Replacement of fishmeal in feeds is critical for sustainable aquaculture growth. However, replacement with plant protein concentrates reduces fish performance. A rainbow trout strain selected for ...high performance on a plant protein diet was compared to a non-selected strain to identify physiological mechanisms associated with improved performance. Nutrient digestibility in fishmeal and plant protein diets was assessed and no strain differences were found. Levels of amino acids in the hepatic portal vein and caudal vein were measured at intervals after a single force-feeding of fishmeal, four plant protein concentrates, and a mixture of the concentrates with or without supplementation of three limiting amino acids. Each ingredient affected plasma amino acid levels in a singular manner when fed individually but without predictable additive effects when fed as a mixture. Amino acid supplementation altered uptake and plasma concentrations of all the essential amino acids. The selected trout strain fed the plant protein mixture with amino acids showed a synchronous and homogenous pattern for essential amino acids over time in the hepatic portal vein in contrast to that of the non-selected strain. The results demonstrate that selection favorably altered temporal dynamics of plant protein digestion.
Plant-based proteins are increasingly being used in aquafeeds, but one of the limitations is taurine deficiency that can be especially detrimental for carnivorous fish. In this study, taurine ...supplementation in high plant protein diets (low fish meal, 15%) was investigated on the growth performance and fillet organoleptic characteristics of European seabass (Dicentrarchus labrax), juveniles (78 ± 0.4 g). Five diets were formulated to contain 0 (C-), 5 (T5), 10 (T10) or 20 (T20) added taurine (g/kg), while a control diet (C+) included two-fold higher amount of fishmeal (30%) with no taurine supplementation. Seabass fed the T20 or C+ diet showed similar growth, which was significantly higher compared to those in the C-treatment. Histological examination of the muscle, liver and intestine were similar among treatments. No effect on spoilage bacterial growth or production of total volatile basic nitrogen was observed. Taurine supplementation significantly reduced fillet drip loss, while the fillets of European seabass fed the T10 and T20 diets showed significant higher and lower hardness and adhesiveness values, respectively. Moreover, fillet chewiness was also found to be significantly higher in fish fed the T20 diet compared to C+ and C- diets. Overall, it seems that high dietary taurine supplementation acted as a growth promoter and concurrently improved significantly the postharvest quality characteristics of seabass, which may be attributed to its role in maintaining cell membrane integrity and permeability.
Finding suitable alternative protein sources for diets of carnivorous fish species remains a major concern for sustainable aquaculture. Through genetic selection, we created a strain of rainbow trout ...that outperforms parental lines in utilizing an all-plant protein diet and does not develop enteritis in the distal intestine, as is typical with salmonids on long-term plant protein-based feeds. By incorporating this strain into functional analyses, we set out to determine which genes are critical to plant protein utilization in the absence of gut inflammation. After a 12-week feeding trial with our selected strain and a control trout strain fed either a fishmeal-based diet or an all-plant protein diet, high-throughput RNA sequencing was completed on both liver and muscle tissues. Differential gene expression analyses, weighted correlation network analyses and further functional characterization were performed. A strain-by-diet design revealed differential expression ranging from a few dozen to over one thousand genes among the various comparisons and tissues. Major gene ontology groups identified between comparisons included those encompassing central, intermediary and foreign molecule metabolism, associated biosynthetic pathways as well as immunity. A systems approach indicated that genes involved in purine metabolism were highly perturbed. Systems analysis among the tissues tested further suggests the interplay between selection for growth, dietary utilization and protein tolerance may also have implications for nonspecific immunity. By combining data from differential gene expression and co-expression networks using selected trout, along with ontology and pathway analyses, a set of 63 candidate genes for plant diet tolerance was found. Risk loci in human inflammatory bowel diseases were also found in our datasets, indicating rainbow trout selected for plant-diet tolerance may have added utility as a potential biomedical model.
