Low Fish Meal Research Articles

Schizochytrium limacinum Supplementation in a Low Fish-Meal Diet Improved Immune Response and Intestinal Health of Juvenile Penaeus monodon.

The aim of the present experiment was to evaluate the effects of Schizochytrium limacinum supplementation on the immune response, gut microbiota, and health of Penaeus monodon fed a low fish-meal (FM) diet. A diet containing 25% FM was used as a control (Diet A), and three other diets were formulated to contain 15% FM and supplemented with 0, 0.75, and 1.5% S. limacinum (Diet B, C, and D, respectively). The experiment was carried out in quadruplicates (30 shrimp per replicate, average weight 1.01 ± 0.01 g), and the shrimps were fed the test diets to apparent satiation three times daily for 8 weeks. Shrimp fed diet B and D showed lower weight gain than those fed diet A. Supplementation of 0.75% S. limacinum enhanced expression of antioxidative genes (superoxide dismutase and catalase) and immune-response-related genes in hepatopancreas but could not affect the gene expression of immune deficiency in hepatopancreas and Tube in the intestine. A low FM diet induced endoplasmic reticulum swelling of the intestinal epithelial cells, which was alleviated by S. limacinum supplementation. Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry was employed to analyze the changes of hemolymph metabolomics, 49 significantly different metabolites were identified, and lysoPCs, deoxyinosine, inosine, and highly unsaturated fatty acids were lower in fish fed with low FM diets. Intestinal microbial diversity was lower in shrimp fed Diet B than those fed the control diet. Dietary supplementation of 0.75% S. limacinum increased intestinal microbial diversity of shrimp and decreased the ratio of pathogenic bacterium (Thalassotalea and Tenacibaculum). These results indicated that supplementing S. limacinum into a low FM diet improves the growth performance, immune response, and intestinal health of P. monodon. The optimum inclusion level of seems to be 0.75% of diet.

Effects of different feeding frequencies on growth, feed utilisation, digestive enzyme activities and plasma biochemistry of gilthead sea bream (Sparus aurata) fed with different fishmeal and fish oil dietary levels

In the context of Mediterranean aquaculture many efforts have been made in terms of reducing marine-derived ingredients in aquafeed formulation. On the other hand, little attention has been paid to the manipulation of feeding frequency at the on-growing phase, where the high costs related to feeding procedures and the optimisation of feed efficiency and fish health are key aspects for the economic and environmental sustainability of the production cycle. The effects of different feeding frequencies (F) (1F) one meal day−1, (2F) two meals day−1, (3F) three meals day−1 on growth, digestive enzyme activity, feed digestibility and plasma biochemistry were studied in gilthead sea bream (Sparus aurata, L. 1758) fed with high (FM30/FO15, 30% fishmeal FM, 15% fish oil, FO) and low (FM10/FO3; 10% FM and 3% FO) FM and FO levels. Isonitrogenous and isolipidic extruded diets were fed to triplicate fish groups (initial weight: 88.3 ± 2.4 g) by a fixed ration over 109 days. No significant effects of feeding frequency on overall performance, feed efficiency and feed digestibility during the on-growing of gilthead sea bream fed high or low fishmeal and fish oil dietary level were observed. Pepsin activity showed an apparent decrease in fish receiving more than one meal a day which was not compensated by an increased production of alkaline proteases (either trypsin or chymotrypsin), particularly in fish fed on low FM. Although there were no effects on growth and feed utilisation at increasing feeding frequency, trypsin decreased significantly with an increasing number of meals only under low FMFO diet. Thus, it seemed that consecutive meals could have amplified the potential trypsin inhibitor effect of the vegetable meal-based diet adopted. Most of the plasma parameters related to nutritional and physiological conditions were not affected by feeding frequency, however an effect on electrolytes (Na+, Cl), cortisol and creatinine was observed. The higher level of plasma creatinine detected in fish fed a single daily meal with high FMFO level seems to be within physiological values in relation to the higher protein efficiency observed with this diet. However, it will require further attention to exclude a possible overload of kidney functionality. According to the results, gilthead sea bream seems able to maximize feed utilisation regardless of the number of meals, and this could be a useful indicator for planning feeding activity at farm level to optimise growth of fish and costs of feeding procedures.

