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Soybean meal is one of the most promising alternatives to replace fishmeal in the aquaculture industry. However, its ingestion triggers an intestinal inflammatory process that compromises fish health and nutrition. Therefore, finding strategies that reduce the deleterious effects of a soy protein-based diet are relevant. In this work we analyzed the effects of an aloe vera (Aloe barbadensis miller, AV) extract on intestinal inflammation and innate immunity of zebrafish by adding it to the water and by supplementing it in a soybean meal-based diet. To search for potential immunomodulatory effects of AV, we tested its effectiveness in two inflammation assays and compared fish fed with either fishmeal or soybean meal-based feed supplemented with AV. Our results show a strong anti-inflammatory effect of AV. Furthermore, while soy-based meal strongly induces the expression of inflammation markers, supplementation with AV reverted this effect. Finally, we show that fish fed with a soy meal diet are highly susceptible to bacterial infection, but that this condition is significantly reduced when the soy meal is supplemented with AV. Our results suggest that AV is a good candidate to be incorporated as an additive in farmed fish diets to facilitate the replacement of fishmeal by soybean meal, maintaining intestinal health.

The molecular mechanisms underlying fish tolerance to soybean meal (SBM) remain unclear. Identifying these mechanisms would be beneficial, as this trait favors growth. Two fish replicates from 19 experimental families were fed fishmeal-(100FM) or SBM-based diets supplemented with saponin (50SBM + 2SPN) from juvenile to adult stages. Individuals were selected from families with a genotype-by-environment interaction higher (HG-50SBM + 2SPN, 170 ± 18 mg) or lower (LG-50SBM + 2SPN, 76 ± 10 mg) weight gain on 50SBM + 2SPN for intestinal transcriptomic analysis. A histological evaluation confirmed middle intestinal inflammation in the LG- vs. HG-50SBM + 2SPN group. Enrichment analysis of 665 differentially expressed genes (DEGs) identified pathways associated with immunity and lipid metabolism. Genes linked to intestinal immunity were downregulated in HG fish (mpx, cxcr3.2, cftr, irg1l, itln2, sgk1, nup61l, il22), likely dampening inflammatory responses. Conversely, genes involved in retinol signaling were upregulated (rbp4, stra6, nr2f5), potentially favoring growth by suppressing insulin responses. Genes associated with lipid metabolism were upregulated, including key components of the SREBP (mbtps1, elov5l, elov6l) and cholesterol catabolism (cyp46a1), as well as the downregulation of cyp7a1. These results strongly suggest that transcriptomic changes in lipid metabolism mediate SBM tolerance. Genotypic variations in DEGs may become biomarkers for improving early selection of fish tolerant to SMB or others plant-based diets.

Melanoidins are complex molecules usually found within dietary matrixes suffering heating steps during the production process. These compounds are known to exert a number of negative effects on the digestibility of nutrients and digestive enzymes in mammals, but also determines an increase in the antioxidant capacity of the diet with potential effects for animal health. In the present work, digestive and nutritional consequences of the ingestion of glucose-glycine melanoidins were tested in juvenile rainbow trout (Oncorhynchus mykiss), which was fed two non-heated, pelletized diets: a control diet without melanoidins and an alternative diet containing 1.2% of glucose-glycine melanoidins. The results pointed to a small effect on gut pH in interaction with digestion time, and a lack of effect on gastric evacuation and digestive proteases. In addition, melanoidins were associated with a small increase in the digestibility of the diet dry matter, leaving unchanged nitrogen and phosphorus digestibility. On the other hand, melanoidins determined a complex increase in the postprandial antioxidant capacity of blood plasma, particularly apparent in the antioxidant components above 3 kDa. Fil: Serrano, Xavier. Universidad Católica de Temuco; Chile Fil: Hernández, Adrián J.. Universidad Católica de Temuco; Chile Fil: Morales, Gabriel Alejandro. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Larson, Majorie. Universidad Católica de Temuco; Chile Fil: Ruiz, Joceline. Universidad Católica de Temuco; Chile Fil: Orellana, Paola. Universidad Católica de Temuco; Chile Fil: Díaz, Manuel. Universidad de Almería; España Fil: Moyano, Francisco J.. Universidad de Almería; España Fil: Márquez, Lorenzo. Universidad Católica de Temuco; Chile

