Juvenile Procambarus clarkii farmed using biofloc technology or commercial feed in zero‐water exchange indoor tanks: A comparison of growth performance,enzyme activity and proximate composition

A 60‐day study comparing the growth performance; proximate composition and the digestive, immune and antioxidant enzyme activities of juvenile red swamp crayfish (Procambarus clarkii) reared using biofloc technology (the biofloc group) or a commercial diet (the control group) in zero‐water exchange indoor tanks was performed. A commercial diet was fed to both groups, and the daily feeding amount in the biofloc group was 40% less than that in the control group. Wheat bran and glucose were used in the biofloc group to ensure a C/N ratio >15 and the same feeding energy as that given to the control group. After 60 days of feeding, the final weight, weight gain and specific growth rate in the biofloc group were significantly higher than those in the control group. Furthermore, proximate composition analysis showed that the total hepatopancreatic lipid and ash contents of the biofloc group were significantly higher than those of the control group, and the intestinal and hepatopancreatic pepsin activities in crayfish in the biofloc group were higher than those in crayfish in the control group. Moreover, higher hepatopancreatic lipase and cellulase activities were observed for the biofloc group than for the control group. Biofloc technology promoted the health of the crayfish in terms of their immune and antioxidant enzyme activities. Based on the results of this study, biofloc technology is more effective than traditional commercial diets for the farming of juvenile crayfish.     

Optimum dietary protein‐to‐energy ratio for juvenile whiteleg shrimp,Litopenaeus vannamei,reared in a biofloc system

An 8‐week feeding trial was conducted to evaluate the optimum dietary protein‐to‐energy (P/E) ratio in juvenile whiteleg shrimp, Litopenaeus vannamei. Six diets were formulated with two protein levels (30% and 35%) and three digestible energy levels (16, 17.5 and 19 kJ/g diet) at each protein level (₃₀P₁₆, ₃₀P_17.5, ₃₀P₁₉, ₃₅P₁₆, ₃₅P_17.5 and ₃₅P₁₉). Fifty shrimp averaging 0.97 ± 0.03g (Mean ± SD) were randomly distributed in biofloc tanks and fed one of the experimental diets. Weight gain (WG), specific growth rate (SGR) and feed efficiency (FE) of shrimp fed the ₃₅P_17.5 diet were significantly higher than those of shrimp fed ₃₀P₁₆, ₃₀P_17.5 and ₃₀P₁₉ diets (p < .05). Results for non‐specific immune responses showed that diet ₃₅P_17.5 caused higher lysozyme activity in shrimp comparing to lower protein diets. Thiobarbituric acid reactive substances (TBARS) of plasma were lower for shrimp fed on diets consisting of higher protein and energy levels than shrimp fed on the ₃₀P₁₉ diet. Analyses of digestive enzyme activities showed higher trypsin activities for shrimp fed on ₃₅P_17.5 and ₃₅P₁₉ diets comparing to ₃₀P₁₆ and ₃₀P_17.5 diets. Also, hepatopancreatic lipase activity of shrimp fed ₃₅P₁₆, ₃₅P_17.5 and ₃₅P₁₉ diets were significantly higher than those of shrimp fed the other diets. In conclusion, based on the results for growth performance, biochemical parameters, immune responses, oxidative stress and enzyme activities, 35% protein and 17.5 kJ/g digestible energy (₃₅P_17.5) could be considered as the optimum protein‐to‐energy ratio in the diet of juvenile whiteleg shrimp reared in a biofloc system.     

