Pacific White Shrimp Litopenaeus Vannamei Research Articles

Effect of recombinant crustacean hyperglycemic hormones rCHH‐B1 and rCHH‐B2 on lipid metabolism in the Pacific white shrimp Litopenaeus vannamei

The crustacean hyperglycemic hormones (CHH) are pleiotropic neuropeptides controlling diverse processes in the life cycle of crustaceans. In the Pacific white shrimp Litopenaeus vannamei, CHH-B1 and CHH-B2 are generated by alternative splicing of the same gene, and the recombinant versions of these peptides have shown differential effects on glucose metabolism and osmoregulation in this species. In this work, we explored the role of both recombinant variants, expressed in yeast Pichia pastoris, on lipid metabolism. The results showed that rCHH-B1 and rCHH-B2 injections into eyestalk-ablated shrimp significantly increased the phospholipid and triglyceride levels in haemolymph and restored free fatty acid levels, suggesting that these CHH variants mobilize lipid reserves in shrimp. The effects on lipids were concomitant to its hyperglycemic activity, suggesting that both variants, in addition to their hyperglycemic activity, have hyperlipidemic functions.

Toxic effect of chronic nitrite exposure on growth and health in Pacific white shrimp Litopenaeus vannamei

Juveniles of the Pacific white shrimp Litopenaeus vannamei were exposed to 0 (control), 2, 6.67, and 20 mg L−1 nitrite-N for 30 days, and the growth, immunity, and gut microbiota were evaluated. The weight gain of shrimp exposed to 20 mg L−1 nitrite-N was significantly lower than that in the control. Antioxidant capacity, measured as superoxide dismutase and glutathione peroxidase activities, catalase expression, and malondialdehyde content, was not affected by chronic nitrite-N exposure. The expressions of immune related genes (IMD and Toll) in shrimp exposed to 20 mg L−1 nitrite-N were significantly higher than that in shrimp exposed to 2 mg L−1 nitrite-N, but no differences were found with the control. Regardless of nitrite-N exposure concentrations, Bacteroidetes, Proteobacteria, and Actinobacteria were the dominant phyla in the gut of L. vannamei. With the increase of nitrite-N concentration, the diversity of gut microbiota increased in L. vannamei. The relative abundance of opportunistic pathogens, such as Pseudoalteromonadaceae and Vibrionaceae, increased in shrimp exposed to 20 mg L−1 nitrite-N. The relative abundance of denitrifying bacteria increased in shrimp exposed to 2 mg L−1 nitrite-N, but decreased in those exposed to 6.67 or 20 mg L−1 nitrite-N relative to those in the control. The predicted microbial-mediated functions showed that pathways for digestive function and metabolic capacity were significantly inhibited. All findings in this study indicate that L.vannamei can deal with the stress caused by nitrite-N within levels lower than 6.67 mg L−1, but chronic exposure to a high concentration (> 6.67 mg L−1) would reduce shrimp growth and alter its immune system by destroying gut microbiota homeostasis.

The effect of feed supplement on growth, survival rate and immunity response of Pacific white shrimp Litopenaeus vannamei

An efforts to improve growth, survival and immunity response are still main issues in shrimp farming. The purpose of this study was to determine the effect of dietary supplements on the growth, survival and immunity response in order to increase phenotypic performance of Litopenaeus vannamei. The experiments were done by supplemented feed using i.e.,(A) Synthetic nucleotides (0.03 % of feed), (B) whole cell of Saccharomyces cerevisiae (100 mL/kg feed) and (C) Control (without feed supplement) and fed to the shrimp, Litopenaeus vannamei. The supplements were mixed in feed formulated and coated with chitosan, while the control without feed supplement. The shrimp larvae were reared in 5 m3 tanks with two replications The result showed that survival rate of shrimp that reared with supplemented synthetic nucleotide was 69,29% and with whole cell was 75,45% and control was 67,61%. Total haemocyte of shrimp before challenge test ranged from 287.2 to 465.7 x 104 cells/mL , but after challenge test with WSSV, have shown different number of cell densities where in the treatments of synthetic nucleotide was 303.63 x104cell/mL, whereas in whole cell and control were 265 x 104 cell / mL and 254,25 x 104 cell / mL respectively. Immunity response of L. vannamei shrimp expressed from ProPO was significantly different between supplemented feed compared to control after challenged with WSSV, TSV and IMNV.

