Effects of different dietary phospholipid levels on growth performance, fatty acid composition, PPAR gene expressions and antioxidant responses of blunt snout bream Megalobrama amblycephala fingerlings

The roles of soybean lecithin in aquafeed: a crucial need and update

Soybean lecithin is extensively used as the dietary supplementation of phospholipids in animal production. Soybean lecithin plays significant roles in aquafeed as growth promoter, feed enhancer, immunity modulator and antioxidant activity stimulator for aquaculture species. Besides, soybean lecithin is also reported to help aquaculture species being resilient to physical and chemical stressors. In this review, common sources, chemical structure and mode of action of lecithin, with highlight on soybean lecithin application in aquaculture over four-decadal studies published between 1983 and 2023, were evaluated and summarized. By far, soybean lecithin is best-known for its beneficial effects, availability yet cost-effective for aquafeed formulation. Findings from this review also demonstrate that although nutritional profile of long-chain polyunsaturated fatty acids and phosphatidylcholine from egg yolk and marine sources are superior to those from plant sources such as soybean, it is rather costly for sustainable application in aquafeed formulation. Moreover, commercially available products that incorporate soybean lecithin with other feed additives are promising to boost aquaculture production. Overall, effects of soybean lecithin supplementation are well-recognized on larval and juvenile of aquaculture species which having limited ability to biosynthesis phospholipids de novo, and correspondingly attribute to phospholipid, a primary component of soybean lecithin, that is essential for rapid growth during early stages development. In addition, soybean lecithin supplementation plays a distinguish role in stimulating maturation of gonadal development in the adults, especially for crustaceans.

Dietary Curcumin Supplementation Could Improve Muscle Quality, Antioxidant Enzyme Activities and the Gut Microbiota Structure of Pelodiscus sinensis

This experiment aimed to assess the impact of different dietary curcumin (CM) levels on growth, muscle quality, serum-biochemical parameters, antioxidant-enzyme activities, gut microbiome, and liver transcriptome in Chinese soft-shelled turtles (Pelodiscus sinensis). Five experimental diets were formulated to include graded levels of curcumin at 0 (control, CM0), 0.5 (CM0.5), 1 (CM1), 2 (CM2) and 4 g/kg (CM4). Each diet was randomly distributed to quadruplicate groups of turtles (164.33 ± 5.5 g) for 6 weeks. Our findings indicated that dietary curcumin supplementation did not have a significant influence on growth performance (p > 0.05); however, it significantly improved the muscular texture profiles (p < 0.05). Serum total superoxide dismutase (SOD), liver catalase (CAT), and total antioxidant capacity (T-AOC) activities increased significantly as dietary curcumin levels rose from 0.5 to 4 g/kg (p < 0.05). Dietary curcumin supplementation improved gut microbiota composition, as evidenced by an increase in the proportion of dominant bacteria such as Lactobacillus and Flavobacterium. Liver transcriptome analysis revealed that curcumin altered metabolic pathways in the liver. In conclusion, based on the evaluation of the activities of SOD in serum and CAT in liver under current experimental design, it was determined that the appropriate dietary curcumin supplementation for Chinese soft-shelled turtles is approximately 3.9 g/kg.

Growth, Biochemical Characteristics, Flesh Quality, and Gut Microbiota of the Pacific White Shrimp (Penaeus vannamei) Fed a Defatted Superworm (Zophobas atratus) Larvae Meal

This study evaluated the effects of defatted superworm (Zophobas atratus) larvae meal (DBWLM) as an alternative protein ingredient for juvenile Pacific white shrimp (Penaeus vannamei). Six isonitrogenous and isolipidic experimental diets were characterized by replacing 0%, 15%, 30%, 45%, 60%, and 75% fish meal (DBWLM0, DBWLM15, DBWLM30, DBWLM45, DBWLM60, and DBWLM75, respectively) with DBWLM on a w/w basis and feeding them to juvenile shrimp (0.34 ± 0.04 g) for 56 days. The results showed that the replacement of up to 75% fish meal by DBWLM had no negative effect on the growth performance of P. vannamei. The survival of shrimp in the DBWLM30 group was the highest, and the weight gain, specific growth rate, feed conversion ratio, condition factor, and apparent digestibility coefficients of dry matter in the DBWLM15 group were the highest. The substitution of DBWLM for fish meal significantly increased the elasticity of flesh, improved the total content of umami amino acids in flesh (aspartic acid, glutamic acid, glycine, and alanine), promoted lipid metabolism in shrimp, and reduced serum lipid levels. With the increase in DBWLM level, serum acid phosphatase, alkaline phosphatase activity, and intestinal inflammatory gene expression (IGF-1 and IL-6) were inhibited, malondialdehyde content decreased, and total antioxidant capacity level and superoxide dismutase activity increased significantly. Histological sections of the hepatopancreas showed that when 60% or more fish meal was replaced, the hepatopancreas atrophied and had irregular lumen distortion, but the cell membrane was not damaged. Microbiome analysis showed that the abundance of Bacteroidetes and Firmicutes increased and the abundance of Proteobacteria decreased in the DBWLM replacement group, and it was rich in "metabolism"-related functional pathways. It is worth mentioning that the expression of amino-acid-related enzymes was upregulated in the DBWLM15 and DBWLM30 groups, and the DBWLM75 group inhibited the biosynthesis of steroids and hormones. To conclude, the replacement of 15%-45% fish meal with DBWLM can result in better growth and immune status, improved meat elasticity, and reduced inflammation in P. vannamei. However, it is recommended that the replacement level should not exceed 60%, otherwise it will cause atrophy of hepatopancreas cells.

