Digestive coordination of the gastric function in Atlantic salmon Salmo salar juveniles

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

Digestive coordination of the gastric function in atlantic salmon salmo salar juveniles

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.Fil: Bravo, Jonathan P.. Universidad Católica de Temuco; ChileFil: Hernández, Adrián J.. Universidad Católica de Temuco; ChileFil: Morales, Gabriel Alejandro. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dantagnan, Patricio. Universidad Católica de Temuco; ChileFil: Márquez, Lorenzo. Universidad Católica de Temuco; Chil

Digestive coordination of the gastric function in Atlantic salmon Salmo salar juveniles

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 similar to 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

Long-term effects of temperatures on the physiological response of juveniles of the eurythermal sub-antarctic notothenioid Eleginops maclovinus

Eleginops maclovinus is a subantartic notothenic with eurythermal characteristics and potential for Chilean aquaculture. However, the information regarding their physiological response to long-term temperatures and optimum temperature range for physiological process is unknown. In the present study, we evaluated under experimental conditions, the long-term effects (60 days) of temperatures of 15 degrees C and high temperatures of 20 and 25 degrees C, (10 degrees C as control) on the physiology of E. maclovinus juveniles. At the end of the experimental period, survival was 36% at 25 degrees C and mortality started after 30 days, while at the other temperatures the survival was 100%. The growth and food intake did not present significant differences at 10, 15 and 20 degrees C, while at 25 degrees C growth decreased at day 15, to subsequently present a compensatory growth at day 30 and finally a decrease in growth and food intake at day 60. In general, the energy substrates in liver, gills, serum, and spleen showed a significant decrease at 25 degrees C, with a marked decrease in triglycerides, while white muscle presented an opposite pattern with an increase in total lipids and glycogen at 25 degrees C. Serum cortisol and ammonium increased at the higher temperature suggesting an increased metabolism. In the brain, high temperatures had a marked effect on monoamine neurotransmitters, with increased levels of serotonin (5-HT) and norepinephrine (NAd). Fatty acids in white muscle were modulated by high temperatures. In general, saturated fatty acids were significantly decreased at higher temperatures, while for monounsaturated fatty acids only C20:1n9 showed a decrease at 25 degrees C. The most abundant polyunsaturated fatty acids in white muscle were C22:6n3 (DHA) and C20:5n3 (EPA), which did not change at a higher temperature, while C20:4n6 (ARA) and C18:3n3 (ALA) showed an increase and a decrease at 25 degrees C, respectively. In conclusion, we suggest that E. maclovinus juveniles tolerate up to 20 degrees C, increasing their metabolism without negatively affecting their physiology, while a temperature of 25 degrees C or higher could be lethal in a long-term scenario

Effect of ration level on growth performance, body composition, intermediary metabolism and serum parameters in juvenile Patagonian blennie Eleginops maclovinus

Eleginops maclovinus is an endemic species of the southern cone with beneficial physiological characteristics for aquaculture. However, this species has a low growth rate under captive conditions, and the optimal feed ration together with the metabolic process is unknown. This study aimed to determine the optimum feed ration during 90 days based on growth performance, body composition, intermediary metabolism, and serum parameters. For this, fish were randomly assigned to rations of 0.5, 1, 2 and 4% of body weight. No fish mortality was registered, but all fish, developed fatty liver. The results of weight, length, growth performance (WGR, SGR), and body parameters (HSI, VSI and K) followed a similar pattern, with the lowest values observed in the 0.5% and no significant differences between rations of 1, 2 and 4%. The feed intake and feces increased with the feed ration. However, the percentage of food consumed by the fish decreased with the ration size and the feed conversion ratio was lowest in the 1% ration. Total serum proteins and calcium were lowest in the 0.5% ration and presented no differences in the rations 1, 2 and 4%, while triglyceride content was significantly different only between the rations of 0.5 and 4%. Blood cortisol levels were significantly higher in the rations of 0.5 and 1%, and decreased in rations of 2 and 4%. The lipids, fiber, and energy of the total body mass increased with the feed ration, while dry matter, proteins, and ash of the body decreased to higher feed ration. In liver, triglyceride and protein levels decreased with a larger feed ration, amino acids increased in the rations of 0.5 and 4%, while glucose levels increased in rations of 2 and 4%. Liver enzymes Glucose-6-phosphate dehydrogenase and Glutamate dehydrogenase increased their activity at a higher feed ration, while Glycogen Phosphorylase, Aspartate aminotransferase and 3-Hydroxyacyl-CoA dehydrogenase presented their highest enzymatic activity only in the 4% ration. Fructose-1,6-bisphosphate showed low enzymatic activity in rations of 2 and 4% and Glycerol-3-phosphate dehydrogenase was significantly different only between the ration of 0.5 and 1%. Finally, our results suggests that optimal feed rations for E. maclovinus corresponds to 1% since this ration size produces the highest growth and metabolism with a minimum loss of food and feces present in the environment. Additionally, we recommend to reduce the percentage of fat in the diet to avoid the development of fatty liver

