The Substitution of Fishmeal with Yeast Culture in the Yellow Catfish (Pelteobagrus fulvidraco) Diet: Growth, Serum Biochemical Indices, and Intestinal and Hepatopancreatic Histology.

Yeast culture is a complex fermentation product consisting of fermentation substrate, yeast cells and their metabolites. This study investigated the potential of yeast culture in replacing fishmeal in the diet of yellow catfish (Pelteobagrus fulvidraco). First, a basal diet was formulated to contain 160 g/kg fishmeal (CON), and then the dietary fishmeal was decreased to 120, 80, 40 and 0 g/kg via yeast culture inclusion, respectively, to form another four isonitrogenous and isolipidic diets (YC-12, YC-8, YC-4 and YC-0). Yellow catfish (3.00 ± 0.10 g) were fed with the above five diets with triplicates per treatment and 40 fish per replicate. After 8 weeks of feeding, the weight gain (WG), protein efficiency rate and protein retention in the YC-12 group and the feed conversion ratio (FCR) in the YC-12 and YC-8 groups showed no significant differences to the CON group (p > 0.05), but the WG in the YC-8, YC-4 and YC-0 groups was significantly lower, and the FCR in the YC-4 and YC-0 groups was significantly higher than in the CON group (p < 0.05). In terms of the whole-body composition, only the crude lipid content in the YC-0 group decreased significantly (p < 0.05). Compared with the CON group, the aspartate aminotransferase and alanine aminotransferase activities and D-lactic acid content in the YC-0 group were significantly increased, and the total cholesterol content was significantly reduced (p < 0.05). The activities of catalase, superoxide dismutase, and alkaline phosphatase, as well as the content of complement C3 and immunoglobulin M, were significantly increased, while the MDA content was significantly reduced in the YC-12 and YC-8 groups (p < 0.05). There were no significant differences in the intestinal amylase and lipase activity among all the groups (p > 0.05), while the trypsin activity in the YC-12 and YC-8 groups, as well as the diamine oxidase in the YC-4 and YC-0 groups, were significantly higher than those in the CON group (p < 0.05). In the intestine histology, there was a significant decrease in the intestinal villus height in the YC-4 and YC-0 groups as well as in the villus width in the YC-0 group (p < 0.05). In the hepatopancreas histology, lipid droplets appeared in the YC-4 and YC-0 groups, and severe cell vacuolation was observed in the YC-0 group. As a summary, in a practical diet containing 160 g/kg fishmeal, yeast culture can effectively replace 40 g/kg fishmeal without negatively affecting the growth performance, nutrient utilization, serum immune and antioxidant, intestinal and hepatopancreas histology of yellow catfish.

Dietary sodium butyrate positively modulated intestinal microbial community, but did not promote growth of largemouth bass (Micropterus salmoides).

This study investigated the effects of dietary sodium butyrate (NaB) on growth, serum biochemical indices, intestine histology, and gut microbiota of largemouth bass (Micropterus salmoides). A basal diet was formulated and used as the control diet (Con), and five additional diets were prepared by supplementing NaB (50%) in the basal diet at 2.0, 4.0, 8.0, 12.0, and 16.0 g/kg inclusion (NaB-2, NaB-4, NaB-8, NaB-12, and NaB-16 diets). Then, the six diets were fed to triplicate groups of largemouth bass juveniles (2.4 ± 0.1 g) for 8 weeks. NaB supplementation linearly and quadratically affected weight gain (WG) and feed intake (FI) (P < 0.05). The NaB-16 group displayed lower WG (- 6.8%) and FI than the Con group (P < 0.05), while no differences were found in WG and feed conversion ratio between the other NaB groups and Con group (P > 0.05). Serum alkaline phosphatase and lysozyme activities were higher in the NaB groups (P < 0.05), and D-lactate content was lower in the NaB-12 group (P < 0.05) than the control. Intestinal lipase activity in NaB-2, NaB-4 group, and villi width in NaB-8 group were also higher than those in the Con group (P < 0.05). Compared to the Con group, the intestinal abundances of Firmicutes and Mycoplasma were increased and the abundances of Proteobacteria, Achromobacter and Plesiomonas were decreased in NaB-4 and NaB-16 groups (P < 0.05). In conclusion, dietary NaB did not promote the growth of juvenile largemouth bass, but positively modulated the intestinal microbial community.

The Combined Supplementation of AZOMITE and Citric Acid Promoted the Growth, Intestinal Health, Antioxidant, and Resistance against Aeromonas hydrophila for Largemouth Bass, Micropterus salmoides.

