The effect of Ibuprofen on female and male reproduction of the open thelyca marine shrimp,Litopenaeus

A research was designed to explore the effect of ibuprofen (IBU) as an intervening agent for prostaglandin biosynthesis on male and female reproduction of three species of Litopenaeus. Ovarian maturation was studied in L. stylirostris and L. vannamei injected periodically with IBU at 0.01 and 0.1 μg g^?1 body weight (b.w.) and treated for unilateral eyestalk ablation. IBU at 0.1 μg induced a statistically (P < 0.05) higher rate of L. vannamei females with developing ovaries (45 ± 19%) as compared with controls (12 ± 8%) during 5 weeks; L. stylirostris did not activate vitellogenesis under this experimental protocol. IBU was also evaluated for male sexuality in L. occidentalis, L. stylirostris and L. vannamei. Periodic injections of IBU had no effect on sperm counts and spermatophore weights; however, sperm abnormalities in IBU 0.1 μg treated L. occidentalis and L. stylirostris were very low. In L. stylirostris, the renovation of normal spermatophores was remarkably improved in IBU treated males as compared with controls, but in L. vannamei spermatophore deterioration was not affected. The findings of this research support the hypothesis that prostaglandins are involved in penaeid reproduction playing a negative physiological role; however, altered steroidogenic pathways could also be involved.     

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.     

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.     

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.     

Effect of l‐ascorbyl‐2‐polyphosphate supplementation on growth performance,body composition,antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei

An 8‐week feeding trial was conducted to evaluate the effects of ascorbic acid (AsA), in the form of l ‐ascorbyl‐2‐polyphosphate (LAPP) on growth performance, body composition, antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei. Five practical diets (46% crude protein and 7.6% lipid) supplemented with graded levels of AsA (14.64, 48.55, 84.98, 308.36 and 639.27 mg kg^?1 diet) were fed to five replicate groups of L. vannamei (mean initial wet weight 0.57 g). No significant differences were found on growth performance among all treatments. However, whole body lipid content significantly decreased with dietary AsA levels increasing. Activities of total antioxidant capacity, glutathione reductase and glutathione peroxidase were significantly affected by dietary AsA levels. Shrimp fed LAPP‐free diet had higher malondialdehyde content than those fed the diets supplemented with LAPP. Dietary AsA levels higher than 308.36 mg kg^?1 diet increased the survival of shrimps after 1, 2 and 3 h of acute salinity change. Broken‐line regression analysis on survival after 3 h of salinity stress and second‐degree polynomial regression analysis on glutathione reductase data indicated that the optimal dietary AsA requirement of L. vannamei was estimated to be 306.39, 319.75 mg kg^?1 diet respectively.     

Effects of aqueous Na/K and dietary K on growth and physiological characters of the Pacific white shrimp,Litopenaeus vannamei,reared in low‐salt well water

The synchronous effects of aqueous Na/K and dietary potassium (K⁺) on growth and physiological characters was studied on the Pacific white shrimp (Litopenaeus vannamei) reared in low‐salinity well water (4 ppt) for 8 weeks with initial weight of 0.28 ± 0.01 g. Three practical diets were formulated with supplement of 0, 0.3%, 0.6% K⁺ which contained 1.29 g/100 g, 1.60 g/100 g, 1.93 g/100 g K⁺ respectively. The supplement of K⁺ to the low‐salinity well water was 10, 20, 40 mg L^?1 which formed Na:K ratios of 42:1, 33:1, 23:1 respectively. Results showed that when the aqueous Na:K ratio was 42 and dietary K⁺ was 1.93 g/100 g K⁺, the WGR and PER of L. vannamei were the highest and the FCR was lower than that of others (P < 0.01). Supplement of K⁺ into well water and diets did not showed significant effects on haemolymph ammonia‐N, uric acid, urea content (P > 0.05), but had a extremely significant effect on arginase activity and Cl^? concentration (P < 0.01). Moreover, similar results were observed in alkaline phosphatase (ALP), bacteriolytic activity (LSZ) and respiratory burst activity (O₂^?) (P < 0.05). These results suggested that aqueous Na/K in the low‐salt well water and dietary K had significant synergistic effect on the growth, osmoregulation and immunity of L. vannamei. Concluded from the growth performance, nitrogen metabolism, osmoregulation and immunity, as the Na/K in the low‐salinity well water descended from 42 to 23, the requirement of dietary K⁺ was also decreased.     