Rearing of the Pacific white shrimp,Litopenaeus vannamei in a biofloc system: The effects of different food sources and salinity levels

The present study assessed the effects of different types of feeds and salinity levels on water quality, growth performance, survival rate and body composition of the Pacific white shrimp, Litopenaeus vannamei, juveniles in a biofloc system. Shrimp juveniles (2.56 ± 0.33 g) were cultured for 35 days in 300 L fibreglass tanks (water volume of 180 L) with a density of 1 g/L in six treatments. Three sources of feed (100% formulated feed, mixture of 66.6% formulated diet and 33.3% wet biofloc, and 100% wet biofloc) and two levels of salinity (10 and 32 ppt) were considered in two control groups and four biofloc treatments. Water quality parameters in the biofloc treatments were significantly better than control groups (p < .05). The highest increase in growth performance and survival rate were obtained in salinity of 32 ppt and mixed feed sources. Analysing the proximate composition of body shrimp indicates an increase in lipid and ash levels in biofloc treatments, which was more evident in the salinity of 32 ppt. In addition, the proximate analysis of shrimp body showed significant differences between biofloc treatments and control groups (p < .05). The highest FCR was found in the treatment with salinity level of 10 ppt and fed only with floc. Overall, it was found that the artificial diet supplemented with biofloc at the salinity of 32 showed better performance in the juvenile stage of Pacific white shrimp.     

Effects of different carbon sources addition on nutrition composition and extracellular enzymes activity of bioflocs,and digestive enzymes activity and growth performance of Litopenaeus vannamei in zero‐exchange culture tanks

A 35‐day feeding experiment was conducted to investigate the effects of different carbon sources addition on nutritional composition and extracellular enzymes activity of bioflocs, and digestive enzymes activity and growth performance of Litopenaeus vannamei juveniles (average 5.52 ± 0.21 g) in zero‐water exchange culture tanks. Molasses, corn flour and wheat bran were used as carbon sources and added into the tanks to promote the development of bioflocs during the experiment. During the entire experiment, good water quality and biofloc development were achieved under the addition of different carbon sources. At the end of the experiment, the proximate composition and extracellular enzymes activities of the collected bioflocs from seven biofloc groups were influenced by the addition of the different carbon sources. Meanwhile, the specific activities of protease, amylase, lipase and cellulase in the hepatopancreas, stomach and intestine of the shrimp showed differences among the seven biofloc groups, and most of them were significantly higher than those obtained in the control group (P < 0.05). There were differences in the performance (growth and FCR) of the shrimp among the seven biofloc groups, and all of them were significantly better than those obtained in the control group (P < 0.05). Based on the results of this study, 60% molasses + 20% corn flour + 20% wheat bran could be an appropriate formula of the addition of carbon sources for intensive culture of L. vannamei (mainly in terms of growth and FCR) in zero‐water exchange culture tanks.     

Effect of low salinity on microbial floc composition and performance of Litopenaeus vannamei (Boone) juveniles reared in a zero‐water‐exchange super‐intensive system

This study aimed to evaluate the effect of low salinity on the water quality, microbial flocs composition and performance of Litopenaeus vannamei juveniles reared over 40 days in a zero‐water‐exchange super‐intensive system at 0, 2, 4 and 25 g L^?1. At 0 g L^?1, the mortality was total at the 26th day, and consequently, these salinity data were not included in the statistical analysis. Among the water quality parameters, only pH and the total suspended solids concentration were significantly influenced by salinity. However, a trend towards intensification of the nitrification processes was observed as the salinity increased, with the lowest ammonia and the highest nitrite and nitrate concentrations found at 25 g L^?1. The concentrations of ciliates and flagellates diminished and increased, respectively, with the increase in salinity. Diatoms predominated at 25 g L^?1, whereas at 2 and 4 g L^?1, chlorophytes were more abundant. Microbial floc crude protein content was reduced with the increase in salinity, whereas ash content demonstrated the inverse trend. The best overall growth performance and survival were observed at 25 g L^?1. However, satisfactory productivity was also found at 4 g L^?1, suggesting the viability of rearing L. vannamei at low salinity under zero‐water‐exchange conditions.     