Citric acid is an organic acid extensively used in feed industry, and AZOMITE is a hydrated aluminosilicate compound rich in rare earth elements and trace mineral elements. This study investigated the supplemental effects of AZOMITE and citric acid individual or in combination on the growth performance, intestinal microbiota, morphology, digestive enzyme activity, serum indexes, and disease resistance of juvenile largemouth bass. Six diets were designed, including the control diet (CON) and the five additive-supplemented diets with the addition of 4 or 8 g/kg citric acid (CA4, CA8), 3 g/kg AZOMITE (A3), and their combined addition as 4 g/kg citric acid + 1.5 g/kg AZOMITE) (C4A1.5) and 8 g/kg citric acid + 3 g/kg AZOMITE (C8A3). Juvenile largemouth bass with initial body weight of 22.01 ± 0.09 g were fed the six diets for 56 days. The results revealed that the combined addition of 4 g/kg citric acid and 1.5 g/kg AZOMITE (C4A1.5) increased weight gain by 7.99% (P < 0.05), and decreased feed conversion ratio by 0.07 (P < 0.05). The protein retention in the C4A1.5 group and the lipid retention in all additive-supplemented groups were significantly higher than those in the control group (P < 0.05). In serum, all additive-supplemented groups showed significantly higher glutathione peroxidase activity than the control group (P < 0.05). The activities of superoxide dismutase and catalase in the CA8, A3, C4A1.5, and C8A3 groups were significantly higher (P < 0.05), while the concentration of malondialdehyde was significantly lower than those in the control group (P < 0.05). Moreover, the total antioxidant capacity in the A3 and C4A1.5 groups, and lysozyme activity in the A3, C4A1.5, and C8A3 groups were significantly increased when compared to the control group (P < 0.05). In digestive enzyme, the protease activity in the A3, C4A1.5 groups, and amylase activity in the CA4, CA8, and C4A1.5 groups were significantly higher than those in the control group (P < 0.05). In intestinal microbiota, Firmicutes abundance was elevated in all additive groups, while the Fusobacteriota and Plesiomonas shigelloides abundance were decreased. In the intestinal histology, the CA8, A3, and C4A1.5 groups showed significantly higher villus height than the control group (P < 0.05). After the infection with Aeromonas hydrophila, the cumulative mortality of all additive-supplemented groups was significantly lower (P < 0.05), and the C4A1.5 group demonstrated the lowest mortality. In conclusion, the combined supplementation of 4 g/kg citric acid + 1.5 g/kg AZOMITE increased the growth, antioxidant, immune capacity, improved the intestinal morphology and microbial flora of juvenile largemouth bass, and promoted the resistance against Aeromonas hydrophila infection.

Dietary Effects of Lipid and Protein Levels on Growth, Feed Utilization, Lipid Metabolism, and Antioxidant Capacity of Triploid Rainbow Trout (Oncorhynchus mykiss).

This study investigated the dietary effects of lipid and protein levels on growth performance, feed utilization, body composition, lipid metabolism, and antioxidant capacity of triploid rainbow trout, Oncorhynchus mykiss. A 3 × 2 two-factor design was conducted with three crude lipid levels of 4%, 9%, and 14% (L4, L9, and L14) and two crude protein levels of 44%, 49% (P44, P49). Therefore, a total of six diets were prepared as P44/L4, P44/L9, P44/L14, P49/L4, P49/L9, and P49/L14. Triploid rainbow trout (initial body weight 65.0 ± 0.1 g) were fed one of the six diets for 80 days. The results showed that weight gain (WG), protein retention (PR), and protein efficiency rate (PER) significantly increased with increasing the dietary lipid level at the same crude protein level, while feed conversion ratio (FCR) and hepatosomatic index significantly decreased (P < 0.05). At the same lipid level, there was no difference in WG, FCR, PR, PER between 44% and 49% crude protein group (P > 0.05). The P49/L14 group had the highest WG (374.6%) and lowest FCR (1.25), while P44/L14 group had the highest PER (1.80) and PR (25.06%) with similar WG and FCR to P49/L14 group. The crude lipid contents in whole fish were significantly higher in the L14 group than those in the L4 and L9 groups (P < 0.05). Muscle n-3 PUFAs, n-6 PUFAs, and PUFAs levels were positively correlated with dietary lipid level, while n-6 PUFAs was negatively correlated with dietary protein level. Dietary protein, dietary lipid, and their interaction significantly affected hepatic malondialdehyde (MDA) content, aspartate aminotransferase, lipase (LPS), and fatty acid synthase (FAS) activities (P < 0.05). In both P44 and P49 groups, LPS and FAS activities increased with increasing the dietary lipid level. MDA content significantly decreased in the P44 group and increased in the P49 group with increasing the dietary lipid level (P < 0.05). As dietary protein level increased, serum total cholesterol level increased, while hepatic phosphoenolpyruvate carboxykinase activity decreased. With increasing the dietary lipid level, total superoxide dismutase, catalase, total nitric oxide synthase, and fructose-1,6-bisphosphatase activities showed an increasing trend, while the opposite was true for alanine aminotransferase activity. In conclusion, based on growth performance and feed utilization, dietary protein level of 44% and dietary lipid level of 14% (measured value, 43.71% and 13.62%) were suggested for young triploid rainbow trout.

Dietary Sodium Butyrate Changed Intestinal Histology and Microbiota of Rainbow Trout (Oncorhynchus mykiss), but Did Not Promote Growth and Nutrient Utilization.

