Effects of dietary phospholipid level in cobia (Rachycentron canadum) larvae: growth, survival, plasma lipids and enzymes of lipid metabolism

Chestnut tannin extract modulates growth performance and fatty acid composition in finishing Tan lambs by regulating blood antioxidant capacity, rumen fermentation, and biohydrogenation

Tannins as plant extracts have emerged as promising and potential alternatives for antibiotics in modern livestock cultivation systems. This study investigates the effect of dietary chestnut tannin extract (CTE) in finishing Tan lambs. Twenty-seven male Tan lambs were randomly divided into three groups: (1) control group (CON; basal diet); (2) low-dose CTE group (LCTE; basal diet + 2 g/kg CTE, dry matter [DM] basis); (3) high-dose CTE group (HCTE; basal diet + 4 g/kg CTE, DM basis). The HCTE group exhibited markedly higher average daily gain (ADG) and DM intake than CON (P < 0.01). The ruminal total volatile fatty acid concentration increased linearly with increasing CTE supplementation (P < 0.01), while the opposite trend was observed for butyrate molar proportion (P < 0.01). Upon increasing CTE dosage, plasma glucose, high-density lipoprotein cholesterol, glutathione peroxidase, and superoxide dismutase content increased linearly (P < 0.05), whereas low-density lipoprotein cholesterol and urea nitrogen decreased linearly or quadratically (P < 0.05), respectively. A linear increase was also observed in ruminal t6 C18:1 and t9, c12 C18:2 proportions (P < 0.01), and plasma C18:2n-6 and n-6 polyunsaturated fatty acids proportions with increased CTE supplementation (P < 0.01). In the longissimus dorsi muscle, the atherogenic index decreased linearly (P < 0.05), while c11 C18:1 and C20:5n-3 increased linearly (P < 0.05). Moreover, c9, t11 conjugated linoleic acids proportion increased in subcutaneous fat with CTE supplementation (P < 0.01). In conclusion, Dietary CTE enhances the ADG of finishing Tan lambs in a dose-dependent manner, modulates plasma metabolites and antioxidant capacity, and improves rumen fermentation and body fatty acid composition. These results provide a reference for the rational application of CTE in ruminant production.

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.

A Comparative Study on Growth Performance, Body Composition, and Liver Tissue Metabolism Rearing on Soybean Lecithin-Enriched Artemia Nauplii and Microdiet in Rock Bream (Oplegnathus fasciatus) Larvae

This study is aimed at establishing optimal soybean lecithin (SL) enrichment protocols in Artemia nauplii and at comparing the growth performance, body composition, and liver tissue metabolism in rock bream (Oplegnathus fasciatus) larvae reared on SL-enriched Artemia nauplii or SL-enriched microdiet (MD). The enrichment protocol experiment results indicated 12 h enrichment, and 10 g SL/m³ seawater could obtain desirable results. Rock bream larvae (25 days posthatching (dph)) were fed Artemia nauplii or MD for 30 days with three replicates. At stage 1 (larval 25-40 dph), significantly higher growth performance was observed in larvae fed the live prey (P < 0.05). Conversely, at stage 2 (41-55 dph), feeding with MD significantly increased larval standard length, and specific growth rate compared with those of larvae fed live prey. Larvae fed a MD showed decreased lipolysis-related lipase activity as well as decreased amino acid catabolism-related alanine aminotransferase and aspartate aminotransferase enzyme activities in liver tissue. RNA sequencing revealed that feeding with the MD primarily increased the expression of lipogenesis-related genes and protein translation-related gene expression in the liver tissue. Notably, feeding with MD significantly increased ribosome biogenesis-related genes as well as mitochondria synthesis-related gene expression, indicating a high protein anabolism rate and high energy production in liver tissue. In conclusion, 10 g SL/m³ seawater and 12 h could effectively enrich SL in Artemia nauplii. Retard weaning onto MD led to lower growth performance, which was likely due to the diversity of lipid and protein metabolism.