Effects of different dietary lipid levels and fatty acids profile in the culture of white shrimp Litopenaeus vannamei (Boone) in biofloc technology: water quality,biofloc composition,growth and health

The objective of this study was to evaluate the influence of different dietary lipid and fatty acids on the nutritional value of bioflocs used as a feed, as well as shrimp performance and health. A total of 1800 Litopenaeus vannamei juveniles (2.87 ± 0.01 g) were cultured in biofloc technology, with a density of 200 shrimp m^?2, and fed with three isoproteic experimental diets at different lipid levels (85 g kg^?1, 95 g kg^?1 and 105 g kg^?1); each treatment was performed in triplicate. After 61 days, no significant difference was observed (P > 0.05) among the water quality parameters. For the shrimp performance, significant difference was observed (P = 0.011) among the values of survival, where treatments with lower lipid levels had higher survival (92.5 ± 3.5% and 91.0 ± 2.5%). Although there are significant differences in survival, no significant differences in the total haemocytes count (THC) were observed. For other growth performance, no differences were observed (P > 0.05). A positive correlation (r = 0.75) has been observed between the dietary oleic acid and bioflocs. The bioflocs showed ‘long‐chain’ polyunsaturated fat acids (lcPUFA), especially arachidonic acid. The shrimp showed similar growth and stayed healthy at the end of the experimental period.     

Effect of carbon and nitrogen ratio (C:N) manipulation on the production performance and immunity of Pacific white shrimp Litopenaeus vannamei (Boone, 1931) in a biofloc‐based rearing system

A 16‐week indoor culture trial was conducted to evaluate the effect of varying C:N ratio on growth performance, physico‐chemical parameters, microbial dynamics, feed utilization, and immunological parameters. The experiment comprised of five biofloc treatment groups (with varying C:N ratio 5:1, 10:1, 15:1, 20:1) and a control with three replicates each, having 100 nos/m³ as stocking density in 500 L tanks with constant aeration. The C:N ratios of the treatments were manipulated using molasses as an organic carbon source whereas there was no carbon source added in control. The water quality parameters monitored throughout the experiment were found to be within permissible limits in shrimp culture. At the end of the experiment, it was observed that there were significant differences between the treatment groups and the control regarding absolute growth, SGR, FCR, PER, and FER. Furthermore, a considerable difference in immunological parameters, namely, THC, phagocytosis, and PO activity (17.5 × 10⁶ cells per ml, 43.5%, 0.112 Units min^?1 mg min^?1), was recorded among the treatments compared to that of the control groups (6.2 × 10⁶ cells per ml, 31.5%, 0.051 Units min^?1 mg min^?1) respectively. Enhanced growth and survival with substantial disease resistance were recorded in C15 treatment. The results indicate that the CN15 ratio coupled with minimal water exchange is optimal for improved survival, growth, and immune activity.     

Nitrogen budget for a low salinity, zero-water exchange culture system: I. Effect of dietary protein level on the performance of Litopenaeus vannamei (Boone)

A 4‐week study was conducted to evaluate the effects of different dietary protein levels (25%, 30%, 35% and 40%) on the growth and survival of juvenile Litopenaeus vannamei raised in a low salinity (4.6 g L⁻¹), zero‐water exchange culture system, as well as on the nitrogen budget and ammonia efflux rate. No significant differences were observed among the dietary treatments for final weight, weight gain or survival of shrimp, although the best performance was observed in the 25% protein treatment group. Both weight and survival decreased as the dietary protein increased. Significant differences (P<0.05) were observed in the ammonia concentration among dietary treatments during the first 2 weeks of the experiment. The highest concentration was measured in the 40% dietary protein treatment (5.88 mg NH4‐N L⁻¹). The nitrogen budget showed that the nitrogen loss increased as the dietary protein increased under the experimental conditions; the largest amount of nitrogen recovered as shrimp biomass (42.9%) was in the 25% protein treatment group, and the largest amount of unaccounted nitrogen (39.5%) was in the 40% protein treatment. Under these conditions, utilization of low‐protein diets resulted in better performance, presumably because they provided more carbon for heterotrophic bacteria and reduced the nitrogen loading of the system.     