Fil: Márquez, Lorenzo. Universidad Católica de Temuco. Facultad de Recursos Naturales. Departamento de Ciencias Agropecuarias y Acuícolas. Núcleo de Investigación en Producción Alimentaria. Temuco, Chile. Fil: Hernández, Adrián J. Universidad Católica de Temuco. Facultad de Recursos Naturales. Departamento de Ciencias Agropecuarias y Acuícolas. Núcleo de Investigación en Producción Alimentaria. Temuco, Chile. Fil: Carvalho, Edison S. M. Instituto Gulbenkian de Ciência, Telomeres and Genome Stability Group. Oeiras, Portugal. Fil: Morales, Gabriel A. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal. Buenos Aires, Argentina. Fil: Dantagnan, Patricio. Universidad Católica de Temuco. Facultad de Recursos Naturales. Departamento de Ciencias Agropecuarias y Acuícolas. Núcleo de Investigación en Producción Alimentaria. Temuco, Chile. Fil: Díaz, Manuel. Universidad de Almería. Departamento de Biología y Geología. Grupo de Nutrición y Alimentación Animal. Almería, España. Fil: Moyano, Francisco J. Universidad de Almería. Departamento de Biología y Geología. Grupo de Nutrición y Alimentación Animal. Almería, España. The activity of fish acid proteases is strongly dependent on the pH, and many basic and applied works had focused on researching the pH-profile of digestive proteases using different buffered media. Nevertheless, enzymatic activity is also known to be affected by the ionic strength (IS) of the medium. The present work is aimed at researching the combined effects of pH (2.5, 3.0, 3.5, 3.75 and 4.0) and IS (50, 100 and 200 mM) on the protease activity of gastric extracts of juvenile Coho salmon Oncorhynchus kisutch. It is concluded that the activity of Coho salmon gastric proteases is maximal at pH 2.5-3.0, drops towards pH 4.0 irrespective of ionic strength, and they showed a lower activity at IS 50 mM in comparison to IS 100 or 200 mM. The present results point out to the convenience of considering the effect of ionic strength when measuring the activity of fish gastric proteases. tbls.

Durvillaea antarctica is a brown seaweed that can be located in the Southern Hemisphere and has a high content of polyunsaturated fatty acids and γ-tocopherol. Aquaculture currently uses vegetable oils for feeding rainbow trout (Oncorhynchus mykiss), but this reduces the omega-3 levels in the fillet. The aim of this study was to evaluate the effect of dietary inclusion of D. antarctica meal on the fillet quality of rainbow trout fed with rapeseed oil. A total of 375 rainbow trout (17.6±0.46 g) were randomly assigned to five treatments with three replicates (25 fish per replicate) in 15 tanks and reared for 9 weeks. Rainbow trout fed with 100% fish oil were considered as a positive control. A negative control corresponded to a diet with a mix of 10% fish oil and 90% rapeseed oil. This diet was used for the other three treatments with the inclusion of 1.5, 3 and 6% of D. antarctica meal respectively. At the end of the feeding trial, the fish were euthanized to evaluate growth, feed utilization and fillet quality. The diets did not affect the growth and feed utilization. However, the fillet of fish fed with 6% D. antarctica meal showed a less acidic pH, higher luminosity, less yellowing and color saturation, compared with the other groups. The fillet of fish fed with D. antarctica meal and rapeseed oil, showed less oxidation. The fatty acid profile was affected by the inclusion of rapeseed oil, reducing the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, diets with D. antarctica meal were able to partially compensate the fish oil intake by reducing some saturated fatty acids, increasing the EPA content and reducing the atherogenic index and thrombogenic index, improving the nutritional value of the fillet. Although the use of D. antarctica meal does not significantly compensate for the effects of rapeseed oil on the fillet, it could be used as an alternative to increase the nutritional value and quality of rainbow trout.

The products resulting from the non-enzymatic browning in processed diets are known to exert negative effects on the digestive enzymes of vertebrates. In addition, browning heavy products (BHP's) are known to co-precipitate with proteins depending on the pH and ionic strength of the medium and on the isoelectric point of the protein. As the manufacture of aquafeeds as well as aquafeed ingredients frequently implies heating processes, the effects of BHP's from a well-known model mixture (glucose + glycine) on the gastric proteases of the rainbow trout Oncorhynchus mykiss were investigated in the present work. The results support that BHP's interact with gastric proteases most probably to form a co-precipitate, thus potentially reducing the protease activity in the fish stomach. The maximal loss of activity found in the experiments was above 20%. The interaction is pH and ionic strength-dependent and relatively stable against mechanical perturbation. In the range of BHP concentration 500-1000 μg/mL, the interaction was dose-dependent at pH 3.5 with a maximum above 20%, and apparently independent of the dose at pH 4.0. Above an ionic strength of 100 mM due to monovalent ions (NaCl), the intensity of the interaction is reduced. On the other hand, divalent cations such as Ca2+ and Mg2+ in the range 30-80 mM disturb the interaction between BHP's and gastric proteases even at ionic strengths below 100 mM, thus alleviating the inactivating effect of BHP's. Fil: Serrano, Xavier. Universidad Católica de Temuco; Chile Fil: Hernández, Adrián J.. Universidad Católica de Temuco; Chile Fil: Larson, Majorie. Universidad Católica de Temuco; Chile Fil: Morales, Gabriel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina Fil: Díaz, Manuel. Universidad de Almería; España Fil: Moyano, Francisco J.. Universidad de Almería; España Fil: Márquez, Lorenzo. Universidad Católica de Temuco; Chile

