Supplementation of potassium, magnesium and sodium chloride in practical diets for the Pacific white shrimp, Litopenaeus vannamei, reared in low salinity waters

The culture of Litopenaeus vannamei in inland low salinity waters is currently being practiced in various countries around the world. These environments are often deficient in key ions essential for normal physiological function, including potassium (K⁺) and magnesium (Mg²⁺). Farmers have sometimes been able to counteract ionic deficiencies in the water profile by adding mineral salts containing sources of K⁺ and Mg²⁺. The purpose of this study was to explore the possibility of correcting deficiencies of K⁺ and Mg²⁺ in the water profile with dietary supplementation of these minerals. Two separate 7‐week experiments were conducted in 4.0 g⁻¹ artificial low salinity water to evaluate the effects of mineral supplements (K⁺, Mg²⁺ and NaCl) to diets of L. vannamei reared in low salinity waters. In trial 1 seven diets were formulated (10 g NaCl kg⁻¹, 20 g NaCl kg⁻¹, 150 mg kg⁻¹ Mg²⁺, 300 mg kg⁻¹ Mg²⁺, 5 g K⁺ kg⁻¹, 10 g K⁺ kg⁻¹, and a basal diet to serve as a control). Minerals were added in the form of purified potassium chloride (KCl), magnesium chloride (MgCl₂·6H₂O) and NaCl. Trial 2 evaluated the use of a coating agent for the Mg²⁺ and NaCl treatments, while a K⁺ amino acid complex was utilized in the K⁺ treatments to reduce mineral leaching. Trial 2 was performed using similar treatment levels as trial 1. Shrimp survival and growth were assessed in both experiments. Results from trial 1 indicated no significant differences in survival, growth or percent weight gain. Results from trial 2 revealed no significant differences in survival and growth in the NaCl and Mg²⁺ treatments. However, significant differences in growth (P < 0.05) were observed when using the 10 g K⁺ kg⁻¹ treatment, suggesting that dietary supplementation of a K⁺ amino acid complex may help improve growth of the species in low salinity waters.     

Effect of dietary protein levels on growth of Penaeus stylirostris juveniles

The shrimp Penaeus stylirostris is currently produced on a commercial scale in Tahiti and New Caledonia. Both super-intensive (80 animals m⁻²) and semi intensive (25 m⁻²) systems are promoted. Locally produced commercial feed contains 380–400 g kg⁻¹ crude protein (CP) without special consideration for environmental impact. The need for a 'low pollution' diet implies reconsideration of the optimum dietary protein level for this species. Under experimental conditions, six isoenergetic practical diets ranging from 270 g kg⁻¹ to 440 g kg⁻¹ CP were formulated and fed to satiation for 30 days to juvenile P. stylirostris ; average growth rates were between 5.5 and 7.5 g per month with survival rates > 90%.
The lowest protein levels 270–310 g kg⁻¹, gave significantly ( P < 0.05) poorer growth (5.5 g per 30 days) than was observed with 330–430 g kg⁻¹ CP; 330 g kg⁻¹ CP may be recommended, and as it is lower than levels in diets used currently, there is a possibility of reducing nitrogenous waste. In addition to growth response, protein efficiency ratio, protein productive value and food conversion (feed/gain) all supported a recommended dietary protein level of 330 g kg⁻¹. Future prospects for practical feeds with even lower CP levels are considered.     

Effects of paraquat treatment on fish transaminase molecular subforms

The effects of paraquat (PQ; 1,1′-dimethyl-4,4′-bipyridylium dichloride) treatment were investigated in carp, silver carp and wels. The serum glutamic-oxalacetic transaminase (GOT; L-aspartate: 2-oxoglutarate aminotransferase, EC 2.6.1.1.) level was enhanced by 50% at 1 ppm exposure and by 100% at 10 ppm exposure in all species, and there was a change in the distribution of the molecular subforms of GOT in the liver and heart. The activities of the individual subforms decreased with increasing PQ concentration or after a longer exposure. In some cases, one of the subforms was no longer present in the liver. An increased serum GOT activity, a decreased enzyme activity in different organs and the disappearance of molecular subform indicate tissue damage.     

The effect of vitamin A supplementation in broodstock feed on reproductive performance and larval quality in Penaeus chinensis

The effect of feeding four semi‐purified diets A1, A2, A3, A4, containing different vitamin A acetate levels 0, 20, 40, 60 mg kg^?1 diet, respectively, on fecundity, egg hatching rate, larval survival rate and vitamin A content in eggs of Chinese shrimp (Penaeus chinensis) broodstock was compared with a fresh clam diet (control) in a 60‐day feeding trial. The broodstock shrimp fed the diet with 60 mg kg^?1 vitamin A acetate added exhibited significantly higher fecundity (P < 0.01). Hatching rate was highest with diet A4 (P < 0.05), whereas hatching rates were similar fed diets A1, A2, A3. Increasing levels of vitamin A in broodstock diet resulted in improvement in larval quality. The vitamin A levels in shrimp eggs from broodstock fed with diet A4 were higher compared with those from broodstock fed with diet A1, A2 (P < 0.01). The fecundity and hatching percentages were positively correlated with the vitamin A content in eggs in the present study. The results of this study showed that higher level of vitamin A in broodstock diet may have positive effects on fecundity and larval quality in P. chinensis.     

