Genetic variation of white spot syndrome virus (WSSV) in Pacific white shrimp Litopenaeus vannamei (Boone 1931) culture of Thailand

White spot syndrome virus (WSSV) is highly pathogenic to penaeid shrimp and has caused significant economic losses in the shrimp farming industry in Thailand. Genotyping analysis was done in 124 WSSV isolates from cultured Pacific white shrimp Litopenaeus vannamei. These samples were obtained during 2007–2014 from eight provinces in Thailand. We investigated five variable loci in the virus genome: deletions in two variable regions, VR14/15 and VR23/24, and three variable number tandem repeats (VNTR) located in open reading frame (ORF) 75, 125 and 94. WSSV genotype was characterized as (X_14/15, X_23/24) (N₇₅‐N₁₂₅‐N₉₄) where X is the number of base pair deletion in the variable region and N is the number of repeat units (RUs) in a specific ORF. The deletion pattern in VR14/15 and VR23/24 regions characterized three WSSV genotypes. The most prevalent genotype was (5950_14/15, 10971_23/24), and it was found in all studied areas. At least 33 genotypes of WSSV were analysed based on 3 VNTR loci, indicating that the VNTRs of WSSV genome are highly variable. From 124 WSSV samples, two samples presented the characteristic of all five variable loci similar to WSSV collected during 2010 in Saudi Arabia (5950_14/15, 10971_23/24) (3₇₅‐6₁₂₅‐7₉₄). Many different WSSV genotypes shown in this study as compared to previously reported genotypes in Thailand suggests current status of disease epidemiology, as well as probable movements of WSSV between countries.     

Proteome modifications of Pacific white shrimp (Litopenaeus vannamei) muscle under biofloc system

The objective of the study was to examine the effects of biofloc technology on the muscle proteome of Litopenaeus vannamei. Two biofloc treatments and one control were compared: biofloc‐based tanks under zero‐water exchange fed with 150 g/kg crude protein (BF15), or with 250 g/kg crude protein (BF25) diets, and clear water tanks with 50% of daily water exchange stocked with shrimp fed with similar amount of a 250 g/kg crude protein diet, referred to as control. The shrimp (5.28 ± 0.42 g) were divided into the 300‐L fibreglass tanks (water volume of 200 L) at a density of 35 shrimp per tank and were cultured for 35 days. The biofloc groups displayed better growth and survival compared to the control. The muscle tissue from the control and BF25 groups was subjected to proteomic analysis. Lactate dehydrogenase, enolase, arginine kinase, mitochondrial ATP synthase subunit alpha, mitochondrial ATPase inhibitor factor 1 precursor, serpin 3 and myeloid differentiation factor 88 had an increased abundance in the BF25 group, while myosin heavy chain type 1 and myosin heavy chain type 2 showed a decreased abundance. The results indicate that biofloc technology could alter the expression of proteins involved in structure, metabolism and immune status of cultured shrimp.     

Quantitative dietary leucine requirement of juvenile Pacific white shrimp,Litopenaeus vannamei (Boone) reared in low‐salinity water

The experiment was conducted to determine the leucine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low‐salinity water (0.50–1.20 g L^?1). Six diets were formulated to contain 410 g kg^?1 crude protein with fish meal, peanut meal and precoated crystalline amino acids with different concentration of l ‐leucine (16.72, 19.60, 22.06, 24.79, 27.28 and 30.16 g kg^?1 dry diet). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.38 ± 0.002 g), and the feed trial lasted for 8 weeks. The results indicated that the maximum weight gain was observed at 24.95 g kg^?1 dietary leucine group, whereas the diets containing higher leucine concentration conversely reduced the growth performance (P < 0.05). Moreover, the highest body protein content and body protein deposition and the lowest haemolymph AST and ALT activities were also found at 24.95 g kg^?1 dietary leucine group. With the increase in leucine in diets, a dose‐dependent increase was found in body lipid content and haemolymph urea concentration. The polynomial regression calculated using weight gain, feed efficiency and body protein deposition indicated that the optimal dietary leucine requirement for L. vannamei reared in low‐salinity water was 23.73 g kg^?1 leucine of dry diet, correspondingly 57.88 g kg^?1 of dietary protein.     