Atlantic salmon (Salmo salar) were fed 6 experimental diets containing three levels of arachidonic acid (ARA) (0.18 g kg−1, 0.28 g kg−1 and 0.63 g kg−1 for low, medium and high levels, respectively) and two levels of vitamin E (150 and 730 mg kg−1 for low and high levels, respectively). At the end of the experimental period, fatty acids in the liver and immunity markers (lysozyme activity, respiratory burst and phagocytic activity) were determined and fish subjected to a challenge test against the salmonid rickettsial syndrome (SRS) pathogen. ARA, vitamin E or their interaction did not exert an effect on fish performance, whereas ARA alone clearly increased the deposition of ARA. Dietary vitamin E only enhanced liver vitamin E deposition, while the interaction of ARA and vitamin E influenced lysozyme activity and EPA/ARA ratio pointing out the effect of both nutrients on the fish immune system and metabolism. Only the medium concentration contributed to reducing mortality when the fish were exposed to the SRS pathogen. In conclusion, different levels of supplementation with ARA and vitamin E in the diet had no effect on productivity, but did have effects on immune markers and cumulative mortality when fish were exposed to the SRS pathogen.

The present study aimed to evaluate the effects of a commercial phytopharmaceutical preparation from herbal and macroalgal origin on the growth and immune response of rainbow trout adapted to seawater and its susceptibility to Piscirickettsia salmonis infection. Preliminary in vitro trials, evaluated the effects of the commercial product Futerpenol® on the expression levels of selected immune-regulatory genes and its protective effect in a challenge against Piscirickettsia salmonis (LF89). Subsequent in vivo feeding trials were conducted to corroborate fish protection against Piscirickettsia salmonis. Control and treatment diets (with or without the commercial product Futerpenol® at a concentration of 1 kg/ton) were fed to triplicate groups of 50 fish (average weight: 100.1 ± 11.1 g) during 30 days. Fish from all dietary groups were equally redistributed in three tanks and challenged by cohabitation with fish infected with P. salmonis (shedders) at the end of the feeding treatment, and mortalities were recorded over 80 days post-infection. A cumulative mortality of 35.0 ± 4.3 and 15.0 ± 6.0% was registered when challenged fish were previously fed during 30 days with the control and treatment diets respectively. Futerpenol® dietary administration preceding the cohabitation challenge gave significant protection from P. salmonis as suggested by the Relative Percent Survival (RPS) values of 62.3 and 57.1% after 60 and 80 days post-infection, respectively. These results suggest that dietary supplementation with Futerpenol® at 1 kg/ton do not affect growth performance and strengthen immunity of Oncorhynchus mykiss against P. salmonis under the experimental conditions applied during this study. Statement of relevance This study demonstrates that dietary supplementation with a phytopharmaceutical preparation, rich in fucoidans and labdane diterpenes strengthen immunity of O. mykiss against P. salmonis. The use of feed supplemented with this kind of phytopharmaceutical preparations in anticipation to potential infections or vulnerable stages of the production could be useful as an alternative method to prevent and limit the outbreak of salmonid rickettsial septicaemia (SRS) which constitutes one of the main infectious diseases causing production problems and substantial loss in salmonids and marine fish aquaculture worldwide.

The study was conducted to compare two plant ingredients as dietary protein sources for rainbow trout on the basis of feed acceptability, survival, growth, feed conversion, nitrogen and phosphorus utilization efficiency and loading. Two extruded diets were formulated with the inclusion of a soybean meal (DS) and a lupin meal (DL). The control diet was a fish meal (FM) based diet. All diets were isonitrogenous and isolipidic. Triplicate groups of 65 fish (5.10 ± 0.10 g) were assigned to each diet. At the end of the experiment (66 days), all groups of fish fed diets had a similar final growth and feed utilization efficiency (P > 0.05). Nitrogen reten- tion rate was higher for the group fed the control diet and in consequence the calculated loading amount of this nutrient resulted lower when compared with the test diets. However, phosphorus retention was higher in the groups of fish fed the experimental diets (DL 26.58 ± 0.22 and DS 27.67 ± 3.05) when compared to the control diet (22.08 ± 1.12) (P < 0.05). This represents a phosphorus loading of 8.33 ± 0.23, 8.96 ± 1.02, and 11.55 ± 0.67 kg/t production for the diets DL, DS, and control, respectively. Therefore, the results indicate that lupin meal can be used as a possible plant protein source for the formulation of low-phosphorus loading diets for rainbow trout without affecting feed acceptability and growth performance. This legume represents a clear opportunity to supply the high demand for plant protein sources for aquaculture. Further studies are needed to evaluate and comapare different lupin species and varieties.

