Submit your research today
Aquaculture Nutrition is now open for submissionsRead our author guidelines
Aquaculture Nutrition provides a global perspective on the nutrition of all cultivated aquatic animals. Topics range from extensive aquaculture to laboratory studies of nutritional biochemistry and physiology.
Chief Editor Erik-Jan Lock is a Research Group Leader in Feed and Nutrition at the Institute of Marine Research in Norway, and Professor at the University of Bergen.
Abstracting and Indexing
Latest ArticlesMore articles
Effects of Dietary Resveratrol, Bile Acids, Allicin, Betaine, and Inositol on Recovering the Lipid Metabolism Disorder in the Liver of Rare Minnow Gobiocypris rarus Caused by Bisphenol A
The fatty liver is one of the main problems in aquaculture. In addition to the nutritional factors, endocrine disrupter chemicals (EDCs) are one of the causes of fatty liver in fish. Bisphenol A (BPA) is a plasticizer widely used in the production of various plastic products and exhibits certain endocrine estrogen effects. Our previous study found that BPA could increase the accumulation of triglyceride (TG) in fish liver by disturbing the expression of lipid metabolism-related genes. How to recover the lipid metabolism disorder caused by BPA and other environmental estrogens remains to be explored. In the present study, Gobiocypris rarus was used as a research model, and 0.01% resveratrol, 0.05% bile acid, 0.01% allicin, 0.1% betaine, and 0.01% inositol were added to the feed of the G. rarus that exposed to 15 μg/L BPA. At the same time, a BPA exposure group without feed additives (BPA group) and a blank group with neither BPA exposure nor feed additives (Con group) were setted. The liver morphology, hepatosomatic index (HSI), hepatic lipid deposition, TG level, and expression of lipid metabolism-related genes were analyzed after 5 weeks of feeding. The HSI in bile acid and allicin groups was significantly lower than that in Con group. The TG in resveratrol, bile acid, allicin, and inositol groups returned to Con level. Principal component analysis of TG synthesis, decomposition, and transport related genes showed that dietary bile acid and inositol supplementation had the best effect on the recovery of BPA-induced lipid metabolism disorder, followed by allicin and resveratrol. In terms of lipid metabolism-related enzyme activity, bile acid and inositol were the most effective in recovering BPA-induced lipid metabolism disorders. The addition of these additives had a restorative effect on the antioxidant capacity of G. rarus livers, but bile acids and inositol were relatively the most effective. The results of the present study demonstrated that under the present dosage, bile acids and inositol had the best improvement effect on the fatty liver of G. rarus caused by BPA. The present study will provide important reference for solving the problem of fatty liver caused by environmental estrogen in aquaculture.
Involvement of Mechanistic Target of Rapamycin (mTOR) in Valine Orexigenic Effects in Rainbow Trout
This study was aimed at clarifying the importance of a mechanistic target of rapamycin (mTOR) in the central orexigenic effect of valine in fish. For this, rainbow trout (Oncorhynchus mykiss) were intracerebroventricularly (ICV) injected with valine alone or in the presence of rapamycin as the mTOR inhibitor, and two experiments were performed. In the first experiment, we evaluated feed intake levels. In the second experiment, we evaluated in the hypothalamus and telencephalon the following: (1) the phosphorylation status of mTOR and its downstream effectors ribosomal protein S6 and p70 S6 kinase 1 (S6K1), (2) the abundance and phosphorylation status of transcription factors involved in appetite regulation, and (3) the mRNA levels of key neuropeptides associated with homeostatic regulation of feed intake in fish. Rising central levels of valine clearly resulted in an orexigenic response in rainbow trout. This response occurred in parallel with mTOR activation in both the hypothalamus and telencephalon, as supported by depressant changes in proteins involved in mTOR signalling (S6 and S6K1). Also, these changes disappeared in the presence of rapamycin. However, it is not clear which precise mechanisms link the activation of mTOR and the alteration in feed intake levels since we did not observe changes in mRNA levels of appetite-regulatory neuropeptides as well as in the phosphorylation status and levels of integrative proteins.