The study investigated the effects of dietary sodium butyrate (SB) on the growth performance, nutrient utilization, intestinal histology, and microbiota of rainbow trout (Oncorhynchus mykiss). A high fishmeal diet and a low fishmeal diet were formulated to contain 200 g/kg or 100 g/kg fishmeal, respectively. Coated SB (50%) was supplemented to each of the diets at levels of 0, 1.0, and 2.0 g/kg to create 6 diets. The diets were fed to rainbow trout with initial body weight of 29.9 ± 0.2 g for 8 weeks. Compared to the high fishmeal group, the low fishmeal group showed significantly lower weight gain (WG), intestine muscle thickness, and significantly higher feed conversion ratio (FCR) and amylase activity (P < 0.05). The supplementation of SB in high or low fishmeal diet did not significantly affect the WG, FCR, protein retention, and the digestibility of dry matter and crude protein (P > 0.05). The supplementation of 2.0 g/kg SB in low fishmeal diet significantly increased the villus height, villus width, and muscular thickness, while the supplementation of 2.0 g/kg SB in high fishmeal diet also significantly increased the intestinal villus height (P < 0.05). In intestinal microbiota, the supplementation of 2.0 g/kg SB significantly increased the abundance of Proteobacteria and Aeromonas, and decreased the abundance of Firmicutes and Mycoplasma (P < 0.05), but the flora at genus and phylum level were not affected by SB supplementation in low fishmeal diet (P > 0.05). In conclusion, the addition of SB in diets containing 100 or 200 g/kg fishmeal did not enhance the growth performance and nutrient utilization of rainbow trout, but improved intestinal morphology and changed intestinal microbial flora.

Effects of Replacing Fishmeal with the Mixture of Cottonseed Protein Concentrate and Clostridium autoethanogenum Protein on the Growth, Nutrient Utilization, Serum Biochemical Indices, Intestinal and Hepatopancreas Histology of Rainbow Trout (Oncorhynchus mykiss).

The purpose of this study was to develop the potential of cottonseed protein concentrate (CPC) and Clostridium autoethanogenum protein (CAP) in the diet of rainbow trout (Oncorhynchus mykiss) by evaluating the effects of substituting fishmeal with a CPC and CAP mixture on growth performance, nutrient utilization, serum biochemical indices, intestinal and hepatopancreas histology. In a basal diet containing 200 g/kg fishmeal (Con), the mixture of CPC and CAP (1:1) was used to reduce dietary fishmeal to 150, 100, 50 and 0 g/kg, to form five diets with the same crude protein and crude lipid contents (CON, FM-15, FM-10, FM-5 and FM-0). Then, the five diets were fed to rainbow trout (35.00 ± 0.05 g) for 8 weeks. The weight gain (WG) and feed conversion ratio (FCR) of the five groups were 258.72%, 258.82%, 249.90%, 242.89%, 236.57%, and 1.19, 1.20, 1.24, 1.28, 1.31, respectively. FM-5 and FM-0 groups showed significantly lower WG and higher FCR than the CON group (p < 0.05). In terms of whole-body composition, such as moisture, crude ash, and crude protein, no significant difference was observed among all the groups (p > 0.05), except that significantly higher crude lipid content was detected in the FM-0 group than in the CON group (p < 0.05). In the FM-5 and FM-0 groups, protein efficiency, protein retention, intestinal protease activity and amylase activity were significantly lower than in the CON group (p < 0.05). Compared to the CON group, the serum contents of glucose and total cholesterol in the FM-0 group as well as MDA in the FM-5 and FM-0 groups were significantly increased, and catalase, superoxide dismutase, and total antioxidant capacity were decreased (p < 0.05). In intestine and hepatopancreas histology, the intestinal villus height in the FM-5 and FM-0 groups and villus width in the FM-0 group were decreased significantly (p < 0.05), while no significant difference in hepatopancreas morphology was observed among all the groups except that some vacuolization was observed in the FM-0 group (p > 0.05). In summary, the mixture of CPC and CAP can effectively replace 100 g/kg fishmeal in a diet containing 200 g/kg fishmeal without adverse effects on the growth performance, nutrient utilization, serum biochemical, or intestinal and hepatopancreas histology of rainbow trout.

Dietary Effect of Clostridium autoethanogenum Protein on Growth, Intestinal Histology and Flesh Lipid Metabolism of Largemouth Bass (Micropterus salmoides) Based on Metabolomics.

Clostridium autoethanogenum protein (CAP) is a new single-cell protein explored in aquatic feeds in recent years. This study investigated the dietary effects of CAP replacing fishmeal (FM) on the growth, intestinal histology and flesh metabolism of largemouth bass (Micropterus salmoides). In a basal diet containing 700 g/kg of FM, CAP was used to substitute 0%, 15%, 30%, 45%, 70% and 100% of dietary FM to form six isonitrogenous diets (Con, CAP-15, CAP-30, CAP-45, CAP-70, CAP-100) to feed largemouth bass (80.0 g) for 12 weeks. Only the CAP-100 group showed significantly lower weight gain (WG) and a higher feed conversion ratio (FCR) than the control (p < 0.05). A broken-line analysis based on WG and FCR showed that the suitable replacement of FM with CAP was 67.1−68.0%. The flesh n-3/n-6 polyunsaturated fatty acid, intestinal protease activity, villi width and height in the CAP-100 group were significantly lower than those in the control group (p < 0.05). The Kyoto Encyclopedia of Genes and Genomes analysis showed that the metabolic pathway in flesh was mainly enriched in the "lipid metabolic pathway", "amino acid metabolism", "endocrine system" and "carbohydrate metabolism". In conclusion, CAP could successfully replace 67.1−68.0% of dietary FM, while the complete substitution decreased the growth, damaged the intestinal morphology and down-regulated the lipid metabolites.

