Aquaculture Nutrition最新文献

Manganese (Mn) is a nutritional element required for fish growth and physiology functions. In this study, we examined the effect of Mn on the intestinal digestive function, antioxidant response, and muscle quality in coho salmon (Oncorhynchus kisutch). Nine hundred salmons with initial weight approximately 0.35 g were fed with six isoproteic and isoenergetic diets formulated to contain 2.4, 8.5, 14.8, 19.8, 24.6, and 33.7 mg/kg Mn for 84 days. The result showed that the activity of trypsin and lipase was elevated, whereas α-amylase activity was not affected by various Mn diets in intestine. Dietary Mn elevated the activity of Mn-superoxide dismutase (Mn-SOD), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX), and catalase (CAT), but had no influence on copper/zinc-superoxide dismutase (Cu/Zn-SOD) in intestine. Dietary Mn at 8.5, 14.8, 19.8, 24.6, and 33.7 mg/kg enhanced the gene expression level of protein kinase B (Akt) and mammalian target of rapamycin (mTOR). In addition, the accumulation of Mn in muscle was enhanced with increasing levels of dietary Mn. Dietary Mn elevated the content of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca), but the content of iron (Fe) and Zn was decreased by dietary Mn in the salmon muscle. The content of fatty acids and amino acids was enhanced by various levels of dietary Mn in muscle. Moreover, a significant quadratic effect was observed on the texture of salmon muscle. The dietary Mn requirement was 16.9–25.7 mg/kg Mn to acquire the highest value of muscle texture using the quadratic regression model. The diets at 14.8 and 19.8 mg/kg Mn had a higher score of sensory evaluation for raw muscle. Our result showed that dietary Mn affected the intestinal digestion function and antioxidant response, which may further result in the change of muscle quality in coho salmon. The result will provide reference for detecting the effect of dietary micronutrients on the muscle quality of salmons.

The circular aquaculture model of largemouth bass pond engineering has the characteristics of high yield and efficiency, but it is prone to stress caused by flow velocity and density, which affects the yield of largemouth bass (Micropterus salmoides). γ-Aminobutyric acid (GABA) is believed to have the effect of improving growth and stress tolerance. We divided the largemouth bass into three groups: a control group, a flow rate and density combined stress group, and a combined stress feed supplemented with GABA (0.9%) group, and conducted a 60-day aquaculture experiment. The results showed that the final weight, weight gain rate (WGR), specific growth rate (SGR), and feed efficiency (FE) of largemouth bass significantly decreased in the combined stress group (P < 0.05). The serum aspartate aminotransferase (AST), alanine transaminase (ALT) activity, and glucose (GLU), malondialdehyde (MDA) level of largemouth bass significantly higher than the control group, and the serum lysozyme (LZM) activity and total antioxidant capacity (T-AOC) were significantly lower than the control group (P < 0.05). After adding GABA, the final weight, WGR, SGR, and FE decreased, and the serum GLU levels, AST, ALT activity, and MDA levels were downregulated, and the serum LZM activity and T-AOC of largemouth bass were upregulated. But most of the above are still at the level of the control group. Under combined stress, the messenger ribonucleic acid (mRNA) expression levels of growth hormone (GH), insulin-like growth factor-Ⅰ (IGF-I), B-cell lymphoma-2 (Blc2), nuclear transcription factor E2-related factor 2 (Nrf2), catalase (CAT), and superoxide dismutase (SOD) genes were significantly reduced (P < 0.05), while the mRNA expression levels of heat stress protein 70 (HSP70), heat stress protein 90 (HSP90), nuclear factor kappa-B (NF-κB), interleukin-1β (IL-1β), Bax and keap1 genes were significantly increased (P < 0.05). After the exogenous addition of GABA, all the above genes have a certain degree of callback, but GH, HSP70, HSP90, IL-1β, Bax, Nrf2, CAT, and SOD have not yet reached the level of the control group. These results indicate that adding GABA to feed can alleviate the adverse effects of combined stress of flow rate and density to a certain extent and provide insights for solving the problems in the circular aquaculture model of largemouth bass.