Genome-wide identification and expression of the peroxisome proliferator-activated receptor gene family in the Tibetan highland fish Gymnocypris przewalskii

Peroxisome proliferator-activated receptor (PPAR) plays an important role in the regulation of lipid metabolism and has been widely identified in diverse species. Gymnocypris przewalskii is a native fish of the Qinghai Tibetan Plateau that survives in a chronically cold environment. In the current study, we conducted genome-wide identification of PPAR genes, revealing the existence of seven PPARs in the G. przewalskii genome. Collinearity was observed between two copies of PPARαb and PPARγ in G. przewalskii, suggesting that the additional copy might be gained through whole genome duplication. Both phylogenetic and multiple sequence alignment analyses indicated that PPARs in G. przewalskii were conserved with teleosts. The cold treatment (10 °C and 4 °C) led to the developmental delay of G. przewalskii embryos. Continuous expression of PPARs was observed during the embryonic development of G. przewalskii under normal and cold conditions, with significantly different transcriptional patterns. These results indicated that PPARs participated in the embryonic development of G. przewalskii, and were involved in the cold response during development. The current study proposed a potential role of PPARs in the cold response in the embryonic development of G. przewalskii, which shed light on understanding cold adaptation in Tibetan highland fish.

Growth, Health, and Gut Microbiota of Female Pacific White Shrimp, Litopenaeus vannamei Broodstock Fed Different Phospholipid Sources

Phospholipids have an important antioxidant effect on animals. The effects of different dietary phospholipid sources on the growth, antioxidant activity, immunity, and gut microbiota of female broodstock of Pacific white shrimp Litopenaeus vannamei were investigated. Four isoproteic and isolipid semi-purified diets containing 4% soybean lecithin (SL), egg yolk lecithin (EL), or krill oil (KO) and a control diet without phospholipid supplementation were fed to female broodstock of L. vannamei (34.7 ± 4.2 g) for 28 days. The growth performance, antioxidative capacity, and innate immunity of the female broodstock fed phospholipid supplemented diets were improved regardless of sources compared with the control shrimp. The effects on growth and antioxidant capacity in female shrimp fed the KO diet were highest. The innate immunity of female shrimp fed the EL and KO diets were significantly higher than shrimp fed the SL diet. Dietary phospholipid supplementation increased gut microbiota diversity and richness, and the Chao1 and ACE values in the KO group were significantly higher than in the control group. The richness of Proteobacteria, Photobacterium, and Vibrio decreased, whereas the richness of Firmicutes and Bacteroidetes increased in the shrimp fed the KO diet compared with the shrimp fed the SL and EL diets. The interactions of gut microbiota in shrimp fed the KO diet were the most complex, and the positive interaction was the largest among all the treatments. The functional genes of gut microbiota in shrimp fed the KO diet were significantly enriched in lipid metabolism and terpenoid/polyketide metabolism pathways. Spearman correlation analysis showed that Fusibacter had significantly positive correlations with antioxidant activity (total antioxidant capacity, superoxide dismutase, glutathione peroxidase), immune enzyme activity (phenoloxidase and lysozyme), and immune gene expression (C-type lectin 3, Caspase-1). All findings suggest that dietary phospholipids supplementation can improve the growth and health status of female L. vananmei broodstock. Krill oil is more beneficial in improving the antioxidant capacity and innate immunity than other dietary phospholipid sources. Furthermore, krill oil can help establish the intestinal immune barrier by increasing the richness of Fusibacter and promote the growth of female shrimp. Fusibacter may be involved in iron metabolism to improve the antioxidant capacity of female shrimp.