Nursery performance of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) cultivated in a biofloc system: the effect of adding different carbon sources

Effect of different carbon sources on nursery performance of Pacific white shrimp (Litopenaeus vannamei) cultivated in biofloc system was investigated. Shrimp postlarvae (98.47 ± 8.6 mg) were fed for 32 days in tanks with water volume of 130 L and density of 1 individual L^?1. One control treatment and four biofloc treatments (BFT1, BFT2, BFT3 and BFT4) with adding different carbon sources including molasses, starch, wheat flour and mixture of them, respectively, were considered at equal weight ratios. According to the results, salinity, dissolved oxygen and pH were not significantly different among the biofloc treatments (P > 0.05). Maximum pH (8.27) and maximum dissolved oxygen (6.35 mg L^?1) were recorded in the control. Maximum (0.43 mg L^?1) and minimum (0.09 mg L^?1) ammonia were recorded in the control and BFT2, respectively (P < 0.05). Using simple carbohydrates (molasses and starch) lowered the ammonia concentration significantly. The highest increase in body weight (1640.43 ± 231.28 mg), growth rate, specific growth rate (8.97 ± 0.42% per day) and biomass (190.29 ± 26.83 mg) were found in BFT1 and the highest survival (90 ± 0.77%) was found in BFT4. The highest feed conversion (1.52 ± 0.23) and the lowest feed efficiency (66.81 ± 7.95) were observed in the control (P < 0.05). The proximate composition analysis revealed an increase in lipid and ash in biofloc treatments. Results indicated that using biofloc technology with zero‐water exchange system and adding carbon sources could help to recycle waste and improve the water quality. Moreover, the type of carbonaceous organic matter as a substrate for heterotrophic bacteria would be effective in degradation and metabolization of ammonia and nitrite.     

White spot syndrome virus epizootic in cultured Pacific white shrimp Litopenaeus vannamei (Boone) in Taiwan

White spot syndrome virus (WSSV) has caused significant losses in shrimp farms worldwide. Between 2004 and 2006, Pacific white shrimp Litopenaeus vannamei (Boone) were collected from 220 farms in Taiwan to determine the prevalence and impact of WSSV infection on the shrimp farm industry. Polymerase chain reaction (PCR) analysis detected WSSV in shrimp from 26% of farms. Juvenile shrimp farms had the highest infection levels (38%; 19/50 farms) and brooder shrimp farms had the lowest (5%; one of 20 farms). The average extent of infection at each farm was as follows for WSSV‐positive farms: post‐larvae farms, 71%; juvenile farms, 61%; subadult farms, 62%; adult farms, 49%; and brooder farms, 40%. Characteristic white spots, hypertrophied nuclei and basophilic viral inclusion bodies were found in the epithelia of gills and tail fans, appendages, cephalothorax and hepatopancreas, and virions of WSSV were observed. Of shrimp that had WSSV lesions, 100% had lesions on the cephalothorax, 96% in gills and tail fans, 91% on appendages and 17% in the hepatopancreas. WSSV was also detected in copepoda and crustaceans from the shrimp farms. Sequence comparison using the pms146 gene fragment of WSSV showed that isolates from the farms had 99.7–100% nucleotide sequence identity with four strains in the GenBank database – China ( AF332093 ), Taiwan ( AF440570 and U50923 ) and Thailand ( AF369029 ). This is the first broad study of WSSV infection in L. vannamei in Taiwan.     

Use of microalgal‐enriched Diaphanosoma celebensis Stingelin, 1900 for rearing Litopenaeus vannamei (Boone, 1931) postlarvae

The present work investigates the effects of Chaetoceros calcitrans, Nannochloropsis oculata, Tetraselmis tetrahele and Isochrysis galbana diets on the lifespan, growth, neonate production and the nutritional profile of Diaphanosoma celebensis. In addition, the effects of enriched D. celebensis on the survival and growth of Litopenaeus vannamei postlarvae (PLs) was compared with Artemia. Results showed that significantly higher (P < 0.05) neonate production of D. celebensis was attained when fed with C. calcitrans compared to the other microalgae. In addition, D. celebensis fed on C. calcitrans had significantly higher levels (P < 0.05) of protein, lipid and carbohydrate compared to the other three microalgae. On the other hand, D. celebensis had a significantly (P < 0.05) longer lifespan when fed on N. oculata and T. tetrahele compared to those fed with C. calcitrans and I. galbana. Shrimp PLs fed D. celebensis enriched with C. calcitrans had higher survival and specific growth rate but it was not significantly different (P > 0.05) from PL fed only Artemia, indicating that D. celebensis has potential to be used as live feed for the hatchery rearing of L. vannamei PLs, in place of Artemia. This study illustrated that the quality of the D. celebensis production and proximate composition was highly correlated with the food type, and it can be used as a valuable live feed for shrimp larviculture.     