Effect of pacific white shrimp (Litopenaeus vannamei) protein hydrolysates (SPH) and (−)-epigallocatechin gallate (EGCG) on sourdough and bread quality

The effects of (−)-epigallocatechin gallate (EGCG) and shrimp protein hydrolysates (SPH) (100–1000 mg/kg) alone or in mixtures on sourdough and bread quality were investigated. Both EGCG and SPH at 1000 mg/kg had the greatest effect on Lactobacillus plantarum PTCC (1896) and Saccharomyces cerevisiae PTCC (5052) growth in vitro. The combined treatment (50% EGCG + 50% SPH) led to the highest growth of L. plantarum (12.2 Log cfu/mL) and S. cerevisiae (8.66 Log cfu/mL). This combination at 3000 mg/kg significantly increased total titratable acidity (TTA) of sourdough after 20 h of fermentation at 30 °C compared with control. The combined treatment increased the specific volume and TTA of bread whereas it decreased hardness, cohesiveness, and chewiness of bread compared to the control. Compared to the control, 50% EGCG +50% SPH also resulted in a lower retrogradation enthalpy and staling, and gave a desirable sensory characteristic to the bread. It also increased the shelf-life of the bread by 2 days at room temperature compared with the control. Thus, 50% EGCG +50% SPH might be suggested for improving dough fermentation and bread quality.

The Polymorphism of LvMMD2 and Its Association with Growth Traits in Litopenaeus vannamei.

The Pacific white shrimp Litopenaeus vannamei is one of the major economic aquaculture species. The growth trait is considered as the most important trait in L. vannamei aquaculture. Identification of the genetic components underlying growth-related traits in L. vannamei could be useful for the selective breeding of growth trait. Our previous work identified several growth-related SNPs by genome-wide association study (GWAS). Based on the assembled genome, we identified a new candidate gene (LvMMD2) beside the associated marker. This gene encodes the progestin and AdipoQ receptor 10 (PAQR10) protein. We further investigate the polymorphisms of LvMMD2 and their association with body weight of L. vannamei. By resequencing the coding region of LvMMD2, a total of 8 SNPs were identified, including 6 synonymous mutations and 2 nonsynonymous mutations. Association analyses based on a population of 322 individuals revealed that several SNPs located in the coding region of LvMMD2 were significantly associated with the body weight, especially the nonsynonymous mutation named as MMD_5 contributed the most association to the trait and it could explain 10.5% of phenotypic variance. In addition, several genes involved in growth and development havebeen identified as LvMMD2-interacting genes. These findings strongly suggested that LvMMD2 might be an important gene regulating the shrimp growth. More importantly, the MMD_5 could be a promising candidate locus for marker-assisted selection (MAS) of the body weight in L. vannamei.

Gut bacterial community profile in Pacific white shrimp Litopenaeus vannamei following 5‐aminolevulinic acid supplementation

Changes in the diet have been previously reported to alter the gut bacterial profile in several organisms, including shrimp. These shifts in microbial structure either promote beneficial effects to the host or cause diseases. Supplementation of 5-aminolevulinic acid (5-ALA), the precursor of tetrapyrroles, has been previously reported to enhance shrimp's immune response. To know whether 5-ALA has effects on the gut bacterial structure in Pacific white shrimp (Litopenaeus vannamei), we investigated the bacterial communities in the intestine and stomach of L. vannamei using high-throughput Illumina sequencing of 16S rRNA gene libraries. One week of 5-ALA supplementation altered the bacterial community structure (beta diversity) in both tissues, as shown by the results of multi-dimensional scaling (MDS) plots and analysis of similarities (ANOSIM). DESeq2 analysis revealed enrichment of differentially abundant taxa in the 5-ALA group (e.g. Enhydrobacter and Oceaniovalibus) and control group (e.g. Tenacibaculum and Mycobacterium). Metagenomic predictions suggested that the control group had more KEGG pathways associated with ‘metabolism’ than the 5-ALA group. This study suggests that 5-ALA supplementation potentially promotes the formation of a beneficial bacterial community structure in shrimp. This is the first report on the effect of 5-ALA supplementation on the bacterial community profile in any organism.