The comparison of largemouth bass (Micropterus salmoides) fed trash fish and formula feeds: Growth, flesh quality and metabolomics.

This study compared the growth, flesh quality and metabolomics of largemouth bass (Micropterus salmoides) fed trash fish and formula feeds. Trash fish (TF), self-made feed (SF) and commercial feed (CF) were prepared with crude protein levels of 172.2 g/kg, 503.5 g/kg and 504.1 g/kg (666.2 g/kg, 547.3 g/kg and 535.1 g/kg based on dry matter), respectively. Then, the three diets were fed to largemouth bass with an initial body weight of 75.0 ± 0.1 g for 12 weeks. SF and CF groups presented significantly lower feed intake (FI), feed conversion ratio (FCR) and higher protein efficiency ratio (PER) than TF group based on dry matter basis without affecting the weight gain (P < 0.05). The yellowness (b*) in dorsal muscle, flesh heat-insoluble collagen and free flavor amino acids contents in SF group were significantly higher (P < 0.05), while drip loss were significantly lower (P < 0.05) than those of TF group. Compared to TF group, SF and CF groups showed significantly higher flesh polyunsaturated fatty acids (PUFAs), n-3 PUFAs and n-6 PUFAs contents, flesh hardness, shear force and muscle fiber density (P < 0.05), and lower flesh total free amino acids, essential amino acids, muscle fiber diameter, intestine villus height and muscular thickness (P < 0.05). The serum total protein, triglyceride and cholesterol levels in SF group were significantly lower than those in TF and CF groups (P < 0.05). In the muscle metabolomics, 177 differential metabolites were detected between SF and TF groups, which mainly enriched in pathways as biosynthesis of amino acid, histidine metabolism, glycine, serine and threonine metabolism, etc. Conclusively, feeding largemouth bass with formula feeds improved flesh fatty acid profile and flesh texture without negative effects on the growth, but the flesh free amino acids contents were lower than the fish fed trash fish.

Dietary effects of aucubin on growth and flesh quality of grass carp (Ctenopharyngodon idellus) based on metabolomics.

This aim of this study was to investigate the effects of dietary aucubin on the growth, flesh quality, and metabolomics of grass carp (Ctenopharyngodon idella). Five diets were designed with the aucubin inclusion of 0 (control diet), 0.2, 0.4, 0.6, and 0.8 g/kg (Auc-0.2, Auc-0.4, Auc-0.6, Auc-0.8) and were fed to grass carp with an initial body weight of 17.0 ± 0.2 g for 60 d. The results indicated that dietary aucubin did not significantly affect the growth performance of grass carp (P > 0.05). Compared to the control, dietary supplementation with 0.2 to 0.8 g/kg aucubin increased flesh hardness, chewiness, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and the contents of total free amino acids (TFAA) and n-3 polyunsaturated fatty acids (n-3 PUFA) (P < 0.05). The contents of malondialdehyde (MDA) and lactic acid (LD) in the flesh were significantly decreased by the addition of 0.4 to 0.6 g/kg aucubin and by the addition of 0.6 to 0.8 g/kg aucubin (P < 0.05), respectively, while the content of delicious amino acids (DAA) was significantly enhanced by the addition of 0.4 to 0.8 g/kg aucubin (P < 0.05). Moreover, the contents of collagen and C22:6n3 (DHA) in the flesh of the Auc-0.8 group were significantly higher than those of the control (P < 0.05). In the metabolomics profiling of flesh, 133 and 135 named differential metabolites were identified in the Auc-0.4 and Auc-0.8 groups, respectively, compared to the control, and these metabolites were found to be involved in the second-grade pathways of "lipid metabolism" and "amino acid metabolism". Regarding gene expression, the mRNA levels of CuZn-SOD, CAT, COL1A1, COL1A2, Smad4, and FAS in flesh were upregulated in the Auc-0.4 and Auc-0.8 groups, and the expression levels of GPx, Nrf2, and TGF-ß1 mRNA were also upregulated in the Auc-0.8 group (P < 0.05). In summary, dietary aucubin did not promote growth, but improved the flesh quality of grass carp, which might be associated with the TGF-ß/Smad and Nrf2 pathways. The recommended supplementation level of aucubin in the diet of grass carp was 0.6 to 0.8 g/kg.

