). Macrophage-like cells were isolated from 2 fish per replicate tank of each dietary group (8 fish from each group in total). The isolated cells from each fish were exposed to PBS (control) or 10 µg ml-1 pIC for 24 h. Samples from 6 individuals (6 PBS and 6 pIC; 12 samples in total per group) in each dietary group were used for microarray experiment. Test samples were labeled with Cy5, whereas the common reference (i.e. a RNA pool of all 24 samples included in microarray experiment) was labeled with Cy3. Each individual test sample was hybridized together with the common reference sample on an array (i.e. 24 arrays in total).
Project description:Current commercially available feeds for salmon are predominantly made of plant ingredients, with consequent changes to the composition and contents of a range of nutrients and other components in the diet. There are concerns that, with these major changes in raw materials, new feeds will affect not only the composition and contents of nutrients, but also the bioavailability and, combined with the limited knowledge of micronutrient requirements for Atlantic salmon, this might impact growth performance and health of the fish. The present study investigated the effects of graded levels of a micronutrient package supplemented to feeds formulated with low levels of marine ingredients and fed to diploid and triploid Atlantic salmon throughout the freshwater phase. Specifically, fish were fed three diets containing low levels of FM and FO and identical in formulation other than being supplemented with 3 levels (L1, 100 %; L2, 200 % and L3, 400 %) of a micronutrient mix formulated as a modification of current nutrient levels reported for salmon. Duplicate groups of diploid and triploid parr were fed the experimental diets from around 30 g to seawater transfer and the effects on growth performance, feed efficiency, biochemical composition, liver histology, hepatic gene expression (transcriptome) and smoltification efficiency determined. Microarray analysis revealed that the hepatic transcriptome profile of diploid fish fed diet L2 was more similar to that observed in triploids fed diet L3 than to those fed L2, suggesting that micronutrient requirements of triploid salmon may differ from levels accepted in diploid salmon. Different levels of micronutrient supplementation affected the expression of key genes involved in lipid metabolism. In particular sterol biosynthesis pathways (steroid and terpenoid backbone synthesis) were down-regulated in both L2-fed diploids and L3-fed triploids when compared with diet L1-fed diploids and triploids, respectively. Gene sets analysis showed an up-regulation of genes involved in immune processes in triploid salmon fed diet L3. Another biological category affected by diet in triploid salmon was genetic information processing. In fish fed diet L3 down-regulation of RNA degradation, proteasome, RNA polymerase, spliceosome and ribosome was observed, suggesting a decrease in protein turnover in this group, which may indicate a decrease in energy expenditure. In addition, one-carbon metabolism was affected by diet in diploid and triploid salmon.
Project description:High-quality sources of protein for the formulation of feeds of carnivorous fish species such as Atlantic salmon are currently being sought. In an earlier screening trial we evaluated for the first time in Atlantic salmon (Salmo salar) the applicability of air-classified faba bean (Vicia faba) protein concentrate (BPC) inclusions in combination with soy protein concentrate (SPC) and fishmeal (FM) using parr as a model. Based on the results in parr in freshwater, the present study tested the hypothesis that BPC can effectively replace SPC as a dietary protein source in post-smolt Atlantic salmon in seawater. Herein we compare three dietary treatments, including BPC0 (no BPC), BPC20 (20% BPC) and BPC40 (40% BPC). Full details on diet formulation are available in the publication.