Choline and phosphatidylcholine, but not methionine, cysteine, taurine and taurocholate, eliminate excessive gut mucosal lipid accumulation in Atlantic salmon (Salmo salar L)

Excessive enterocyte lipid accumulation, with the suggested term lipid malabsorption syndrome (LMS), is frequently observed in Atlantic salmon (Salmo salar L), in small fish in fresh water as well as in large fish in seawater. The symptoms indicate insufficient supply of components involved in lipid assimilation. The questions addressed in the present work were whether dietary supply of components involved in phospholipid and sterol metabolism might prevent LMS. Atlantic salmon (35 fish, 330 g per 600 L tank) were fed a low fish meal diet (LF) as such or supplemented with taurocholate at two levels (3.5 and 6.9 g/kg), cholesterol (2.0 g/kg), taurine (0.8 g/kg), phosphatidylcholine (15.1 g/kg), choline (3.7 g/kg), cysteine (0.8 g/kg) or methionine (1.0 g/kg). A high fish meal diet (HF) was also included. The overall growth rate of the fish was high (TGC>4.2) with no significant effects of diet. Fish fed the LF diet showed increased relative weight of the pyloric and mid intestine and excessive lipid accumulation in the enterocytes, characteristics which were nearly absent in fish fed the HF diet and the LF diet supplemented with choline and phosphatidylcholine. The phosphatidylcholine supplemented diet showed significantly higher lipid digestibility than the LF diet. None of the other supplements eliminated the signs of excessive enterocyte lipid accumulation. Phosphatidylcholine down-regulated pcyt1a, involved in the phosphatidylcholine synthesis, and both choline and phosphatidylcholine induced apoaIV, important in lipoprotein assembly, and markedly suppressed the lipid droplet marker plin2. Methionine supplementation did not stimulate endogenous synthesis of choline. Cholesterol supplementation suppressed sterol uptake and de novo cholesterol synthesis, and induced sterol efflux from the intestinal mucosa. Taurocholate and taurine induced their respective metabolic pathways. All feed supplements, in particular cholesterol and cysteine, down-regulated genes related to antiviral, chemokine, antigen presentation, immunoglobulinfunctions, as well as of extracellular proteases. The results of this study confirm the results from our previous study showing that choline or phosphatidylcholine is a necessary ingredient in low fish meal diets.

Evaluation of shrimp or tilapia protein hydrolysate at graded dosages in low fish meal diet for olive flounder (Paralichthys olivaceus)

Evaluation of shrimp or tilapia protein hydrolysate at graded dosages in low fish meal diet for olive flounder (<i>Paralichthys olivaceus</i>)

Dietary micronutrient supplementation in low fishmeal based diets for optimum growth and immune status of European sea bass (Dicentrarchus labrax) juveniles

The present study aimed to evaluate the optimal dietary micronutrient supplementation of plant-based diets for juvenile European sea bass. A 90-day feeding trial was performed, where fish were fed a high fishmeal (FM) based diet (62% DM; positive control) or low FM diets (12.5% FM and krill meal), supplemented with increasing levels of a micronutrient mixture (Nutrient Package, NP) consisting of vitamins, minerals and other micronutrients. The supplementation levels ranged from 0% (no supplementation, negative control) to 400%, where 100% supplementation level corresponded to the requirement levels recommended for other fish species. Fish growth and feed performance (SGR, DGI, FCR, PER) were significantly impaired at levels NP0 and NP25 compared to the FM control. Body Fe and Zn concentrations were positively affected by the graded levels of the NP, while Mn and Se concentrations remained stable. Growth parameters were particularly correlated to body Fe and Zn, while immune parameters were mainly correlated to body Zn. Significant immunosuppression was evidenced (concerning the respiratory burst activity) when low FM diets were not supplemented with NP. High inclusion levels of the NP showed a negative impact on lysozyme activity. Histological examinations did not reveal any significant effects on gills, gut and liver morphology. At identical NP supplementation level (50%), fish fed low and high FM diets showed similar growth and innate immunity suggesting that long-term feeding with plant-based diets do not significantly affect the fish when adequate minerals and vitamins supplementation is provided. Quadratic regression analysis showed that the inclusion of the NP between 260 and 300% improves growth and immune parameters of fish fed low-FM diets as well as Zn body incorporation. Overall, the present study suggested the positive impact of NP supplementation of PM-based diets on both fish growth and health but future NP could include less Mn, more Fe, closer to levels obtained in fish fed FM (245 mg·kg−1), and Zn at 122 mg·kg−1.