Aucubin is an iridoid glycoside that is widely distributed in green plants and exhibits various biological activities such as antioxidant, anti-inflammatory, and protecting the liver. In previous studies, we explored the effects of different dietary levels of iridoids including geniposide and geniposide acid, on the flesh quality of grass carp. As aucubin shares a similar chemical structure to that of geniposide and geniposide acid, it was speculated that aucubin might exhibit the same function of promoting flesh quality in fish. Our study was conducted to explore the effects on the growth and flesh quality of grass carp. We found that dietary aucubin did not affect the growth of grass carp but improved flesh quality by increasing the contents of collagen, free amino acids, and n-3 PUFA; increasing the activities of CAT, SOD, and GPx; and decreasing the contents of MDA and PC in flesh, which might be associated with the TGF-ß/Smad and Nrf2 pathways.

Transcriptomic and biochemical analyses revealed the improved growth, lipid metabolism, and flesh quality of grass carp (Ctenopharyngodon idellus) by dietary Eucommia ulmoides bark and leaf supplementation.

The objective of this study was to investigate the dietary effects of Eucommia ulmoides bark and leaf (EB, EL) supplementation on the growth, lipid metabolism, flesh quality, and transcriptome of grass carp (Ctenopharyngodon idellus). EB and EL were individually added to the basal diet (control) at concentrations of 20 g/kg and 40 g/kg, respectively, and then the three diets were fed to grass carp (59.7 ±â€…0.3 g) for 60 d. The results showed that the weight gain was improved, and the feed conversion ratio was decreased by supplementation with EB and EL (P < 0.05). Compared to the control, the EB and EL groups showed higher flesh hardness; water-holding capacity; and collagen, docosahexaenoic acid (DHA), and n-3 polyunsaturated fatty acids (n-3PUFAs) contents and lower mesenteric lipid and muscle crude lipid contents (P < 0.05). Moreover, dietary EB and EL supplementation increased the activities of superoxide dismutase and glutathione peroxidase and decreased the contents of malondialdehyde and protein carbonyl in flesh (P < 0.05). In muscle transcriptome profiling, a total of 979, 1980 differentially expressed genes (DEGs) were identified, and 29, 199 Gene Ontology (GO) terms and 13, 39 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were significantly enriched in the EB and EL groups, respectively. Some key pathways and genes involved in promoting growth, lipid metabolism and flesh quality were obtained, including mTOR and PPAR signaling pathways, muscle cytoskeleton- and extracellular matrix-related genes (myosin and collagen), etc. Overall, dietary EB and EL supplementation improved the growth, lipid metabolism, and flesh quality of grass carp, and several potential pathways and genes were identified behind the improvement mechanism of EB and EL supplementation.

As a traditional herb, Eucommia ulmoides (E. ulmoides) has been utilized in East Asia for at least 2 000 years. In recent years, E. ulmoides has been applied in the culture of fish for its functions of promoting growth, lipid metabolism, and flesh quality. However, the underlying molecular mechanism of improving growth, lipid metabolism, and flesh quality is not well understood. Our study showed that the improvement of flesh quality is the combined effect of antioxidant capacity, muscle texture, water-holding capacity, and nutritional composition. Additionally, several potential pathways and differentially expressed genes were identified through RNA sequencing to further study the improvement mechanism of dietary E. ulmoides bark and leaf supplementation on growth, lipid metabolism, and flesh quality in fish.

In vitro effects of Eucommia ulmoides and its active components on the growth, lipid metabolism and collagen metabolism of grass carp (Ctenopharyngodon idellus) hepatocyte and intramuscular fibroblast.

Two experiments were conducted to investigate the in vitro effects of Eucommia ulmoides (E. ulmoides) and its active components on the growth, lipid metabolism and collagen metabolism of grass carp's (Ctenopharyngodon idellus) hepatocytes and intramuscular fibroblasts. In experiments 1 and 2 (Expt. 1, 2), hepatocytes and intramuscular fibroblasts were treated with 2.5, 5, 10, 20, 40 and 80 µg ml-1 of Eucommia bark extract (EBE), Eucommia leaf extract (ELE), pinoresinol diglucoside (PDG), chlorogenic acid (CGA), quercetin (QC) and aucubin (AU) for 24 h, respectively, then the cell growth, lipid and collagen metabolism-related gene expressions were evaluated. The results showed that the cell proliferation rate of hepatocytes and intramuscular fibroblasts was significantly improved by the supplementation of EBE, ELE, CGA, QC and AU. Moreover, triglyceride concentration of hepatocytes was significantly decreased by the EBE, ELE, CGA and QC supplementations compared to the control. Meanwhile, EBE, ELE, CGA, QC and AU supplementations significantly upregulated the relative gene expressions of insulin-like growth factor-1 (igf1), protein kinase B (akt), target of rapamycin (tor) and eukaryotic initiation factor 4E binding protein 1 (4ebp1) in hepatocytes, and ribosomal protein S6 kinase 1 (s6k1) transcription was significantly activated by ELE, CGA and QC supplementations. Nonetheless, phosphatidylinositol 3-kinase (pi3k) was unaffected by any of the supplements. In addition, the mRNA expressions of genes associated with lipid metabolism (peroxisome proliferator activated receptor α pparα, carnitine palmitoyltransferase 1 cpt1, adipose triglyceride lipase atgl, hormone-sensitive lipase hsl, peroxisome proliferator activated receptor γ pparγ) were significantly upregulated by EBE, ELE, CGA and QC. In intramuscular fibroblasts, the EBE, ELE, CGA, QC and AU supplementations significantly increased in vitro hydroxyproline concentrations, promoted the relative expressions of transforming growth factor-ß1 (tgfß1), connective tissue growth factor (ctgf), collagen type I alpha 1/2 chain (col1a1, col1a2), lysine oxidase (lox) and tissue inhibitor of matrix metalloproteinase-2 (timp2), and decreased matrix metalloproteinase-2 (mmp2) gene expression. Also, the gene expressions of drosophila mothers against decapentaplegic protein 2/4 (smad2, smad4) and proline hydroxylase (phd) were significantly upregulated by ELE, CGA, QC and AU supplementations. Based on the present in vitro results of grass carp, EBE, ELE, CGA, QC and AU improved the growth and lipid metabolism (except AU) in hepatocytes, and promoted the collagen deposition in intramuscular fibroblast, which is partly attributed to the signalling pathways of AKT/TOR, PPARα and TGF-ß/Smads/CTGF.