Dietary thiamin could improve growth performance,feed utilization and non‐specific immune response for juvenile Pacific white shrimp (Litopenaeus vannamei)

This study evaluated the effect of dietary thiamin on growth performance, feed utilization and non‐specific immune response for juvenile Pacific white shrimp, Litopenaeus vannamei. Six isonitrogenous and isolipidic practical diets were formulated with graded thiamin levels of 6.9, 32.7, 54.2, 78.1, 145.1 and 301.5 mg kg^?1 of dry diet, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile shrimp and provided four times each day to apparent satiation. Weight gain (WG) and specific growth rate (SGR) of the shrimp were significantly influenced by the dietary thiamin levels, the maximal WG and SGR occurred at 54.2 mg kg^?1 dietary thiamin level. However, with further increase in dietary thiamin level from 54.2 to 301.5 mg kg^?1, the WG and SGR significantly decreased. Shrimp fed the 54.2 mg kg^?1 thiamin diet exhibited higher feed efficiency, protein efficiency ratio and protein productive value than those fed the other diets. Dry matter and protein content in whole body were significantly affected by the dietary thiamin levels. Thiamin concentration in hepatopancreas significantly increased when the dietary thiamin level increased from 6.9 to 145.1 mg kg^?1. The total protein, glucose, triacylglycerol and cholesterol contents in hemolymph were not significantly affected by the dietary thiamin levels. Dietary thiamin had significantly influenced superoxide dismutase, catalase and lysozyme activities in hemolymph. Results of this study indicated that the optimal dietary thiamin requirements estimated using a two‐slope broken‐line model based on WG and thiamin concentration in hepatopancreas were 44.66 and 152.83 mg kg^?1, respectively.     

Effect of different biofloc system on water quality,biofloc composition and growth performance in Litopenaeus vannamei (Boone, 1931)

The experiment was conducted with three biofloc treatments and one control in triplicate in 500 L capacity indoor tanks. Biofloc tanks, filled with 350 L of water, were fed with sugarcane molasses (BFT_S), tapioca flour (BFT_T), wheat flour (BFT_W) and clean water as control without biofloc and allowed to stand for 30 days. The postlarvae of Litopenaeus vannamei (Boone, 1931) with an Average body weight of 0.15 ± 0.02 g were stocked at the rate of 130 PL m^?2 and cultured for a period of 60 days fed with pelleted feed at the rate of 1.5% of biomass. The total suspended solids (TSS) level was maintained at around 500 mg L^?1 in BFT tanks. The addition of carbohydrate significantly reduced the total ammonia‐N (TAN), nitrite‐N and nitrate‐N in water and it significantly increased the total heterotrophic bacteria (THB) population in the biofloc treatments. There was a significant difference in the final average body weight (8.49 ± 0.09 g) in the wheat flour treatment (BFT_W) than those treatment and control group of the shrimp. Survival of the shrimps was not affected by the treatments and ranged between 82.02% and 90.3%. The proximate and chemical composition of biofloc and proximate composition of the shrimp was significantly different between the biofloc treatments and control. Tintinids, ciliates, copepods, cyanobacteria and nematodes were identified in all the biofloc treatments, nematodes being the most dominant group of organisms in the biofloc. It could be concluded that the use of wheat flour (BFT_W) effectively enhanced the biofloc production and contributed towards better water quality which resulted in higher production of shrimp.     