Beneficial impacts on growth, intestinal health, immune responses and ammonia resistance of pacific white shrimp (Litopenaeus vannamei) fed dietary synbiotic (mannan oligosaccharide and Bacillus licheniformis)

The impacts of dietary mannan oligosaccharide (MOS) and Bacillus lincheniformis (B. lincheniformis) on growth performance, immune responses, intestinal health and ammonia resistance of Litopenaeus vannamei were explored. Four resultant diets (control diet (CON), 0.2 % MOS (MOS), 0.1 % B. lincheniformis (BL), 0.2 % MOS plus 0.1 % BL (SYN)) were produced to feed shrimps for 8 weeks. Results showed that significantly higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and protein productive value (PPV) were found in shrimp fed the SYN diet (P < 0.05). The villus number (VN) and villus height (VH) of shrimps fed the SYN diet were significantly higher than those of shrimps fed the CON diet (P < 0.05). Moreover, significantly thicker submucosa (SM) of shrimp fed the MOS diet than that of shrimps fed BL and CON diets were found (P < 0.05). Intestinal acetic acid content was significantly higher in shrimps fed supplemented diets (P < 0.05). Meanwhile, the propionic acid content in shrimps fed BL and SYN diets were significantly higher than those in shrimps fed the other diets (P < 0.05). The expression levels of catalase (CAT), glutothion peroxidase (GPX), superoxide dismutase (SOD), penaeidin -3a (Pen-3a) and heat shock protein (Hsp-70) were significantly upregulated by supplemented diets at some time points (P < 0.05). The survival rates of shrimps fed supplemented diets after ammonia challenge were significantly higher (P < 0.05). The expression levels of CAT, SOD, Pen-3a and Hsp-70 in shrimps fed supplemented diets were upregulated after ammonia challenge. In conclusion, dietary synbiotic could enhance growth performance, feed utilization and intestinal morphology, while dietary MOS and/or B. lincheniformis supplementation could positively influence the intestinal SCFAs content, increase immune responses and ammonia resistance of Litopenaeus vannamei.

Enhanced intestinal health, immune responses and ammonia resistance in Pacific white shrimp (Litopenaeus vannamei) fed dietary hydrolyzed yeast (Rhodotorula mucilaginosa) and Bacillus licheniformis

To explore the impacts of dietary hydrolyzed yeast (Rhodotorula mucilaginosa) and Bacillus licheniformis (B. licheniformis) on the growth, intestinal histology, innate immune response and ammonia resistance of Litopenaeus vannamei, four experimental diets (basal diet (Control); 0.5 % hydrolyzed yeast (HY); 0.1 % B. lincheniformis (BL) and 0.5 % hydrolyzed yeast + 0.1 % B. licheniformis (SYN)) were fed shrimps for 8 weeks. Results showed no significant differences on growth and body composition among all treatments, while a significantly higher feed efficiency (FE) in shrimp fed BL diet and a significantly higher protein efficiency ratio (PER) in shrimp fed BL and SYN diets were found compared to those in shrimp fed the Control diet (P < 0.05). At week 4, significantly higher intestinal villus height in shrimp fed supplemented diets were observed (P < 0.05). At week 8, significantly higher villus number in shrimp fed BL and SYN diets, and significantly higher villus height in shrimp fed supplemented diets were observed compared to those in shrimp fed the Control diet (P < 0.05). Compared to Control diet, the GPX, SOD and ACP activities were significantly increased, and the MDA content was decreased in hepatopancreas of shrimp fed supplemented diets (P < 0.05). The expression levels of CAT, GPX, SOD, Pen-3a and PPO were upregulated by supplemented diets at week 1, 2, 4 and 8. In addition, the expression levels of these genes, especially Pen-3a and SOD, were appeared in a trend of first increased and then decreased during the feeding. After ammonia challenge at week 8, shrimps fed HY and SYN diets showed significantly higher survival rate than that in shrimp with the Control diet (P < 0.05). Furthermore, the expression of Pen-3a, PPO and SOD in supplemented treatments were significantly upregulated after ammonia challenge. Results demonstrated that either dietary hydrolyzed yeast, B. licheniformis or their combination showed no significant effects on growth performance and body composition, but affected intestinal health, immune responses and ammonia resistance of Litopenaeus vannamei.