An Evaluation of Replacing Fishmeal with Chlorella Sorokiniana in the Diet of Pacific White Shrimp (Litopenaeus Vannamei): Growth, Body Color, and Flesh Quality.

This study was conducted to investigate the effects of replacing fishmeal (FM) with Chlorella sorokiniana on growth and flesh quality of Pacific white shrimp, Litopenaeus vannamei. A control diet was formulated to contain 560 g/kg FM, and then chlorella meal was used to replace 0% (C-0), 20% (C-20), 40% (C-40), 60% (C-60), 80% (C-80), and 100% (C-100) of dietary FM, respectively. The six isoproteic and isolipidic diets were fed to shrimp (1.37 ± 0.02 g) for 8 weeks. The results showed that weight gain (WG) and protein retention (PR) of C-20 group were significantly higher than those of C-0 group (P < 0.05), while no significant differences were observed in WG and PR between C-0 and C-40 groups (P > 0.05). When the replaced level of FM by chlorella meal reached 60%, the WG of shrimp decreased and feed conversion ratio (FCR) increased significantly (P < 0.05). The quadratic regression analysis indicated that substituted fishmeal levels with chlorella meal were 20.50% and 28.25%, respectively, to obtain the highest WG and lowest FCR. In C-40 and C-60 groups, the body surface presented higher redness than the control (P < 0.05). No significant differences in the whole body and muscle composition, SOD, T-AOC, GSH-PX activities, MDA contents, total collagen content, steaming loss, texture property, free delicious amino acids contents, PUFAs, and n-3/n-6 PUFAs in flesh were observed among the three groups of C-0, C-20, and C-40 (P > 0.05). Compared to the control group, C-60, C-80, and C-100 groups showed lower flesh hardness, chewiness, shear force, and higher steaming loss and resilience (P < 0.05). There were no significant differences in serum TP, TG, GLU, and ALB contents, boiling loss, freezing loss, total free amino acids, SAFs and MUFAs among all the groups (P >0.05). Conclusively, in a diet containing 560 g/kg FM, chlorella meal could replace 40% dietary FM without negative effects on the growth and flesh quality, while increase the body redness of white shrimp.

Dietary effects of Clostridium autoethanogenum protein substituting fish meal on growth, intestinal histology and immunity of Pacific white shrimp (Litopenaeus vannamei) based on transcriptome analysis.

The study investigated the dietary effects of Clostridium autoethanogenum protein (CAP) substituting fish meal on the growth, intestinal histology, serum immune indexes and transcriptome of Pacific white shrimp, Litopenaeus vannamei. Four isonitrogenous and isolipidic diets were designed as the control diet (CON) containing 560 g/kg fish meal, and three fish meal-substituted diets in which 30% (CAP-30), 45% (CAP-45) and 70% (CAP-70) fish meal were replaced with CAP, respectively. The four diets were fed to shrimp with initial body weight of 2.78 ± 0.13 g for 8 weeks. The results showed that the weight gain, feed intake, survival and intestinal villus height in CAP-45 and CAP-70 groups were lower than those of the control and CAP-30 groups (P < 0.05). In addition, the serum aspartate aminotransferase and phenol oxidase activities in all fish meal-substituted groups, and the lysozyme activity in CAP-45 and CAP-70 groups were increased, while the total protein content in CAP-45 and CAP-70 groups was decreased when compared with the control (P < 0.05). Transcriptome profiling of hepatopancreas indicated that high inclusion of CAP negatively affected the protein synthesis and the utilization of nutrients by regulating pancreas secretion, protein digestion and absorption, ribosome pathways, and disturbed the immune system and metabolic processes by phagosomes and lysosomes pathways, thereby affecting the growth performance and immune function of shrimp. In conclusion, CAP could substitute 30% fish meal in a diet containing 560 g/kg fish meal without adverse effects on the growth, intestinal histology and immunity of Pacific white shrimp.

Dietary Lactobacillus casei K17 Improves Lipid Metabolism, Antioxidant Response, and Fillet Quality of Micropterus salmoides.