The growth rate of farmed fish is an important factor regarding aquaculture success. An understanding of the cellular events that occur in skeletal muscle when fish undergo periods of fasting and ...refeeding provides information useful in developing alternative feeding strategies for improving muscle growth in commercially cultivated species. To evaluate the effect of 1–3 weeks of fasting and 10 weeks of refeeding in Nile tilapia juveniles, we analyzed the growth performance and changes in muscle cellularity and the expression of the following growth and muscle related genes: MyoD, myogenin, IGF-1, IGF-1 receptor, MuRF-1, atrogin-1 and myostatin. Reduced body mass was observed in all three groups of fasted fish during their time off feed, and 10 weeks of refeeding resulted in partial compensatory growth of body mass. No differences in the frequency of white muscle fiber diameters were observed between fasted and fed control fish treatments. However, changes in gene expression induced by fasting and refeeding were found. IGF-1 receptor, ubiquitin ligases MuRF1 and atrogin-1 expression increased during the 1–3 weeks of fasting, while IGF-1 levels dropped significantly (
P
< 0.001) compared to the control treatment. Furthermore, myogenin mRNA level in fish submitted to 3 weeks of fasting was higher in comparison to the control treatment (
P
< 0.05). Overall, our results showed that 1–3 weeks of fasting can induce muscle atrophy activation in Nile tilapia juveniles, and 10 weeks of refeeding is enough to induce only partial compensatory growth.
Bile is a yellow‐green liquid produced in the liver from cholesterol and stored in the gallbladder of vertebrates. Bile improves the efficacy of lipid digestion by acting as an emulsifier and is ...essential in activating bile salt lipase, an enzyme that has broad substrate specificity. Bile improves the absorption of lipid soluble nutrients while also facilitating the excretion of cholesterol and toxic metabolites, particularly bilirubin. Dietary fishmeal alternatives often disturb bile acid status in fish resulting in either increased excretion/decreased intestinal reabsorption and/or decreased bile acid synthesis. Saponins and high molecular mass proteins are believed to contribute to altered bile acid status, which may reduce fish productivity. This situation can worsen with increased incorporations of plant‐based proteins in aquafeeds, but also may be mitigated by processing of fishmeal alternatives as well as the dietary inclusion of some bile acids/salts. This area of research will likely increase due to the roles dietary bile acids/salts can have on protecting digestive organs and improving nutrient utilization. This, however, depends on the bile type, level and fish species. This review discusses these aspects in regard to fish nutrition to help increase the inclusion of dietary fishmeal alternatives and thus enhance aquaculture sustainability.
This study evaluated the effects of taurine supplementation to diets containing a high dietary inclusion of soybean meal and soy protein concentrate on growth performance and fillet quality of ...juvenile European sea bass (Dicentrarchus labrax). A control diet (C+) was produced containing high levels of fishmeal (30% FM) and soybean meal (20% SBM). Three other experimental diets were prepared to contain a lower FM inclusion (25%), and a higher amount of soy products (20% of SBM plus 12% soy protein concentrate, SPC) supplemented with three graded levels of crystalline taurine, 0.2%, 0.5% and 1.0% (T0.2, T0.5 and T1.0), respectively. A fifth diet was also prepared having a similar composition as the latter three diets but without the addition of crystalline taurine (negative control diet, C-). All diets were iso-nitrogenous (44%), iso-lipidic (20%) and iso-energetic (22 MJ kg−1) and were fed to five triplicate groups of sea bass (initial weight 86 g) over the course of a 12-week trial. Dietary taurine supplementation did not affect the growth performance and feed efficiency (P > 0.05). Proximate composition of whole body and muscle were similar among groups (P > 0.05). Taurine dietary supplementation had no effect on the level of intraperitoneal fat deposition (P > 0.05). However, muscle taurine concentration was found to increase gradually in sea bass fed the elevated levels of taurine (P < 0.05). Interestingly, the hardness and chewiness of the fillet, recorded by texture analysis, increased significantly at higher dietary taurine levels (P < 0.05). The highest adhesiveness values were obtained in sea bass fed the C- diet, whereas the lowest ones were found in fish fed the T1.0 diet (P < 0.05). No significant (P > 0.05) impact of diets on texture fillet springiness and cohesiveness was found (P > 0.05). In general, no significant differences were observed by the test panel, however, fish fed the diet supplemented with 1.0% taurine exhibited lower fillet elasticity, thus indicating a potential textural difference in accordance with those obtained from the texture analysis of fish muscles. The histological analysis did not indicate any differences in the gut and liver of the fish fed the experimental diets. Overall, the findings of the present study showed that 1.0% taurine supplementation in diets incorporating high levels of soy products might have a pronounced effect on flesh quality of European sea bass.