A MicroRNA-1-Mediated Inhibition of the NF-κB Pathway by the JAK-STAT Pathway in the Invertebrate Litopenaeus vannamei.

The JAK-STAT and NF-κB pathways are conserved cellular signaling cascades orchestrating a variety of biological processes. The regulatory interactions between these two pathways have been well studied in vertebrates but less concerned in invertebrates, hindering further understanding of immune signaling evolution. The Pacific white shrimp Litopenaeus vannamei is now an important model for studying invertebrate immunity and cellular signaling mechanisms. In this study, the microRNA-1 (miR-1) molecule from L. vannamei was identified, and its mature and precursor sequences were analyzed. The miR-1 promoter contained a STAT binding site and its transcriptional activity could be regulated by the JAK-STAT pathway. The target gene of miR-1 was identified as MyD88, the upstream component of the Dorsal (the NF-κB homolog) pathway. By suppressing the expression of MyD88, miR-1 attenuated activation of the Dorsal pathway. With miR-1 as the mediator, STAT also exerted a negative regulatory effect on the Dorsal pathway. Moreover, miR-1 was involved in regulation of the expression of a set of immune effector genes and the phagocytic activity of hemocytes and had an inhibitory or excitatory effect on antibacterial or antiviral responses, respectively. Taken together, the current study revealed a microRNA-mediated inhibition of the NF-κB pathway by the JAK-STAT pathway in an invertebrate, which could contribute to immune homeostasis and shaping immune responses.

The performance of juvenile Litopenaeus vannamei fed commercial diets of differing protein content, in a super-intensive biofloc-dominated system

ABSTRACT The effect of two commercial feeds of differing protein content, 35% or 40% (HI-35 and EXP), on Pacific White Shrimp Litopenaeus vannamei, performance, and system water quality were investigated. Juvenile shrimp were reared in six 40 m3 indoor raceways containing biofloc-dominated water for 77 days. Performance of EXP-fed shrimp was superior for much of the trial. However, a Vibrio outbreak constrained final production. Final survival was significantly higher (P < .05) with HI-35 (93.1 ± 1.8%) than EXP (83.4 ± 1.6%). No problematic heavy metal accumulation was observed in culture water or shrimp tissue. Higher feed protein content increased nitrite and nitrate concentrations (maximum of 3.6 mg L−1 NO2-N and 401 mg L−1 NO3-N in EXP), and alkalinity consumption. Both feeds supported high growth rates (>2 g week−1) and yields (7.79–8.21 kg m−3), demonstrating their suitability for shrimp culture in super-intensive, biofloc-dominated no exchange systems.

Identification and characterization of p38MAPK in response to acute cold stress in the gill of Pacific white shrimp (Litopenaeus vannamei)

Acute cold snaps induce a sudden reduction in water temperature and lead to high mortality of cultured Pacific white shrimp (Litopenaeus vannamei); however, little is known about the regulatory mechanisms in this shrimp species when adapting to acute cold stress. Mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved and well known for their important roles in transducing environmental stress signals into the cell nucleus. In this study, the potential roles of p38MAPK in the response to acute cold stress in L. vannamei were identified. The transcript levels of p38MAPK in the gills were found to be significantly upregulated after challenge with acute cold stress for the first 12 h, while no distinctly differential expression was detected in the other two types of MAPKs (JNK and ERK). The phosphorylation levels of p38MAPK under acute cold stress continued to increase and reached a peak 1 h after cold exposure. The phosphorylation signaling of p38MAPK in re-chilled shrimp (5 min) appeared more quickly than that in primary shrimp (15 min). The results suggest that p38MAPK might play an essential role in transducing acute cold stress signals from the environment to the cell nucleus in L. vannamei. Our study is the first to characterize p38MAPK during acute cold stress adaptation, and the results will contribute to further research.