Porphyra polysaccharide (PPS), derived from marine red seaweeds of the Porphyra genus, has been reported to improve growth performance, lipid metabolism, and antioxidant capability in animals. The present study investigated the effects of PPS supplementation to a high-carbohydrate diet on growth performance, lipid metabolism, immunity, antioxidant capacity, intestinal morphology, and microbial composition in rabbitfish (Siganus canaliculatus). Rabbitfish were fed a basal starch diet (BSD, 15% starch) and high-starch diets (HSD, 25% starch) supplemented with varying levels of PPS (0%, 1.25%, 2.5%, and 5%) for 8 weeks. The results showed that HSD intake significantly decreased body weight and increased hepatosomatic index compared to rabbitfish fed BSD. But all dietary levels of PPS reversed these two indicators of fish fed HSD. In addition, the supplementation of 2.5% and 5% PPS significantly reduced the higher lipid contents in whole fish and abdominal muscle of fish fed HSD. Notably, 2.5% PPS reduced lipid droplets in the liver, possibly through the downregulation of genes associated with lipid synthesis and the upregulation of genes associated with lipid catabolism. Moreover, all levels of PPS supplementation decreased the higher serum alanine aminotransferase activity in fish fed HSD, indicating the alleviation of HSD-induced liver impairment. Additionally, PPS inclusion significantly increased the activity of serum lysozyme, superoxide dismutase, and catalase while decreasing serum malondialdehyde in fish fed HSD, suggesting improvements in immunity and antioxidant capacity. Furthermore, PPS inclusion mitigated damage to intestinal villi induced by HSD. Interestingly, 2.5% PPS increased the abundance of Bacteroidetes and Tenericutes while reducing the abundance of Proteobacteria and Spirochetes, indicating the reshaping of gut microbiota. In summary, dietary PPS alleviated the negative effects of HSD on growth performance, lipid metabolism, immunity, antioxidant capacity, and intestinal morphology and altered microbial composition in rabbitfish. This highlighted the beneficial effects of dietary PPS in fish and suggested it could contribute to the new strategies for treating metabolic syndrome and health impacts in aquatic animals.

Long-term consumption of high-carbohydrate feed may adversely affect intestinal health of fish; however, the underlying roles remain ambiguous. This study examined the effects of varying carbohydrate levels on the intestinal flora of common carp and assessed how microbial metabolites influence intestinal health. Two hundred seventy common carps were chosen and distributed randomly into three groups that fed diets containing starch at levels of 15% (low-carbohydrate diet [LCD]), 28% (medium-carbohydrate diet [MCD]), and 45% (high-carbohydrate diet [HCD]) for 60 days. A significant increase in final body weight, weight gain rate, and specific growth rate within the MCD group, while feed conversion ratio exhibited a decrease in comparison to the other groups (p < 0.05). Feeding with a HCD led to decreased activity of catalase and increased malondialdehyde content, which was consistent with reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) analysis results (p < 0.05). Specifically, the RT-qPCR results revealed that HCD treatment significantly upregulated il1β, il6, and il8 transcript levels. Whereas, the il10 messenger RNA (mRNA) was markedly reduced in comparison to the LCD group. Furthermore, the HCD group exhibited an increased abundance of Proteobacteria, accompanied by a reduction in Fusobacteria abundance, and also revealed an upsurge in opportunistic pathogenic bacteria, such as Aeromonas and Shewanella. The correlation analysis demonstrated negative correlations of anti-inflammatory active substances such as fucoxanthin, (S)-reticuline, hecogenin, and uridine with Aeromonas, but positive correlations with Luteolibacter. In summary, dietary carbohydrates might mediate intestinal flora to regulate their metabolites and affect intestinal inflammatory response.