Effect of γ‐aminobutyric acid supplementation on growth performance,endocrine hormone and stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei,fed low fishmeal diet

An 8‐week feeding trial was conducted to evaluate the optimum dietary γ‐aminobutyric acid (GABA) level in low fishmeal diet for juvenile Pacific white shrimp, Litopenaeus vannamei. Six practical diets (449 g kg^?1 protein, 87 g kg^?1 lipid) supplemented with graded levels of GABA (0, 50, 100, 150, 200, 250 mg kg^?1) were formulated. Each diet was randomly assigned to triplicate groups of 30 shrimps (approximately 0.44 g), and the shrimps were fed four times a day to apparent satiation. Weight gain and gain rate were significantly increased with the supplementation of GABA (P < 0.05). Hepatosomatic index and survival were also significantly influenced by the dietary GABA levels (P < 0.05) and show a similar trend to those of growth performance. Insulin and neuropeptide Y concentrations in blood were increased with the supplementation of GABA. In total, 150 mg GABA kg^?1‐supplemented diets significantly increased the survival after 12, 24 and 36 h of NH₃ stress, also increased the total antioxidant capacity, total superoxide dismutase, catalase, antihydroxyl radical and phenoloxidase activities before and after the 36 h NH₃ stress compared to basic group. These results clearly indicated that GABA could improve growth performance, antioxidative capacity and resistance against NH₃ stress in L. vannamei, and 150 mg kg^?1 GABA supplementation was suitable for L. vannamei fed with low fishmeal diet.     

Growth,body composition,ammonia tolerance and hepatopancreas histology of white shrimp Litopenaeus vannamei fed diets containing different carbohydrate sources at low salinity

Juvenile Litopenaeus vannamei farmed at 3.0 psu were fed five diets containing glucose, sucrose, wheat starch, corn starch or potato starch as the carbohydrate (CBH) source. Shrimp were fed for 50 days to explore the effect of dietary CBH source on growth, body composition and ammonia tolerance. The specific growth rate of body length of shrimp fed glucose was the highest and significantly higher than those fed potato starch. The survival rate of shrimp fed glucose was 89.44%, and it was the highest and significantly higher than those fed wheat starch. Whole shrimp body crude protein and lipid of the corn starch group were 140.2 g kg^?1 and 10.1 g kg^?1 respectively. And they were significantly higher than those fed wheat starch. Shrimp fed potato starch had higher hepatopancreas and muscle glycogen. Shrimp fed sucrose had higher glucose‐6‐phosphate dehydrogenase and lower pyruvate kinase activities (P < 0.05). Besides, shrimp fed starch produced more B cells in hepatopancreas tubules than those fed glucose or sucrose. Shrimp fed different sources of CBH differed in the number of R cells. After 96‐h of ammonia nitrogen challenge, the survival rate of the treatments from high to low in turn was glucose, wheat starch, corn starch, sucrose and potato starch, and no significant differences were observed among all treatments. Based on shrimp growth and the economic problems of practical production, we recommend wheat starch as CBH source in practical diets for L. vannamei farmed at low salinities.     

Changes in the intestinal bacterial community during the growth of white shrimp,Litopenaeus vannamei

In this study, we documented the changes in the intestinal bacterial community at four stages in Litopenaeus vannamei: 14 days postlarvae (L14) and 1‐, 2‐ and 3‐month old juveniles (J1, J2, J3), using 454 pyrosequencing techniques. The intestinal bacterial community was dominated by three bacterial phyla, Proteobacteria, Bacteroidetes and Actinobacteria at all stages. However, the relative abundance and bacterial lineages varied at the family level. The intestinal bacterial community of L14 and J1 was similar, with dominant members belonging to the Comamonadaceae of Betaproteobacteria. Conversely, bacterial members affiliated to Flavobacteriaceae of Bacteroidetes were dominant in J2 and Vibrionaceae of Gammaproteobacteria was dominant in J3. The abundance of Microbacteriaceae of Actinobacteria also fluctuated during the four stages. Bacterial members of Flavobacteriaceae and Rhodobacteraceae (Alphaproteobacteria) were present through all growth stages, and likely form the intestinal core microbiome of L. vannamei. However, they varied at the operational taxonomic unit (OTU) level through the growth stages. The intestinal bacterial community of pond‐rearing shrimp included the three main bacterial phyla identified above, and an additional group, Mycoplasmataceae of Mollicutes. Our results demonstrate that the intestinal bacterial community of L. vannamei was highly dynamic during the growth stages. Bacterial members belonging to Commamonadaceae dominated in the earlier growth stage of shrimp, possibly influenced by feeding with Artemia nauplii, but there was a shift to Flavobacteriaceae in the mid and Vibrionaceae in the late growth stages.     