Evaluation of ultra‐low gossypol cottonseed and regular glandless cottonseed meals as dietary protein and lipid sources for Litopenaeus vannamei reared under zero‐exchange conditions

The current study evaluated transgenic cotton lines with normal levels of gossypol/terpenoids in the vegetative and floral tissues, but with ultra‐low gossypol in the seeds as a replacement for glandless cottonseed meal (GCSM) and fishmeal. A 64‐day growth trial evaluated the ability of cottonseed meals from a natural glandless cotton variety/mutant, two transgenic Ultra‐low Gossypol Cottonseed (ULGCS) lines, a non‐transgenic parental control and a commercial variety, to replace 355 g kg^?1 fishmeal in a diet containing 350 g kg^?1 crude protein. Juvenile Litopenaeus vannamei (1.48 ± 0.29 g) were stocked (40 shrimp m^?3) with six replicates. No significant differences were found between all formulated diets in terms of final weight, survival and feed conversion ratio. The commercial cottonseed variety displayed a significantly lower feed efficiency ratio and protein efficiency ratio than one of the ULGCS diets. These results suggest that GCSM and/or transgenic ULGCS meals can be used to replace fishmeal in commercial shrimp diets.     

Effect of the C/N ratio on inorganic nitrogen control and the growth and physiological parameters of tilapias fingerlings,Oreochromis niloticu reared in biofloc systems

The objective of this study was to document the effects of different C/N ratios on inorganic nitrogen control and the growth and health of tilapia (Oreochromis niloticus) fingerlings reared in biofloc systems. The fish (0.50 ± 0.02 g) were randomly assigned to the control group (clear water) or to one of three biofloc groups (added glucose) with a C/N ratio of 10, 15, or 20 (CN‐10, CN‐15, or CN‐20, respectively). All four groups were cultured for 120 days. The inorganic nitrogen dynamics showed that heterotrophic and autotrophic bacteria existed in the low C/N ratio group, and heterotrophic bacteria dominated the high C/N ratio group. In addition, growth was significantly better in the CN‐10 and CN‐15 groups (15.67 ± 0.78 g and 14.75 ± 0.54 g, respectively) compared to the CN‐20 (13.04 ± 0.94 g) and control (13.04 ± 0.46 g) groups (p < .05). Activities of the digestive enzymes lipase and trypsin were significantly higher in the CN‐10 and CN‐15 groups than in the control group (p < .05). In addition, activities of lysozyme, alkaline phosphatase, superoxide dismutase, glutathione and malondialdehyde were significantly higher in the CN‐10 and CN‐15 groups than in the control group (p < .05). Finally, the concentrations of glucose and cortisol in the biofloc systems were significantly lower than those in the control group (p < .05). However, the concentrations of triglyceride, aspartate transaminase and alanine aminotransferase did not differ significantly among the four groups (p > .05). At the end of the trial, an acute crowding and hypoxia stress test performed for 3 days showed that the CN‐10 and CN‐15 groups had the best survival.     

Effect of dietary protein level on growth, survival and ammonia efflux rate of Litopenaeus vannamei (Boone) raised in a zero water exchange culture system