Effect of dietary differences on changes of intestinal microbiota and immune-related gene expression in juvenile olive flounder (Paralichthys olivaceus)

This study was carried out to investigate the effect of dietary differences on intestinal microbial population alteration and its relationship to immune-related gene expression in juvenile olive flounder (Paralichthys olivaceus). Initially, flounder were divided into three groups and supplemented with fishmeal diet (FM), fishmeal replaced by plant protein (termed low-fishmeal (LFM)), and Bacillus sp. SJ-10 probiotic-inoculated LFM (Pro) for 4 weeks. At the start (Initial group) and after completing the feeding trial, intestines were subjected to microbiota analysis and immune-related gene expression. The results of the intestinal microbiota analysis demonstrated that the FM and LFM groups' microbial richness (Chao1, ACE, and Jackknife) and diversity (Shannon and Simpson) did not differ significantly (P > .05) compared to the Initial group. However, the Pro group exhibited increased (P < .05) richness compared to all other groups, but its diversity was lower than that of the Initial group. A similar alteration phenomenon was also found in community composition between these two groups. At the phylum level, the most abundant phylum was Proteobacteria for all groups, but the second most abundant phylum in the Initial and Pro groups was Bacteroidetes, whereas in the FM and LFM groups, it was Firmicutes. An additional analysis of genus-level community composition and prediction of functional composition analysis showed differences among the groups. In the intestine, the transcription of interleukin (IL)-10 and IL-1β was increased more in the LFM and Pro groups compared to the FM group. IL-6 was increased only in the Pro group, and tumor necrosis factor-α (TNF-α) gene expression did not differ significantly among the groups. Therefore, we concluded that dietary changes affect intestinal microbiota composition and immune-related gene expression; in particular, diets containing probiotics can lead to greater change during the same feeding period.

Effect of soybean antigenic protein on feed palatability of fishmeal replaced diets for obscure puffer (Takifugu fasciatus) and the alternation of diet preference by domestication

Ingredient Y-maze choice test, feed intake test and rare earth elements trace test were conducted in obscure puffer (Takifugu fasciatus) to study whether soybean antigenic protein would affect diet palatability when fishmeal was partially replaced by soybean products. Another eight-week domestication trial was conducted to research the possible alternation of such diet preference. In Y-maze test, both aqueous and ethanol solutions of five ingredients (fishmeal, soybean meal, fermented soybean meal, casein, and antigenic protein) were used to study the ingredient preference. Four practical diets (FMH-diet with high fishmeal, FML-diet with low fishmeal, FMLF-diet with 18.56% fishmeal replaced by fermented soybean meal, FMLS-diet with 18.56% fishmeal replaced by soybean meal) and four semi-purified diets (AP0, AP5, AP8, AP12.5) containing corresponding levels of soybean antigenic protein) were all or partially used in feed intake test and rare earth elements trace test. The results showed that the ingredient preference differed with aqueous solutions and ethanol solutions. Feed intake ratio of FMLF was significantly higher than FMH and least in FMLS, AP0 was significantly higher than AP12.5 for undomesticated fish. In rare earth element trace test, before domestication, puffer showed higher preferences of FML than FMLF and FMH and least in FMLS; after 8-week-domestication, all groups showed higher preferences to FMLS than FML and FMLF, least in FMH. In semi-purified diet groups, before domestication, the preference decreased as dietary antigenic protein increase; after domestication, all groups showed higher preferences to AP8 and least in AP12.5. These indicated that undomesticated obscure puffer had higher preference to fermented soybean meal than soybean meal. Antigenic protein might be contributed to such preference, and domestication increased the preference of puffer to diet containing 8% soybean antigenic protein. Thus, domestication can be a potential method to improve the acceptance of puffer to diet with fishmeal replaced by soybean products.

Effects of fish origin probiotics on growth performance, immune response and intestinal health of shrimp (Litopenaeus vannamei) fed diets with fish meal partially replaced by soybean meal