Ingestion of food pellets containing Escherichia coli overexpressing the heat‐shock protein DnaK protects Penaeus vannamei (Boone) against Vibrio harveyi (Baumann) infection

Feeding aquatic animals with bacterial encapsulated heat‐shock proteins (Hsps) is potentially a new method to combat vibriosis, an important disease affecting aquatic animals used in aquaculture. Food pellets comprised of shrimp and containing Escherichia coli overexpressing either DnaK‐DnaJ‐GrpE, the prokaryotic equivalents of Hsp70‐Hsp40‐Hsp20, or only DnaK were fed to juveniles of the white leg shrimp Penaeus vannamei, and protection against pathogenic Vibrio harveyi was determined. Maintaining pellets at different temperatures for varying lengths of time reduced the number of live adhering E. coli, as did contact with sea water, demonstrating that storage and immersion adversely affected bacterial survival and attachment to pellets. Feeding P. vannamei with E. coli did not compromise their survival, indicating that the bacteria were not pathogenic to shrimp. Feeding P. vannamei with pellets containing bacteria overproducing DnaK (approximately 60 cells g^?1 pellets) boosted P. vannamei survival twofold against V. harveyi, suggesting that DnaK plays a role in Vibrio tolerance. Pellets containing DnaK were effective in providing protection to P. vannamei for up to 2 weeks before loss of viability and that DnaK encapsulated by these bacteria enhanced shrimp resistance against Vibrio infection.     

Apparent digestibility coefficient of poultry by‐product meal (PBM) in diets of Penaeus monodon (Fabricius) and Litopenaeus vannamei (Boone), and replacement of fishmeal with PBM in diets of P. monodon

Nutrient apparent digestibility coefficients (ADCs) of pet food grade poultry by‐product meal (PBM) were determined for black tiger prawn, Penaeus monodon and Pacific white shrimp, Litopenaeus vannamei by the indirect method (reference diet and test diet at 7:3 ratio). Subsequently, an 8‐week growth trial was conducted to evaluate the effects of substitution of fishmeal (FM) with PBM in diets of P. monodon (initial weight = 0.21 ± 0.01 g). In the growth trial, six isonitrogenous and isoenergetic diets PBM0, PBM25, PBM50, PBM75, PBM100 and PBMA100, containing a gradient of PBM 0, 88.7, 177.4, 266, 354.7 and 354 g kg^?1 to replace 0, 92.5, 185, 277.5, 370 and 370 g kg^?1 FM were fed to four replicate groups respectively. The diet PBMA100 was supplemented with DL‐Met to be similar to PBM0. The results showed that both P. monodon and L. vannamei had relatively high ADC of crude protein (77.6% and 84.2% respectively) and gross energy (72.8% and 84.0% respectively) for PBM. Litopenaeus vannamei showed significantly higher digestion ability for PBM than P. monodon (P < 0.05). In growth trial, no significant difference in growth performance was observed among shrimp fed the experimental diets. DL‐Met supplementation did not improve the growth of P. monodon. PBM is a suitable protein ingredient for P. monodon feeds and can be used up to 354.7 g kg^?1 to totally replaced FM.     

Effects of dietary taurine,carnitine and cholesterol supplementation on growth performance and immunological status of Litopenaeus vannamei under cold exposure

The aim of this study was to investigate effects of dietary feed additives on growth and immunological status of Litopenaeus vannamei under cold exposure. Four experimental diets with 0.2% taurine, 0.01% carnitine, 0.1% cholesterol supplementation and control were fed to L. vannamei (IBW 0.86 ± 0.03 g) for 30 days at 30 ± 1°C before water temperature was dropped to 16°C with a rate of ?4°C h^?1. Growth performance parameters including weight gain rate (WGR), feed conversion ratio (FCR) and survival rate before the cold exposure, as well as immunological parameters related to haemocytes including total haemocyte count (THC), percentages of hyaline cells (SC%), granular cells and semigranular cells (SC + GC%), non‐specific esterase (NSE) activity and apoptotic cell ratio before and after the cold exposure were determined. The results showed that: (1) WGR, FCE and survival rate were not significantly different among groups before the cold exposure. Most of immunological parameters did not differ either, except the apoptotic cell ratio of carnitine and cholesterol groups was significantly lower than that of control and taurine groups (P < 0.05). (2) After the cold exposure, THC was decreased by 48.1% (P < 0.05), 54.1% (P < 0.05), 30.1% and 2.2%; NSE activity was decreased by 31.7% (P < 0.05), 21.4%, 7.0% and 3.5% in control, taurine, carnitine and cholesterol respectively. (3) Conversely, ROS production was increased by 23.8% (P < 0.05), 15.1%, 7.2% and 13.0%; apoptotic cell ratio was increased by 10.4%, 12.8%, 6.4% and 7.2% in control, taurine, carnitine and cholesterol respectively. (4) An increase in HC%, decrease in SC + GC% in all groups was observed after cold exposure, and was significant in cholesterol group. This study showed that cholesterol, carnitine and taurine affected immunological status of L. vannamei under cold exposure to different degrees, possibly by modulating some immunological parameters, as discussed. Present study provides theoretical data for nutritional strategies to enhance cold resistance of shrimp.     