Acute toxicity of nitrite on white shrimp Litopenaeus vannamei (Boone) juveniles in low‐salinity water

The nitrite toxicity was estimated in juveniles of L. vannamei. The 24, 48, 72 and 96 h LC₅₀ of nitrite‐N on juveniles were 8.1, 7.9, 6.8 and 5.7 mg L^?1 at 0.6 g L^?1; 14.4, 9.6 8.3 and 7.0 mg L^?1 at 1.0 g L^?1; 19.4, 15.4, 13.4 and 12.4 mg L^?1 at 2.0 g L^?1 of salinity respectively. The tolerance of juveniles to nitrite decreased at 96 h of exposure by 18.6% and 54.0%, when salinity declined from 1.0 to 0.6 g L^?1 and from 2.0 to 0.6 g L^?1 respectively. The safe concentrations at salinities of 0.6, 1.0 and 2.0 g L^?1 were 0.28, 0.35 and 0.62 mg L^?1 nitrite‐N respectively. The relationship between LC₅₀ (mg L^?1), salinity (S) (g L^?1) and exposure time (T) (h) was LC₅₀ = 8.4688 + 5.6764S – 0.0762T for salinities from 0.6 to 2.0 g L^?1 and for exposure times from 24 to 96 h; the relationship between survival (%) and nitrite‐N concentration (C) for salinity of 0.6–2.0 g L^?1, nitrite‐N concentrations of 0–40 mg L^?1 and exposure times from 0 to 96 h was as follows: survival (%) = 0.8442 + 0.1909S – 0.0038T – 0.0277C + 0.0008ST + 0.0001CT–0.0029SC, and the tentative equation for predicting the 96‐h LC₅₀ to salinities from 0.6 to 35 g L^?1 in L. vannamei juveniles (3.9–4.4 g) was 96‐h LC₅₀ = 0.2127 S² + 1.558S + 5.9868. For nitrite toxicity, it is shown that a small change in salinity of waters from 2.0 to 0.6 g L^?1 is more critical for L. vannamei than when wider differences in salinity occur in brackish and marine waters (15–35 g L^?1).     

Effects of Lactobacillus pentosus on the growth performance,digestive enzyme and disease resistance of white shrimp,Litopenaeus vannamei (Boone, 1931)

The objective of this study was to evaluate the probiotic properties of lactic acid bacteria (LAB) strains isolated from digestive tract of white shrimp Litopenaeus vannamei. Eighteen LAB colonies were isolated and one bacterium was found capable of producing three extracellular enzymes (protease, cellulose and lipase) simultaneously and exhibited antagonistic activity against shrimp pathogens (Vibrio vulnificus, V. rotiferianus and V. campbellii). The putative probiotic strain AS13 was identified as Lactobacillus pentosus based on 16S rRNA sequencing. The L. vannamei were fed diet containing 0 (control), 10⁶, 10⁷ and 10⁸ CFU g^?1 bacterial cells of AS13 for 28 days. The results showed that supplementation of L. pentosus significantly improved the growth performance and feed utilization in the treated groups over the control. Similarly, digestive enzyme activities were elevated in the intestines of treated groups. Moreover, feeding of supplemented diets containing AS13 significantly reduced the mortality rate caused by pathogenic Vibrio species (V. vulnificus, V. rotiferianus and V. campbellii). Our results indicated L. pentosus AS13 addition at 10⁷ CFU g^?1 can effectively enhance the growth performance, feed utilization, digestive enzymes and disease resistance of L. vannamei in the laboratory condition.     

Evaluation of Schizochytrium meal in microdiets of Pacific white shrimp (Litopenaeus vannamei) larvae

A feeding trial was conducted to assess the effects of dietary Schizochytrium meal supplementation on survival, growth performance, activities of digestive enzymes and fatty acid composition in Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Four isonitrogenous and isolipidic diets were formulated to contain graded levels of Schizochytrium meal: 0% (S0, the control diet), 2% (S2), 4% (S4) and 6% dry matter (S6). Results showed that there was no significant difference in survival of shrimps among dietary treatments (P > 0.05). Shrimps fed diets with 2% and 4% microalgae meal had significantly higher specific growth rate (SGR) than that of shrimps fed diets with 0% and 6% microalgae meal, and no significant differences were observed between shrimps fed diets with 2% and 4% microalgae meal (P > 0.05). Activity of trypsin in the pancreatic and intestinal segments, and activity of amylase in the pancreatic segments were not significantly affected by dietary microalgae meal levels (P > 0.05). Specific activities of both alkaline phosphatase and leucine‐aminopeptidase in intestine and purified brush border membrane of intestine were significantly higher in shrimps fed diet with 2% microalgae meal (P < 0.05). There were no significant differences in C18:2n‐6, n‐3 fatty acids, n‐6fatty acids, PUFA and n‐3/n‐6 in muscle samples among dietary treatments. C16:1n‐7, C18:1n‐9, MUFA, C18:3n‐3 and C20:5n‐3 decreased, however, C20:4n‐6 increased in the muscle as dietary microalgae meal level increased. In conclusion, 4% Schizochytrium meal in microdiets of shrimps can improve growth performance and may be a valuable additive in the microdiets of shrimps.     