The effects of artificial substrate and stocking density on Pacific white shrimp (Litopenaeus vannamei) performance and water quality dynamics in high tunnel-based biofloc systems

The use of artificial substrates in shrimp aquaculture may allow for production of shrimp at increased densities while providing a growth medium for microbes that assist with water quality processes and provide supplemental nutrition for shrimp. Greenhouse-based shrimp production systems can extend the shrimp production season in temperate climates while conserving water and energy. For this study, we evaluated the effects of providing extra substrate and shrimp density on water quality and shrimp production in greenhouse-based biofloc systems. Four 11-m3, wood framed, and rubber-lined tanks were constructed in each of four high tunnel greenhouses (for a total of 16 tanks). Four treatments were evaluated: high-density stocking with substrate (HDS), high-density stocking with no substrate (HDNS), low-density stocking with substrate (LDS), and low-density stocking with no substrate (LDNS). Each treatment was randomly assigned to one tank in each tunnel to block for location. No artificial heat was used, and shrimp were grown for 120 days. High-density systems were stocked at 200 shrimp/m³ while low-density tanks had 100 shrimp/m³. Adding substrate increased total in-tank surface area by 13.4%. The addition of substrate had no significant effect on any shrimp production or standard water quality parameters. Shrimp had significantly greater final weight, faster growth rate, and lower feed conversion rate in low-density treatments (P ≤ 0.02 for all). Total shrimp biomass production was significantly higher in high-density treatments (HD: 4.0 kg/m3; LD: 2.3 kg/m3; P < 0.05). There were no significant differences in survival between densities (HD: 91.3%; LD: 94.5%; P = 0.43). Peak and overall mean nitrite levels were significantly higher in high-density treatments compared to low-density treatments. Dissolved oxygen levels and pH over the course of the study were significantly lower in high-density treatments, likely due to increased respiration rates in the water column. This project shows the feasibility of shrimp production in temperate climates with no artificial heat using high tunnel greenhouses, few impacts of added substrate on shrimp production, and increased shrimp density can result in much larger harvests with few negative impacts on production metrics.

Improvement of growth, intestinal short-chain fatty acids, non-specific immunity and ammonia resistance in Pacific white shrimp (Litopenaeus vannamei) fed dietary water-soluble chitosan and mixed probiotics

This study was to explore the impacts of water-soluble chitosan and mixed probiotics on growth performance, intestinal short-chain fatty acids (SCFAs) and immunity and ammonia resistance in Litopenaeus vannamei. Shrimp were fed one of four experimental diets including basal diet (CON), 0.10% water-soluble chitosan diet (WSC), 0.30% mixed probiotics (MP) and 0.10% water-soluble chitosan +0.30% mixed probiotics (SYN) for 8 weeks. Results showed shrimp fed with dietary MP and SYN diets could significantly improve growth performance and feed utilization in comparison with those of shrimp fed with CON diet (P < 0.05). Acetic acid content was significantly higher in shrimp fed with all supplemented diets compared to that in shrimp fed with CON diet (P < 0.05). Compared to shrimp fed with CON diet, dietary WSC and MP significantly influenced the contents and/or activities of aspartate aminotransferase (AST), total protein (TP), superoxide dismutase (SOD), lysozyme (LZM) in serum, SOD, malondialdehyde (MDA), acid phosphatase (ACP) in hepatopancreas and SOD and MDA in intestine. In addition, the gene expression levels of prophenoloxidase (proPO), penaiedin 3a (Pen-3a), crustin (Crustin), serine proteinase (SP), GPX and SOD in hepatopancreas, were significantly upregulated compared to those in CON diet at some time points (P < 0.05). Significantly higher survival rate in all supplemented diets were observed after ammonia challenge (P < 0.05). Therefore, the above results indicated dietary WSC and MP or SYN could enhance intestinal SCFAs content, stimulated antioxidant capacity and immune response, and increase the ammonia resistance of Litopenaeus vannamei. Besides, the growth performance was also improved by dietary MP and SYN.