Effect of Marine Red Yeast Rhodosporidium paludigenum on Diarrhea Rate, Serum Antioxidant Competence, Intestinal Immune Capacity, and Microflora Structure in Early-Weaned Lambs

In this study, the influences of marine red yeast Rhodosporidium paludigenum (MRYP) on diarrhea rate, serum antioxidant capacity, intestinal immunity capacity, and microflora structure of early-weaned lamb were investigated in a 60-day feeding trial. A total of 96 early-weaned lambs were utilized in this study. The lambs were divided into four experimental groups based on the percentage of marine red yeast Rhodosporidium paludigenum (MRYP) as milk replacer supplement. The rates of milk replacer supplement for the four groups were 0, 0.1%, 0.3%, and 0.5% of marine red yeast Rhodosporidium paludigenum (MRYP), respectively. The study was continued for 30 days. The results showed that (1) compared with control group, 0.5% marine red yeast Rhodosporidium paludigenum (MRYP) supplementation caused significantly decreases in average fecal score and diarrhea frequency by 33.74% and 40.23% (P < 0.05). (2) No significant difference was found in all tested related antioxidant indexes in serum of four treatments (P > 0.05). (3) The concentrations of SIgA, IgG, and IL-10 of group IV was significantly increased by 17.78%, 18.27%, and 8.17%, but the IL-6 and TNF-α were significantly decreased by 21.20% and 31.80%, compared to group I in the colon (P < 0.05). (4) The number of Bifidobacterial and Lactobacilli of group IV was significantly increased by 14.87% and 15.09%, but Escherichia coli and Salmonella were significantly decreased by 20.19% and 10.15%, compared to group I in the colon (P < 0.05). (5) A portion of marine red yeast Rhodosporidium paludigenum (MRYP) survived in the intestine of early-weaned lamb, and the number of survival marine red yeast Rhodosporidium paludigenum (MRYP) increased as the addition of marine red yeast Rhodosporidium paludigenum (MRYP) increased from 0.1 to 0.5% in milk replacer. Therefore, marine red yeast Rhodosporidium paludigenum (MRYP) has a potential to be a replacer of antibiotics for prevention and treatment of diarrhea in early-weaned lambs.

Effects of Lysophospholipid Supplementation in Feed with Low Protein or Lipid on Growth Performance, Lipid Metabolism, and Intestinal Flora of Largemouth Bass (Micropterus salmoides)

The largemouth bass (Micropterus salmoides) were fed diets with three experimental feeds, a control diet (Control, crude protein (CP): 54.52%, crude lipid (CL): 11.45%), a low-protein diet with lysophospholipid (LP-Ly, CP: 52.46%, CL: 11.36%), and a low-lipid diet with lysophospholipid (LL-Ly, CP: 54.43%, CL: 10.19%), respectively. The LP-Ly and LL-Ly groups represented the addition of 1 g/kg of lysophospholipids in the low-protein and low-lipid groups, respectively. After a 64-day feeding trial, the experimental results showed that the growth performance, hepatosomatic index, and viscerosomatic index of largemouth bass in both the LP-Ly and LL-Ly groups were not significantly different compared to those in the Control group (P > 0.05). The condition factor and CP content of whole fish were significantly higher in the LP-Ly group than those in the Control group (P < 0.05). Compared with the Control group, the serum total cholesterol level and alanine aminotransferase enzyme activity were significantly lower in both the LP-Ly group and the LL-Ly group (P < 0.05). The protease and lipase activities in the liver and intestine of both group LL-Ly and group LP-Ly were significantly higher than those of the Control group (P < 0.05). Compared to both the LL-Ly group and the LP-Ly group, significantly lower liver enzyme activities and gene expression of fatty acid synthase, hormone-sensitive lipase, and carnitine palmitoyltransferase 1 were found in the Control group (P < 0.05). The addition of lysophospholipids increased the abundance of beneficial bacteria (Cetobacterium and Acinetobacter) and decreased the abundance of harmful bacteria (Mycoplasma) in the intestinal flora. In conclusion, the supplementation of lysophospholipids in low-protein or low-lipid diets had no negative effect on the growth performance of largemouth bass, but increased the activity of intestinal digestive enzymes, enhanced the hepatic lipid metabolism, promoted the protein deposition, and regulated the structure and diversity of the intestinal flora.