Effects of Dietary Lysophospholipid Inclusion on the Growth Performance, Nutrient Digestibility, Nitrogen Utilization, and Blood Metabolites of Finishing Beef Cattle

This study was conducted to evaluate the effect of dietary supplementation with lysophospholipids (LPLs) on the growth performance, nutrient digestibility, nitrogen utilization, and blood metabolites of finishing beef cattle. In total, 40 Angus beef bulls were blocked for body weight (447 ± 9.64 kg) and age (420 ± 6.1 days) and randomly assigned to one of four treatments (10 beef cattle per treatment): (1) control (CON; basal diet); (2) LLPL (CON supplemented with 0.012% dietary LPL, dry matter (DM) basis); (3) MLPL (CON supplemented with 0.024% dietary LPL, DM basis); and (4) HLPL (CON supplemented with 0.048% dietary LPLs, DM basis). The results showed that dietary supplementation with LPLs linearly increased the average daily gain (p < 0.01), digestibility of DM (p < 0.01), crude protein (p < 0.01), and ether extract (p < 0.01) and decreased the feed conversion ratio (p < 0.01). A linear increase in N retention (p = 0.01) and a decrease in urinary (p = 0.04) and fecal N (p = 0.02) levels were observed with increasing the supplemental doses of LPLs. Bulls fed LPLs showed a linear increase in glutathione peroxidase (p = 0.04) and hepatic lipase (p < 0.01) activity and a decrease in cholesterol (p < 0.01), triglyceride (p < 0.01), and malondialdehyde (p < 0.01) levels. In conclusion, supplementation with LPLs has the potential to improve the growth performance, nutrient digestibility, and antioxidant status of beef cattle.

Effects of Dietary Phospholipids on Growth Performance, Digestive Enzymes Activity and Intestinal Health of Largemouth Bass (Micropterus salmoides) Larvae

While the beneficial roles of dietary phospholipids on health status and overall performances of fish larvae have been well demonstrated, the underlying mechanisms remain unclear. To address this gap, the present study was conducted to investigate the effects of dietary phospholipids on growth performance, intestinal development, immune response and microbiota of larval largemouth bass (Micropterus salmoides). Five isonitrogenous and isolipidic micro-diets were formulated to contain graded inclusion levels of phospholipids (1.69, 3.11, 5.23, 7.43 and 9.29%). Results showed that the supplementation of dietary phospholipids linearly improved the growth performance of largemouth bass larvae. The inclusion of dietary phospholipids increased the activity of digestive enzymes, such as lipase, trypsin and alkaline phosphatase, and promoted the expression of tight junction proteins including ZO-1, claudin-4 and claudin-5. Additionally, dietary phospholipids inclusion alleviated the accumulation of intestinal triacylglycerols, and further elevated the activity of lysozyme. Dietary phospholipids inhibited the transcription of some pro-inflammatory cytokines, including il-1β, and tnf-α, but promoted the expression of anti-inflammatory cytokines tgf-β, with these modifications being suggested to be mediated by the p38MAPK/Nf-κB pathway. The analysis of bacterial 16S rRNA V3-4 region indicated that the intestinal microbiota profile was significantly altered at the genus level with dietary phospholipids inclusion, including a decreased richness of pathogenic bacteria genera Klebsiella in larval intestine. In summary, it was showed that largemouth bass larvae have a specific requirement for dietary phospholipids, and this study provided novel insights on how dietary phospholipids supplementation contributes to improving the growth performance, digestive tract development and intestinal health.