Litopenaeus vannamei postlarvae (1.96±0.07 g) were reared in a zero water exchange system for 25 days at 28°C. They were fed four commercial diets containing 25%, 30%, 35% or 40% crude protein in three replicate aquaria per dietary treatment. Total ammonia, nitrite, nitrate and pH were monitored weekly and total ammonia levels were additionally measured every 3 days using the flow injection analysis method. Total ammonia efflux rates were measured at days 0, 14 and 21, and survival and growth rates were recorded at the end of the experiment. No significant differences between water quality parameters such as temperature, salinity, dissolved oxygen and pH were found. Nitrite concentration remained low in all dietary treatments up to the second week increasing considerably from day 14 onwards suggesting the initiation of the nitrification process. Water total ammonia of all experimental groups exhibited a gradual increase up to day 13; however, following this time ammonia levels of all experimental groups decreased, probably due to either the action of bacterial nitrification or ammonia‐N uptake by the animals. High ammonia efflux rates were recorded at day 14, especially after the first hour of immersion in the 25% protein group, but no significant changes occurred in any experimental group after 3 h. No significant differences in weight gain, final weight or survival of shrimp were observed under these experimental conditions. The importance of zero water exchange systems and their effects on the nitrogen metabolism of crustaceans are discussed.     

Artificial substrates in zero‐water‐exchange culture system regulate the rearing performance of Pacific white shrimp Litopenaeus vannamei (Boone, 1931) under the winter indoor condition

Effects of artificial substrates in zero‐water‐exchange culture system on the rearing performance of Litopenaeus vannamei under winter indoor condition were investigated in this study. Growth, survival, feed conversion rate (FCR), production rate of L. vannamei and water quality were compared between artificial substrate‐treated group (AST) and control group (without artificial substrates presented in the rearing environment). Artificial substrates can significantly improve the water quality, the ammonia and nitrite‐N concentrations in the AST group were significantly lower than in the control group (P < 0.05), and the total heterotrophic bacteria and Vibrio spp. were also significantly lower in the AST group (P < 0.05). The survival, growth and production rate of L. vannamei in the AST group were significantly higher than in the control group (P < 0.05). Significantly lower FCR was observed in the AST group (P < 0.05). Results from this study indicate that the utilization of artificial substrates in the indoor shrimp culture system could effectively control the water quality, improve the survival and growth of shrimp and significantly reduce the FCR. This study provides a guideline for employing artificial substrates in rearing of shrimp in the zero‐water‐exchange culture system under lower temperature, which could be applicable to other similar species.     

Nitrogen budget for a low-salinity, zero-water exchange culture system: II. Evaluation of isonitrogenous feeding of various dietary protein levels to Litopenaeus vannamei (Boone)

This study evaluated the effects of isonitrogenous feeding (60 g dietary protein per kilogram of body weight per day) using experimental feeds with 25%, 30%, 35% and 40% protein on the nitrogen budget, ammonia efflux rate, growth and survival of juvenile Litopenaeus vannamei raised in a low-salinity (4 g L⁻¹) zero-water exchange culture system for 4 weeks. No significant differences in weight gain or instantaneous growth rate were observed between the dietary treatments with 35% and 40% protein after 3 weeks of study, or between treatments with 25% and 30% protein after 4 weeks of study. High mortality rates were observed for the 35% and 40% protein treatments, probably associated with high nitrite levels (4.80 and 7.36 mg NO₂-NL⁻¹ respectively) in water. Among the various dietary treatments, 39–46.3% of feed nitrogen was converted to shrimp biomass, 32.8–38.0% and 14.4–39.9% remained within the system as organic and inorganic nitrogen, respectively, and 32.5–39.3% was unaccounted for. The results of the present study showed high nitrogen utilization efficiencies. However, as the nitrogen loading of the zero-water exchange system increased, so did the nitrogen excretion of shrimp, causing a deteriorated general condition of the shrimp, demonstrated by the low ammonia efflux rates recorded at the end of the trial. This study confirms that low-salinity closed systems are particularly susceptible to nitrogen loading. Thus, in these culture systems, low-protein feeds may perform better as they provide more carbon for heterotrophic bacteria and less nitrogen to be degraded and transformed into nitrogenous wastes.     

