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Abstract: The biofloc technology was proposed as a sustainable solution to culture shrimp with low protein feeds even in intensive systems, which can effectively control water quality under negligible water exchange and sustain healthy culture of shrimp. This study was conducted to evaluate the effects of four dietary protein levels (20%, 25%, 30% and 35%) on selected parameters of immune and antioxidant systems, and growth performance of Litopenaeus vannamei juveniles reared in zero-water exchange biofloc-based intensive culture tanks for a period of 7weeks. Good water quality was maintained with the promotion and development of biofloc through sucrose addition during the feeding experiment. At the end of the experiment, the total hemocyte count in the hemolymph, phagocytic activity of the hemocyte, and antibacterial activity and bacteriolytic activity in the plasma of shrimp showed no significant differences (P >0.05) among the four treatments with four dietary protein levels. The shrimp in the treatment with 20% dietary protein level had the lowest total antioxidant capacity (T-AOC) in both the plasma and the hepatopancreas, and the lowest reduced glutathione/oxidized glutathione (GSH/GSSG) ratio in the plasma. No significant differences were found in the antioxidant status (in terms of T-AOC, superoxide dismutase activity, GSH level and GSH/GSSG ratio in the plasma and the hepatopancreas) of shrimp fed with 25%, 30% and 35% dietary protein levels. Furthermore, except for the suboptimal growth performance of shrimp in the treatment with 20% dietary protein level, the growth (in terms of final weight, weight gain and specific growth rate) and feed conversion rate (FCR) of shrimp in treatments with 25%, 30% and 35% dietary protein levels showed no significant differences (P >0.05). Mean survival rates were above 85%, with no significant differences (P >0.05) among the four treatments with four dietary protein levels. The results of this study demonstrated that, when juveniles of L. vannamei were reared in zero-water exchange biofloc-based intensive culture tanks, dietary protein level can be reduced from 35% to 25% without affecting survival, growth, FCR, and physiological status of immune response and antioxidant capability, indicating that the promoted biofloc could contribute to the protein nutrition and physiological health of cultured shrimp. [Copyright &y& Elsevier]

Abstract: Biofloc technology (BFT) is a microbial manipulation technique used recently in intensive shrimp aquaculture. The driving force of BFT culture systems is microbial biofloc that is responsible for enhancing water quality, supplementing natural food, and improving growth and health of cultured shrimp. The aim of this study was to investigate the effects of biofloc on immune response and antioxidant status of Litopenaeus vannamei juveniles reared in biofloc-based tanks through manipulating high C/N ratio of feed input. Two biofloc treatments and one control were compared: Biofloc-based tanks under zero-water exchange with two levels of C/N ratio (15:1, 20:1) by addition of carbohydrate referred to as ‘CN15’ and ‘CN20’ and clear water tanks operated with high water exchange and without addition of carbohydrate referred to as ‘control’. The shrimp were cultured for 30days. The water quality in biofloc-based tanks was maintained with the promotion and development of biofloc through sucrose addition during the experiment. At the end of the experiment, the total hemocyte count in the hemolymph and the phagocytic activity of the hemocyte of the shrimp in the two biofloc treatments were significantly higher than those of the shrimp in the control group (P <0.05). Furthermore, the total antioxidant capacity in both the plasma and the hepatopancreas of the shrimp in the two biofloc treatments was significantly higher than those of the shrimp in the control group (P <0.05). Increased superoxide dismutase activity in the plasma, and increased reduced/oxidized glutathione ratio in both the plasma and the hepatopancreas were found in the shrimp of the two biofloc treatments (P <0.05). There were no significant differences in all of the above parameters between the CN15 and CN20 treatments (P >0.05). The results indicated that promoting biofloc through carbohydrate addition in zero-water exchange systems could enhance immune cellular response and antioxidant status of cultured shrimp under the conditions of the present study. [Copyright &y& Elsevier]