Assessment of Growth, Lipid Metabolism and Gene Expression Responses in Senegalese Sole Larvae Fed With Low Dietary Phospholipid Levels

Phospholipids (PL) are essential molecules for larval growth and development. In this study, growth, lipid metabolism and gene expression responses associated with different dietary PL levels in pelagic sole larvae were evaluated. In a first trial, the long-term effects on growth and survival of two experimental microdiets (MD) containing high (High-PL) or low (Low-PL) PL levels were tested and compared to a diet based on live prey (rotifers). The MD were supplied from 3 to 10 days post-hatch (dph) and Artemia from day 8 to 29 dph. High-PL fed larvae had higher dry mass (1.2-fold) than Low-PL fed larvae at 8 dph and both MD were smaller (2.9-fold) than larvae fed live preys. However, a compensatory growth (33% between 8 and 20 dph) occurred when MD were substituted by Artemia and by the end of the trial no significant differences in mass or survival occurred between the dietary treatments. In a second trial, growth, lipid metabolism and gene expression profiles of larvae fed with MD up to 8 dph were analyzed. Growth data confirmed that mass of larvae fed with High-PL was higher (1.3-fold) than the those fed Low-PL and they had lower levels of triacylglycerol (2.8-fold), cholesterol (1.2-fold) and cetoleic acid (1.7-fold). Histological analysis indicated an excess of lipid vacuoles in larvae fed with Low-PL and the expression analysis revealed a coordinated response to enhance lipid mobilization since the expression of genes involved in PL intermediate synthesis, PL remodeling as well as eight apolipoprotein was up-regulated. The down-regulation of apolipoprotein apob2 in larvae fed with Low-PL indicated a specific regulation by PL levels. The present work provides insight into the responses associated with dietary PL in early fish larvae, which will be of use for future studies aimed as designing effective larval sole diets.

Changes in lipid profiles in Daphnia magna individuals exposed to low environmental levels of neuroactive pharmaceuticals

Disruptive effects of chemicals on lipids in aquatic species are mostly limited to obesogens and vertebrates. Recent studies reported that antidepressants, anxiolytic, antiepileptic and β-adrenergic pharmaceuticals, with putative distinct mechanisms of action at low environmental relevant concentrations, up-regulated common neurological and lipid metabolic pathways and enhanced similarly reproduction in the crustacean Daphnia magna. Conversely CRISPR mutants for the tryptophan hydrolase enzyme gene (TRH) that lack serotonin had the opposed phenotype: the lipid metabolism down-regulated and impaired reproduction. Lipid metabolism is strongly linked to reproduction in D. magna. The aim of this study is to test if the above mentioned neuro-active chemicals disrupted common lipid groups and showed also the opposed lipidomic effects as those individuals lacking serotonin. This study used ultra-high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOFMS) to study how neuro-active chemicals (carbamazepine, diazepam, fluoxetine and propranolol) at low (0.1 μg/L) and higher concentrations (1 μg/L) and three CRISPR TRH mutant clones disrupt the dynamics of glycerophospholipids and glycerolipids in Daphnia adults. Lipidomic analysis identified 267 individual lipids corresponding to three classes of glycerolipids, eleven of glycerophospholipids, one of sterols and one of sphingolipids, of which 132 and 125 changed according to the chemical treatments or across clones, respectively. Most pharmaceutical treatments enhanced reproduction whereas mutated clones lacking serotonin reproduced to a lesser extent. Except for carbamazepine, most of the tested pharmaceuticals increased some triacylglycerol species and decreased monoacylglycerols, lysophospholipids, sphingomyelins and cholesterol esters in exposed females. Opposed lipidomic pattern was observed in mutated clones lacking serotonin. Lipidomic data, thus, indicate a close link between reported transcriptomic and lipidomic changes, which are likely related to serotonin and other neurological signalling pathways.

Choline supplementation prevents diet induced gut mucosa lipid accumulation in post-smolt Atlantic salmon (Salmo salar L.)

Background

Various intestinal morphological alterations have been reported in cultured fish fed diets with high contents of plant ingredients. Since 2000, salmon farmers have reported symptoms indicating an intestinal problem, which we suggest calling lipid malabsorption syndrome (LMS), characterized by pale and foamy appearance of the enterocytes of the pyloric caeca, the result of lipid accumulation. The objective of the present study was to investigate if insufficient dietary choline may be a key component in development of the LMS.

