Chitin derived from the American cockroach (Periplaneta americana) is a sustainable biopolymer with significant potential in aquafeeds. In this study, a 56-day feeding trial was conducted to evaluate its dose-dependent effects on juvenile common carp (Cyprinus carpio). A total of 300 healthy juvenile carp with an average initial body weight of 4.96 ± 0.013 g were randomly assigned to 5 experimental groups. Each group consisted of 3 replicates, with 20 fish per replicate. Diets containing 0%, 2.5%, 5%, 10%, and 20% chitin were assessed. Results showed that 5% chitin inclusion significantly enhanced growth performance, including final body weight (FBW, P = 0.002) and specific growth rate (SGR, P = 0.001), maximized crude protein and chitin apparent digestibility coefficients (ADC), and upregulated intestinal chitinase gene expression. However, higher dosages (10% and 20%) compromised intestinal integrity and significantly reduced crude protein apparent digestibility (P < 0.001). Notably, the 20% inclusion level suppressed growth, with the specific growth rate (SGR) decreasing by approximately 6.2% compared to the control group (P = 0.001). Interestingly, a decoupling of trypsin gene expression (downregulated) and enzyme activity (unchanged) was observed. Combined with a sharp decline in nutrient ADC in high-dosage groups, this supports a “physical suppression mechanism,” where excess chitin physically impedes enzyme-substrate interactions. Multi-omics analysis revealed that high chitin levels induced gut dysbiosis, characterized by an abundance of opportunistic pathogens (Pseudomonadota and Plesiomonas) and disruption of the Aminoacyl-tRNA biosynthesis pathway. In conclusion, P. americana chitin serves as a beneficial functional additive at 5% but exceeds the host’s physiological tolerance at ≥10%, and induces intestinal structural damage and metabolic disorders.

This study evaluated the efficacy of post-extraction American cockroach (Periplaneta americana) residue (PAR) as a dietary feed ingredient on the growth performance, antioxidant defense, and whole-body amino acid profile of juvenile black carp (Mylopharyngodon piceus). A total of 300 juvenile black carp (initial weight 17.19 ± 0.20 g) were fed five isonitrogenous and isolipidic diets for 64 days. PAR was supplemented at inclusion levels of 0% (control), 5%, 10%, 15%, and 20% (corresponding to progressive reductions in dietary fishmeal). The results showed that fish fed the diet with 5% PAR inclusion maintained growth performance and feed conversion efficiency comparable to those of the control group (p > 0.05). Thus, 5% PAR did not significantly improve growth performance, but it did not impair growth under the present experimental conditions. Moreover, 5% PAR supplementation significantly increased hepatic catalase activity and was associated with numerically higher values of several other antioxidant- and immune-related indices. PAR inclusion also increased whole-body glycine deposition, whereas high inclusion levels reduced whole-body methionine content and crude protein deposition. Dietary PAR inclusion at higher levels, especially 20%, was associated with a possible reduction in feed utilization, altered organ indices, altered serum glucose levels, suppressed hepatic transaminase activities, and changes in digestive enzyme activities. However, these responses should be interpreted as the combined outcome of ingredient substitution, amino acid imbalance, altered lipid source, possible essential fatty acid changes, chitin/fiber-like fractions, and metabolic burden, rather than as effects of chitin alone. In conclusion, 5% PAR may be a suitable practical inclusion level for juvenile black carp under the present experimental conditions, whereas excessive inclusion should be used with caution and may require amino acid balancing, improved processing, and further evaluation of dietary gross energy, fatty acid profile, and chitin content.