This study was conducted to evaluate the application of four fish origin probiotics to relieve the side effects induced by SBM in shrimp. Shrimps were fed with high fish meal diet (C0, positive control containing 500 g/kg FM and 0 g/kg SBM), low fish meal diet (C, control containing 250 g/kg FM and 340 g/kg SBM) or the control diet (C) supplemented, respectively, with 1.0 × 10⁸ CFU/g Bacillus pumilus SE5 (T1), Psychrobacter sp. SE6 (T2), Enterococcus faecium MM4 (T3) or Bacillus claussi DE5 (T4). After 6 weeks of feeding, the growth performance, hepatopancreatic digestive enzymes, intestinal histological structure and immune parameters were determined. The results showed that compared with high FM group (C0), significantly lower WGR and SGR as well as higher FCR were observed in the low FM group (C) (p < .05). Compared with the control, significantly lower FCR was observed in treatment T1 (p < .05), but not in treatments T2–T4. Protease, amylase and lipase activities in all the treatments (T1‐T4) were significantly higher than the control (p < .05). GOT and GPT activities in the control were significantly lower than the C0 (p < .05), while higher MDA level was recorded in the control (p < .05). Meanwhile, higher GPT activities were observed in treatments T1‐T4 compared with the control (p < .05). Compared with the C0, lower SOD, ACP and AKP activities were observed in the control. Significantly improved SOD and AKP activities were observed in all probiotic feeding groups compared with the control (p < .05). The control diet led to significant reduction of intestinal wall thickness and villus height compared with the C0 (p < .05), while significantly higher intestinal wall thickness and villus height were exhibited in all the probiotic groups compared with the control (p < .05), except intestinal wall thickness in treatment T3. Thus, these results demonstrated that the four fish origin probiotic strains could relieve the side effects induced by high level of SBM in shrimp, while probiotic B. pumilus SE5 showed the best performance.

Assessment of dietary supplementation with galactomannan oligosaccharides and phytogenics on gut microbiota of European sea bass (Dicentrarchus Labrax) fed low fishmeal and fish oil based diet.

There is an increasing interest from the aquafeed industry in functional feeds containing selected additives that improve fish growth performance and health status. Functional feed additives include probiotics, prebiotics, organic acids, and phytogenics (substances derived from plants and their extracts). This study evaluated the effects of dietary inclusion of a mucilage extract rich in galactomannan oligosaccharides (GMOS), a mixture of garlic and labiatae-plants oils (PHYTO), and a combination of them (GMOSPHYTO), on gut microbiota composition of European sea bass (Dicentrarchus labrax) fed with a low fishmeal (FM) and fish oil (FO) diet. Three experimental diets and a control diet (plant-based formulation with 10% FM and 6% FO) were tested in a 63-days feeding trial. To analyze the microbiota associated to feeds and the intestinal autochthonous (mucosa-adhered) and allochthonous (transient) microbial communities, the Illumina MiSeq platform for sequencing of 16S rRNA gene and QIIME2 pipeline were used. Metabarcoding analysis of feed-associated bacteria showed that the microbial communities of control (CTRL) feed deeply differed from those of experimental diets. The number of reads was significantly lower in CTRL feed than in other feeds. The OTU (operational taxonomic unit) number was instead similar between the feeds, ranging from 42 to 50 OTUs. The variation of resident gut microbiota induced by diet was lower than the variation of transient intestinal microbiota, because feedstuffs are a major source of allochthonous bacteria, which can temporarily integrate into the gut transient microbiome. However, the composition of transient bacterial communities was not simply a mirror of feed-borne bacteria. Indeed, the microbial profile of feeds was different from both faecal and mucosa profiles. Our findings suggest that the dietary inclusion of GMOS (0.5%) and PHYTO (0.02%) in a low FM and FO diet induces changes in gut microbiota composition of European sea bass. However, if on allochthonous microbiota the combined inclusion of GMOS and PHYTO showed an antagonistic effect on bactericidal activity against Vibrionales, at mucosa level, only GMOSPHYTO diet increased the relative abundance of Bacteroidales, Lactobacillales, and Clostridiales resident bacterial orders. The main beneficial effects of GMOS and PHYTO on gut microbiota are the reduction of coliforms and Vibrionales bacteria, which include several potentially pathogenic species for fish, and the enrichment of gut microbiota composition with butyrate producer taxa. Therefore, these functional ingredients have a great potential to be used as health-promoting agents in the farming of European sea bass and other marine fish.

Evaluation of seven different functional feed additives in a low fish meal diet for olive flounder, Paralichthys olivaceus