Effects of a yeast‐based additive on growth and immune responses of white shrimp,Litopenaeus vannamei (Boone, 1931), and aquaculture environment

A 60 days feeding experiment was conducted to determine the effects of YK‐6 (a yeast culture feed supplement) on growth and immune responses of white shrimp, Litopenaeus vannamei and aquaculture environment in commercial scale farms composed of nine ponds. Three treatments (control, Diet 1 and Diet 2) were designed to contain YK‐6 levels of 0.0, 1.0 and 1.5 g kg^?1 respectively. At the end of the test, the mean production of Diet 1 (0.649 ± 0.030 kg m^?2) and Diet 2 (0.648 ± 0.033 kg m^?2) were significantly higher than that of the control by 29.5% and 29.3% respectively. The feed conversion ratio decreased significantly by 12.3% (Diet 1) and 8.5% (Diet 2) compared with the control group respectively. The environmental indices indicate that the quality of water and pond sediment was improved. The endotoxin concentrations, the number of Vibrios and heterotrophic bacteria in the shrimp intestine of the treatment groups were significantly lower than that of the control, particularly in the later stage of the farming period. The YK‐6 extended positive effects on growth, improved sediment quality, reduced endotoxin in shrimp intestine, and enhanced activities of lysozyme and phenoloxidase.     

Effect of different total suspended solids levels on a Litopenaeus vannamei (Boone, 1931) BFT culture system during biofloc formation

In a Biofloc Technology System (BFT), there is constant biofloc formation and suspended solids accumulation, leading to effects on water quality parameters that may affect the growth performance of cultured shrimp. This study aimed to analyse during biofloc formation the effect of different total suspended solids (TSS) levels on water quality and the growth performance of Litopenaeus vannamei shrimp in a BFT system. A 42‐day trial was conducted with treatments of three ranges of TSS: 100–300 mg L^?1 as low (TL), 300–600 as medium (TM) and 600–1000 as high (TH). The initial concentrations of 100 (TL), 300 (TM) and 600 mg L^?1 (TH) were achieved by fertilization before starting the experiment. Litopenaeus  vannamei juveniles with an average weight of 4.54 ± 1.19 g were stocked at a density of 372 shrimp m^?3. Physical and chemical water parameters and shrimp growth performance were analysed. After 6 weeks, TSS mean concentrations were 306.37, 532.43 and 745.2 mg L^?1 for, respectively, TL, TM and TH treatments. Significant differences (P < 0.05) were observed in TSS, settleable solids, pH, alkalinity and nitrite, especially between the TL and TH treatments. Similarly, differences (P < 0.05) were observed in the growth performance parameters, specifically final weight, survival, feed conversion and productivity. The water quality parameters at lower range of total suspended solids concentration (TL) treatment resulted in a better performance of L. vannamei in the BFT system. The maintenance at range of 100–300 mg L^?1 TSS is thus important to the success of shrimp culture.     

Comparison of growth and reproduction performance of broodstock Pacific white shrimp Litopenaeus vannamei reared in oceanic and brackish water

This study provides a preliminary evaluation of feasibility of brackish water breeding. Shrimps were initially cultured at brackish water. Shrimps were reared at different stages (5, 6, 7 and 8 months, respectively), and 300 female shrimps were selected from each stage for growth at an enhanced salinity of 30 ppt. When the shrimps were sexually mature, the reproductive characteristics (mating rate, egg number and nauplii number) of the broodstock shrimps, quality of nauplii (malformation rate of nauplii) and quality of postlarvae (survival rate and desalination stress) were tested to evaluate of the effects of brackish water (10 ppt) on these shrimps. Oceanic water (30 ppt) for rearing shrimps was used as control group. Histopathological analysis of gonads and hepatopancreases from oceanic and brackish water shrimp was performed. The results showed that shrimps cultured for a maximum of 8 months in brackish water remained sexually mature. There were no significant differences regarding the quality of shrimps in the oceanic water and brackish water. However, the brackish water cultured shrimps were easily adapted to salinity changes. Our results demonstrate the good feasibility of the present scheme, in which the broodstock shrimps were cultured at a salinity of 10 ppt.     