This study systematically investigates the immunomodulatory and antioxidant properties of dietary chitin derived from the American cockroach (Periplaneta americana) in juvenile common carp (Cyprinus carpio), with emphasis on its tissue-dependent regulation of antioxidant and inflammatory responses. Juvenile carp (initial weight ∼5 g) were fed five isonitrogenous and isoenergetic diets supplemented with 0%, 2.5%, 5%, 10%, and 20% P. americana chitin for nine weeks. Results demonstrated that 2.5% chitin supplementation improved selected innate immune and antioxidant parameters, as evidenced by elevated serum immunoglobulin M (IgM), total antioxidant capacity (T-AOC), and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). At the tissue level, 2.5% inclusion reduced intestinal malondialdehyde (MDA) content, indicating mitigated lipid peroxidation, while enhancing specific antioxidant enzyme activities across the spleen, intestine, and head kidney. Mechanistically, the 2.5% dietary chitin modulated the expression of genes associated with the Nrf2-Keap1 axis in a tissue-dependent manner, rather than uniformly suppressing keap1 transcription. Furthermore, the 2.5% inclusion level was associated with the regulation of inflammatory homeostasis, as indicated by changes in the anti-inflammatory cytokine gene il-10, nf-κb, and downstream pro-inflammatory cytokine genes, including tnf-α and il-1β, in a tissue-dependent manner. Transcriptomic profiling (RNA-Seq) further corroborated these findings, identifying broad transcriptional changes across tissues, ranging from 1240 differentially expressed genes (DEGs) in the spleen to 5689 DEGs in the head kidney. These critical DEGs exhibited significant enrichment in core immune and redox pathways, including Toll-like receptor signaling, NOD-like receptor signaling, phagosome, and cytokine-cytokine receptor interactions. Notably, the modulatory effects exhibited tissue specificity and dose dependence; conversely, the high-dose inclusion level (20%) was associated with intestinal oxidative stress and reduced immune-related responses. In conclusion, 2.5% dietary P. americana chitin showed beneficial effects on selected antioxidant and innate immune responses in juvenile common carp, possibly associated with tissue-dependent modulation of Nrf2-Keap1 and NF-κB-related signaling.

The successful establishment of non-native fish often relies on life-history plasticity and opportunistic trophic strategies. This study elucidates the invasion mechanisms of the non-native yellow catfish (Pelteobagrus fulvidraco) in Lake Erhai, a plateau lake in China, by integrating morphometrics, stable isotope analysis, and DNA metabarcoding. Our results reveal a "triple mechanism" driving this invasion success. First, the population exhibits significant phenotypic plasticity, manifesting as enhanced somatic growth and superior body condition (mean condition factor: 1.92) and sexually dimorphic growth favoring males. Second, DNA metabarcoding confirms a broad trophic niche dominated by zooplankton (31.70%) and, critically, other non-native fishes (Hypomesus nipponensis and Neosalanx taihuensis), providing strong empirical support for the synergistic effects of multiple non-native species. This predation on high-energy forage fish likely fuels the observed somatic growth and high reproductive output, counteracting the typical size-reduction trade-offs often seen in biological invasions. Third, reproductive assessment indicates a protracted spawning period (spanning at least from spring through summer) and an absolute fecundity (mean: 8471 +/- 2194 eggs) consistent with its strategy of producing larger, high-quality eggs, significantly exceeding that of native riverine populations. These findings suggest that P. fulvidraco effectively exploits altered food webs-specifically pre-existing invasive prey-to maximize somatic growth and reproductive output, thereby establishing dominance in the plateau lake ecosystem. Therefore, effective management strategies must go beyond single-species control and prioritize controlling pre-existing invasive forage fish to disrupt the facilitation pathway driven by ecosystem alteration by invasive species.

Chitin derived from the American cockroach (Periplaneta americana) is a sustainable biopolymer with significant potential in aquafeeds. In this study, a 56-day feeding trial was conducted to evaluate the dose-dependent effects of P. americana chitin on juvenile common carp (Cyprinus carpio). A total of 300 healthy juvenile carp with an average initial body weight of 4.93 ± 0.013 g were randomly assigned to five experimental groups, with three replicates per group and 20 fish per replicate. Diets containing 0%, 2.5%, 5%, 10%, and 20% chitin were evaluated. Results showed that the 5% chitin group exhibited numerically higher final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) than the other groups, although these growth indices did not differ significantly from those in the 0%, 2.5%, and 10% groups. The 5% inclusion level also showed relatively favorable crude protein and chitin apparent digestibility coefficients (ADC) and increased intestinal chitinase gene expression. In contrast, high chitin inclusion levels, especially at 20%, significantly reduced growth performance and crude protein apparent digestibility. Histological analysis indicated mild intestinal morphological changes at high inclusion levels, mainly reflected by reduced villus length and muscular layer thickness in some intestinal segments, whereas several other histological parameters were not significantly affected. A decoupling between trypsin gene expression and enzyme activity was also observed, suggesting that digestive responses to dietary chitin may involve complex post-transcriptional or physiological regulation. Multi-omics analyses suggested that high chitin inclusion may be associated with shifts in gut microbial composition and metabolite profiles, including changes related to Pseudomonadota, Plesiomonas, and aminoacyl-tRNA biosynthesis. These findings indicate that P. americana chitin has dose-dependent effects on growth, nutrient utilization, intestinal morphology, and gut microbial-metabolic profiles in juvenile common carp. In conclusion, P. americana chitin may be used as a functional additive at approximately 5%, whereas inclusion levels ≥ 10% should be applied cautiously.