Comparative analysis of growth performance and liver transcriptome response of juvenile Ancherythroculter nigrocauda fed diets with different protein levels

This study aimed at investigating the effects of dietary protein levels on the growth and liver transcriptome in juvenile Ancherythroculter nigrocauda. Six semi-purified diets were formulated containing 25 (control), 30, 35, 40, 45, and 50% protein. Each diet was fed to three groups of 35 fish (mean initial weight: 5.86 ± 0.10 g) for 56 days. The rate of weight gain and specific growth rate increased with dietary protein levels from 25% to 40%, but remained unchanged when fed with 45 or 50% dietary protein. The feed conversion ratio was significantly influenced by the dietary protein levels, being the lowest in fish fed 40% protein. Illumina RNA-seq analysis was performed to investigate liver gene expression changes under different dietary protein treatments. A total of 367.78 million clean reads were obtained from the six libraries. Compared with 25% protein treatment library, there were 734, 1946, 1755, 2726, and 1523 upregulated genes, and 407, 1882, 1865, 2216 and 1624 downregulated genes in the 30, 35, 40, 45, and 50% protein treatment libraries, respectively. Trend analysis of these differentially expressed genes (DEGs) identified six statistically significant trends. A series of DEGs that related to protein metabolism, growth and development, lipid metabolism and immune and stress response were identified. Moreover, gene ontology enrichment analysis of the DEGs demonstrated that cellular process, single-organism process, metabolic process and biological regulation were the most highly overrepresented biological processes. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that protein processing in endoplasmic reticulum, PPAR signaling pathway, complement and coagulation cascades, and cytochrome P450 (CYP450s) were significantly enriched in the dietary protein treatment groups. Furthermore, qPCR results showed excellent agreement on those of RNA-seq for both up- and down-regulated genes (including fasn, accα, SCD, CPT-I, igf1, ST, AST, trdmt1, hsp70, cyp450, MHC-II, C4, tgfβ, ube4b, apoE and abcb7). Thus, our results provide the baseline information for the feed formulation and nutritional research for A. nigrocauda.

The mechanism of action of a fat regulator: Glycyrrhetinic acid (GA) stimulating fatty acid transmembrane and intracellular transport in blunt snout bream (Megalobrama amblycephala)

High-fat diets are associated with fatty liver and aberrant hepatic lipid metabolism, and glycyrrhetinic acid (GA) has been shown to exert a beneficial effect on lipolysis and fat deposition in fish. In the present study, we evaluated the effect of GA on the growth performance and expression of hepatic lipid transport related genes in blunt snout bream (Megalobrama amblycephala) fed a high fat diet. Two hundred and sixteen fish (average body weight: 45.57 g ± 0.98 g) were fed three experimental diets (6% fat/L6 group, control, 11% fat/L11 group, and 11% fat with 0.3 mg kg^-1 GA/L11GA group) for 8 weeks. Compared to the control group, the weight gain and specific growth rate of high-fat fed group at the end of the trialwere significantly improved (P < .05).However, GA showed no effect on animals' growth performance(P > .05). Dietary supplementation with 0.3 mg kg^-1 GA significantly decreased the hepatosomatic index, viscera/body ratio, and intraperitoneal fat ratio (P < .05), and up-regulated the expression levels of fatty acids transport protein (FATP), fatty acids binding protein (FABP), fatty acid translocase (CD36), carnitine palmitoyl transferase I (CPT1) and peroxisome proliferators-activated receptors α (PPARα) compared to both the L6 group and L11 group (P < .05). However, no significant difference was observed in fatty acid synthetase (FAS), acetyl-CoA carboxylase α (ACCα), or lipoprotein lipase (LPL) between groups (P > .05). In conclusion, GA significantly rescued high-fat diet induced hepatic lipid accumulation and metabolism dysfunction in M. amblycephalaby stimulating hepatic fatty acid transport and β-oxidation. Dietary GA may be used as a promising supplement to alleviate high-fat diet induced side effects on M. amblycephala.

Effect of dietary phospholipid levels on growth, lipid metabolism, and antioxidative status of juvenile hybrid snakehead (Channa argus×Channa maculata)