Results

The results showed that Atlantic salmon (Salmo salar), average weight 362 g, fed a plant based diet for 79 days developed signs of LMS. In fish fed a similar diet supplemented with 0.4% choline chloride no signs of LMS were seen. The relative weight of the pyloric caeca was 40% lower, reflecting 65% less triacylglycerol content and histologically normal gut mucosa. Choline supplementation further increased specific fish growth by 18%. The concomitant alterations in intestinal gene expression related to phosphatidylcholine synthesis (chk and pcyt1a), cholesterol transport (abcg5 and npc1l1), lipid metabolism and transport (mgat2a and fabp2) and lipoprotein formation (apoA1 and apoAIV) confirmed the importance of choline in lipid turnover in the intestine and its ability to prevent LMS. Another important observation was the apparent correlation between plin2 expression and degree of enterocyte hyper-vacuolation observed in the current study, which suggests that plin2 may serve as a marker for intestinal lipid accumulation and steatosis in fish. Future research should be conducted to strengthen the knowledge of choline’s critical role in lipid transport, phospholipid synthesis and lipoprotein secretion to improve formulations of plant based diets for larger fish and to prevent LMS.

Conclusions

Choline prevents excessive lipid accumulation in the proximal intestine and is essential for Atlantic salmon in seawater.

Effect of dietary soybean lecithin on fish performance, hemato-immunological parameters, lipid biochemistry, antioxidant status, digestive enzymes activity and intestinal histomorphometry of pre-spawning Caspian brown trout (Salmo trutta caspius)

A feeding experiment was conducted to evaluate the effects of dietary soybean lecithin (SBL) supplementation on performance, hemato-immunological parameters, lipid biochemistry, antioxidant status, digestive enzymes activity and intestinal histomorphometry of Caspian brown trout, Salmo trutta caspius in the pre-spawning stage. The basal diet was supplemented with 0% (control), 3%, 6%, 9% and 12% of SBL to obtain five experimental diets. Fish with an average weight of 350 ± 10 g were randomly distributed among five experimental groups and fed for 90 days. Dietary SBL resulted in better performance including specific growth rate (SGR), weight gain (WG) and feed conversion ratio (FCR) (p < 0.05). Among the different hemato-immunological parameters, white blood cell counts (WBC), lysozyme, alternative complement activity (ACH50) and total immunoglobulin (IgM) content of serum were significantly increased with dietary SBL inclusion (p < 0.05). For antioxidant enzymes, glutathione S-transferase (GST) and catalase (CAT) showed significant differences among various experimental diets (p < 0.05). Furthermore, digestive enzymes activity including alkaline protease, lipase and amylase were increased in those fish received SBL supplemented diets (p < 0.05). Our results revealed that the dietary SBL improved some physiological responses of the fish and indicate 6-9% dietary SBL supplementation would improve the physiological competence of the pre-spawning Caspian brown trout breeders.

Skeletal Muscle Lipidomics as a New Tool to Determine Altered Lipid Homeostasis in Fish Exposed to Urban and Industrial Wastewaters

This work applies ultrahigh performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS) to characterize for the first time the lipidome of the skeletal muscle of two fish species (Barbus meridionalis, Squalius laietanus) collected in a Mediterranean River affected by urban and industrial wastewater outflows. The untargeted analysis allowed a clear separation of the lipidome of fish from polluted and reference sites; phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), and their lyso and ether-linked forms were among the distinctive features. The targeted analysis consistently detected a decrease in PC-plasmalogens (36:4, 36:6, 38:6) and highly unsaturated PCs (36:5, 36:6, 38:6, 40:6, 40:7) and an increase in plasmanyl-PCs (36:5, 38:5), lyso-PCs (16:1, 18:1, 22:4) and cholesteryl esters (CEs) (16:0, 18:0, 20:4) in fish from polluted sites. These lipid profiles were indicative of oxidative stress and dysregulation of cholesterol homeostasis in fish from polluted sites. This methodology represents a promising tool for the development of novel noninvasive diagnostic methods based on muscle tissue biopsies to assess the effects of water pollution in wildlife.