Replacement of Dietary Fishmeal Protein with Degossypolized Cottonseed Protein on Growth Performance, Nonspecific Immune Response, Antioxidant Capacity, and Target of Rapamycin Pathway of Juvenile Large Yellow Croaker (Larimichthys crocea)
A 70-day feeding experiment was carried out to assess the replacement of dietary fishmeal (FM) protein with degossypolized cottonseed protein (DCP) on large yellow croaker (Larimichthys crocea) with initial body weight (). Five isonitrogenous and isolipidic diets replaced fishmeal protein with 0%, 20%, 40%, 60%, and 80% DCP were formulated and named as FM (the control group), DCP20, DCP40, DCP60, and DCP80, respectively. Results displayed that weight gain rate (WGR) and specific growth rate (SGR) in the DCP20 group (263.91% and 1.85% d-1) were significantly increased compared with the control group (194.79% and 1.54% d-1) (). Furthermore, fish fed the diet with 20% DCP significantly increased the activity of hepatic superoxide dismutase (SOD) compared with the control group (). Meanwhile, the content of hepatic malondialdehyde (MDA) in the DCP20, DCP40, and DCP80 groups was significantly lower than that in the control group (). The activity of intestinal trypsin in the DCP20 group was significantly degraded compared with that in the control group (). The transcription of hepatic proinflammatory cytokine genes (interleukin-6 (il-6); tumor necrosis factor-α (tnf-α); and interferon-γ (ifn-γ)) in the DCP20 and DCP40 groups was significantly upregulated compared with that in the control group (). As to the target of rapamycin (TOR) pathway, the transcription of hepatic target of rapamycin (tor) and ribosomal protein (s6) was significantly up-regulated, while the transcription of hepatic eukaryotic translation initiation factor 4E binding protein 1 (4e-bp1) gene was significantly downregulated in the DCP group compared with the control group (). In summary, based on the broken line regression model analysis of WGR and SGR against dietary DCP replacement levels, the optimal replacement level was recommended to be 8.12% and 9.37% for large yellow croaker, respectively. These results revealed that FM protein replaced with 20% DCP could promote digestive enzyme activities and antioxidant capacity and further activate immune response and the TOR pathway so that growth performance of juvenile large yellow croaker was improved.
Growth, Nutrient Retention, Waste Output, and Antioxidant Capacity of Juvenile Triangular Bream (Megalobrama terminalis) in Response to Dietary Selenium Yeast Concentration
An 8-week feeding trial was conducted to investigate the effects of different dietary selenium yeast levels on growth, nutrient retention, waste output, and antioxidant capacity of juvenile triangular bream (Megalobrama terminalis). Five isonitrogenous (320 g/kg crude protein) and isolipidic (65 g/kg crude lipid) diets were formulated, with supplementation of graded levels of selenium yeast at 0 (diet Se0), 1 (diet Se1), 3 (diet Se3), 9 (diet Se9), and 12 g/kg (diet Se12). No significant differences were found in initial body weight, condition factor, visceral somatic index, hepatosomatic index, and whole body contents of crude protein, ash, and phosphorus among fish fed different test diet. The highest final body weight and weight gain rate were found in fish fed diet Se3. The specific growth rate (SGR) is closely related to dietary selenium (Se) concentrations with a relationship described as . Higher feed conversion ratio was found, while lower retention efficiencies of nitrogen and phosphorus were found in fish fed diets Se1, Se3, and Se9 than in fish fed diet Se12. Contents of selenium in whole body, vertebra, and dorsal muscle increased with dietary supplementation of selenium yeast increased from 1 mg/kg to 9 mg/kg. Lower nitrogen and phosphorous waste was found in fish fed diets Se0, Se1, Se3, and Se9 than in fish fed diet Se12. Fish fed diet Se3 exhibited the highest activities of superoxide dismutase, glutathione peroxidase, and lysozyme while the lowest malonaldehyde content in both the liver and kidney. Our results showed that the optimal dietary selenium requirement for triangular bream should be 12.34 mg/kg based on the nonlinear regression on SGR, and fish fed diet Se3 in which selenium concentration (8.24 mg/kg) was close to the optimal requirement displayed the best growth performance, feed nutrient utilization, and antioxidant capacity.