The American cockroach (Periplaneta americana) residue is a by-product obtained after extracting active ingredients from the American cockroach. This residue remains rich in protein and lipids, making it a potential protein source for aquatic feed. In this study, five isonitrogenous and isolipidic diets were formulated to replace varying amounts of fish meal (0 %, 12.5 %, 25 %, 37.5 %, and 50 %) with American cockroach residue (ACR). A 9-week feeding trial was conducted on juvenile rainbow trout (Oncorhynchus mykiss) to investigate the effects of dietary fish meal replacement with ACR on growth, physiological metabolism, intestinal health, and nitrogen and phosphorus emissions. The results showed that replacing 0-50 % of fish meal with ACR in the diet had no significant effects on the growth performance, proximate composition, or amino acid content of juvenile O. mykiss. The activities of trypsin and chitinase in the stomach of juvenile O. mykiss were highest in the 50 % replacement group. As the dietary fish meal replacement level increased, the levels of aspartate aminotransferase, total cholesterol, and glucose in the liver decreased. However, the levels of serum alanine aminotransferase and urea nitrogen in serum increased with a 37.5-50 % replacement level. The activities of head kidney acid phosphatase and catalase were highest in the 25 % fish meal replacement group. Replacing fish meal with ACR had no significant effects on the levels of active phosphate, ammonia nitrogen, and total phosphorus in cultured water. In conclusion, replacing 0-50 % of the fish meal with ACR in the feed of juvenile O. mykiss had no negative effects on their growth performance, feed utilization, body composition, or nitrogen and phosphorus emissions. Replacement levels of 12.5-50 % improved antioxidant capacity, immunity, and maintained intestinal health.

The green alga Haematococcus pluvialis, rich in natural astaxanthin, is a key feed additive for salmonid pigmentation. This study evaluated dietary micro-algal astaxanthin effects on structure, antioxidative and immune response, as well as microbiota in different gut segments of rainbow trout Oncorhynchus mykiss (initial average weight: 0.67 ± 0.02 kg). Three diets contained 0 (Diet 1, control), 18.57 (Diet 2) and 31.25 mg/kg (Diet 3) micro-algal astaxanthin. After a 4-month feeding trial, dietary astaxanthin promoted the goblet cell proliferation of pyloric caeca and increased hindgut tunica muscularis thickness (p < 0.05). It also improved antioxidant capacity, characterized by the upregulation of gpx and cat expression in the midgut, accompanied by a significant decrease in MDA content (p < 0.05). Furthermore, dietary astaxanthin could upregulate tgf-β, tor1 and pcna levels in midgut and igm in hindgut, while il1β, il6, il8 and tnfα in hindgut were significantly downregulated in Diet 2 (p < 0.05). Additionally, dietary astaxanthin also enhanced the α-diversity of hindgut and altered the core microbiota (reduced Proteobacteria, increased Actinobacteria). Diet 2 increased microbic abundance associated with reducing gut inflammation and promoting nutrient absorption while decreasing that of pathogenic bacteria. Overall, dietary 18.57 mg/kg astaxanthin supplementation could promote gut structure, antioxidant and immune capacity, reduce inflammation and modulate microbiota. These findings indicate that natural astaxanthin from H. pluvialis has potential as an immunostimulant to promote gut health in salmonids.