Efficacy of crystalline methionine and microencapsulation methionine in diets for Pacific white shrimp Litopenaeus vannamei

An 8‐week growth trial was conducted to evaluate the efficacy of crystalline methionine (C‐Met) or microencapsulated methionine (M‐Met) in practical diets for Pacific white shrimp Litopenaeus vannamei. A high fishmeal reference diet was formulated with 15% fishmeal, and then, soybean meal (SBM) was used to replace 50% fishmeal as a low fishmeal basal diet (7.5% fishmeal). Graded levels (0.1%, 0.15% and 0.2%) of methionine originating from C‐Met or M‐Met were added to the basal diet. Each diet was randomly assigned to three tanks (40 shrimps per tank) in an indoor flow through seawater system. The results showed that the shrimp fed the basal diet with 0.15% or 0.20% methionine originating from 0.375% or 0.5% M‐Met had significantly higher final weight and weight gain as compared to shrimp fed the basal diet. The supplementation M‐Met in the basal diets resulted in increased serum ammonia in shrimp. Hepatopancreas amylase activity of shrimp showed a decreasing trend with increasing methionine supplementation, which is in contrast with the upswing trend in trypsin at pancreatic segment. This study indicated that the diets supplemented with 0.15% or 0.20% of methionine from M‐Met (0.58% or 0.65% of dietary methionine respectively) were effective in improving the nutritional value of SBM‐based diets deficient in methionine (0.48%) for the Pacific white shrimp.     

Induction of spawning in Pacific white shrimp Litopenaeus vannamei (Boone, 1931) by injection of its molt inhibiting hormone isoform II produced in E. coli

The optimization of reproductive parameters in shrimp farming continues to be a challenge for most producing countries. Although the crustacean neuropeptides have been studied extensively in the last two decades, the functions of most of these neuropeptides remained putative. Among them, molt‐inhibiting hormone isoform II (MIH II) has shown an important role in vitellogenesis. In this study, the cDNA encoding mature MIH II peptide was isolated by RT‐PCR from the L. vannamei eyestalk. The cDNA was cloned into pET28a bacterial expression vector. Recombinant MIH II was obtained in the form of insoluble inclusion bodies and purified to ~88% purity. Two doses of rMIH II and a negative control group were assayed in vivo. The stages of ovarian maturation and spawning were recorded during 72 hr post‐injection. The results showed that ovarian maturation occurred approximately in 9% and 33% of females injected with rMIH II at the doses of 300 and 600 ng/gbw respectively. Neither maturation nor spawning was detected in the negative control group. Females injected with 600 ng/gbw, which showed vitellogenic stages III and IV, spawned. These preliminary results argue that the hormone rMIH II could be a promising candidate to induce spawning in L. vannamei shrimp.     

The contribution of diatoms to bioflocs lipid content and the performance of juvenile Litopenaeus vannamei (Boone, 1931) in a BFT culture system

This study aimed to evaluate the contribution of three diatom species on the lipid content of bioflocs, their permanence on the bioflocs and influence on the growth performance of juvenile shrimps. Juveniles of Litopenaeus vannamei were reared (30 days; three replicates per treatment) in biofloc systems inoculated with diatoms Amphora coffeaeformis (A), Cylindrotheca closterium (C), Conticribra weissflogii (W), or biofloc only (BF, chlorophycean rich). Water quality parameters were monitored daily and the microbiota on days 1, 10, 20 and 30. The lipid content and fatty acid profiles of bioflocs were analyzed at the end of the experiment. Shrimp survival rate (99%) at treatment A was significantly higher than at BF. The bioflocs in A treatment presented the highest lipid content, differing significantly from BF and W. The content of EPA (20:5) (n‐3) was significantly higher in A and lower in BF, while linoleic acid (18:2) (n‐6) was significantly higher in BF. The results indicate that high cell density of diatoms can be successfully maintained with silicate addition in biofloc systems and that the pennate A. coffeaeformis and the centric C. weissflogii are potentially better suited than the pennate C. closterium as food supplements for shrimp diets in biofloc nurseries system.     