Melanoidins, a product of advanced browning reactions due to the thermal treatment of the diet, has been previously demonstrated to inhibit the activity of trypsins from mammalian origin, but no data exists in relation to fish trypsins. The present work is devoted to the investigation of the effects of glucose-glycine melanoidins on the trypsin-like activity contained in intestinal crude extracts (ECIs) prepared from juvenile individuals of the rainbow trout Oncorhynchus mykiss. A turbidity assay was conducted to test for the existence of precipitation or aggregation phenomena in mixtures of ECIs and melanoidins, but no consequences were observed. Three experiments were conducted to test for the effects on the trypsin-like activity on the hydrolysis of the substrate BAEE (Nα-Benzoyl- L -arginine ethyl ester). Glucose-glycine melanoidins can inhibit the intestinal trypsin-like activity of the rainbow trout, but the effect is modulated by the pH and ionic strength of the reaction medium. The inhibition dropped when the pH was changed from 7.5 to 8.5, also when the ionic strength of the buffer was raised from 40 to 140 mM, while it was undetected at 180 mM. It is concluded that the effect of this type of melanoidins on the trypsin-like activity from the rainbow trout is probably low in the ionic conditions prevailing in the intestine of this species.

Artificial diets have been reported to produce suboptimal pH values in the stomach of salmonid species. Therefore, it is interesting to investigate the gastric function of different species fed commercial diets. In the present work, two groups of Atlantic salmon juveniles were either fasted or fed with a commercial diet. The gastric and duodenal pH values were measured over a 25 h post-prandial period and, dry matter, moisture and protease activity in the gastric chyme of the fed group were also determined. In the fed group, the gastric pH dropped to 3.5, and duodenal pH increased from 7.0 to 7.5 at the 4th h post-feeding, whereas fasted fish showed no significant changes in the gastric pH or duodenal pH. Fed animals showed: i) two discrete events of evacuation, before the 2nd hand after the 8th h of digestion, ii) a change in the moisture of the gastric chyme from less than 10% in the diet to 60% at the 2nd h post-feeding, and iii) a maximal gastric proteases activity of 600 U mL -1 at the 2nd h followed by a nearly constant of value of ~300 U mL -1 . It can be concluded that the juveniles of the Atlantic salmon can suitably acidify a commercial diet to a value generally accepted as optimal for gastric proteases of fish, and to retain about 2/3 of the ingested diet under such conditions and at a nearly constant protease activity until the 8th h of digestion. Normal 0 21 false false false ES-CL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-fareast-language:EN-US;}

This study aims to evaluate the effect of different sources of inorganic phosphate, monosodium phosphate (MSP), monocalcium phosphate (MCP) and monoammonium phosphate (MAP), included in a diet for rainbow trout, on growth performance, nutrient digestibility, nutrient retention efficiency and discharge of nutrients to the water. Juvenile rainbow trout (Oncorhynchus mykiss) with an initial weight of 120 g were fed for 56 days four experimental diets: basal diet containing 430 g kg−1 protein, 210 g kg−1 lipids and 6.7 g kg−1 total phosphorus (P) (Control), and three experimental diets consisting in the basal diet plus 4 g P kg−1 from MSP, MCP and MAP, respectively. Both MSP and MAP resulted in higher levels of P apparent digestibility (≈90%) compared to MCP (70%), increasing the dry matter digestibility of the nutrient in the feed. The retention efficiency of P in fish tissues was increased by nearly 15% units over the Control when MSP and MAP were used as P supplement, whereas in agreement with the lower digestibility observed in MCP, P retention efficiency from this phosphate source was lower than the other sources. Total P discharge to the water was similar for MSP, MCP and MAP (4.12–4.58 g kg−1 BW fish gain). However, fish fed with MCP showed higher solid/particulate P discharge to the water through faeces due to the lower digestibility of this P–source within the gut of the fish. Among the phosphate salts evaluated, fish fed MSP and MCP did not show differences for soluble or solid N discharged fractions. However, fish fed the diet supplemented with MAP released a higher amount of non–protein N fraction to the water, probably as undigested ammonium through the faeces released by fish. Fil: Morales, Gabriel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; Argentina Fil: Azcuy, Rosendo Lucas. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Casaretto, Matías Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; Argentina Fil: Márquez, Lorenzo. Universidad Católica de Temuco; Chile Fil: Hernández, Adrián J.. Universidad Católica de Temuco; Chile Fil: Gómez, Federico. Yara International ASA; Noruega Fil: Koppe, Wolfgang. Simplyfish AS; Noruega Fil: Mereu, Alessandro. Yara International ASA; Noruega