Evaluation of the utility of genomic information to improve genetic evaluation of feed efficiency traits of the Pacific white shrimp Litopenaeus vannamei

This study evaluated the utility of genomic information to improve genetic evaluation of feed efficiency traits of the Pacific white shrimp Litopenaeus vannamei. Three methods including the pedigree-based best linear unbiased prediction (BLUP), genomic best linear unbiased prediction (GBLUP) and single-step GBLUP (ssGBLUP) were compared for the prediction accuracy of feed efficiency ratio (FER) and residual feed intake (RFI), as well as a growth trait, average daily weight gain (ADG). The dataset used for analysis consisted of 474 offspring from 34 full-sib families, with a pedigree of three generations, and all the offspring were genotyped on 35,869 SNPs. Two univariate animal models were used, one with the common environmental effect (Model 1) and one without (Model 2). The genomic and pedigree-genomic relationship matrices based heritability estimates of RFI, FER and ADG by Model 1 ranged from 0.187 ± 0.156 to 0.388 ± 0.167, with the common environmental effect in the range of 0.057 ± 0.080 to 0.283 ± 0.108, but it was unable to estimate both additive genetic and common environmental effects simultaneously using the pedigree-based relationship matrix. Across the three matrices, heritability estimates of RFI, FER and ADG by Model 2 ranged from 0.476 ± 0.101 to 0.796 ± 0.146, higher than the corresponding ones using Model 1. Cross-validation was used to evaluate the prediction accuracy of breeding values. For GBLUP and ssGBLUP, genomic prediction accuracy using Model 1 was significantly increased by 28.6–29.0% for RFI, 11.6–12.5% for FER and 62.2–69.4% for ADG, compared with using Model 2, indicative of the advantage of Model 1 over Model 2. When using Model 2, genomic predictions were more accurate than the pedigree-based predictions, with an increase of accuracy ranging from 8.9% to 13.3% across the three traits. Furthermore, accuracy of GBLUP was slightly higher than that of ssGBLUP. The results indicate that the genomic-based methods, especially GBLUP, combined with an animal model containing the common environmental effect, have obvious advantage in estimating variance components and predicting breeding values for feed efficiency traits as well as growth of L.vannamei compared with traditional BLUP.

Evaluation of Stocking Density and Dietary Fish Meal Inclusion for Intensive Tank Production of Pacific White Shrimp Litopenaeus vannamei Cultured in Low‐Salinity Waters of Western Alabama

AbstractShrimp farmers in Alabama are seeking to increase efficiency and intensify production. Semi‐intensive earthen ponds are the traditional production system used by Alabama shrimp farmers; however, there is interest in evaluating intensive pond‐based production systems, such as split ponds. These alternative systems are more intensive and require higher stocking densities to offset capital investment costs required for initial construction and maintenance. Two trials were carried out with Pacific white shrimp Litopenaeus vannamei using on‐levee flow‐through systems (twelve 800‐L tanks per system) at an Alabama shrimp farm to evaluate stocking densities of 29, 88, 176, and 264 shrimp/m2 (trial 1) and higher levels of fish meal (5, 10, and 20%) at a high density of 264 shrimp/m2 (trial 2). Results from trial 1 revealed that as stocking density was increased Pacific white shrimp final weight decreased, while shrimp biomass and feed conversion ratio increased. Survival of Pacific white shrimp at the two highest densities (176 and 264 shrimp/m2) was lower than at the two lowest densities (29 and 88 shrimp/m2). There were no significant differences in performance for Pacific white shrimp offered diets with varying levels of fish meal in trial 2; however, overall survival in trial 2, which was carried out at a high density (264 shrimp/m2), ranged between 47.9% and 65.5%.