Dietary effects of succinic acid on the growth, digestive enzymes, immune response and resistance to ammonia stress of Litopenaeus vannamei

Organic acids acts as an growth promoter and antimicrobial agent in aquaculture. The present study investigated the effects of a natural organic acid - succinic acid (SA) on the growth, digestive enzymes, immune response and resistance to ammonia stress of Litopenaeus vannamei. The shrimps were firstly fed with diets containing different levels of SA: 0% (Control), 0.25% (SA1), 0.50% (SA2), and 1.0% (SA3) (w/w) for 56 days, followed by an acute ammonia stress for 48 h. The results indicated that dietary of SA improved the growth of shrimp, and increased the survival rate of shrimp after ammonia stress for 48 h. The amylase, lipase and pepsin activity increased in hepatopancreas in three SA group, while trypsin activity was only increased in the SA1 and SA2 groups. At 56 d, T-NOS activity, proPO and HSP70 gene expression level increased in the three SA group, PO activity increased in the SA1 and SA2 groups, T-AOC content and Toll gene expression level increased in the SA2 and SA3 groups, Trx and SOD gene expression level increased in the SA2 group, while Imd, GS and GDH gene expression level was no changes. After exposure to ammonia stress for 48 h, immune biochemical parameters (T-AOC and PO) and genes (proPO, HSP70, Trx and GDH) expression level increased in the three SA group, T-NOS activity, Toll, Imd and GS gene expression level increased in the SA2 and SA3 groups, while SOD gene expression level increased in the SA1 and SA2 groups. These results indicated that SA improved growth, enhanced digestive and immune capacities of L. vannamei against ammonia stress, and may be a potential feed additive for shrimp. The optimal dietary supplementation dosage is 0.50% (w/w) in diet.

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.

Dietary phosphatidylcholine impacts on growth performance and lipid metabolism in adult Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia Oreochromis niloticus

This study aimed to determine the effects of supplementing the diet of adult Nile tilapia Oreochromis niloticus with phosphatidylcholine (PC) on growth performance, body composition, fatty acid composition and gene expression. Genetically Improved Farmed Tilapia fish with an initial body weight of 83·1 (sd 2·9) g were divided into six groups. Each group was hand-fed a semi-purified diet containing 1·7 (control diet), 4·0, 6·5, 11·5, 21·3 or 41·0 g PC/kg diet for 68 d. Supplemental PC improved the feed efficiency rate, which was highest in the 11·5 g PC/kg diet. Weight gain and specific growth rate were unaffected. Dietary PC increased PC content in the liver and decreased crude fat content in the liver, viscera and body. SFA and MUFA increased and PUFA decreased in muscle with increasing dietary PC. Cytoplasmic phospholipase A 2 and secreted phospholipase A 2 mRNA expression were up-regulated in the brain and heart in PC-supplemented fish. PC reduced fatty acid synthase mRNA expression in the liver and visceral tissue but increased expression in muscle. Hormone-sensitive lipase and lipoprotein lipase expression increased in the liver with increasing dietary PC. Growth hormone mRNA expression was reduced in the brain and insulin-like growth factor-1 mRNA expression in liver reduced with PC above 6·5 g/kg. Our results demonstrate that dietary supplementation with PC improves feed efficiency and reduces liver fat in adult Nile tilapia, without increasing weight gain, representing a novel dietary approach to reduce feed requirements and improve the health of Nile tilapia.