In an eight-week feeding trial, encapsulated sodium butyrate (ESB), gamma-aminobutyric acid (GAB), selenium-yeast (SeY), yeast extract nucleotides (YEN), yucca meal (YUM), song-gang stone (SGS) and protease (PRT) were evaluated as functional feed additives in a low fishmeal (FM) diet for olive flounder Paralichthys olivaceus. Eight experimental diets were fed to 5.26 ± 0.17 g (mean ± SD) juvenile olive flounder in triplicates. A low-FM basal diet without feed additive was considered as control (CON); seven other diets were prepared by adding 4 g ESB, 158 mg GAB, 2 g SeY, 4 g YEN, 1.5 g YUM, 4 g SGS, and 175 mg PRT per kg of basal diet. Weight gain, specific growth rate, feed efficiency, and protein efficiency ratio of fish fed diets YEN, GAB, and SGS were significantly higher than those of fish fed CON diet (P < .05). Superoxide dismutase activity of fish fed YEN and myeloperoxidase (MPO) and nitroblue tetrazolium (NBT) of fish fed YEN, GAB, SGS, ESB, and YUM were significantly higher than those of fish fed CON diet. Whereas, there were no significant differences in non-specific immune responses among fish fed YEN, GAB, SGS, ESB, and YUM and diets (P > .05). Heat shock protein 70 gene expression of fish fed YEN and SeY was significantly higher than those of fish fed the CON diet. Intestinal villi length of fish fed YEN, GAB, SGS, and ESB was significantly higher than those of fish fed CON. Also, intestinal trypsin activity of fish fed YEN, GAB, SGS, ESB, and PRT was significantly higher than those of fish fed CON diet (P < .05). After seven days of challenge test, fish fed diets YEN, GAB, SGS, PRT, and YUM had higher cumulative survival than those of fish fed CON diet. In conclusion, YEN, GAB, and SGS could have beneficial effects on growth and feed utilization performance, MPO and NBT activity, intestinal villi length, intestinal trypsin activity, and cumulative survival of olive flounder fed low-FM diets.

Dietary taurine improves muscle growth and texture characteristics in juvenile turbot (Scophthalmus maximus)

A 70-day feeding trial was conducted to analyze the effects of dietary taurine on the muscle growth and texture characteristics in juvenile turbot (Scophthalmus maximus). For the feeding trial, five experimental diets were formulated. The two control diets were designed as follows: the positive control diet (C+) with 60 % of dietary fish meal, the negative control diet (C-) with 45 % of dietary fish meal. Based on the C-, 0.4 %, 1.2 % and 2.0 % of dietary taurine were supplemented, respectively, to formulate the other three experimental diets (T1, T2 and T3, respectively). Results showed that, in regard to the muscle fiber frequency distribution, diameter class 20 was significantly higher in all the dietary taurine supplemented groups than that in the two control groups. Muscle fibers density was significantly higher in 1.2 % of dietary taurine supplemented group than that in the other all groups. The muscle in the T2 group had the highest adhesiveness, and that in the T3 group had the highest hardness. The group with 1.2 % of dietary taurine supplementation had the significantly highest values of the total hydroxyproline (0.48 mg/g) and the total collagen (3.84 mg/g) among all the groups. In conclusion, 1.2 % of taurine supplementation in low fish meal (45 %) diet showed the significantly higher hyperplasia fiber growth and textural properties in turbot muscle.

Prebiotics and phytogenics functional additives in low fish meal and fish oil based diets for European sea bass (Dicentrarchus labrax): Effects on stress and immune responses

The use of terrestrial raw materials to replace fish meal (FM) and fish oil (FO) in marine fish diets may affect fish growth performance and health. In the last years functional additives have been profiled as good candidates to reduce the effects on health and disease resistance derived from this replacement, via reinforcement of the fish immune system. In the present study, three isoenergetic and isonitrogenous diets with low FM and FO (10% and 6% respectively) were tested based on supplementation either with 0.5% galactomannanoligosaccharides (GMOS diet) or 0.02% of a mixture of essential oils (PHYTO diet), a non-supplemented diet was defined as a control diet. Fish were fed the experimental diets in triplicate for 9 weeks and then they were subjected to a stress by confinement as a single challenge (C treatment) or combined with an experimental intestinal infection with Vibrio anguillarum (CI treatment). Along the challenge test, selected stress and immunological parameters were evaluated at 2, 24 and 168h after C or CI challenges. As stress indicators, circulating plasma cortisol and glucose concentrations were analyzed as well as the relative gene expression of cyp11b hydroxylase, hypoxia inducible factor, steroidogenic acute regulatory protein, heat shock protein 70 and heat shock protein 90 (cyp11b, hif-1α, StAR, hsp70 and hsp90). As immune markers, serum and skin mucus lysozyme, bactericidal and peroxidase activities were measured, as well as gene expression of Caspase-3 (casp-3) and interleukin 1β (il-1ß).The use of functional additives induced a significant (p < 0.05) reduction of circulating plasma cortisol concentration when confinement was the unique challenge test applied. Supplementation of PHYTO induced a down-regulation of cyp11b, hif-1α, casp-3 and il-1β gene expression 2h after stress test, whereas StAR expression was significantly (p < 0.05) up-regulated. However, when combination of confinement stress and infection was applied (CI treatment), the use of PHYTO significantly (p < 0.05) down-regulated StAR and casp-3 gene expression 2h after challenge test, denoting that PHYTO diet reinforced fish capacity of stress response via protection of head kidney leucocytes from stress-related apoptotic processes, with lower caspase-3 gene expression and a higher il-1β gene expression when an infection occurs. Additionally, dietary supplementation with GMOS and PHYTO compounds increased fish serum lysozyme after infection. Both functional additives entailed a better capability of the animals to cope with infection in European sea bass when fed low FM and FO diets.