Fish Oil Replacement with Poultry Oil in the Diet of Tiger Puffer (Takifugu rubripes): Effects on Growth Performance, Body Composition, and Lipid Metabolism
Booming fish farming results in relative shortage of fish oil (FO), making it urgent to explore alternative lipid sources. This study comprehensively investigated the efficacy of FO replacement with poultry oil (PO) in diets of tiger puffer (average initial body weight, 12.28 g). An 8-week feeding trial was conducted with experimental diets, in which graded levels (0, 25, 50, 75, and 100%, named FO-C, 25PO, 50PO, 75PO, and 100PO, respectively) of FO were replaced with PO. The feeding trial was conducted in a flow-through seawater system. Each diet was fed to triplicate tanks. The results showed that FO replacement with PO did not significantly affect the growth performance of tiger puffer. FO replacement with PO at 50-100% even slightly increased the growth. PO feeding also had marginal effects on fish body composition, except that it increased the liver moisture content. Dietary PO tended to decrease the serum cholesterol and malondialdehyde content but increase the bile acid content. Increasing levels of dietary PO linearly upregulated the hepatic mRNA expression of the cholesterol biosynthesis enzyme, 3-hydroxy-3-methylglutaryl-CoA reductase, whereas high levels of dietary PO significantly upregulated the expression of the critical regulatory enzyme of bile acid biosynthesis, cholesterol 7-alpha-hydroxylase. In conclusion, poultry oil is a good substitution for fish oil in the diets of tiger puffer. Poultry oil could replace 100% added fish oil in the diet of tiger puffer, without adverse effects on growth and body composition.
Assessment of Performance, Microbial Community, Bacterial Food Quality, and Gene Expression of Whiteleg Shrimp (Litopenaeus vannamei) Reared under Different Density Biofloc Systems
Biofloc shrimp culture, as a way of improving shrimp production, gains worldwide consideration. However, the effects of the biofloc system on shrimp culture at high densities could be a challenge. Here, this study is aimed at identifying a better stocking density of whiteleg shrimp (Litopenaeus vannamei) between two intensive biofloc systems of 100 and 300 org./m2. Achieving that was done by comparing growth performance, water quality, feed utilization, microbial loads from water and shrimps, and gene expression of growth, stress, and immune-related genes. Shrimp postlarvae with a mean weight of mg were reared in six indoor cement tanks (36 m3 total capacity each) at two stocking densities (3 replicates each) for a rearing period of 135 days. Better final weight, weight gain, average daily weight gain, specific growth rate, biomass increase percentage, and survival rate were associated with lower density (100/m2), whereas high-density showed significantly higher total biomass. Better feed utilization was found in the lower density treatment. Lower density treatment enhanced water quality parameters, including higher dissolved oxygen and lower nitrogenous wastes. Heterotrophic bacterial count in water samples was recorded as and log CFU/ml from the high- and low-density systems, respectively, with no significant difference. Beneficial bacteria such as Bacillus spp. were identified in water samples from both systems, still, the Vibrio-like count was developed in the higher density system. Regarding shrimp food bacterial quality, the total bacterial count in the shrimp was recorded as log CFU/g in the 300 org./m2 treatment compared to log CFU/g in the lower density. Escherichia coli was isolated from the shrimps in a lower density group while Aeromonas hydrophila and Citrobacter freundii were associated with shrimps from a higher density system. Immune-related genes including prophenoloxidase, superoxide dismutase (SOD), and lysozyme (LYZ) expressions were all significantly higher expressed in the shrimp from the lower density treatment. Toll receptor (LvToll), penaiedin4 (PEN4), and stress-related gene (HSP 70) showed a decreased gene expression in the shrimp raised in the lower density. Significant upregulation of growth-related gene (Ras-related protein-RAP) expression was associated with the lower stocking density system. In conclusion, the current study found that applying high stocking density (300 org./m2) contributes negatively to performance, water quality, microbial community, bacterial food quality, and gene expression of immune, stress, and growth-related genes when compared with the lower stocking density system (100 org./m2) under biofloc system.