Development of electronic nose (Shrimp-Nose) for the determination of perishable quality and shelf-life of cultured Pacific white shrimp (Litopenaeus Vannamei)

Production and consumption of Pacific white shrimp (Litopenaeus vannamei) have drastically increased over the years, owing to its taste and high nutritional value. At the same time, monitoring its perishable quality and shelf-life to meet export standards is proving to be a major concern. In this context, Shrimp-Nose has been designed and developed using six partially selective metal oxide-based gas sensors (TGS 880, 823, 826, 2600, 2602, and 822 (Figaro, Japan)) for the rapid freshness assessment. To extensively investigate the quality changes in both the perishable and iced storage conditions, Shrimp-Nose measurements were observed at different time intervals (in terms of hours (h) for un-iced conditions and days for 2 °C refrigerated storage conditions). Pattern recognition algorithms based on multivariate analyses such as Principal Component Analysis (PCA), Decision Tree, Random Forest, K-Nearest Neighbour (KNN) and Soft-max Regression were implemented in which Soft-max Regression algorithm showed the decision accuracies of 96.29% and 95.73% towards un-iced and iced samples respectively. Supporting experiments such as pH, Total Volatile Base Nitrogen (TVBN), Fourier Transform Infrared (FTIR) spectra, texture, microbial, and sensory analysis were investigated at different time intervals to monitor the quality changes. Also, melanosis was investigated at different time intervals to estimate the shelf-life of shrimp samples. Shrimp-Nose measurements are found to be in good agreement with the results observed using supporting experiments.

Regulation of growth, fatty acid profiles, hematological characteristics and hepatopancreatic histology by different dietary n-3 highly unsaturated fatty acids levels in the first stages of juvenile Pacific white shrimp (Litopenaeus vannamei)

An 8-week feeding experiment was conducted to investigate the effects of dietary n-3 highly unsaturated fatty acids (n-3 HUFAs) on growth performance, fatty acid profiles, hematological characteristics and hepatopancreatic histology in juvenile Pacific white shrimp (Litopenaeus vannamei) (initial average weight, 0.14 ± 0.01 g). Six isoproteic and isolipidic diets were formulated with graded levels of n-3 HUFA (0.24, 0.53, 0.86, 1.25, 1.58 and 1.97 % of dry matter), and the 0.24 % group was used as control group. The results revealed that shrimp fed the diet containing 0.86 % n-3 HUFA had highest weight gain (WG) and specific growth rate (SGR), and the feed conversion ratio (FCR) showed the minimum at the same level. Shrimp muscle fatty acid profiles reflected that of diet. The contents of triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) in serum decreased along with n-3 HUFA levels increasing. The activity of superoxide dismutase (SOD) in hepatopancreas was highest significantly at the level of 0.86 % n-3 HUFA group than that in other groups. The content of malondialdehyde (MDA) in hepatopancreas increased with the increasing of n-3 HUFA levels, which reached the maximum value in 1.97 % group and was significantly higher than that in control group. The levels of n-3 HUFA could obviously affect on the cell morphology and lipid deposition in hepatopancreas of L. vannamei. Results of this study suggested that shrimp fed moderate dietary n-3 HUFA could enhance growth, feed utilization, antioxidant capacity and reduces excess lipid deposition.

The immune defense response of Pacific white shrimp (Litopenaeus vannamei) to temperature fluctuation

Temperature is a significant environmental factor contributing to the success of aquaculture. To investigate the immune defense response during temperature fluctuation, Litopenaeus vannamei (L. vannamei) was treated under conditions of gradual cooling from an acclimation temperature of 28 °C (C group) to 13 °C (T group) in 2 days with a cooling rate of 7.5 °C/d and then rewarmed to 28 °C (R group) using the same rate. Relative expression of immune defense system-related genes and intestinal microbial composition in L. vannamei were investigated. The results showed that with a decrease in temperature, the expression of TLR, IMD, proPO and Casp3 in intestine was significantly decreased, while the expression of Muc-3A, Muc-5AC, Muc-17, IAP, p53, HSP70, MT and Fer was significantly increased after cooling. After temperature recovery, gene expression generally showed a trend of recovering to the normal level (C). Intestinal microbial analysis showed that, compared with the C group, the Chao and Ace indexes, the relative abundance of microflora from the Phylum Bacteroidetes, Class Alphaproteobacteria, and Class Bacteroidia, significantly decreased in the R group. The results revealed that cold-stress may decrease microbial community richness, alter the bacterial community in general and reduce shrimp immunity to pathogens and antibacterial activity. As a result, during temperature fluctuation shrimp may mobilize the immune defense system through upregulating the expression of Muc genes, anti-apoptosis related genes, and antioxidant related genes in order to maintain organism homeostasis as well as to repair damaged intestinal tissue.