•Effects of taurine supplementation in a high-soy diet of European sea bass.•Fed a diet that contains 20% SBM and 12% SPC without impeding fish performance.•Taurine supplementation affected the hardness, chewiness and elasticity of European sea bass fillet.
Replacement of fishmeal as the major protein source in feeds is critical for continued growth and sustainability of the aquaculture industry. However, numerous studies have shown suboptimal fish ...growth performance and reduced protein retention efficiency when carnivorous fish species are fed low fishmeal-high plant protein feeds. A study was conducted using a commercial strain and a genetically improved strain of rainbow trout selected for improved performance when fed an all plant protein diet to identify physiological differences associated with growth performance in the selected trout strain. Fifty individuals per strain (average weight ~ 580 g) were force-fed a plant-protein blend with and without amino acid supplementation (lysine, methionine and threonine) at 0.5% body weight and sampled at intervals over 24 h. Samples from intestine and liver were analyzed for specific gene expression analysis related to amino acid transporters, digestive process control, protein degradation and amino acid metabolism. The results showed that expression levels of various intestinal amino acid transporters (SLC1A1, SLC7A9, SLC15A, SLC1A5 SLC6A19 and SLC36A1) were affected by strain, diet and time. Moreover, significant interactions were found regarding the temporal expression levels of cholecystokinin (CCK-L), Krüppel-like factor 15 (KLF15) and aspartate aminotransferase (GOT) transcripts in the examined tissues. The results provide evidence that improved growth and protein retention of the selected strain fed an all-plant protein diet is a result of nutritional adaptation and an overall change in physiological homeostatic control.
•Genetically selected and non-selected rainbow trout were compared to identify physiological differences in with nutrient utilization•Both strains of trout were force-fed a plant-protein blend with and without amino acid supplementation•Results showed that expression levels of intestinal amino acid transporters were affected by strain, diet and time•Improved weight gain and protein retention in the selected (vegetarian) trout strain is the result of nutritional adaptation to an all plant-protein diet
An 8‐week feeding trial was conducted to determine the dietary lysine requirement of greater amberjack, Seriola dumerili. Six experimental diets resulting from a practical basal formulation were ...produced to containing mainly plant ingredients (25% fish meal) were supplied with graded levels of crystalline L‐lysine‐HCl and the analysed lysine concentration in each diet was found to be 1.93 (basal diet; CL1.93), 2.01 (CL2.01), 2.11 (CL2.11), 2.15 (CL2.15), 2.20 (CL2.20) and 2.29 (CL2.29) g/100 g diet respectively. Seriola dumerili of 32.8 g ± 3.0 (mean ± SD) were randomly assigned to 18 experimental small cages, and each was stocked with 25 fish per cage in triplicates. The fish were hand‐fed with the experimental diets twice daily (09:00 h and 15:00 h) to apparent satiation, 6 days a week for 56 days. No significant differences were observed in weight gain (WG), daily growth index (DGI), specific growth rate (SGR) and protein efficiency ratio (PER) among the dietary groups. However, the pairwise linear regression of WG showed that the dietary lysine requirement of greater amberjack juvenile is 2.11% of the diet. The activity of catalase enzyme among the dietary treatments differed significantly (p < .05) in both the liver and intestine. Similar results were found for the heat shock proteins (HSP70 and HSP90) with a tissue‐specific response. Based on the results obtained, the dietary lysine requirements that can support maximum WG and PER of greater amberjack juvenile were found to be between 2.03% and 2.11% of the diet (4.55%–4.73% of dietary protein).