Evaluation of Antarctic krill ( Euphausia superba ) meal supplementation in diets for olive flounder ( Paralichthys olivaceus )

The supplemental effect of Antarctic krill meal (KM) into a low fish meal (FM) diet was evaluated for olive flounder (Paralichthys olivaceus). A 56% FM-based diet was regarded as a high FM inclusion diet (HFM), and a low-FM diet (LFM) was prepared by replacing 50% FM from the HFM. Four other diets were prepared by supplementing 3%, 6%, 9% and 12% KM into the LFM diet gradually replacing soy protein concentrate and tankage meal (designated as KM3, KM6, KM9 and KM12 respectively). Quadruplicate groups of fish were fed one of the diets for 12 weeks. The growth performance and feed utilization efficiency were improved by the dietary KM supplementation. Digestibility of dietary protein and dry matter was increased by the KM3-9 diets. Haematocrit and haemoglobin were increased by KM supplementation. The innate immunity and antioxidant capacity assessed by Ig, antiprotease, lysozyme, GPx and SOD and the condition factor of fish were significantly increased by KM3-9 diets. Moreover, goblet cell counts, villi length and fillet yield of fish were significantly improved by all the KM-containing diets (KM3-12). A 25-day-long challenge test with the Edwardsiella tarda pathogen showed that the cumulative mortality was higher in fish fed the LFM diet than in fish fed the HFM or KM-supplemented diets. The results indicate that dietary KM supplementation in a LFM diet can increase growth performance and feed utilization efficiency, diet digestibility, intestinal development and functions, innate immunity and disease resistance of olive flounder. The recommended level of KM inclusion in a LFM diet seems to be 6.6% according to quadratic regression analysis.

Effects of dietary nucleotides on growth, survival and metabolic response in whiteleg shrimp, Litopenaeus vannamei against ammonia stress condition

This trial was conducted to evaluate the effects of nucleotides on growth of whiteleg shrimp, Litopenaeus vannamei, and the survival and metabolic responses to ammonia stress test. Experimental diets were as follows: low fish meal diet (LFMD), and four LFMD test diets, each supplemented with 0.1% guanosine monophosphate (GMP), 0.1% inosine monophosphate (IMP), 0.1% mixture of GMP and IMP and 0.1% mixture of GMP, IMP, uridine monophosphate (UMP) and cytidine monophosphate (CMP). The shrimp specimens (initial body weight: 0.99 ± 0.01 g) were randomly allocated into five groups and fed four times daily for 8-weeks. After the trial, final body weight was recorded and haemolymph was withdrawn for haematological analysis. The shrimp was then challenged with 70 mg/L ammonia (LC50) for 10 days. Survival and haemolymph of the shrimp were taken after exposure to ammonia. The highest growth performance was observed in the shrimp fed diet supplemented with GMP (p < .05), while survival was not influenced by the test diets in the feeding trial. In the ammonia challenge test, the highest survival was observed in the shrimp fed GMP supplemented diet compared to others. The plasma protein, glucose and cholesterol levels increased in all the treatments while triglycerides level decreased post challenge. Cortisol level recovered at day 10th after the challenge. Shrimps fed with nucleotides diets showed higher protein and glucose level compared to control groups post challenge. In general, nucleotides supplemented in the diet enhanced growth, improved stress resistance while modulating the haemolymph metabolites in L. vannamei under ammonia stress.