Response of a Mu-class glutathione S-transferase from black tiger shrimp Penaeus monodon to aflatoxin B1 exposure

Glutathione S-transferases (GSTs) are a family of multifunctional phase II enzymes that are involved in the detoxification of exogenous and endogenous compounds. In this study, a full-length cDNA of Mu-class GST (PmMuGST) was isolated from the hepatopancreas of Penaeus monodon using rapid amplification of cDNA ends method. The full length cDNA of PmMuGST is 867 bp, contains an open read frame of 660 bp, and encodes a polypeptide of 219 amino acids with a molecular mass of 25.61 kDa and pI of 6.15. Sequence analysis indicated that the predicted protein sequence of PmMuGST was very similar to (86 %) that of Litopenaeus vannamei. A conserved domain of GST_N_Mu_like (PSSM: cd03075) and GST_C_family_superfamily_like (PSSM: cl02776) was indentified in PmMuGST. Real time quantitative RT-PCR analysis indicated that PmMuGST was present in all of the tested tissues. PmMuGST transcripts both in the hepatopancreas and in the muscle were significantly induced after 14 days of treatment with a low dosage of AFB1 (50 μg/kg) exposure and were significantly inhibited after 42 and 56 days of a high dosage of AFB1 (1000, 2500 μg/kg AFB1) exposure. Taken together, the Mu-class GST from P. monodon was inducible and was involved in the response to AFB1 exposure.

Modulation of immune response, physical barrier and related signaling factors in the gills of juvenile grass carp (Ctenopharyngodon idella) fed supplemented diet with phospholipids

This study was conducted to investigate the effects of dietary phospholipids (PL) on the gill immune response and physical barrier of juvenile grass carp (Ctenopharyngodon idella). A total of 1080 juvenile grass carp with an average initial weight of 9.34 ± 0.03 g were fed six semi-purified diets containing 0.40% (unsupplemented control group), 1.43%, 2.38%, 3.29%, 4.37% and 5.42% PL for 2 months. Compared with the control group, optimal PL supplementation increased (P < 0.05): (1) the lysozyme activity, acid phosphatase activity, complement component 3 (C3) content, liver expressed antimicrobial peptide 1 (LEAP-1) and LEAP-2 mRNA expression; (2) the relative mRNA expression of interleukin 10, transforming growth factor β1, inhibitor factor κBα (IκBα) and target of rapamycin (TOR); (3) the activities of anti-superoxide anion (ASA), anti-hydroxyl radical (AHR), copper/zinc superoxide dismutase (SOD1), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR), glutathione content and mRNA levels of SOD1, CAT, GPx, GR and NF-E2-related factor 2 (Nrf2) genes; (4) the transcription abundance of occludin, claudin b, claudin c, claudin 12 and zonula occludens 1 genes. At the same time, appropriate PL supplementation decreased (P < 0.05): (1) tumor necrosis factor α, interleukin 1β, nuclear factor κB p65 (NF-κB p65), IκB kinase β (IKKβ) and IκB kinase γ (IKKγ) mRNA expression; (2) malondialdehyde (MDA), protein carbonyl (PC) and reactive oxygen species (ROS) content and the relative mRNA expression of Kelch-like-ECH-associated protein 1a (Keap1a) and Keap1b; (3) the transcription abundance of myosin light chain kinase (MLCK) and p38 mitogen-activated protein kinase (p38 MAPK) genes. In conclusion, the positive effect of PL on gill health is associated with the improvement of the immunity, antioxidant status and tight junction barrier of fish gills. Finally, based on ACP activity, C3 content, PC content and ASA activity in the gills, the optimal dietary PL level for juvenile grass carp (9.34-87.50 g) was estimated to be 3.62%, 4.30%, 3.91% and 3.86%, respectively.