In the past decade, insect meal has gained popularity in the animal feed industry, particularly in aquafeed, due to rising costs and decreased availability of fish meal (FM) and fish oil. Initially met with skepticism, insect meal is now seen as a promising ingredient because of its high nutrient profile. Research worldwide is exploring its potential as a FM replacement. Insects are abundant, nutritious, and environmentally friendly, as they can be reared on organic waste, minimizing the need for land, water, and energy. This research aims at obtaining a comprehensive and in-depth understanding of the current status and research trend patterns in this research field. To achieve this goal, this study conducts a mini systematic review and scientometric analysis of the global research published from 2013 to 2022 on the usage of insect meal in aquaculture. In the scientometric analysis, a total of 354 papers published by 1800 authors in 124 different journals from the Web of Science (WoS) core collection were analyzed, evaluating the number of publications, most relevant authors, organizations, top cited countries, most globally cited publications, and trending research themes in this field. The result showed that the University of Turin was the leading organization in insect meal research, whereas aquaculture was the leading journal, and author Laura Gasco was the prominent researcher in this field in the studied time frame (2013–2022). Italy was the leading country in Europe, while China dominated Asia in terms of the number of publications. The annual growth rate in insect meal research was found to be positive (23.11%), with 36.95 average citations per document. This study helps practitioners and scholars understand the current state of insect meal in aquaculture and identifies research requirements that can benefit both academia and industry.

Astaxanthin (Ax) determines the flesh redness of a salmonid fish which is the most desirable quality indicator by consumers. Fish cannot synthesize Ax de novo, therefore, the only way to increase flesh redness is to increase dietary input or improve the absorption and retention rate of dietary Ax. As a hydrophobic carotenoid, the absorption of Ax can be modulated by other lipid molecules in the diet. The present study explored the effect of three lipids, cholesterol (CH), phytosterol (PS), and docosahexaenoic acid (DHA) on Ax absorption, transport, and retention in rainbow trout. Dietary CH significantly improved Ax absorption by elevating plasma Ax levels (p < 0.05); however, it had no effect on the whole body Ax or flesh color. Dietary PS appears to inhibit Ax absorption since fish had significantly (p < 0.05) reduced whole body Ax. Dietary DHA appeared to have no effect on Ax absorption or retention. By comparing intestinal transcriptomes, a low density lipoprotein receptor (ldlr) gene was significantly downregulated in fish fed the CH diet as compared to the control diet. Since LDLR protein plays a major role in plasma lipoprotein turnover, we hypothesized that the inhibition of ldlr gene by high dietary CH resulted in higher retention of plasma Ax. The elevation of plasma Ax was not reflected in higher flesh coloration, which suggested other limiting factors governing Ax retention in the muscle. On the other hand, the transcriptomic and proteomic analyses found no changes of genes or proteins involved in Ax absorption, transport, or excretion in fish fed PS or DHA diets as compared to the control diet. In conclusion, this study has suggested that CH promotes Ax absorption by regulating lipoprotein retention and provide evidence for improving Ax absorption via dietary modulation.

Biofloc technology offers a viable choice for the rearing of fish seed by offering a safe and protected habitat for young fish. Nevertheless, it is crucial to establish a standardised stocking density and implement effective ameliorative steps in order to successfully utilise this technology. In this study, a 90-day investigation was conducted to assess the effect of stocking density and dietary vitamin C (Vit C) levels on the growth and immunity of Labeo gonius fry (1.03 ± 0.01 g) reared in a biofloc system. Three stocking density groups (5, 10 and 15 fish per 50 L) were established, and each experimental group was supplemented with three levels of Vit C (0, 500 and 1000 mg kg⁻¹). The highest survival rate was observed in the lowest density group (five fish per 50 L) fed with 1000 mg kg⁻¹ Vit C. A better feed conversion ratio and significantly higher protein efficiency ratio were found in the moderate stocking density group (10 fish per 50 L) fed with 500 mg kg⁻¹ Vit C. Total leukocyte count (TLC), haemoglobin, and packed cell volume improved in Vit C-fed groups. The total erythrocyte count (TEC) increased in groups fed Vit C and stocked at lower densities (5 and 10 fish per 50 L). Total serum protein (TPP) content increased when Vit C was added at a rate of 500 mg kg⁻¹. Serum glucose and cortisol levels were significantly reduced in Vit C-supplemented groups. Supplementation of Vit C at 500 mg kg⁻¹ resulted in a significantly lower value of malondialdehyde (MDA). Thus, the findings confirm that the incorporation of Vit C in the basal diet promotes the growth and health status of L. gonius fry reared in the biofloc system at high-density rearing.