Microalgal Schizochytrium limacinum Biomass Improves Growth and Filet Quality When Used Long-Term as a Replacement for Fish Oil, in Modern Salmon Diets

Aquaculture contributes to global food security but sustainable aquaculture development in terms of biodiversity impacts requires the establishement of viable solutions in replacement of the fisheries-based components in aquafeeds. In the current work, pit-tagged Atlantic salmon individuals were grown, from fresh water (18g body weight) to salt water in tanks (up to 800g body weight), on diets with low fish meal (10%) and 1-1.25% total n-3 LC-PUFA levels balanced acccross the experimental diets. Dietary n-3 LC-PUFAs were supplemented by 1) fish oil (FO), 2) Schyzochytrium limacinum biomass (ScB) or 3) a mix of the two (FO/ScB). Further, the fish from all treatments were mixed and redistributed in sea cages reared to slaughter (ca. 3kg body weight) on either FO or ScB. As fish oil was rich in both EPA and DHA and ScB was rich in DHA ands nearly devoid of EPA, the experimental diets differed significantly in DHA/EPA ratio (0.8 vs 10.5 in average for FO and ScB, respectively). ScB treatment fish grew to significantly higher body weight in the end of the experiment (2.8kg vs 3.3kg, for FO and ScB, respectively) but similar FCR, survival rate and biometric indexes as compared to the FO groups. ScB fish contained higher levels of EPA+DHA in the fillet but lower in the liver, and better fillet pigmentation already from the tank phase of the experiment as determined chemically, by salmonfan and a trained sensory panel, and lower prevalence of melanin spots at slaughter. The trained sensory panel found no differences in flavor or odour in the fillets from the different dietary groups, however fillets in the FO group were percieved as softer and juicier compared to ScB. The pre-diets up to 800 g body weight had minor effects on fish performance. Global transcriptomics in liver and intestinal tissues revealed significant dietary effects on the expression of immune modulating, as well as ion, lipid, protein and xenobiotic metabolism genes.

Black soldier fly larvae meal as a protein source in low fish meal diets for Atlantic salmon (Salmo salar)

This study determined the optimal dietary inclusion level of black soldier fly larvae meal (BSFM) on the digestibility and growth of Atlantic salmon (Salmo salar). In the digestibility experiment, salmon were fed diets that contained a 70:30 blend of reference diet to test ingredient, comparing BSFM, soy protein concentrate, and corn protein concentrate as the test ingredients. In the growth study, salmon (mean initial weight 2.8 ± 0.1 g fish−1), were fed diets containing 0.0 g kg−1 (control), 100 g kg−1, 200 g kg−1 and 300 g kg−1 BSFM. Four hundred and eighty fish were held in a flow-through freshwater system, with 30 fish / tank (30L), 4 tanks / diet. Salmon were fed for 112 days with measurements recorded every 28 days. Digestibility coefficients of BSFM was generally over 75%, with dry matter and gross energy showing higher coefficients in BSFM than CPC and SBM. Mineral digestibility was generally higher in BSFM compared with CPC and SBM. Salmon fed up to 200 g kg−1 showed similar growth performance to salmon fed the control diet. However, salmon fed 300 g kg−1 BSFM diet gained significantly less weight, had the lowest SGR, TGC and the highest FCR than salmon fed any other treatment, while all other treatments were not different from each other (p < .01). The PER was highest in salmon fed the 300 g kg−1 BSFM diet compared to salmon fed the control and 200 g kg−1 BSFM, but did not differ from salmon fed 100 g kg−1. Feed consumption was the same among treatments. Including BSFM at 200 g kg-1 in diets for Atlantic salmon shows promise as a complementary protein source in low fish meal, high plant protein diets.

Dietary effect of low fish meal aquafeed on gut microbiota in olive flounder (Paralichthys olivaceus) at different growth stages.

This study was conducted to investigate the long‐term effect of a low fish meal (FM) diet comprising plant‐based protein sources (PPS) on changes of gut microbial diversity in olive flounder (Paralichthys olivaceus) over the course of life. Two experimental diets were prepared to contain 74% FM (control) or 52% FM with 22% PPS (30% FM replacement, FM30). Fish were fed one of the two experimental diets for 8 months, and we collected the midgut contents to analyze the gut bacterial community by Illumina MiSeq based on the metagenomic sequences in the V3–V4 regions of 16S rRNA. We found that there were nine dominant phyla, which in turn presented Proteobacteria, Firmicutes, and Actinobacteria as the three major phyla in the gut microbiota of the flounder. At genus level, the dominant genera were Delftia, Prevotella, and Chthoniobacter at the juvenile stage (below 100 g/fish); Chthoniobacter, Bacillus, and Bradyrhizobium at the grower stage (400 g/fish); Chthoniobacter, Bacillus, and Delftia at the subadult stage (800 g/fish); and Lactobacillus and Prevotella at the adult stage (over 1,000 g/fish). The microbial diversity in olive flounders arched from the juvenile and subadult stage and reached a plateau thereafter. The fish fed the FM30 diet significantly had an increased abundance of Lactobacillus and Photobacterium and had less abundance of Prevotella and Paraprevotella than the control. However, the effect of dietary PPS was not significant on total microbial richness, indicating no negative effect as feed sources on the intestinal microbiota in olive flounder. These results indicate that the life stage of olive flounder is more important in modulating intestinal microbiota than is the diet. It could also be concluded that dietary PPS might be used as a potential fish meal alternative without any compromising effects on microbial diversity of olive flounder for long‐term feeding.