The American cockroach (Periplaneta americana) is a highly nutritious insect containing protein and bioactive compounds, making it a promising feed ingredient for livestock. This study evaluated the effects of replacing varying proportions (0 %, 25 %, 50 %, 75 %, and 100 %) of fishmeal with P. americana meal (PAM) in diets for juvenile Nile tilapia (Oreochromis niloticus) over a nineweek feeding trial. Results showed no significant differences in growth performance, crude protein, total lipids, or amino acid content in whole fish across treatment groups. Enzymatic activities of trypsin, amylase, and lipase in the esophagus and intestines were significantly higher in the control group (0 % PAM) compared to groups receiving 50-100 % PAM substitution. Similarly, serum and liver glucose levels were significantly higher in the 0 % and 25 % PAM groups. Serum malondialdehyde levels increased in the 25 % and 50 % PAM groups, while intestinal malondialdehyde content showed a decreasing trend with higher fishmeal replacement levels. Intestinal villi counts decreased with increasing PAM substitution, with the 75 % and 100 % PAM groups having significantly lower counts than the control. Interestingly, fishmeal replacement exceeding 50 % increased the relative abundance of Microbacteriaceae, Clostridiaceae, Lactobacillus, and Clostridium, while decreasing Bacteroidaceae and Bacteroides. In conclusion, while fishmeal replacement exceeding 25% resulted in altered intestinal structure and shifts in the microbial community, replacing 25 % of dietary fishmeal with PAM had no adverse effects on growth, physiological metabolism, intestinal morphology, or microbial community structure, suggesting PAM represents a promising sustainable alternative protein source at this substitution level.

Fishmeal represents an indispensable protein source in aquaculture. However, increasing resource scarcity and rising prices have made the development of alternative protein sources an urgent priority. American cockroach (Periplaneta americana) residue, a nutrient-rich insect byproduct with high protein content and advantages in sustainable production, presents a promising alternative to fishmeal. This study integrates metabolomics and transcriptomics to systematically investigate the effects of replacing fishmeal with P. americana residue on the physiological metabolism, immune function, and antioxidant defense of juvenile rainbow trout (Oncorhynchus mykiss). Metabolomic analysis revealed significant alterations in amino acid metabolism, lipid metabolism, and energy metabolism-related metabolites in the serum of juvenile O. mykiss fed with the P. americana residue replacement diet (PAR group). The cAMP signaling pathway, phenylalanine metabolism pathway, and mTOR pathway were significantly enriched, indicating that the replacement feed reshaped the energy supply and protein synthesis networks in juvenile O. mykiss. Transcriptomic studies demonstrated that immune-related genes, including MHC I protein complexes (GO:0042612) and intermediate filament cytoskeletons (GO:0045111), were significantly upregulated in the head kidney tissue. In the liver, heme oxygenase activity (GO:0004392) was increased, and the antioxidant pathway (KEGG ferroptosis pathway) was activated, suggesting that the alternative feed may alleviate metabolic stress by enhancing antigen presentation capacity and antioxidant levels. The P. americana residue exerts its effects through a three-pronged synergistic mechanism: “amino acid metabolism reprogramming - antioxidant network activation - immune signaling cascade.” On one hand, it upregulates the arginine-NO-cAMP axis to enhance immune surveillance; on the other hand, it activates the hepatic heme oxygenase system to maintain metabolic homeostasis. This study not only confirms that P. americana residue can effectively replace fishmeal in juvenile O. mykiss feed but also provides deeper insights into its molecular mechanisms in regulating immunometabolic homeostasis. These findings establish a theoretical foundation for developing sustainable, immune-enhancing aquaculture feeds.

A 9-week feeding experiment was conducted to investigate the effects of substituting dietary fish meal with fermented American cockroach residue (FACR) on the growth, metabolism, antioxidant capacity, immunity, and intestinal health of juvenile largemouth bass. Five diets were prepared, where FACR replaced fish meal at 0 %, 15 %, 30 %, 45 %, and 60 % levels, and were fed to juvenile largemouth bass. The results showed that fish in the 0 %, 15 %, and 30 % replacement groups had higher final body weight, weight gain rate, and specific growth rate than those in the 45 % and 60 % groups. The 45 % replacement group had the highest whole-body crude protein content, and the crude lipid content peaked at 30 % replacement. Trypsin activity in the liver and stomach decreased significantly in the 45 % and 60 % groups, whereas the intestinal alpha-amylase activity exhibited a significant reduction in the 60 % group. Serum total protein was highest in the 45 % replacement group, and serum aminotransferase activities were lower in the 15 %, 30 %, 45 %, and 60 % groups compared to the control. The 30 % group had the lowest serum urea nitrogen content. Liver and serum triglyceride and total cholesterol levels decreased with increasing FACR, while liver glucose increased. Immunological indicators were enhanced at 15 % and 30 % replacement but decreased at higher levels. Histological analysis showed that the 15 % group had thicker muscle, the 30 % group had the widest villi, and the control group had the greatest crypt depth. Intestinal microbiota analysis indicated a reduction in richness and diversity with increasing FACR. PCA showed different microbial compositions between FACR and control groups. In summary, replacing 15 % of dietary fish meal with FACR did not harm growth performance but improved body crude protein content, digestive enzyme activity, antioxidant capacity, immunity, and intestinal microbiota composition, promoting the overall health and growth of juvenile largemouth bass.