Exogenous phospholipids supplementation improves growth and modulates immune response and physical barrier referring to NF-κB, TOR, MLCK and Nrf2 signaling factors in the intestine of juvenile grass carp (Ctenopharyngodon idella)

This study was conducted to investigate the effects of dietary phospholipids (PL) on the growth performance, intestinal enzyme activity and immune response and intestinal physical barrier of juvenile grass carp (Ctenopharyngodon idella). A total of 1080 juvenile grass carp with an average initial weight of 9.34 ± 0.03 g were fed six semi-purified diets containing 0.40% (unsupplemented control group), 1.43%, 2.38%, 3.29%, 4.37% and 5.42% PL for 2 months. Results indicated that 3.29% PL increased lysozyme (LZ) and acid phosphatase (ACP) activities and complement component 3 (C3) content (P < 0.05), up-regulated the mRNA relative expression levels of interleukin 10, transforming growth factor β1 (TGF-β1), inhibitor protein κBα (IκBα), target of rapamycin (TOR) and casein kinase 2 (CK2) (P < 0.05), and down-regulated tumor necrosis factor α (TNF-α), interleukin 1β, nuclear factor κB p65 (NF-κB p65), IκB kinase β (IKKβ) and IκB kinase γ (IKKγ) mRNA relative expression levels (P < 0.05) in the intestine, suggesting that optimum PL could improve fish intestinal immunity. In addition, 3.29% PL increased the activities of anti-superoxide anion (ASA), anti-hydroxyl radical, copper/zinc superoxide dismutase (SOD1), glutathione peroxidase (GPx) and glutathione reductase (GR), the content of glutathione (P < 0.05), and the mRNA relative expression levels of occludin, zonula occludens 1 (ZO-1), claudin 3, claudin 12, claudin b, claudin c, SOD1, GPx, GR and NF-E2-related factor 2 (Nrf2) and decreased malondialdehyde (MDA), protein carbonyl (PC) and ROS content (P < 0.05), the mRNA relative expression levels of Kelch-like-ECH-associated protein 1a (Keap1a), myosin light chain kinase (MLCK) and p38 mitogen-activated protein kinase (p38 MAPK) in the intestine, indicating that the optimum PL could improve fish intestinal physical barrier. Finally, based on the PWG, C3 content in the DI, ACP activity in the DI, intestinal PC content and intestinal ASA activity, the optimal dietary PL levels for juvenile grass carp (9.34-87.50 g) were estimated to be 3.46%, 3.79%, 3.93%, 3.72%, and 4.12%, respectively.

Effects of dietary chlorogenic acid on growth performance, antioxidant capacity of white shrimp Litopenaeus vannamei under normal condition and combined stress of low-salinity and nitrite

An eight-week feeding trial followed by an acute combined stress test of low-salinity and nitrite were performed to evaluate effects of chlorogenic acid (CGA) on growth performance and antioxidant capacity of white shrimp Litopenaeus vannamei. Shrimp were randomly allocated in 12 tanks (30 shrimp per tank) and triplicate tanks were fed with a control diet or diets containing different levels of CGA (100, 200 and 400 mg kg(-1) feed) as treatment groups. Growth performance including weight gain (WG), biomass gain (BG), feed conversion ratio (FCR), and feed intake were determined after feeding for 56 days. Antioxidant capacity were evaluated by determining the activity of total antioxidant status (TAS), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) as well as the gene expression of GSH-Px and CAT in the hepatopancreas of shrimp at the end of feeding trial and again at the end of the combined stress test. The results indicated that supplemention of CGA had no significant effects on the growth performance and the activities of TAS, SOD, GSH-Px and CAT in hepatopancreas of shrimp cultured under normal conditions for 56 days. However, compared with the control group, CGA (200, 400 mg kg(-1) feed) significantly improved the resistance of L. vannamei against the combined stress of low-salinity and nitrite, as indicated by the significant (P < 0.05) higher survival, higher activities of TAS, GSH-Px and CAT, as well as higher transcript levels of GPx and CAT gene in shrimp treated with CGA in the combined tress test. Our findings suggested that CGA possessed dual-modulatory effects on antioxidant capacity of L. vannamei and could be a potential feed additive that can enhance shrimp resistance against environmental stresses. The recommended application dosage is 200 mg kg(-1) and further studies are needed to clarify the action model of CGA efficiency.