A 30-day experiment was performed to investigate the effects of bioflocs on water quality, and survival, growth and digestive enzyme activities of the white shrimp Litopenaeus vannamei. Altogether 28 shrimp (7.4 ± 0.1 g) were stocked in each 150 L tank. Two bioflocs treatments and one control were managed: 'bioflocs 1' and 'bioflocs 2' based on two different densities of the bioflocs, and clean water control without the bioflocs. Brown sugar was added to the bioflocs 1 and bioflocs 2 treatment tanks accounting for 28% and 80% of the shrimp feed respectively (corresponding to proximate C/N ratios of 10 and 14 in daily additions of organic matter respectively), so as to promote bioflocs production and approximately 14 mL L−1 in treatment bioflocs 1 and 20 mL L−1 in treatment bioflocs 2 were maintained from day 15. Monitoring of selected water quality parameters throughout the whole experiment period showed that all parameters remained within recommended levels for shrimp culture in the bioflocs treatments at zero-water exchange, especially low total ammonia nitrogen and nitrite nitrogen levels. By the end of the experiment, shrimp survival rates were above 86%, with no significant differences ( P > 0.05) among the three groups. Both weight gain rate and special growth rate tended to increase in the bioflocs treatments compared to those in the control. Meanwhile, the overall specific activities of protease, amylase, cellulase and lipase of the shrimp in the bioflocs treatments were all higher than those in the control; and for the specific activity of the same digestive enzyme, the differences between the bioflocs treatments and the control performed inconsistently among different organs: hepatopancreas, stomach and intestine. Present results suggest that the bioflocs can not only maintain favourable water quality conditions for shrimp culture and help shrimp grow well in zero-water exchange culture systems, but may also have a positive effect on digestive enzyme activities of the shrimp. [ABSTRACT FROM AUTHOR]

Abstract: A 30-day feeding experiment was conducted to investigate the effects of promoted bioflocs on growth performance, feed utilization, digestive enzyme activity and whole body composition of Litopenaeus vannamei juveniles (average 6.95±0.22g) in zero-water exchange culture tanks. Two bioflocs treatments and one control were evaluated: Bioflocs-based tanks with two levels of C/N ratio (15, 20) by addition of carbohydrate referred to as ‘CN15’ and ‘CN20’, and clear water tanks operated with water exchange and without addition of carbohydrate referred to as ‘Control’. Each group consisted of quadruplicate tanks (125L) and each tank contained 28 shrimp (equivalent to shrimp density of 224 individuals and biomass of ~1.56kg per cubic meter of water volume). Original concentrated bioflocs were collected from an indoor bioflocs-based shrimp culture pond, and inoculated into all bioflocs-based tanks with the same amount (0.5mLL−1 bioflocs volume) just before stocking shrimp. Sucrose was applied as a source of carbohydrate and added separately to the CN15 and CN20 treatment tanks in addition to the applied feed (35% crude protein), so as to raise the C/N ratio of the feeds input (feed and sucrose) to 15 and 20 and subsequently promote the development of bioflocs. The monitoring of water quality parameters showed that they all remained within recommended levels for shrimp culture in the three groups. At the end of the experiment, survival rates of the shrimp were above 90%, with no significant differences among the three groups (P >0.05); and the growth (in terms of final weight, weight gain and specific growth rate) of the shrimp in both bioflocs treatments were significantly better (P <0.05) than that obtained in the control while the feed conversion rate was significantly lower (P <0.05). An overall enhancement in protease and amylase activities of the shrimp in both bioflocs treatments was observed, though the effect of the bioflocs on each enzyme activity performed inconsistently among different digestive tissues: digestive gland, stomach and intestine. Proximate composition analysis showed that the crude lipid and ash contents of the shrimp in both bioflocs treatments tended to increase. The bioflocs collected from both bioflocs treatments showed good prime nutritional values and appropriate extracellular enzymes activities. The crude protein and crude lipid contents ranged from 27.3% to 31.6% and 3.7% to 4.2%, respectively; and protease and amylase activities ranged from 10.7 to 14.4μmolmin−1 g−1 TSS and 293.5 to 335.5μmolmin−1 g−1 TSS, respectively. The results from this study suggest that the promoted bioflocs can improve growth performance and feed utilization of the cultured shrimp, probably through providing a supplemental food source and enhancing feed digestion and utilization. [Copyright &y& Elsevier]

Abstract: A 7-week experiment was conducted to investigate the contribution of bioflocs on protein nutrition of Litopenaeus vannamei juveniles (average 6.68±0.09g) through feeding with different crude protein (CP) levels in zero-water exchange culture tanks. Four bioflocs treatments (BFT) and one control group were managed: BFT fed diets of 20% CP (BFT-20%), 25% CP (BFT-25%), 30% CP (BFT-30%) and 35% CP (BFT-35%), and clear water control without bioflocs fed with 35% CP (CW-35%). Each group consisted of quadruplicate tanks (125L) and each tank contained 28 shrimp (equivalent to a shrimp density of 224m−3 water volume). During the culture period, brown sugar was added into the BFT tanks to promote the development of bioflocs based on initial inoculation, which not only maintained suitable water quality but also provided supplemental protein source (protein content of the bioflocs ranging from 25.61 to 31.14%) for cultured shrimp. At the end of the experiment, the shrimp in all the bioflocs treatments showed higher activities of total proteinases and trypsin in the digestive gland than those in the control (P<0.05). The feed conversion rate of the shrimp in BFT-35% was significantly lower than that in the control (P<0.05); and for protein efficiency ratio and protein productive value, better values were observed in all the bioflocs treatments compared to those in the control (P<0.05). Moreover, the shrimp in both BFT-30% and BFT-35% gained better growth performance (in terms of final weight, weight gain and specific growth rate) than that in the control (P<0.05). Survival rates of the shrimp were above 85%, with no significant differences among all experimental groups (P>0.05). Besides, for all above indicators, there were no significant differences among BFT-25%, BFT-30% and BFT-35% (P>0.05). Present results demonstrated that bioflocs could provide a supplemental source of food protein and stimulate activities of digestive proteinases, both of which made contributions on protein nutrition of cultured shrimp as indicated by improved feed utilization, protein retention and growth performance. Results also showed that, when L. vannamei juveniles were reared in zero-water exchange bioflocs-based tanks, dietary protein level could be reduced to 25% without affecting shrimp growth. [Copyright &y& Elsevier]