Astaxanthin is an important pigment for the rainbow trout Oncorhynchus mykiss. This study was conducted to investigate the effects of different sources of dietary astaxanthin on the growth, coloration, and antioxidant capacity of the commercial-sized O. mykiss during long-term feeding. Haematococcus pluvialis (HP), yeast Phaffia rhodozyma (PR), and synthetic astaxanthin (SA) were added to the basic feed (no astaxanthin, NA) to prepare the isonitrogenous and isolipidic experimental diets; the actual astaxanthin content values in the diets were 31.25, 32.96, and 31.50 mg/kg, respectively. Eighteen hundred O. mykiss, averaging 670 ± 20 g, were randomly divided into four groups and then fed with the experimental diet for four months. Dietary supplementation of P. rhodozyma and synthetic astaxanthin had no significant effects on the growth and tissue indexes of O. mykiss. In contrast, dietary supplementation with astaxanthin from H. pluvialis significantly increased the weight gain rate after four months of feeding. The fillet lightness of O. mykiss in the PR and SA was statistically lower than that in the NA and HP; the redness and astaxanthin content of fillet in the HP, PR, and SA groups were statistically higher than those in the NA. The total antioxidant capacity of the liver and serum in the HP was statistically higher than that in other diet groups, and a higher liver total superoxide dismutase activity was detected in the HP compared with the PR. Dietary supplementation of astaxanthin significantly increased the glutathione peroxidase activity in the liver and serum, and the highest serum glutathione peroxidase activity was detected in the HP, while dietary astaxanthin significantly decreased the malondialdehyde content in the liver and serum. Dietary supplementation of PR significantly increased the fillet ash content, while the highest fillet total lipid content was detected in the HP. Dietary astaxanthin significantly improved fillet redness and antioxidant capacity, among which H. pluvialis astaxanthin has greater effects on improving weight gain, antioxidant capacity, and fillet total lipid content.

The American cockroach (Periplaneta americana) residue is a by-product of P. americana meal after extracting active ingredients with ethanol, and it still contains high protein, lipid, and a certain amount of active ingredients, may be a potential fish meal alternative. Five isonitrogenous and isolipidic experimental diets were formulated to replace 0%, 25%, 50%, 75%, and 100% of dietary fish meal with P. americana residue, and defined as Diet 1, Diet 2, Diet 3, Diet 4, and Diet 5, respectively. The juvenile Nile tilapia (Oreochromis niloticus) with an initial body weight of 2.98 ± 0.01 g was fed with respective diets for 10 weeks, which was conducted to investigate the effects of dietary fish meal replacement by P. americana residue on the growth performance, proximate composition, amino acid profile, metabolism, antioxidant capacity, and immunity of juvenile O. niloticus. There were no significant differences in the final body weight, weight gain rate, and specific growth rate among five diet groups, while the highest feed conversion ratio and the lowest protein efficiency ratio were recorded in Diet 4. There were no significant differences in the contents of crude protein, total lipid, ash, and total amino acid in the whole fish body among all groups. The Diet 1 and Diet 2 had higher activities of trypsin, α-amylase, and chitinase in the intestine and α-amylase in the liver. The highest serum urea content was detected in Diet 4, while the lowest liver urea content and the highest serum total protein content were detected in Diet 3. A higher liver catalase, glutathione peroxidase, and serum lysozyme activities were detected in Diet 2, and the lowest serum malondialdehyde content was detected in Diet 2. In conclusion, dietary fish meal replacement by the P. americana residue had no negative effects on the growth performance and body composition of juvenile O. niloticus, and significantly improved the antioxidant capacity and immunity, while feed utilization rate was reduced when dietary fish meal replacement levels exceeded 75%.