Project description:The inclusion of intact phospholipids in the diet is essential during larval development and can improve culture performance of many fish species. The effects of supplementation of dietary phospholipid from marine (krill) or plant (soy lecithin) sources were investigated in Atlantic salmon, Salmo salar. First feeding fry were fed diets containing either krill oil supplying phospholipid at 2.6% of diet (named K2.6) or soybean lecithin supplying phospholipid at 2.6 % (S2.6), 3.6 % (S3.6) of diet. A control diet (B) without supplemented phospholipid was also supplied. Fish were sampled at ~ 2.5 g (~1990 ˚ day post fertilization, dpf) and ~10 g (2850 ˚dpf). By comparison of the intestinal transcriptome in specifically chosen contrasts, it was determined that by 2850˚dpf fish possessed a profile that resembled that of mature and differentiated intestinal cell types with a number of changes specific to glycerophospholipid metabolism. It was shown that intact phospholipids and particularly phosphatidylcholine are essential during larval development and that this requirement is associated with the inability of enterocytes in young fry to endogenously synthesize sufficient phospholipid for the efficient export of dietary lipid. In the immature phase (~1990 ˚dpf), the dietary phospholipid content as well as its class composition impacted on several biochemical and morphological parameters including growth, but these differences were not associated with differences in intestinal transcriptomes. The results of this study have made an important contribution to our understanding of the mechanisms associated with lipid transport and phospholipid biosynthesis in early life stages of fish.
Project description:There is an increasing drive to replace fish oil (FO) in finfish aquaculture diets with vegetable oils (VO), driven by the short supply of FO derived from wild fish stocks. Little is known of the consequences for fish health after such substitution. The effect of dietary VO on hepatic gene expression was determined in Atlantic salmon (Salmo salar) byg a cDNA microarray analysis. Post-smolt farmed salmon were reared for x weeks on diets where the FO component of the feed was replaced with one of three different VOs - rapeseed (RO), soybean (SO) or linseed (LO). RNA from five fish fed on each diet was extracted. A total of 20 cDNA microarray hybridisations - TRAITS / SGP Atlantic salmon 17k feature cDNA microarray - were performed - 4 diets (three VO + FO control) x 5 individuals - using a common pooled reference control design. Data were obtained from 19 of the 20 hybridisations.
Project description:BACKGROUND: The use of phytochemicals is a promising solution in biological control against salmon louse (Lepeophtheirus salmonis). Glucosinolates (Gls) belong to a diverse group of compounds used as protection against herbivores by plants in the Brassicaceae family, while in vertebrates, ingested glucosinolates exert health-promoting effects due to their antioxidant and detoxifying properties as well as effects on cell proliferation and growth. The aim of this study was to investigate if Atlantic salmon fed two different doses of glucosinolate-enriched feeds would be protected against lice infection. The effects of feeding high dose of glucosinolates before the infection, and of high and low doses 5 weeks into the infection were studied. METHODS: Skin was screened by 15k oligonucleotide microarray and qPCR. RESULTS: 25% reduction (p < 0.05) in lice counts was obtained in the low dose group and 17% reduction in the high dose group compared to fish fed control feed. Microarray analysis revealed induction of over 50 interferon (IFN)-related genes prior to lice infection. Genes upregulated 5 weeks into the infection in glucosinolate-enriched dietary groups included Type 1 pro-inflammatory factors, antimicrobial and acute phase proteins, extracellular matrix remodeling proteases and iron homeostasis regulators. In contrast, genes involved in muscle contraction, lipid and glucose metabolism were found more highly expressed in the skin of infected control fish. CONCLUSIONS: Atlantic salmon fed glucosinolates had a significantly lower number of sea lice at the end of the experimental challenge. Feeding glucosinolates coincided with increased expression of IFN-related genes, and higher expression profiles of Type 1 immune genes late into the infection. In addition, regulation of genes involved in the metabolism of iron, lipid and sugar suggested an interplay between metabolism of nutrients and mechanisms of resistance. Overall design: Atlantic salmon received feeds enriched in plant derived glucosinolates (Gls), with the approximate GLs content of 7.3 μmol/g and 26.4 μmol/g in the low dose group (LD) or the high dose group (HD), respectively.The treatment groups tested in this part of the study were named: infected C (I-C) infected LD (I-LD) and infected HD (I-HD), in three tank replicates. Skin samples were collected before infection and after 31-35 days of experimental lice infection. In addition, six tanks of fish were used in a parallel feed study to assess the effect of GLs feeding per se (without infection). These groups of fish were named not-infected high dose (NI-HD) and not-infected control (NI-C) respectively. Sampling of skin tissue was performed after 17-18 days of feeding using the same protocol as for the infected fish. Five individuals from each group were analyzed with microarrays, and 4 fish from NI-HD. Pooled skin samples of two salmon from each dietary group were used as a reference.