Dietary concentration of marine oil affects replacement of fish meal by soy protein concentrate in practical diets for the white shrimp,Litopenaeus vannamei

This work aimed to determine whether a minimum provision of marine oil in practical diets for Litopenaeus vannamei is required when replacing fish meal (FM) by soy protein concentrate (SPC). The study consisted of three growth experiments conducted in 500‐L tanks with 70 shrimp m^?2. In experiment #1, FM was progressively replaced by SPC as fish oil (FO) levels increased with a consistent input of whole squid meal (WSM). In experiment #2, FM was replaced by SPC under two levels of FO (10 or 20 g kg^?1) without the presence of a feeding effector. In experiment #3, three dietary levels of krill meal (KRL) and WSM (5, 10 and 20 g kg^?1) were included in a basal diet containing SPC and low levels of FM. Results showed that under a clear‐water condition, the dietary levels of FO in practical diets for L. vannamei have a significant impact on the amount of FM that can be replaced by SPC. As much as 31% replacement of FM/SPC was possible with 20 g kg^?1FO. Whenever dietary fat was adjusted by using FO as a lipid source, complete replacement of FM by SPC was achieved with no negative effect on shrimp growth.     

Effect of polysaccharides extracts of algae Ulva rigida on growth,antioxidant, immune response and resistance of shrimp,Litopenaeus vannamei against Photobacterium damselae

This study was carried out to investigate the effect of water‐soluble polysaccharides extract of algae Ulva rigida (WPU) as dietary supplement on growth performance, antioxidant enzyme activity, lysozyme and phenoloxidase activity, and resistance of shrimp (Litopenaeus vannamei) subjected to bacterial infection with Photobacterium damselae. Three replicate groups of shrimp (1.0 g) were fed four diets containing four levels, 0 or control, 0.5, 1 and 1.5 g/kg of WPU for 8 weeks over the growth trial. Thereafter, 30 shrimps from each dietary treatment were infected with bacteria P. damselae to evaluate disease resistance of infected shrimp. The results of this study showed that WPU was effective as a growth promoter for L. vannamei. The best growth rate was observed in shrimp fed 1.5 g/kg of WPU diet. Regarding antioxidant defences, the diets supplemented with three levels of WPU stimulated glutathione peroxidase and catalase activates in experimental shrimps. MDA content of L. vannamei‐fed diet containing WPU 1.5 and WPU 1.0 was lower than WPU 0 and WPU 0. 5 diets. Also, lysozyme and phenoloxidase activities of shrimp receiving WPU at 1.0 and 1.5 level were significantly higher than those fed WPU 0 and WPU 0.5 diets. In addition, using WPU extract in all diets decreased mortality in L. vannamei in a dose‐dependent manner after challenge with P. damselae. These results suggest that incorporation of water‐soluble polysaccharides from green algae U. rigida at 1.5 g/kg doses improves growth and antioxidant activity and enhances the immune responses in shrimp L. vannamei.     

Isolation and identification of Vibrio campbellii as a bacterial pathogen for luminous vibriosis of Litopenaeus vannamei

Outbreak of luminescent disease was reported from Litopenaeus vannamei shrimp farms in Zhangpu County, Southern China during May–July 2011. The clinical signs included fluorescent, less food consumption and high mortality. Bacteria were isolated from the infected shrimps. The pathogen, a luminescent bacterium named VH1 was identified as Vibrio campbellii based on MLSA analysis (16S rDNA, rpoD and toxR). The haemolysin (hly) gene specific in V. campbellii was detected in strain VH1. Pathogenicity test using immersion infection confirmed that strain VH1 was virulent to L. vannamei postlarvae and juveniles, and the LC₅₀ value was 1.55 × 10⁶ CFU mL^?1 and 1.7 × 10⁶ CFU mL^?1 respectively.     