Feed management for Pacific white shrimp Litopenaeus vannamei under semi‐intensive conditions in tanks and ponds

To improve feed management strategies for the semi‐intensive culture of Litopenaeus vannamei, outdoor tank and pond trials were conducted. In the tank trial, shrimp (35 shrimp/m², n = 4) were offered feed for 6 weeks based on a standard feeding protocol (SFP, designed as T100) with five variations (T80:90:100, T90, T90:100, T100:110, T110) of this protocol produced by varying the feed inputs and expressing the treatments as a percentage. Results demonstrated no significant differences in survival rate and feed conversion ratio (FCR) among treatments. The mean final weight and final biomass in the treatments T100:110 and T110 were significantly higher than those in treatment T90 but were not different from the other treatments. In the pond trial, juvenile shrimp (28 shrimp/m², n = 4) were stocked into twelve 0.1‐ha ponds over a 16‐week period. Three feeding protocols were evaluated including a SFP, a 10% reduction in the SFP (SFP:90), and a variable feed input (SFP:80:90:100), which included 80% SFP at week 4th–8th, 90% SFP from week 9th–12th and 100% SFP for week 12th–16th. There were no significant differences in growth performance and economic return among treatments. Based on previous studies, in which higher feed inputs were evaluated, and results of this study, it does not appear to be economically beneficial to use high feed inputs. Instead, feed input could be either applied at a standard ration to optimize growth and economic return or at restricted rations to reduce FCR (feed cost) albeit at the expense of some growth.     

Effects of replacement of fish meal with fermented cottonseed meal on growth performance,body composition and haemolymph indexes of Pacific white shrimp,Litopenaeus vannamei Boone, 1931

A feeding trial was performed for 28 days to evaluate the effects of replacement of fish meal (FM) with fermented cottonseed meal (FCM) on growth, body composition and haemolymph indexes of juvenile Litopenaeus vannamei. Four isonitrogenous and isoenergetic diets were formulated by using FCM (96.4, 206, 317 and 417 g kg^?1) to substitute 25%, 50%, 75% and 100% of FM in a control diet respectively. Each diet was randomly allotted to four tanks with 20 shrimp per tank. The feeding trail was conducted in an indoor flow‐through aquaculture system. Shrimp fed diets containing 317 and 417 g kg^?1 of FCM obtained lower (P < 0.05) final weight, weight gain, specific growth ratio, protein efficiency ratio as well as a higher (P < 0.05) feed conversion ratio compared with shrimp fed the control diet. The body ash content decreased (P < 0.05) in shrimp fed the diet with complete replacement of FM than those in other treatments. Moreover, increasing the dietary inclusion of FCM linearly raised (P < 0.05) the concentrations of total gossypol, (?) and (+) gossypol enantiomers in the whole shrimp body. No difference (P > 0.05) was observed in haematological parameters among the treatments. The results suggest that up to 50% of FM can be replaced by FCM without adverse effects on growth and feed utilization of L. vannamei.     

Apparent energy,dry matter and amino acid digestibility of differently sourced soybean meal fed to Pacific white shrimp Litopenaeus vannamei

Due to the variations in nutrient quality of soybean meal (SBM) that is a result of differences in production location and processing specifications, a study was conducted to determine the fluctuations in apparent digestibility coefficients of differently sourced SBM fed to Pacific white shrimps (Litopenaeus vannamei). Twenty‐four SBM‐based diets were formulated by mixing a basal diet and test ingredients on a dry matter basis (70:30 ratio), while 1% chromic oxide was used as the inert marker. The digestibility trial was carried out in a semi‐closed recirculation system with six replicate groups per treatment (mean shrimp weight of 10.2 g). Significant differences were observed for apparent dry matter, energy and protein digestibility coefficients (p < .05 was considered significant) among 24 sources of SBM and digestibility values ranged from 45% to 90%, 56% to 93% and 87% to 98%, respectively. Based on multivariate analysis, acid detergent fibre, neutral detergent fibre, lignin, raffinose and trypsin inhibitor were screened as the key chemical characteristics in SBM that influenced digestibility of nutrients in Pacific white shrimps. Variations in growth performances of shrimp were in line with the variations in apparent digestibility coefficients of SBM verifying the importance of digestibility data in shrimp feed formulations.