We previously demonstrated that Lactobacillus casei K17, isolated from Korean kimchi, has high antioxidant levels in vitro and in vivo. However, its effect on Micropterus salmoides is unknown. In this study, we investigated the impact of L. casei K17 supplementation on the lipid metabolism, antioxidant response, liver histology, and fillet quality of M. salmoides. We randomly assigned 450 M. salmoides (33.0 ± 0.5 g) to six diet groups for 69 days. The diets were as follows: 0.85% normal saline; 10% skim milk powder; 1 × 108 CFU/g live L. casei K17 (LB); 1 × 108 live L. casei K17 protected by skim milk powder (MB); 1 × 108 dead L. casei K17 (DB); and L. casei K17 fermentation supernatant. MB significantly improved the crude protein, total collagen, alkaline-insoluble collagen, fiber numbers, hardness, chewiness, and gumminess of M. salmoides fillets (p < 0.05). LB significantly improved crude protein and fiber numbers (p < 0.05). Furthermore, dietary supplementation with LB, MB, and DB maintained normal liver histology, preserved liver function, and increased hepatic and hemal antioxidant status by enhancing antioxidant enzyme activities. Meanwhile, the three diets also promoted lipid metabolism by increasing HDL-C effectiveness and reducing total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels in serum and liver tissues, indicating that dietary supplementation with DB, LB, and MB had hypolipidemic effects on M. salmoides. MB and LB significantly improved fillet quality and LB, MB, and DB improved hemal and hepatic lipid metabolism and antioxidant response and reduced reactive oxygen species production, protecting M. salmoides hepatic cells from injury.

Creatine improves the flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in freshwater.

Creatine improves flesh quality on mammalian but studies on crustaceans are scarce. In the present study, diets with six levels of creatine (1.23, 2.58, 5.12, 8.28, 14.12, 24.49 g kg-1 diet) were hand-fed to juvenile Litopenaeus vannamei (IBW: 1.50 ± 0.02 g) reared in freshwater for 46 days. Results showed creatine supplementation did not affect the growth performance (FBW: 17.04 ± 1.28 g) or the content of guanidinoacetic acid in muscle and hepatopancreas whereas significantly increased muscular creatine content. Diet with 8.28 g kg-1 creatine significantly increased muscular hardness and chewiness by decreasing myofiber diameter and increasing myofiber density. Additionally, creatine downregulated the mRNA expression of fast sMyHC1, sMyHC2, sMyHC6a and upregulated slow sMyHC5 and sMyHC15 mRNA expression. Muscular protein, collagen, total amino acid and flavor amino acid contents increased with creatine supplementation. In conclusion, the diet with 8.28 g kg-1 creatine improved the flesh quality of L. vannamei.

Effects of dietary synbiotics supplementation methods on growth, intestinal health, non-specific immunity and disease resistance of Pacific white shrimp, Litopenaeus vannamei.

The present study aims to investigate the effects of dietary synbiotics supplementation methods on growth, feed utilization, hepatopancreas and intestinal histology, non-specific immunity and microbiota community of Pacific white shrimp (Litopenaeus vannamei). A control diet was designed to contain 18% fish meal (CON), and then 3 g kg-1 synbiotics (Bioture, consisting of Bacillus subtilis, Saccharomyces cerevisiae, ß-glucan and mannan oligosaccharide, etc) was supplemented to the control diet with three methods, directly adding in diets for pelleting (DAP), spraying diets after pelleting at once (SDA), spraying diets before feeding every day (SDE). Shrimp with initial body weight of 1.5 ± 0.12 g were fed one of the four diets for 56 days. The results showed that dietary synbiotics significantly increased the weight gain (WG), apparent digestibility coefficient (ADC) of crude protein (CP) and dry matter (DM), hepatopancreatic protease activity and decreased feed conversion ratio (FCR) (P < 0.05). Among the three synbiotics-added diets, SDE group showed the best growth with significantly higher WG than DAP group (P < 0.05). Serum activities of total superoxide dismutase, catalase, acid phosphatase, lysozyme and alkaline phosphatase of synbiotics-added groups were significantly higher, and serum malondialdehyde level was significantly lower than those of the control (P < 0.05). The intestinal villus width and villus number were also increased by the supplementation of synbiotics. The cumulative mortality was reduced in the three synbiotics-added groups after challenging with Vibrio parahaemolyticus (P < 0.05), and SDE group showed a significantly lower mortality than the control and DAP groups (P < 0.05). In intestinal microbiota composition, the abundance of Lactococcus tended to increase and Vibro tended to decreased in SDA and SDE groups. In conclusion, dietary synbiotics improved the growth, feed utilization, intestine health and non-specific immunity of Pacific white shrimp, and spraying synbiotics on diet presented better performance than adding synbiotics in diet for pelleting.

Dietary Azomite, a natural trace mineral complex, improved the growth, immunity response, intestine health and resistance against bacterial infection in largemouth bass (Micropterus salmoides).