The effect of replacement of fish meal with Amino Acids and Optimized Protein Levels in the diet of the Nile Tilapia Oreochromis niloticus.

This study was conducted to determine an appropriate replacement of fishmeal with amino acids (AAs) and optimized protein levels in practical diets for Oreochromis niloticus with mean initial body weight 12.52±0.63g. Six experimental and a control diet (total 7 diets) divided into two groups, and a control diet (D1) containing 32% protein. The first group contained three diets that included different dietary protein levels, viz. 20 (D2), 25 (D3), and 30% (D4) with AAs when replacing fishmeal by plant protein sources. In the second group, the diets were contained 20 (D5), 25 (D6), and 30% (D7) without AAs. The best growth performance was achieved in fish fed with diet D1. Total feed intake was increased with an increase in dietary protein level with AAs. The specific growth rate showed a similar pattern with a significant difference between control, D4 and D7 compared to other groups. The feed conversion ratio decreased when protein levels in the diets increased. The protein efficiency ratio showed a similar performance, with a slight increase between the control diet and diets with AAs. However, insignificant differences (P>0.05) were observed between diets with and without AAs. An economic evaluation indicated that inclusion of low fishmeal in tilapia diets reduced the price/kg of diets compared to control.

The effects of different fishmeal level diets with or without phytase supplementation on growth performance, body composition, digestibility, immunological and biochemical parameters of juvenile hybrid sturgeon ( Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂)

A 12‐week growth trial was conducted to evaluate the effect of low fishmeal and phytase replacing inorganic phosphorus on juvenile hybrid sturgeon (Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂). Four experimental diets were designed as FM100p, FM100, FM250p and FM250, which represented 10% and 25% fishmeal with or without phytase, respectively. The results showed that although growth parameters had no significant difference in all treatments, low fishmeal obviously decreased the culture cost of hybrid sturgeon. Lipid content of body composition was obviously increased in low fishmeal treatments (p < .05). The interaction of low fishmeal and phytase significantly enhanced apparent digestibility coefficients of crude protein (p < .05). Two‐way ANOVA analysis showed that input and output of phosphorus were significantly affected by fishmeal level, phytase and interaction of both factors (p < .05). For the immunological and hepatic function parameters, fishmeal level and phytase had significant effects on the activities of lysozyme, myeloperoxidase, malondialdehyde, alanine aminotransferase, lactate dehydrogenase and alkaline phosphatase (p < .05). The present study potentially justifies that a diet containing 10% fishmeal can be used for hybrid sturgeon. Moreover, replacement of monocalcium phosphate by phytase not only has no adverse effect on the growth of hybrid sturgeon, but also reduces phosphorus emission and protects aquaculture environment.

Taurine modulates hepatic oxidative status and gut inflammatory markers of European seabass (Dicentrarchus labrax) fed plant feedstuffs-based diets.

This study aimed to evaluate the effect of taurine (tau) supplementation to low fishmeal (FM) diets on growth performance, oxidative status, and immune response of European seabass juveniles. Four isoproteic (46% crude protein) and isolipidic (19% crude lipid) diets were formulated to contain either 25 or 12.5% FM and a mixture of plant feedstuffs, supplemented or not with 1% tau. Twelve groups of 20 fish (IBW = 9.4g) were fed each diet for 9weeks. Reduction of dietary FM from 25 to 12.5% impaired growth performance, feed efficiency, and protein efficiency ratio but had no effect on nitrogen retention (% N intake). Independently of FM level, dietary tau supplementation improved growth performance and nitrogen retention without affecting feed efficiency. Dietary FM level reduction increased liver G6PDH activity, but did not affect lipid peroxidation or activities of redox key enzymes. Contrarily, dietary tau supplementation decreased hepatic G6PDH and GPX activities and lipid peroxidation. Gene expression COX-2 was not affected either by FM or tau levels but TNF-α increased with the reduction of FM level but not with the tau level. Dietary tau supplementation decreased Casp3 and Casp9 expression regardless of dietary FM level. Overall, this study evidenced that dietary tau supplementation improved growth performance and antioxidant response and reduced intestine inflammatory and apoptosis processes.