A digestibility trial was conducted to assess the effect of dehulling, steam-cooking and microwave-irradiation on the apparent digestibility of nutrients in white lupin (Lupinus albus) seed meal when fed to rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). Six ingredients, whole lupin seed meal (LSM), dehulled LSM, dehulled LSM steam-cooked for 15 or 45 min (SC15 and SC45, respectively) and LSM microwave-irradiated at 375 or 750 W (MW375 and MW750, respectively), were evaluated for digestibility of dry matter, crude protein (CP), lipids, nitrogen-free extractives (NFE) and gross energy (GE). The diet-substitution approach was used (70% reference diet + 30% test ingredient). Faeces from each tank were collected using a settlement column. Dehulled LSM showed higher levels of proximate components (except for NFE and crude fibre), GE and phosphorus in comparison to whole LSM. Furthermore, SC15, SC45, MW375 and MW750 showed slight variations of chemical composition in comparison to dehulled LSM. Results from the digestibility trial indicated that dehulled LSM, SC15, SC45 and MW375 are suitable processing methods for the improvement of nutrients' apparent digestibility coefficient (ADC) in whole LSM. MW750 showed a lower ADC of nutrients (except for CP and lipids for rainbow trout) in comparison with MW350 for rainbow trout and Atlantic salmon, suggesting a heat damage of the ingredient when microwave-irradiation exceeded 350 W.

Despite the well known importance of ω-3 polyunsaturated fatty acids (PUFA) in marine and freshwater fish larvae, there are few studies on how essential fatty acid requirements and composition on whole body can be altered by changes in water salinity. The present study aimed to determine the effect of salinity on ω-3 PUFA requirements, larval growth survival and fatty acid composition of G. maculatus larvae cultured at two different salinities (0 and 15 g∙L-1) for 20 days while fed rotifers containing two different levels of ω-3 PUFA (1.87 and 3.16%). The results denoted a marked difference in ω-3 PUFA requirements and in the pattern of fatty acid deposition in the whole body of larvae reared at different salinities, depending of ω-3 PUFA in diets. Thus, to improve growth and survival larvae of G. maculatus reared at 0 g∙L-1 require higher levels of ω-3 PUFA, principally 18: 3ω-3. Larvae reared at salinities of 15 g∙L-1 require low levels of ω-3 PUFA for optimal survival, especially 18: 3ω-3. Eicosapentaenoic acid and docosahexaenoic acid content in the whole body of larvae was also affected by water salinity.

A.J. Hernández, S. Satoh, and V. Kiron. 2013. The effect of citric acid supplementation on growth performance, phosphorus absorption and retention in rainbow trout (Oncorhynchus mykiss) fed a low-fishmeal diet. Cien. Inv. Agr. 40(2): 397-406. Two feeding experiments were conducted to investigate the effect of a low-phosphorus (P) diet in combination with citric acid (CA) on rainbow trout growth performance and P utilization. In the first 12-week trial, duplicate groups of 30 fish (12.0±1.7 g) were fed one of five diets. The basal diet was formulated with low-P protein sources and 15% fishmeal (FM) without inorganic P supplementation. The test diets contained 0.5% monocalcium phosphate (MCP), 3% CA or both. A FM-based diet served as the positive control. The diet with MCP showed good growth and feed performance comparable to the control. Growth was not improved by the addition of 3% CA. In the second trial, duplicate groups of 20 fish (80.5±18.5 g) were offered one of four diets during a 12-week period. The basal diet from the first trial with MCP supplementation served as the positive control, and the same basal diet without MCP supplementation again served as the negative control. The test diets were supplemented only with CA at 1 and 2%. The diet with 1% CA had growth performance similar to the positive control. Thus, the addition of 1% CA to a low-FM diet containing no inorganic P liberated enough available P to produce juvenile fish performance similar to that achieved with a diet containing supplemental inorganic P. A.J. Hernández, S. Satoh y V. Kiron. 2013. Efecto de la suplementación de ácido cítrico sobre el crecimiento y la absorción y retención de fósforo en trucha arcoíris (Oncorhynchus mykiss) alimentada con una dieta basada en un bajo contenido de harina de pescado y formulada con ingredientes proteicos vegetales alternativos. Cien. Inv. Agr. 40(2):397-406. Se llevaron a cabo dos ensayos de alimentación, con el fin de evaluar el efecto de dietas con bajo contenido de fósforo (P) e inclusión de ácido cítrico (CA) sobre el rendimiento del crecimiento en trucha arco iris y la utilización de P. En el primer ensayo, de 12 semanas de duración, grupos duplicados de 30 peces (12,0±1,7 g) se alimentaron con cinco dietas experimentales. La dieta basal fue formulada con fuentes proteicas bajas en P y 15% de harina de pescado (FM), sin suplementación de P inorgánico. Las dietas experimentales contenían 0,5% de fosfato mono cálcico (MCP), 3% de CA o ambos. La dieta control estuvo formulada con un alto contenido de FM. Los peces alimentados con la dieta con MCP mostraron un buen crecimiento y un rendimiento alimenticio comparable al grupo control. El crecimiento no fue mejorado por la adición de 3% de CA. En el segundo ensayo, grupos duplicados de 20 peces (80,5±18,5 g) fueron alimentados durante un período de 12 semanas. La dieta basal usada en la primera prueba con suplementación de MCP sirvió como control. Las dietas experimentales se complementaron sólo con CA a 1 y 2%. Los peces alimentados con la dieta con 1% CA tuvieron un crecimiento similar al control. Así, la adición de 1% de CA a una dieta baja en FM, que no contiene P inorgánico, liberó suficiente P disponible como para permitir un rendimiento similar al alcanzado con una dieta que contenía P inorgánico suplementario.