Soy protein concentrate (SPC) rarely replaces fishmeal (FM) completely in marine finfish diets without eliciting adverse effects on fish performances. The inclusion of brown seaweed (Sargassum ...fulvellum) could alleviate the negative effects linked to high SPC dietary inclusion. In the current study, the dietary effects of S. fulvellum inclusion in diets for Japanese flounder (Paralichthys olivaceus) in which FM was partially replaced with SPC were evaluated. A FM‐based positive control (Con+) diet with FM protein partially replaced with SPC protein (Con−) was supplemented with S. fulvellum at levels of 30, 60 and 90 g/kg to formulate SF3, SF6 and SF9 diets, respectively. The five diets were fed to fish (0.52 g) in triplicate groups up to apparent satiety for 56 days. The dietary brown seaweed significantly increased (p < .05) growth performance, showing significantly higher per cent weight gain (p < .05) and specific growth rate in fish fed SF6 and SF9 compared to other treatments. Seaweed inclusion also significantly increased (p < .05) feed intake and feed utilization performances. Fish fed Con− diet exhibited significantly lower (p < .05) growth and feed utilization performances. The highest muscular and hepatic total lipids were observed in fish fed Con+. Seaweed inclusion significantly increased and decreased (p < .05) muscular and hepatic total lipid contents, respectively, when compared to Con− diet. The muscle fatty acids were not significantly (p > .05) affected by dietary S. fulvellum. Hepatic Σn‐3 and Σn‐3+Σn‐6 fatty acids were significantly higher (p < .05) in supplemented groups compared to Con+ and Con−. Finally, S. fulvellum inclusion at 60 g/kg is found to be beneficial for increasing growth, feed utilization and some fatty acid restoration in SPC‐incorporated Japanese flounder fry diets.
A selected rainbow trout strain was used as a model to identify physiological parameters associated with improved performance when fed all plant-protein feed. Results from a digestibility trial ...showed that selection had no measurable effect on apparent digestibility coefficients of nutrients in the all plant-protein or a conventional fishmeal-based diet. While this result validated apparent digestibility as an evaluation tool for ingredient and diet quality, it demonstrated that other physiological mechanisms are responsible for the improved performance of the selected strain when fed an all plant-protein, high-soy diet. A subsequent experiment was conducted to evaluate the effects that alternate protein ingredients and plant protein mixtures with or without amino acid supplementation have on trout digestive physiology. Results from temporal plasma amino acids measurements at the absorption site (hepatic portal vein) and from the systemic blood (caudal vein) demonstrated that plasma amino acid level in the hepatic portal vein, measured at intervals following a single meal, are a valuable tool to evaluate the effects of candidate alternate proteins on fish digestive physiology. The findings showed that each ingredient affects digestive physiology of the fish in a singular manner when ingredients are fed individually. However, they do not have any predictable additive effect when fed together as a mixture. Moreover, the addition of crystalline amino acids to an all-plant protein mixture altered the plasma concentrations of all the amino acids as it did for uptake reflected in the hepatic portal vein. A major finding in the study was that the selected trout strain fed the plant protein mixture with amino acid supplemention showed a noteworthy difference compared to an unselected strain, specifically, a synchronous and homogenous decreasing pattern for all the essential amino acids over time in the hepatic portal vein. This indicates that homogeneous dietary amino acid uptake in the hepatic portal vein and rapid postprandial plasma amino acid disappearance are results of nutritional adaptation driven by selection for growth on and tolerance of all-plant protein diet. Results from gene expression of amino acid transporters, cholecystokinin and genes related with protein and amino acid metabolism supported the findings from the plasma amino acids. In conclusion, the results of the research described in this dissertation demonstrated that improved performance of the selected trout strain is associated with synchronous protein digestion of the plant protein mixture and synchronization of amino acid absorption leading to improved amino acid availability and utilization.
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