The study was conducted to evaluate the effect of dietary phospholipids (PLs) on growth, lipid metabolism, and antioxidative status of hybrid snakehead (Channa argus × Channa maculata). Five isonitrogenous and isolipidic diets with graded levels of PLs (8.5, 19.3, 30.7, 41.5, and 50.8 g kg^-1) were fed to triplicate groups of juveniles (initial body weight 12.6 ± 0.23 g) for 8 weeks. Results showed that dietary PL supplementation significantly improved growth of juveniles. The final body weight (FBW) and specific growth rate (SGR) significantly increased with dietary PLs increasing from 8.5 to 41.5 g kg^-1 (P < 0.05). Fish fed with the diet containing 8.5 g kg^-1 PLs showed higher feed conversion ratio (FCR) compared to the other treatments (P < 0.05). Survival rate (SR) was not affected by dietary PL levels (P > 0.05). Liver lipid contents, serum triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) contents significantly decreased with the increasing levels of dietary PLs (P < 0.05). However, serum total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) contents and HDL-C/TC and HDL-C/LDL-C value significantly increased with increasing dietary PL levels (P < 0.05). The catalase (CAT), superoxide dismutase (SOD), and carnitine palmitoyl transferase I (CPT-1) activities in the liver significantly increased with incremental dietary PL level (P < 0.05), while the liver malondialdehyde (MDA) contents and fatty acid synthase (FAS) activity significantly reduced (P < 0.05). No significant difference was observed in the glutathione peroxidase (GPx) activity among dietary treatments (P > 0.05).These results confirmed that dietary PL supplementation has beneficial effects on growth performance and antioxidant capacity of juvenile hybrid snakehead. Dietary PLs might reduce lipid deposition in the liver of juvenile hybrid snakehead.

Growth performance, fatty-acid composition, lipid deposition and hepatic-lipid metabolism-related gene expression in juvenile pond loach Misgurnus anguillicaudatus fed diets with different dietary soybean oil levels

A 10 week feeding trial was conducted to evaluate the effects of different dietary soybean oil (SO) levels on growth performance, fatty-acid composition and lipid deposition in viscera, histology and histochemistry of liver, intestine and hepatic-lipid metabolism-related gene expressions in pond loach Misgurnus anguillicaudatus juveniles. Misgurnus anguillicaudatus (mean ± s.d. mass 0·40 ± 0·01 g) were fed five experimental diets containing SO at different concentrations: 0, 20, 32, 56 and 100% SO and a diet containing 100% fish oil (100% FO). The mass gains and specific growth rates of M. anguillicaudatus fed 20% SO and 100% FO diets were significantly higher than those of the other groups (P < 0·05). The lipid content of viscera and the amount of cytoplasmic vacuolation in the liver increased with incremental dietary SO level. Meanwhile, increasing dietary SO levels up-regulated the messenger (m)RNA levels of lipogenic genes (such as Δ6fad, scd, pparγ, fas and srebp-1) and down-regulated the mRNA levels of the lipolytic genes (such as pparα, cpt1, atgl and hsl) in the liver. The percentage of 20:4n-6 significantly (P < 0·05) increased with increasing dietary SO level, which might be correlated with the up-regulation of the mRNA level of Δ6fad. The highest levels of dietary SO, however, had a negative effect on growth performance, lipid deposition of viscera and histology and histochemstry of liver and intestine. The increased lipid accumulation induced by incremental dietary SO level probably occurred through different strategies for lipid metabolism as a result of competition between lipolysis and lipogenesis and between export and import of lipids in this species.

Effects of dietary vitamin E supplementation on growth performance, fatty acid composition, lipid peroxidation and peroxisome proliferator-activated receptors (PPAR) expressions in juvenile blunt snout bream Megalobrama amblycephala

A 9-week feeding experiment was conducted to evaluate the effects of dietary vitamin E (VE) supplementation on growth performance, liver fatty acid composition, lipid peroxidation and peroxisome proliferator-activated receptors (PPAR) genes expressions in blunt snout bream juveniles. Fish (average initial weight: 0.59 g) were fed diet supplemented with 0, 50, 100, 300 and 500 mg α-tocopherol acetate/kg in triplicates, which were found to, respectively, contain 11.2, 56.3, 114.6, 306.5 and 588.4 mg α-tocopherol/kg diet. Results showed that final weight, body weight gain and specific growth rate significantly increased with increasing dietary VE supplemented level from 11.2 to 56.3 mg/kg. When the broken-line model was employed to estimate the adequate requirement of vitamin E based on body weight gain, the optimal level was 55.5 mg/kg in diet. Hepatosomatic index value significantly decreased with incremental dietary VE levels. However, liver VE concentration showed a direct relationship with the dietary VE level. The percentages of 20:5n-3, 22:6n-3 and total n-3 long chain polyunsaturated fatty acids in liver increased with increasing dietary VE supplementation. Meanwhile, the expressions of PPAR-α, PPAR-β and PPAR-γ in liver were down-regulated by supplementation of dietary VE level from 56.3 to 588.4 mg/kg. In conclusion, supplementation of more than 55.5 mg/kg vitamin E may improve growth and increase n-3 LC-PUFA content in blunt snout bream, which is beneficial to human consumer.