Azomite is a hydrated calcium sodium aluminosilicat rich in rare earth elements. To investigate the dietary effects of Azomite on growth, intestine microbiota and morphology, immunohematological changes and disease resistance, seven diets with Azomite supplementation of 0 (the control), 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 g/kg (A0, A1, A2, A3, A4, A5, A6), were prepared and fed to largemouth bass, Micropterus salmoides (7.96 ± 0.19) for 60 days. The results revealed that the weight gain (WG) increased first and then decreased with the increasing dietary Azomite, and the A2 group presented the highest WG and lowest feed conversion ratio among all the groups. The supplementation of 2.0 g/kg Azomite significantly increased the intestine protease activity, the crude protein of whole body and protein retention (P < 0.05), and high inclusion of Azomite (6.0 g/kg) significantly reduced the lipid retention (P < 0.05). The amounts of red blood cells in A5, A6 groups, white blood cells in A3, A5, A6 groups and lymphocyte in A2-A6 groups were all significantly higher than those in the control group (P < 0.05). In addition, serum superoxide dismutase and catalase activities in A5, A6 groups, and serum alkaline phosphatase and lysozyme activities in A2-A4 groups showed significantly higher values than the control group (P < 0.05). Intestinal microbiota analysis indicated that the Tenericutes abundance was increased, whereas Proteobacteria abundance was decreased in all Azomite supplemented groups. The villus height in A2-A4 groups, and the villus width in A2 group were significantly higher than those of the control group (P < 0.05). The cumulative mortality was reduced by the addition of 2.0-5.0 g/kg Azomite after challenging with A. hydrophila (P < 0.05). In conclusion, proper addition of Azomite in diets improved the growth, intestine morphology, immune response and disease resistance in largemouth bass, and the optimal inclusion was estimated to be 2.0-3.0 g/kg diet.

Cloning, molecular characterization, and tissue differential expression of connective tissue growth factor (ctgf) of grass carp.

Connective tissue growth factor (ctgf) is involved in the proliferation, migration, adhesion of cell, and the constituent of extracellular matrix, which plays an important role in embryogenesis, angiogenesis, wound repair, and fibrosis diseases. In this study, the cDNA sequence of grass carp ctgf gene was cloned by rapid amplification of cDNA ends (RACE) method; then, the characteristics of this gene and the predicted protein sequence were analyzed by bioinformatics methods, and the tissue differential expression pattern was detected by the quantitative real-time PCR. The results showed that the grass carp ctgf gene has a full-length of 2223 bp, encoding 343 amino acids. The deduced CTGF protein is a hydrophilic and secretary protein with a molecular mass of 37,978.2 Da and an isoelectric point of 8.22. The signal peptide locates between residue positions 1 and 22 of the polypeptide chain. The protein contains α-helix, ß-strand, and loops. The CTGF protein of grass carp shows a homology of 98%, 96%, 91%, and 91% with Wuchang bream (Megalobrama amblycephala), zebrafish (Danio rerio), common carp (Cyprinus carpio), and Mexican tetra (Astyanax mexicanus). The grass carp ctgf gene expressed significantly higher in blood and spleen than that in other tissues (P < 0.05). The low expression tissues included the heart, gill, skin, muscle, kidney, brain, and intestinal, and the lowest expression tissue was the liver. The results are consistent with the function of this gene.

Cloning, molecular characterization, and expression analysis of the unc45 myosin chaperone b(unc45b)gene of grass carp (Ctenopharyngodon idellus).

Unc45 myosin chaperone b(unc45b)gene is a molecular chaperone that mediates the folding, assembly and accumulation of thick-filament myosin in the formation of sarcomere, which plays an important role in the development of striated muscle and the stability of sarcomere. In this study, the complete cDNA sequence of unc45b gene of grass carp was obtained by rapid amplification of cDNA ends (RACE), and the characteristics of the unc45b protein predicted from gene sequence was analyzed by bioinformatics methods. The differential expression pattern in tissues was also detected by quantitative real-time PCR. The results showed that the full-length of unc45b gene of grass carp is 3163 bp, which contains a 60 bp 5'UTR, a 298 bp 3'UTR, and a 2865 bp open reading frame (ORF) encoding a 934 amino acid peptide. The deduced unc45b protein exhibits a homology of 92, 86, 86 % with the protein of zebrafish (Danio rerio), channel catfish (Ietalurus punctatus) and tilapia (Oreochromis niloticus) respectively, and the protein contains UCS myosin head binding domain and TPR peptide repeat domain. The protein is a hydrophilic and non-secretory protein with a molecular mass and isoeletronic point of 103,699.8 and 7.39 Da. The structural elements of the protein includes α-helixes and loops, and the unc45b gene highly expresses in skeletal muscle and heart in grass carp. This study laid a foundation for further research in explaining the myofibril accumulation in crisped grass carp.

The complete mitochondrial genome of Protomelas annectens (Regan, 1922) (Perciformes: Cichlidae).

In this study, the complete mitogenome sequence of Protomelas annectens Regan 1922 has been sequenced by next-generation sequencing method. The assembled mitogenome consisting of 16 583 bp, includes 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and 1 control region. The overall base composition of P. annectens is 27.41% for A, 30.07% for C, 15.88% for G, 26.64% for T and shows 94% identity to threadfin cichlid, Petrochromis trewavasae. These data will provide useful molecular information for phylogenetic relationships within the family Cichlidae species.