Abstract: We used semi-quantitative reverse transcription and the polymerase chain reaction (RT-PCR) to identify and characterize the mRNA of Na+/K+-ATPase α-subunit and Vacuolar-type H/-ATPase (V-ATPase) β-subunit prepared from gills of the white shrimp Litopenaeus vannamei. Western blot and immunocytochemistry analysis were employeed to investigate the effects of biogenic amines such as dopamine (DA) and 5-hydroxytryptamine (5-HT) injection on expression of protein abundance and immunostained sites. Our results show that the gill Na+/K+-ATPase of 5-HT treatments increased lag to those of DA treatments. However, the DA and 5-HT have no significant effects on the activity of V-ATPase. The biogenic amines could induce the synthesis of Na+/K+-ATPase α-subunit mRNA in the first 12 h. The degree of change in Na+/K+-ATPase α-subunit mRNA expression were different between DA and 5-HT treated groups which depend on the dose. The expression of V-ATPase β-subunit mRNA was not markedly affected by the biogenic amines. Concomitant elevation of Na+/K+-ATPase activity, α-subunit mRNA as well as protein abundance in response to injected biogenic amines was also found in Na+/K+-ATPase immunostained sites within the gill epithelium. [Copyright &y& Elsevier]

Abstract: In this paper, we compared systematically the temporal and dose response relationship and physiological significance among biogenic amines injection, changes of ion concentration, FAA concentrations and composition and protein in context of osmoregulatory ability in marine euryhaline shrimp: Litopenaeus vannamei. The dopamine (DA) and 5-hydroxytryptamine (5-HT) injection all had transient effects on hemolymph osmolality, ion concentrations but which occurred in different time and were dose-dependent. The highest concentrations of FAAs in hemolymph of L. vannamei were alanine, glycine, argnine, proline, lysine which were considered to be specific osmotic effectors. Contrary to the reduction of hemocyanin, injection of DA 10−6 mol shrimp−1 and 5-HT 10−6 mol shrimp−1 induced notable protein increase respectively, which led to the rapid reduction of hemocyanin/protein ratio in range of 63.2% to 78.3%. The increase of hemolymph FAAs might come from the new amino acid synthesis or degradation of muscle protein to FAAs or denovo synthesis of FAAs. Our study showed that dopamine plays an important role in neurotransmission and causes osmoregulation response modulation and 5-HT has different activation mechanism on osmoregulation. [Copyright &y& Elsevier]

Abstract: Water temperature changes (higher and lower than 24°C) were shown to have a significant effect on dopamine (DA) concentration, haemocyte count and the proPO system in the white shrimp Litopenaeus vannamei. No significant difference in any of the parameters was observed in the control group. DA concentration in haemolymph in the experimental groups increased to a peak value at 0.5 days; meanwhile serine protease (SP) activity and proteinase inhibitor (PI) activity decreased. Total haemocyte count (THC), differential haemocyte count (DHC) and PO activity were lowest at 1 day. All defence parameters became stable after 1–3 days, while the total haemocyte and large granular cell count stabilized after 6 days. After these stabilized, there was no significant difference in DA concentration and PI activity between the control and experimental groups, as was the case for the THC, DHC, PO and SP activities of shrimp held at higher temperatures. However these latter four parameters in the lower temperature groups were distinctly lower than the control group. α2-Macroglobulin activity in the experimental groups increased to a peak value after 1 day compared with the control and then stabilized after 6 days when the activity levels in higher temperature groups were higher than the control, while the lower temperature groups had no significant difference from the control. It was therefore concluded that water temperature changes modulated the immune system of L. vannamei. [Copyright &y& Elsevier]