Schizothorax lissolabiatus and Schizothorax griseus are native Chinese fish species with significant ecological and economic importance. We wanted to support sustainable aquaculture practices by exploring the differences in metabolic, histological, and microbiota between the two Schizothorax species. This study analyzed and compared the digestive enzyme activities, metabolic indicators, gut histology, and microbiota composition of S. lissolabiatus and S. griseus under identical farming conditions. Our comparative analysis reveals both shared characteristics and species-specific differences. While a-amylase and trypsin activities showed no significant differences between species, a consistent trend was observed, with enzyme activity highest in the hindgut, followed by the midgut, foregut, esophagus, and liver. In terms of specific metabolic markers, S. griseus shows higher lipase activity in the liver and foregut, as well as higher aspartate aminotransferase and catalase levels in the liver, along with an increased serum glucose content compared to S. lissolabiatus. Serum metabolomics analysis revealed 21 differentially abundant metabolites linked to glycerophospholipid metabolism, autophagy, purine metabolism, and necroptosis, reflecting distinct metabolic adaptations and nutritional needs for each species. These metabolic differences provide a basis for optimizing feed composition and aquaculture practices tailored to each species. Notably, S. lissolabiatus displays a significantly higher goblet cell count in the hindgut compared to S. griseus. Additionally, both species exhibit greater villi number, length, width, crypt depth, and muscle thickness in the esophagus than in the foregut, midgut, and hindgut. S. griseus also has a higher number of operational taxonomic units (OTUs) and greater microbial diversity in its intestinal microbiota, which may enhance its nutrient utilization capabilities. While both species’ dominant microbial phyla include Fusobacteria, Firmicutes, Proteobacteria, and Bacteroidetes, S. griseus demonstrated superior lipid digestion capabilities. Furthermore, the midgut and hindgut in both species display higher starch and protein digestive enzyme activities than other digestive tissues. These findings highlight the physiological differences between the two Schizothorax species, suggesting targeted strategies to improve health, growth, and sustainability in aquaculture.

Five isonitrogenous and isolipidic diets (Diet 1–Diet 5, with Diet 1 as the control) were formulated to replace 0%, 20%, 40%, 60%, and 80% of fishmeal with American cockroach residue. Juvenile Cyprinus carpio (initial body weight approximately 74 g) were randomly assigned to these diets for a 10-week feeding trial. The Diet 3 group (40% replacement) showed significantly higher final body weight, weight gain rate, specific growth rate, and protein efficiency ratio compared to other groups. No significant differences were observed in crude protein, ash, and total amino acid content across the diets. Groups fed Diet 1 and Diet 2 exhibited higher intestinal trypsin, lipase, α-amylase, and hepatic trypsin activities. Serum triglyceride (TG) levels were highest in the Diet 5 group. Hepatic aspartate aminotransferase (AST) activity was significantly lower in the Diet 3 and Diet 5 groups compared to Diet 1. Serum urea nitrogen levels followed a non-linear trend, initially increasing, then decreasing, and rising again with increasing fishmeal replacement. No significant differences were found in serum total protein (TP) levels among the dietary groups. Intestinal villus number, muscle layer thickness, villus height, villus width, and crypt depth remained consistent across groups. However, goblet cell numbers were significantly reduced at the 60% replacement level, which could impair intestinal barrier function. Diet 3 showed higher serum and hepatic total superoxide dismutase (T-SOD) activity, while Diet 2 had the highest hepatic total antioxidant capacity (T-AOC) activity. Hepatic malondialdehyde (MDA) levels were lowest in the Diet 2 and Diet 5 groups. Immunoglobulin M (IgM) levels showed an increasing trend with higher fishmeal replacement levels. In conclusion, replacing fishmeal with American cockroach residue did not adversely affect growth performance or body composition in juvenile C. carpio. Substituting 20–40% of fishmeal with American cockroach residue enhanced antioxidant capacity and immune function in juvenile C. carpio.