Effects of soy protein ratio,lipid content and minimum level of krill meal in plant‐based diets over the growth and digestibility of the white shrimp,Litopenaeus vannamei

This study evaluated the effects of soy protein ratio, lipid content and the minimum dietary level of krill meal in plant‐based diets over the growth performance and digestibility of Litopenaeus vannamei. Nine plant‐based diets varied the soybean meal (SBM) and soy protein concentrate (SPC) inclusion ratio at 1 : 2.3, 1 : 1 and 2.5 : 1, and their dietary lipid content at 121.4 ± 9.4, 102.3 ± 1.2, and 79.9 ± 1.2 g kg^?1 (in a dry matter basis). An additional diet containing 120 g kg^?1 of fish meal (salmon by‐product) was used as a control. Krill meal was included at 0, 5, 10, 20 and 30 g kg^?1 in a new set of plant‐based diets. After 10 weeks in clear‐water tanks of 0.5 m³, no effect of SBM:SPC ratio and dietary lipid content was detected on shrimp survival. However, dietary lipid levels of 80 and 121 g kg^?1 combined with a high SPC to SBM resulted in the lowest final body weight and the poorest apparent crude protein digestibility, respectively. Krill meal increased feed intake at only 10 g kg^?1, while at 20 g kg^?1, it accelerated shrimp growth, increased yield and reduced food conversion ratio.     

The effect of soybean oil containing stearidonic acid on growth performance,n‐3 fatty acid deposition and sensory characteristics of pacific white shrimp (Litopenaeus vannamei)

The ability of shrimp Litopenaeus vannamei to utilize soy oil (SO) modified to contain stearidonic acid (SDA) in replacement of fish oil (FO) by converting SDA to highly unsaturated fatty acids (HUFA) was examined. Six diets with either supplemental modified SO or FO and three levels of fishmeal (FM) replacement (0%, 50% and 100%) by soybean meal (SBM) were fed to shrimp (1.7 g) for 12 weeks. The effect of oil source at the three SBM levels on growth and fatty acid profiles was examined by contrast analysis and sensory attributes by t‐tests (5% error rate). At 0% SBM inclusion, there was no effect of dietary oil source, while at the highest SBM inclusion level, shrimp fed the FO diet outperformed those fed the corresponding SO diet. Oil source had no effect on sensory attributes. The fatty acid profiles of the shrimp reflected that of the diets. SDA SO can replace supplemental FO in diets for shrimp with no reduction in growth when there is sufficient oil present from FM. At low FM, however, replacing FO with SDA SO reduces shrimp performance and tissue n‐3 HUFA levels. It is concluded that SDA is unable to meet the essential fatty acid needs of shrimp.     

Effects of biofloc under different carbon sources and protein levels on water quality,growth performance and immune responses in black tiger shrimp Penaeus monodon (Fabricius, 1978)

A 75‐day 2 × 3 factorial experiment was conducted to evaluate the effect of two levels of dietary protein (32 and 40%) and two different carbon sources (rice flour–R and molasses‐M), and without carbohydrate (control–C) in black tiger shrimp Penaeus monodon juveniles (3.37 ± 0.04 g) at 100 nos. m^?3 in 100 L fibre reinforced plastic tanks. Biofloc volume and total suspended solid were higher in molasses added groups (32 + M and 40 + M) followed by rice flour (32 + R and 40 + R) and controls (32C and 40C). Molasses and rice flour addition significantly reduced (P < 0.01) the total ammonia–N compared to controls. The highest Vibrio, Bacillus and Lactobacillus counts were recorded in 40 + M, 32 + M and 32 + R respectively. Among the treatments, significantly higher (P < 0.01) final body weight was recorded in 40 + R (8.5 ± 0.3 g), 40 + M (7.8 ± 0.3 g) and 32 + R (7.5 ± 0.4 g) compared to control groups, 32C (6.1 ± 0.3 g), 40C (6.4 ± 0.3 g) and molasses added group, 32 + M (5.7 ± 0.4 g). Rice flour supplementation significantly increased (P < 0.01) the total haemocyte count (×10⁶ cells mL^?1) in 32 + R (45.7 ± 3.7) and 40 + R (44.3 ± 3.1) compared to controls, 32C (27.3 ± 3.4) and 40C (25.8 ± 0.9). Similarly, higher superoxide dismutase, catalase, serum protein and glucose were recorded in the rice flour added groups, 40 + R followed by 32 + R. Among the treatments, the highest level of prophenoloxidase (OD 490 nm, 0.3 ± 0.0) and survival after challenge with Vibrio harveyi (55.6%) was observed in 32 + R. The study elucidates that rice flour addition produces optimum level of biofloc with better growth and immune responses compared to molasses and control. Furthermore, rice flour addition at 32% protein level could replace 40% protein feed.     