A 10-week feeding trial was conducted to investigate the dietary pyridoxine requirements of coho salmon (Oncorhynchus kisutch) post-smolts with an initial mean body weight of 180.22 ± 0.41 g. Seven diets were prepared with gradient pyridoxine levels of 0.32, 1.25, 2.56, 4.08, 8.24, 16.02, and 32.32 mg/kg, respectively, and each diet was assigned to three replication groups of 10 fish. The results revealed that coho salmon fed the diet with pyridoxine supplementation gained more final body weight (FBW), specific growth rate (SGR), and better feed conversion ratio (FCR). FBW and SGR of the fish fed the diet with 8.24 mg/kg pyridoxine were significantly higher than those of the other groups (P < 0.05). An inverse trend was observed for FCR, which was the lowest in fish fed the diet with 8.24 mg/kg pyridoxine. The gradient pyridoxine levels did not yield any statistically (P > 0.05) significant impact on the whole-body composition including moisture, ash, crude lipid, and crude protein. The hepatic pyridoxine concentration, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities increased significantly with dietary pyridoxine levels increasing from 0.32 to 4.08 mg/kg (P < 0.05) and plateaued after that (P > 0.05). The coho salmon fed the diet with 8.24 mg/kg pyridoxine achieved the maximum superoxide dismutase and catalase, as well as the minimum total cholesterol, triglyceride, and malondialdehyde. Broken line analysis of SGR, FCR, AST, and ALT activities reflected the optimal dietary pyridoxine requirements for coho salmon post-smolts from 3.92 to 7.08 mg/kg diet.

A nutritional bottleneck in salmonid aquaculture is the procurement of marine-derived compounds, such as essential amino and fatty acids, including omega-3 fatty acids, lysine, and methionine. Therefore, insects containing these compounds are highly promising as feed ingredients. The present study evaluates larvae of a “marine” insect (Coelopa frigida, the bristly-legged seaweed fly larvae, SWFL) reared on brown algae side streams as a feed ingredient for rainbow trout (Oncorhynchus mykiss). SWFL contained, on a dry matter basis, 60% crude protein (CP), 3.5% lysine, and 1.5% methionine, as well as 17% lipids, including 4% eicosapentaenoic acid and docosahexaenoic acid. Four isoenergetic (ca. 23 MJ kg⁻¹ gross energy) and isoproteic (ca. 45% CP) feeds were evaluated in a 10-week feeding trial. The diets included a control containing 25% fish meal, a commercial reference, and two diets substituting 40% fish meal with either SWFL or partially defatted black soldier fly larvae (BSFL) meal (Hermetia illucens). SWFL-fed fish displayed higher specific growth rates (SGR) compared to BSFL-fed fish and similar SGR compared to control and reference diet-fed fish. Feed intake in SWFL-fed fish was higher than for the control and BSFL diets and similar to the reference diet. The feed conversion ratio of fish fed the BSFL and SWFL diets was higher compared to the control, suggesting lower bioavailability of both insect meals compared to fish meals. No difference in intestinal health parameters was noted between the insect diets and the control diet, indicating good intestinal health across all treatments. However, changes in electrogenic intestinal transport were observed between the SWFL and BSFL diets, illustrating the heterogeneous effect of different insect products. Overall, SWFL meal is a promising alternative marine feed ingredient, compatible with circular production systems, as it can be efficiently cultivated using marine side streams.