Intestinal inflammation is a harmful condition in fish that can be triggered by the ingestion of soybean meal. Due to the positive costs-benefits ratio of including soybean meal in farmed fish diets, identifying additives with intestinal anti-inflammatory effects could contribute to solving the issues caused by this plant protein. This study evaluated the effect of incorporating lactoferrin (LF) into a soybean meal-based diet on intestinal inflammation in zebrafish. Larvae were fed with diets containing 50% soybean meal (50SBM) or 50SBM supplemented with LF to 0.5, 1, 1.5 g/kg (50SBM+LF0.5; 50SBM+LF1.0; 50SBM+LF1.5). The 50SBM+LF1.5 diet was the most efficient and larvae had a reduced number of neutrophils in the intestine compared with 50SBM larvae and an indistinguishable number compared with control larvae. Likewise, the transcription of genes involved in neutrophil migration and intestinal mucosal barrier functions (mmp9,muc2.2, andβ-def-1) were increased in 50SBM larvae but were normally expressed in 50SBM+LF1.5 larvae. To determine the influence of intestinal inflammation on the general immune response, larvae were challenged withEdwardsiella tarda. Larvae with intestinal inflammation had increased mortality rate compared to control larvae. Importantly, 50SBM+LF1.5 larvae had a mortality rate lower than control larvae. These results demonstrate that LF displays a dual effect in zebrafish, acting as an intestinal anti-inflammatory agent and improving performance against bacterial infection.

This study was conducted to evaluate the effect of citric acid (CA) and amino acid chelated trace elements (AA) on the growth, phosphorus (P) utilization efficiency and loading in rainbow trout fed a diet formulated with a low-fish meal (FM) concentration. A low-FM basal diet with or without monocalcium phosphate supplementation served as positive and negative control correspondingly. Dietary treatments consisted of the basal diet supplemented either with 1% CA, AA (equivalent to 40 Zn, 20 Mn, and 4 Cu mg/Kg of diet instead of inorganic trace element mix) or a combination of both. Duplicate groups of 35 fish (13.2 g) were fed until apparent satiation during 12 wk. Group of fish fed diets supplemented with 1% CA or AA had a final growth and feed utilization similar to that observed in fish fed the positive control diet (P > 0.05). P absorption was increased with the addition of CA or AA. P retention efficiency rates for these diets were higher in comparison with the rest of the treatments consequently showing the lowest P loading values (P < 0.05). The results indicate that addition of 1% CA or AA, to a low-FM diet without inorganic P supplementation enhanced fish growth, P retention, and decreased P load to the environment.

The synergistic effect of arachidonic acid (ARA) (20:4n-6) and α-tocopherol on the accumulation of fatty acids and the peroxidation of lipids in liver and muscle was evaluated in Atlantic salmon ( Salmo salar ) juveniles. Triplicate groups were fed during 12 weeks with eight experimental diets with different levels of ARA and α-tocopherol. In all experimental diets the productive parameters were not affected ( P > 0.05). ARA accumulation in muscle and liver showed significant differences ( P < 0.05) between treatments. The synergic relationship between ARA/α-tocopherol was influenced ( P < 0.05) only in the liver, showing that high levels of α-tocopherol and ARA favored the fatty acids accumulation in this organ. Results indicate that a dietary concentration up to 0.6% ARA, the increment of α-tocopherol is not necessary. The data obtained in this study demonstrated that the interaction between the ARA and α-tocopherol influenced the accumulation of fatty acids in the liver.

The effect of dietary inclusion of whole grain white lupin (Lupinus albus) on growth performance, histology, muscle fatty acid composition and nutrient digestibility was investigated in an 11-week growth and a 4-week digestibility trial with rainbow trout (initial body weight of 54.0 ± 6.2 and 181.9 ± 3.4 g respectively). Four experimental extruded diets were formulated to contain 0%, 30%, 40% and 50% of whole grain lupin and fed to triplicate groups of fish twice a day until apparent satiation. Faeces were collected daily from each digestibility tank by decantation. No significant trends were observed with respect to growth, feed utilization, apparent digestibility coefficients or whole-body composition (P>0.05). Conversely, increasing levels of dietary lupin led to significant decreases in the Hepatosomatic index (R2=0.75, P