Francisella noatunensis modulates the hepatic profile of fatty acids in Patagonian blennie Eleginops maclovinus

Fatty acids (FA) have been reported to play a role in the defense against bacterial pathogens. However, studies in fish are limited and no information exists on the modulation of FA of Eleginops maclovinus challenged with the pathogen of aquaculture relevance Francisella noatunensis. We inoculated 144 fish intraperitoneally with 3 doses (low dose [LD]: 1 x 101 bact/mu L; medium dose [MD]: 1 x 105 bact/mu L; high dose [HD]: 1 x 1010 bact/mu L) and a control dose (sterile culture medium, [C]) of the bacteria F. noatunensis and took liver samples at 1, 3, 7, 14, 21, 28 days post-inoculation (dpi). The LD of F. noatunensis did not present significant differences to the C, except for the C20:4n6 (ARA) at day 28, while the MD and HD of F. noatunensis did generate a significant effect of the FA profile of E. maclovinus. We observed a greater modulation after administering the HD of bacteria and detected significant differences from day 3 post-inoculation (P < 0.05). Significantly high levels of C18:0 was detected at day 28 (P < 0.05), while significantly low levels of C14:0, C20:0, C16:1, C18:1n9, C18:2n6; C18:3n3, and C20:5n3 were detected at different dpi of F. noatunensis (P < 0.05). ARA and C22:6n3 (DHA) showed a significant decrease during the first dpi (P < 0.05) but later they showed an increase in their levels, with ARA increasing its levels from day 14 (P < 0.05), while DHA increased its levels only at day 28 (P < 0.05). A large number of FA were highly correlated with each other and multivariate statistical analyzes (PCA and random forest) were able to detect the HD of F. noatunensis as the dose that most affects the FA profile of E. maclovinus, while the LD, MD and C cannot be differentiated in their FA profile. The FA most affected by the challenge with F. noatunensis were C18:2n3 and C18:3n3 (P < 0.05). Our results suggest a relationship between the bioavailability of FA in the liver and the level of the physiological response of E. maclovinus to an experimental challenge with F. noatunensis and suggest that hepatic FA modulation may explain or be part of the high tolerance to bacterial infections reported for E. maclovinus, although more studies are necessary to clarify the roles of the different types of FA on pathogen-host dynamics and its potential use in combating fish pathogenic bacteria.info:eu-repo/semantics/publishedVersio

Variations of chemical composition and energy content in natural and genetically defined cultivars of Macrocystis from Chile

Seasonal and intra-thallus variations of energy content and chemical composition were assessed in an intertidal population of Macrocystis in southern Chile. Phylloid protein and lipid from cultured material were compared with seasonal variation in native Macrocystis. Furthermore, populations in northern and southern Chile and Falkland Islands were compared with various intra-/inter-cultivar genotypes of Chilean Macrocystis. Energetic values did not show seasonal or intra-thallus variations, with the exception of pneumatocysts, which had high levels of ash (49.9% DW) and low values of total energy (8.3% DW). Seasonal patterns were detected in protein and carbohydrate composition, with opposite trends. Likewise, holdfasts contained high amounts of protein (21.0% DW), and phylloids were high in soluble carbohydrates (4.5% DW). Lipids instead showed two peaks per year in an intertidal population and reached up to 0.4% DW. Alginic acid was the major organic compound in intertidal Macrocystis (46.8% DW), with differences on seasonal and intra-thallus levels. Mannitol content, in contrast, was erratic and lower than in other Laminariales (<5% DW). In general, protein and lipid content in our cultivars were 20% higher than in natural populations. Our experimental results indicate the possibility to manipulate the chemical composition of Macrocystis thalli through inter-/intra-specific crosses. This will be a basis, upon which selected genotypes can open new perspectives to Macrocystis mariculture industries in Chile