Genetic parameters for spawning and growth traits in the Pacific white shrimp (Penaeus (Litopenaeus) vannamei)

The aim of this study was to estimate genetic parameters for spawning traits and growth traits in a breeding line of Pacific white shrimp, Penaeus (Litopenaeus) vannamei, selected for growth and survival. Traits studied were number of eggs (NE) and number of nauplii (NN) and female body weight at insemination (FWI) and body weight at 130 days of age (BW130). Genetic parameters were estimated using a multivariate animal model. Heritability for NE and NN were estimated as 0.13 ± 0.04 and 0.03 ± 0.04 respectively. The contribution to NN total variation due to ‘factors associated with male’ effect was estimated as 0.47 ± 0.07. In the cases of FWI and BW130, heritability was estimated as 0.44 ± 0.08 and 0.19 ± 0.03 respectively. Genetic correlation between FWI and NE was estimated as 0.49 ± 0.15, between FWI and NN as 0.54 ± 0.39 and between NE and NN as 0.27 ± 0.41, whereas the genetic correlations of FWI, NE and NN with BW130 were 0.30 ± 0.13, ?0.21 ± 0.19 and ?0.25 ± 0.38 respectively. Although it is important to perform more studies on this issue, our results found no evidence of a genetic antagonistic effect between female reproductive traits and body weight at harvesting (130 days of age) in P. vannamei.     

Utilization of sorghum distillers dried grains in extruded and steam pelleted shrimp diets

Use of distillers dried grain with solubles from sorghum (sDDGS) was studied with respect to processing and physicochemical quality of shrimp feed, followed by growth trials with Litopenaeus vannamei (Pacific white shrimp). Shrimp diets with 0%, 10%, 20%, 30% and 40% sDDGS inclusion, as a replacement for soybean meal, were produced using extrusion and steam pelleting. Bulk density of extruded feed (0.53–0.58 g cm^?3) was lower than that of pelleted feed (0.61–0.65 g cm^?3), although sDDGS level did not have an impact. Finished diets were 100% sinking, with some exceptions in the case of extruded feed. Pellet durability index (89.4–96.3%) had an increasing trend up to 20% and 30% sDDGS for extruded and pelleted diets respectively. Extruded feed had higher degree of gelatinization than pelleted feed, although proportion of gelatinized starch generally decreased with sDDGS level. Water stability (76.2–91.6%) was higher for extruded feed as compared to pelleted feed, and remained unchanged or decreased with sDDGS level. The extruded and pelleted diets were evaluated in two growth trials with L. vannamei for duration of 9 and 6 weeks in 40 and 60 tanks (initial weight 0.36–0.38 g; 10 shrimps per tank) respectively. Significant differences were not observed in final mean weight and survival with respect to sDDGS level, indicating that up to 40% of this novel protein source can be used in feed formulations without affecting the performance of L. vannamei. Comparison of extruded feed with pelleted feed for impact on mean weight and feed conversion ratio did not yield conclusive results.     

Use of new soybean varieties in practical diets for the Pacific white shrimp,Litopenaeus vannamei

This study was designed to evaluate the efficacy of eight sources (designated A–H) of soybean meal (SBM) which included six new non‐genetically modified soya varieties in practical feed formulation for Pacific white shrimp, Litopenaeus vannamei, using both growth and digestibility trials. A soybean meal‐based reference diet was formulated using conventional soybean meal (527 g kg^?1 diet), which was then replaced on an isonitrogenous basis with various other experimental soybean meals. In a 6‐week growth trial, shrimp in four replicate tanks per dietary treatment (10 shrimp per tank, initial weight 0.52 ± 0.04 g) were cultured in a recirculating system. There were no significant differences with respects to per cent weight gain and survival across all dietary treatments; however, final weights and feed conversion ratio (FCR) were lower in shrimp offered diet 3. Apparent digestibility coefficients for the eight (A–H) different soybean meals were determined in L. vannamei for dry matter (ADMD), gross energy (ADE) and crude protein (ADP) using 10 g kg^?1 chromic oxide as inert marker with 70 : 30 replacement techniques. Coefficients ranged from 71.3% to 88.3%, from 76.6% to 91.3% and from 93.6% to 99.8%, for ADMD, ADE and ADP, respectively. Improved digestibility values were observed in soybean C which was characterized by crude protein (471 g kg^?1), crude fat (97 g kg^?1), low cooking temperature (180 °C), higher nitrogen solubility index (689 g kg^?1) and protein dispersibility index (619 g kg^?1). This indicates that new lines of soybean meal can be used to improve digestibility coefficients in shrimp feeds.     

Successful rearing of whiteleg shrimp Litopenaeus vannamei larvae fed a desiccation‐tolerant nematode to replace Artemia

The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso^®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.