Ultrastructure of the anterior intestinal epithelia of the orange-spotted grouper Epinephelus coioides larvae under different feeding regimes

Enterocytes of the anterior to midsection of the intestine in grouper Epinephelus coioides larvae were compared among different treatments: unfed to the point-of-no-return (PNR), fed natural food only, and co-fed natural food and artificial diet. On day 3, the nutritional condition of unfed grouper larvae regressed with its reduced enterocyte heights which were further degraded on day 4, the PNR, when all the enterocytes were in advanced stages of apoptosis. The apoptosis appeared to be internally directed via the mitochondria. Among day 3 fed larvae, enterocyte heights of those fed artificial diet did not differ from those fed natural food only. Dietary phospholipid deficiency was indicated in larvae co-fed artificial diet on day 3 with an unusually large chylomicron opening into the inter-enterocyte space, and on days 6 and 33 by intestinal steatosis. On day 19, scant to absent lipid droplets in enterocytes of larvae disclosed heightened nutritional requirement preparatory to metamorphosis. As observed in unfed day 3 and premetamorphic day 19 E. coioides, larvae undergoing critical periods and starvation during development employ apoptosis to dispose of degenerated enterocytes that are phagocytosed by adjacent healthy enterocytes without causing inflammatory distress. Upon metamorphosis, grouper larval gut develops better immunity fitness with eosinophilic granule cells observed in the intestinal epithelia of day 33 larvae. Future studies on grouper larval nutrition may consider the appropriate dietary phospholipid levels and larval competence to biosynthesize highly unsaturated fatty acid from linoleic acid vis-à-vis the use of plant ingredients in artificial diet formulations. In vivo challenge tests may validate appropriate dietary nutrient supplementation and lead to better feed formulation, matching the varying energetic demands and digestive capacities of developing E. coioides larvae.

Morphological development of larval cobia Rachycentron canadum and the influence of dietary taurine supplementation

The morphological development of larval cobia Rachycentron canadum from 3 days post hatch (dph) until weaning (27 dph) was examined using S.E.M. Two groups of fish were studied: a control group (CF), reared under standard feeding protocol, and a group in which prey items were enriched with supplemental taurine (4 g l(-1) day(-1) ; TF). TF fish grew faster (P < 0·001), attained greater size (mean ±s.e. 55·1 ± 1·5 v. 33·9 ± 1·0 mm total length) and had better survival (mean ±s.e. 29·3 ± 0·4 v. 7·1 ± 1·2 %) than CF fish. Canonical variance analysis confirmed findings with respect to differences in growth between the treatment groups with separation being explained by two cranial measurements. S.E.M. revealed that 3 dph larvae of R. canadum (in both groups) possess preopercular spines, superficial neuromasts on the head and body, taste buds in the mouth, an olfactory epithelium which takes the form of simple concave depressions, and primordial gill arches. Gill filaments start to form as early as 6 dph and lamellae buds are visible at 8 dph in both groups. In CF fish, the cephalic lateral line system continues its development at 12-14 dph with invagination of both supra- and infraorbital canals. At the same time, a thorn-like or acanthoid crest forms above the eye. At 14 dph, invaginations of the mandibular and preopercular canals are visible and around 22 dph enclosure of all cranial canals nears completion. In CF larvae, however, completely enclosed cranial canals were not observed within the course of the trial, i.e. 27 dph. In TF larvae, grooves of the cephalic lateral line system form 4 days earlier than observed in CF larvae of R. canadum (i.e. at 8 dph), with enclosure commencing at 16 dph, and completed by 27 dph. Along the flanks of 6 dph larvae of either treatment, four to five equally spaced neuromasts delineate the future position of the trunk lateral line. As myomeres are added to the growing larvae, new neuromasts appear such that at 16 dph a neuromast is associated with each myomere. By 27 dph, the trunk lateral line starts to invaginate in CF larvae, while it initiates closure in TF larvae. These findings elucidate important features of the larval development of R. canadum and show that dietary taurine supplementation benefits larval development, growth and survival in this species. Moreover, they suggest a conditional requirement for taurine in larval R. canadum.