Cholesterol requirement and phytosterols efficiency in semi‐purified diets of juvenile Pacific white shrimp Litopenaeus vannamei

Studies pertaining to cholesterol requirement are limited based on the levels evaluated and statistical analysis. Two trials were conducted to refine cholesterol requirement in Pacific white shrimp Litopenaeus vannamei feeds. The basal diet was supplemented with graded levels of cholesterol (ranging from 0.48 to 1.85 g/kg) in trial 1. Since the shrimp (initial weight: 0.24 g) growth response was very linear without reaching a plateau, it was not clear whether the requirement was met. Hence, a second trial was designed using eight diets designed with an increased range of cholesterol levels from 0.45 to 4.57 g/kg of diets. The shrimp (0.38 g initial weight) reached a final weight of (4.31–7.43 g) or per cent weight gain from 1,014%–1,874% (n = 4) after 6 weeks. Saturation kinetic model and broken‐line models with linear or quadratic ascending portions were used to evaluate dose–response relationships of feed efficiency (FE), thermal‐unit growth coefficient (TGC), whole‐body cholesterol (CHOL) and cholesterol deposition (CHOLD) against dietary cholesterol. The cholesterol requirement of shrimp was estimated at 1.9 (1.1–4.3) g/kg, 1.7 (1.1–3.4) g/kg, 2.5 (2.3–2.9) g/kg and 2.7 (2.4–3.1) g/kg of shrimp diet for FE, TGC, CHOL and CHOLD, respectively. Additionally, based on improved growth, the inclusion of phytosterol can serve as a partial replacement for cholesterol.

Astaxanthin Attenuates Fish Oil-Related Hepatotoxicity and Oxidative Insult in Juvenile Pacific White Shrimp (Litopenaeus vannamei).

The present study investigated the effect of dietary astaxanthin (AX) on the growth performance, antioxidant parameters, and repair of hepatopancreas damage in Pacific white shrimp (Litopenaeus vannamei). To evaluate the hepatopancreas protective function of AX in shrimps, we compared the effect of five isonitrogenous and isoenergetic diets under oxidized fish oil conditions with varying AX levels during the 50-day experimental period. The formulated diets were as follows: (i) OFO (oxidized fish oil); (ii) OFO/AX150 (oxidized fish oil + AX150 mg/kg); (iii) OFO/AX250 (oxidized fish oil + AX250 mg/kg); (iv) OFO/AX450 (oxidized fish oil + AX450 mg/kg); and, (v) control group (fresh fish oil). Results showed that the oxidized fish oil with 275.2 meq/kg peroxide value (POV) resulted in a substantial decrease in the final body weight of L. vannamei (P > 0.05) and induced some visible histopathological alterations in the hepatopancreas. Growth performance was significantly higher in shrimps fed with the OFO/AX450 diet than those fed with the OFO diet (p < 0.05). However, no significant difference was observed when the OFO/AX450 diet was compared to the control diet containing fresh fish oil (p > 0.05). Moreover, shrimps under the OFO/AX450 diet displayed a significant improvement in hepatopancreatic health and showed a reduction of malondialdehyde (MDA) compared to those under the OFO diet (p < 0.05). Dietary AX improved the antioxidant capacity of L. vannamei by increasing the catalase (CAT) activity in the hemolymph. Acute salinity change test showed a higher shrimp survival rate under OFO/AX450 diet than the OFO diet (p < 0.05), suggesting that AX can contribute to enhanced stress tolerance. In conclusion, our data suggest that AX confers dose-dependent protection against OFO-induced oxidative insults and hepatopancreatic damage in shrimp.