Astaxanthin is an important aquatic feed additive that enhances the antioxidant capacity, and immune function of rainbow trout (Oncorhynchus mykiss); however, very limited information is available on its underlying molecular mechanisms. Haematococcus pluvialis powder, Phaffia rhodozyma powder, and synthetic astaxanthin were added to the commercial feed (no astaxanthin, NA) to prepare three experimental feeds, referred to as the HPA, PRA, and SA groups, respectively, and their actual astaxanthin contents were 31.25, 32.96, and 31.50 mg.kg-1, respectively. A 16-week feeding trial was conducted on the O. mykiss with an initial body weight of 669.88 ± 36.22 g. Serum and head kidney samples from commercial-sized O. mykiss were collected for metabolomics and transcriptomics analysis, respectively. Metabolomics analysis of the serum revealed a total of 85 differential metabolites between the astaxanthin-supplemented group and the control group. These metabolites were involved in more than 30 metabolic pathways, such as glycerophospholipid metabolism, fatty acid biosynthesis, linoleic acid metabolism, and arginine and proline metabolism. It is speculated that different sources of dietary astaxanthin may regulate antioxidant capacity and immunity mainly by affecting lipid metabolism and amino acid metabolism. Transcriptomic analysis of the head kidney revealed that the differentially expressed genes between the astaxanthin-supplemented group and the control group, such as integrin beta-1 (ITGB1), alpha-2-macroglobulin (A2M), diamine acetyltransferase 1 (SAT1), CCAAT/enhancer-binding protein beta (CEBPB) and DNA damage-inducible protein 45 alpha (GADD45A), which are involved in cell adhesion molecules, the FoxO signaling pathway, phagosomes, and arginine and proline metabolism and play regulatory roles in different stages of the antioxidant and immune response of O. mykiss.

为研究人工合成虾青素和红发夫酵母(Phaffia rhodozyma)虾青素对虹鳟红肌抗氧化和脂质代谢的影响,在基础饲料中分别添加31.50 mg/kg红发夫酵母虾青素(P-AST)和32.96 mg/kg人工合成虾青素(S-AST),饲喂虹鳟16周后,分析虹鳟红肌中抗氧化指标、抗氧化及脂质代谢相关基因表达的变化.结果表明:P-AST组总超氧化物歧化酶(T-SOD)活性较对照组提高38.04％(P<0.05),且P-AST组SOD1 mRNA水平较对照组增加58.54％(P<0.05).与对照组相比,P-AST组和S-AST组过氧化氢酶(CAT)活性无显著性变化,但S-AST组和P-AST组CAT基因表达分别低于对照组30.23％和31.78％(P<0.05).P-AST组总谷胱甘肽(T-GSH)、氧化型谷胱甘肽(GSSG)、还原型谷胱甘肽(GSH)含量均低于其他两组,其中GSSG含量较对照组降低24.73％(P<0.05).与对照组相比,S-AST组过氧化物酶体增殖物激活受体(pparα1)基因表达高于对照组147.69％(P<0.05)、P-AST组sirtuin1(Sirt1)基因表达高于对照组49.37％(P<0.05),而pparα2、肉碱棕榈酰基转移酶1(CPT1)和脂肪酸合成酶(FASN)基因的表达无显著性变化.上述结果表明,S-AST和P-AST均能够调节虹鳟红肌抗氧化系统的功能及脂质代谢相关基因的表达,但是两种虾青素之间存在差异.

Periplaneta americana is an insect protein source, rich in protein, fat and bioactive components, which may become a potential alternative source of fishmeal for development and application. In order to study the effects of dietary fishmeal replacement by P. americana meal on the growth, biochemical indexes, disease resistance and metabolomics of juvenile Oncorhynchus mykiss, we formulated two isonitrogen and equal energy diets to replace 0% and 50% of the dietary fishmeal with P. americana meal, and had fed the juveniles with an initial body mass of 3 g for 18 weeks. At the end of feeding trial, we challenged the juveniles with Aeromonas hydrophila. The results showed that: 1) The growth performance and survival rate after the challenge in the experimental group were significantly higher than those in the control group (P<0.05). 2) The levels of serum immunoglobulin (IgM), total antioxidant capacity (T-AOC), lysozyme (LZM) in liver and catalase (CAT) in head kidney in the experimental group were significantly higher than those in the control group (P<0.05). 3) The results of metabolomics analysis showed that the differential metabolites in serum mainly involved in eight biochemical metabolic pathways, including glycerophospholipid metabolism, sphinolipid metabolism, valine, leucine and isoleucine of biosynthesis and so on. The contents of lysophosphatidylcholine (LysoPC) and phosphatidylcholine (PC) which involved in glycerophospholipid metabolism were significantly up-regulated in the experimental group. In conclusion, 50% dietary fishmeal replacement with P. americana meal could improve the growth performance, antioxidant capacity, immunity and resistance to A. hydrophila of juvenile O. mykiss significantly.