A. Hernandez, A. Borquez, L. Alcaino, J. Morales, P. Dantagnan, and P. Saez. 2010. Effects of autoclaving on the apparent digestibility coefficient of dehulled pea seed meal (Pisum sativum) in Rainbow trout (Oncorhynchus mykiss). Cien. Inv. Agr. 37(3): 39-46. The effect of autoclaving on the nutrients’ apparent digestibility coefficient (ADC), digestible protein and energy of pea seed meal (P. sativum) fed to Rainbow trout (O. mykiss) was examined. Two samples of the pea meal were autoclaved at 121oC and 1.1 atm for 5 min (5’APM) or 15 min (15’APM), respectively. A third sample, used as control, was not treated (RPM). One reference diet (Basal diet) and 3 experimental diets were elaborated and labelled based on autoclaving time applied to the ingredient (RPM, 5’APM and 15’APM). The four diets were assigned using a completely randomised design, with each treatment having three replicates. 12 tanks were stocked each with 15 trouts with an average weight of 235 ± 10.4 g. Faeces were collected over a 7-day period using a settlement column and pooled within the tank. ADCs were determined using chromium oxide (Cr 2 O 3 ) as an inert digestibility indicator. No significant differences (P>0.05) regarding protein ADC were found among all treatments. On the other hand, dry matter, energy and nitrogen free extract (NFE) ADC showed significant differences (p

Despite the importance of certain highly unsaturated fatty acids in osmotic regulation, few studies have been addressed to determine the essential fatty acid requirements for a given species cultured under different salinities. As Galaxias maculatus is a diadromic species, the present study aimed to determine the effect of salinity on the optimum dietary EPA/docosahexaenoic (DHA) ratio for survival and growth during the larval stages. Larvae were fed for 20 days with rotifers containing two different EPA/DHA ratios (low: 0.64 and high: 2.18) at three different salinities (0, 10 and 15 g L−1). The results of this study showed a marked effect of water salinity on larval dietary lipid utilization in G. maculatus larvae. These results suggested that G. maculatus larvae reared at higher salinities may have a higher dietary requirement for DHA, whereas larvae reared at 0‰ showed higher requirements for EPA. The overall results of the present study indicate that even small changes in salinity can determine the optimum dietary EPA/DHA ratio and the quantitative essential fatty requirements of fish. This may have important repercussions and affect the rearing performance of G. maculatus cultured under different salinities.

The use of macroalgae as an additional component in animal feeding has been studied. However, information on how it could influence muscle composition of fish body is scarce. This study evaluates four diets with different macroalgae inclusion levels (0%, 1.5%, 3% and 6%) to test the effect on body fatty acid composition of rainbow trout. Tanks with a volume of 600 L were stocked with 60.6 ± 7.9 g fish at a density of 45 individuals tank−1 and fed for 124 days. At the end of the experiment there were not significant differences (P

In order to verify methods for minimizing waste output of phosphorus (P) into the water and preserve an adequate growth rate in rainbow trout, a succession of two feeding trials were performed employing three test diets that were formulated with a low proportion of fish meal (FM), low-P ingredients (defatted soybean meal, corn gluten meal, feather meal, and blood meal), and varying levels of monocalcium phosphate (MCP) as a P supplement (0,05 and 1% of diet which represent 0, 1 and 2 mg/g of available P, respectively). Total P concentrations achieved were 6.2, 8.7 and 9.6 mg/g, respectively. A control diet was formulated with FM as the main protein source and without MCP (total P content was 17.0 mg/g). Diets were fed until apparent satiation to duplicate groups of 50 (1.5 g) and 15 fish (147.8 g) during 24 and 14 weeks, respectively. In both cases, the lowest growth was observed in fish fed the basal diet without MCP. The test diet supplemented with 0.5% MCP provided growth and feed performance comparable to that obtained in fish fed the control diet. These results suggest that diets formulated with low-P ingredients should be supplemented with an adequate amount of P in order to meet the fish requirements and reduced diet-related P loading.

Two experiments were conducted to evaluate feed quality and body phosphorus (P) and nitrogen (N) retention by rainbow trout fed test diets with low amounts of fish meal content and alternative low-P protein sources. A fish meal (FM) diet was used as control. Fish weighing 2.0 g and 134.7 g on average were reared with the experimental diets for 30 weeks and 15 weeks, respectively. The experimental diets had a good growth rate and feed utilization. In the first experiment the P retention was higher in the group of fish fed test diets (56 and 69%) compared to the FM-based diet (36%); N retention rates were similar for all groups. In the second experiment, fish were fed the test diet that had the best P retention in the earlier experiment. The P retention was lower than the values obtained in the first experiment (smaller fish), but still higher in the group of fish fed the low FM diet in comparison with the control group (36.0% and 22.2%, respectively). This represents a P loading into the water of 5.9 kg/t and 12.8 kg/t production for the test and the control diet, respectively. Therefore, low-P-loading diets for rainbow trout can be developed through the appropriate combination of alternative protein sources.