Dietary protein level and natural food management in the culture of blue (Litopenaeus stylirostris) and white shrimp (Litopenaeus vannamei) in microcosms

The effect of dietary protein level and natural food management on the production parameters of blue and white shrimp, as well as on water quality, was evaluated in a microcosms system (plastic pools simulating aquaculture ponds). Two experimental trials were carried out in the facilities of DICTUS, University of Sonora, Northwest México. Treatment with low protein diet (LP) consisted of a low protein input (diet with 250 g kg^?1 crude protein) through the culture period; treatment with high protein diet (HP) consisted of a high protein input (diet with 400 g kg^?1 crude protein) through the trial, and finally treatment VP consisted of an adjustment of protein input (diets with 250, 350 or 400 g kg^?1 crude protein), depending on the abundance of biota (zooplankton and benthos) in the system. Each species responded differently to the treatments. For blue shrimp, low protein input resulted in the lowest final body weight (12.9 ± 0.6 g) and biomass (696.0 g pool^?1). Survival and feed conversion ratio were similar in the three treatments. For white shrimp, the best growth, biomass and food conversion ratio were obtained in the low protein input treatment. Water quality parameters such as nitrate, ammonia and organic matter during the two trials, were better for LP and VP treatments. White shrimp seems to have lower protein requirements than blue shrimp. For the blue shrimp culture, adjusting protein input according to natural food abundance (zooplankton and benthos) in the system, seems to be advantageous because of the possibility of getting a production similar to that obtained with a high protein input through the farming period, but at lower feed cost, and with a lower environmental impact. It is concluded that a high protein input through the whole farming period is not the best feeding strategy for any of the two species.     

Properties of cod metallothionein,its presence in different tissues and effects of Cd and Zn treatment

One isoform of the low-molecular-weight metal-binding protein metallothionein (MT) has been isolated from the liver of Atlantic cod by size-exclusion and ion-exchange chromatography. Cod MT contained 33% cysteine, no aromatic amino acids or arginine. As is the case for other piscine MTs, the N-terminus of cod MT lacked the asparagine in position 4 which is present in mammalian MTs. In addition, cod MT differed from all other vertebrate MTs described in that the N-terminal methionine was not acetylated. Antibodies were raised in rabbits against hepatic MT from cod by repeated injections of native protein mixed with adjuvant. Anti-cod MT antisera cross reacted with similarly-sized proteins in liver, brain, anterior kidney, posterior kidney, spleen, intestine, gills and ovaries. The putative MT in cod brain migrated differently to that of the other tissues in native gel electrophoresis. Intraperitoneally injected Cd (1 mg/kg) was nearly entirely associated with the MT-peak in hepatic and renal cytosols, whereas a single injection of Zn (10 mg/kg) resulted in increases in all cytosolic Zn pools of the liver and no apparent change in cytosolic Zn, Cu, Ni or Cd in kidney.     

A review of extracellular virulence product of Vibrio species important in diseases of cultivated shrimp

Shrimp aquaculture is an important industry that experiences significant losses from Vibrio species, especially at the larval and juvenile stages. Proteinaceous virulence factors, including alkaline proteases, metalloproteases, cysteine proteases and alkaline serine proteases, have been identified as important elements in Vibrio pathogenesis. This review summarizes current knowledge regarding the principal pathogenic Vibrio species in shrimp, with emphasis on relevant exotoxins and their modes of action, principal characteristics and molecular database. This pathogenic factors and their relation with other molecules produced by microorganisms may be help to understand the virulence mechanisms present in Vibrio strain.     

Effect of salinity on natural community and production of Litopenaeus vannamei (Boone), within experimental zero-water exchange culture systems

Recent efforts have been made to culture marine shrimp in systems operating under low or zero‐water exchange and with decreased water salinity. The aim of this study was to investigate the impact of various salinity levels on qualitative and quantitative characteristics of the natural community and, more particularly, ciliated protozoa, and compare this information with shrimp growth and survival. Tanks with 9‰ salinity were characterized by a higher pH, but also by a significantly higher concentration of chlorophyll a (Chl a) per weight of suspended matter (1.93 ± 0.72 µg Chl a/mg TSS) than tanks with 18‰ (1.29 ± 0.68 µg Chl a/mg TSS) or 36‰ (1.37 ± 0.61 µg Chl a/mg TSS) salinity. Concentrations of ciliates (max 6000 cells mL^?1) showed considerable fluctuations over the sampling period, reflecting the impact of water salinity, dynamic interactions between ciliates and their diverse roles within the shrimp production system. There was no significant difference between survival rates of shrimp reared at 9‰, 18‰ or 36‰, but decreasing salinity from 36‰ to 9‰ led to a significant decrease in final shrimp body weight (from 13.40 ± 0.26 g to 10.23 ± 2.72 g). Future work should address the potential of ciliates as an indicator of aquaculture water quality, as is currently being done in the wastewater industry, and the contribution of ciliates as food sources.     

Characterization by whole-cell hybridization of bacterial populations associated with shrimp hatchery biofilms

The impact of shrimp larvae development, as well as water and food inputs upon the increase of bacterial populations within the bacterial community of hatchery tank biofilms, was studied. For this study, a total of 68 biofilm samples were collected from concrete tanks at three larvae production times in a commercial shrimp hatchery. Seventeen samples were taken at each larval development stage (Zoea I, Mysis I, postlarvae 1 and postlarvae 16), as well as 37 samples from water, shrimp nauplii and food, introduced into the shrimp hatchery tanks. Culturable and direct bacterial counts were performed and 16S‐rRNA‐targeted oligonucleotide probes were used to quantify the presence of specific bacterial groups. An average of 27–70% of DAPI total cell counts were detected with the EUB338 probe, while the GAM42a probe signal ranged from 1% to 11%. Vibrio‐like bacteria (VLB) counts in TCBS agar ranged from <10 to 10¹ VLB/cm⁻², with a tendency to increase at the last postlarvae stage. The most significant external source of bacteria registered with GAM42a probe and TCBS agar were found in live Artemia nauplii, used as food; nevertheless, biofilms remain with low counts of these groups.