Project description:Following an infection with a specific pathogen, the acquired immune system of many teleostean fish, including salmonids, is known to retain a specific memory of the infectious agent, which protects the host against subsequent infections. For example Atlantic salmon (Salmo salar), which have survived an infection with a low-virulence infectious salmon anemia virus (ISAV) isolate are less susceptible against subsequent infections with high-virulence ISAV isolates. A greater understanding of the mechanisms and immunological components involved in this acquired protection against ISAV is fundamental for the development of efficacious vaccines and treatments against this pathogen. To better understand the immunity components involved in this observed resistance, we have used an Atlantic salmon DNA microarray and RT-qPCR assays to study the global gene expression responses of preexposed Atlantic salmon (fish having survived an infection with a low-virulence ISAV isolate) during the course of a secondary infection with a high-virulence ISAV isolate Overall design: Atlantic salmon which had survived a primary infection with a low-virulence ISAV isolate (preexposed H5R fish) were reinfected by cohabitation (H5Rc fish) or IP injection (H5Rip fish) with a high-virulence ISAV isolate and compared to preexposed H5R fish non-reinfected and naïve Atlantic salmon infected by cohabitation (Nc fish) with the high-virulence ISAV isolate using 4x44k Agilent arrays. H5Rc fish (n~6) and Nc fish (n~6) were sampled at 20d, 23d, 29d, 41d and 63d following the infection, while H5Rip fish (n~6) were sampled at 6h, 24h, 3d, 10d, 20d and 63d. Microarrays were performed using a 1-color approach
Project description:Infectious diseases among fish present an important economic burden for the aquaculture and fisheries industries around the world. For example, the infectious salmon anemia virus (ISAV) is known to infect farmed Atlantic salmon (Salmo salar), and results in millions of dollars of lost revenue to salmon farmers. Although improved management and husbandry practices over the last few years have minimized the losses and the number of outbreaks, the risk of new virulent isolates emerging is still a looming threat to the viability and sustainability of this industry. An understanding of the host-pathogen interactions at the molecular level during the course of an infection thus remains of strategic importance for the development of molecular tools and efficient vaccines capable of minimizing losses in the eventual case of a new outbreak. Using a 32 k cDNA microarray platform (cGRASP), we have studied various signaling pathways and immune regulated genes, activated or repressed, in Atlantic salmon head-kidney during the course of an ISAV infection. Gene expressions were measured at 5 different time-points: 6h, 24h, 3d, 7d and 16d post infection to get an overall view of changes as they occurred in time. The earliest time points showed only a few differentially expressed genes in infected fish, relative to controls, although as time progressed, many additional genes involved in key defense pathways were up-regulated including MHC type I, beta-2 microglobulin, TRIM 25 and CC-chemokine 19. During the latest stage of the infection process, many genes related to oxygen transportation were under-expressed, which correlates well with the anemia observed prior to death in Atlantic salmon infected with virulent strains of ISAV. Overall design: Atlantic salmon smolts from 2 families of Atlantic salmon were IP injected with either 0.1mL of 10e5 TCID50 mL-1 of virus or 0.1mL of sham solution (L15 culture medium) and divided equally in four 1000 L tanks: 2 duplicate tanks containing ISAV injected fish and 2 duplicate control tanks containing sham solution injected fish. Four fish per family were sampled immediately prior to injection. An additional two fish per family per tank (four fish per family total) were sampled at 6h, 24h, 3d, 7d and 16d post injection. Head-kidney was dissected from each fish and used for microarray analysis. ISAV infected Atlantic salmon were compared to non-infected Atlantic salmon for each time-point.
Project description:Atlantic salmon was fed with diets based on five plant protein sources combined with soyabean saponins. Diets with corn gluten, sunflower, rapeseed and horsebean produced minor effects while combination of saponins with pea protein concentrate caused enteritis and major transcriptome changes in the distal intestine. Overall design: Microarray analyses were perfromed in distant intestine. Individual samples from fish that received saponing were hybridized to pools from salmon fed with the same feeds without saponins.