Aimed at developing environment-friendly aquatic feeds, a trial on rainbow trout to reduce phosphorus (P) loading is reported. Growth, feed quality performance, whole body P retention and the calculated P loading were compared between triplicate groups of fish reared with a commercial feed and an experimental diet formulated with low level of fish meal (FM, 20%) and low-P ingredients: defatted soybean meal (20%), corn gluten meal (25%) and blood meal (5%). The total P content was 18.1 and 9.9 g/kg, for the commercial and experimental diets, respectively. Fifty fish with an average weight of 1.9 g were allotted in tanks of 60 l and maintained at water temperature ranging between 12 and 20 °C. Fish were hand-fed twice a day to apparent satiety for 48 weeks. At the end of the trial, growth was comparable among fish from different treatments, although it was highest for commercial feed. Dietary treatments did not affect final specific growth rate (SGR), thermal-unit growth coefficient (TGC) or feed gain ratio (FCR). P retention levels were found to be significantly higher in the fish fed the experimental diet (35.9%) than those fed the commercial diet (18.5%). Moreover, P loading was much lower for this group than for fish fed the commercial feed (7.8 kg/ton of fish produced versus 17.3 kg/ton). The results indicate that practical low-P loading diets can be developed for rainbow trout through combinations of alternative protein sources. Furthermore, an optimal combination of diverse low-P protein sources could enhance the feed performance to a level comparable to conventional fish meal (FM) based diets.

Varying levels of lupin (Lupinus albus), peas (Pisum sativum) and rapeseed (Brassica napus) meals were evaluated as partial replacements for fishmeal in extruded diets for rainbow trout, with particular emphasis on the effect on growth performance and the expression of three genes associated with immune response. A series of 10 isonitrogenous (450 g kg−1 crude protein) and isolipidic (17 g kg−1 crude lipid) diets were formulated to contain different levels of lupin (150 g kg−1, 250 g kg−1 and 350 g kg−1), rapeseed cake (100 g kg−1, 200 g kg−1 and 300 g kg−1) and pea (50 g kg−1, 150 g kg−1 and 250 g kg−1) meals. The control diet was prepared with fish meal as the sole source of protein. Triplicate groups of fish (37.08 ± 3.58 g) were assigned to each experimental diet. The feeding experiment was conducted for 9 weeks at 14.3 ± 0.4 °C. The fish were hand fed three times per day, 6 days per week to apparent satiation level. Growth performance, feed utilization and immunological response were significantly affected by the type of plant protein as well as level of inclusion. Hepatosomatic index (HSI) increased in all groups of fish fed diets with pea and rapeseed cake meal. Dietary inclusion of lupin did not affect the expression of Mx-1 gene. Our results suggest that fish meal can be replaced by lupin in the diet of rainbow trout without any apparent adverse effects on key innate immunological genes.

“Puye” (Galaxias maculatus) is a small freshwater fish species of great interest to Chilean aquaculture diversification, because of the high commercial value reached by its transparent larvae or “cristalino”. This study presents the first data with regard to blood cytology in larvae and adults of this specie. Blood smears stained with May Grünwald-Giemsa were analysed through optical microscopy. The results show that in G. maculatus larvae the flowing blood has a transparent look and mature erythrocytes were not observed, as opposed to the adults of this species where the complete erythrocyte developmental line could be observed. In leucocytes, there was no presence of coarse grain cells such as basophils and eosinophyls. In general, the morphology of the blood cells found in larvae and adults of G. maculatus have the same characteristic traits as described elsewhere in reports of other teleosts.

The need of quality protein in the aquaculture sector has forced the incorporation of alternative plant proteins into feeding diets. However, most plant proteins show lower digestibility levels than fish meal proteins, especially in carnivorous fishes. Manipulation of protein content by plant breeding can improve the digestibility rate of plant proteins in fish, but the identification of low digestibility proteins is essential. A reduction of low digestibility proteins will not only increase feed efficiency, but also reduce water pollution. Little is known about specific digestible protein profiles and/or molecular identification of more bioavailable plant proteins in fish diets. In this study, we identified low digestibility L. luteus seed proteins using Atlantic salmon (Salmo salar) crude digestive enzymes in an in vitro assay. Low digestibility proteins were identified by comparing SDS-PAGE banding profiles of digested and non-digested lupin seed proteins. Gel image analysis detected a major 12 kDa protein band in both lupin meal and protein isolate digested products. The 12 kDa was confirmed by 2D-PAGE gels and the extracted protein was analyzed with an ion trap mass spectrometer in tandem mass mode. The MS/MS data showed that the 12 kDa low digestibility protein was a large chain δconglutin, a common seed storage protein of yellow lupin. Comparison of the protein band profiles between lupin meal and protein isolates showed that the isolatation process did not affect the low digestibility of the 12 kDa protein.