Dietary 5‐aminolevulinic acid enhances adenosine triphosphate production,ecdysis and immune response in Pacific white shrimp,Litopenaeus vannamei (Boone)

Previous studies have shown that 5‐aminolevulinic acid (5‐ALA), a precursor of haem, can enhance haem synthesis and the activity of haemoproteins. Here, we investigated the effects of dietary 5‐ALA on Pacific white shrimp, Litopenaeus vannamei (Boone). Dietary groups included basal diet (BD, control) and BD plus 15, 30 and 60 ppm 5‐ALA (ALA15, ALA30 and ALA60 respectively). Hepatopancreas adenosine triphosphate (ATP) levels increased with increasing 5‐ALA concentration (ALA60 p < 0.05) after 2 weeks of feeding. 5‐aminolevulinic acid diets significantly increased the expression of ecdysis‐related genes: nuclear receptor E75 and chitinase 4 (ALA15, ALA30, ALA60), cytochrome P450 Shade (ALA60), chitinase 1 (ALA60) and chitinase 3 (ALA15, ALA60). Catalase (CAT) and prophenoloxidase gene expression levels were also significantly higher in ALA60 after 12 weeks of feeding. Six hours after L. vannamei were exposed to Vibrio parahaemolyticus, total haemocyte count (ALA60) and gene expression levels of CAT (ALA30, ALA60) were significantly higher in 5‐ALA groups compared to the control. 5‐aminolevulinic acid diets also increased survival of L. vannamei following V. parahaemolyticus immersion challenge. These results suggest that supplementing L. vannamei diets with 5‐ALA can enhance ATP production, immune response against V. parahaemolyticus, total haemocyte count and expression of some immune‐related genes. 5‐aminolevulinic acid can also induce ecdysis‐related gene expressions, without adversely affecting growth.     

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.     

Use of biofloc technology during the pre‐maturation period of Litopenaeus vannamei males: effect of feeds with different protein levels on the spermatophore and sperm quality

The objectives of this study were: (1) Compare two systems for pre‐maturation of Litopenaeus vannamei in terms of spermatophore and sperm quality, (2) Compare the effect of feeds with different protein levels on reproductive quality of males reared in a biofloc‐dominated system. Animals (36.40 ± 3.13 g) reared under biofloc technology (BFT) were used in the 30‐day experiment, which involved four treatments: one in a clear water system (CW) and other three in a BFT system. The BFT treatments were differentiated by feed: mix of fish, squid and crab (BFT+FF) composed of 68.48% dietary protein (DP); broodstock feed (BFT+BF) composed of 52.51% DP; and juvenile feed (BFT+JF) composed of 39.91% DP. Feed in the CW was also the mix of fresh food. Spermatophore and sperm quality were analyzed at the beginning and end of the experiment. Higher normal sperm rate was recorded in the CW compared with the BFT+FF. Among the BFT treatments, the BFT+FF had the lowest normal sperm rate. Thus, the use of BFT for pre‐maturation of L. vannamei allowed the reduction in dietary protein levels from 68.48% (BFT+FF) to 39.91% (BFT+JF) and the maintenance of spermatophore and sperm quality compared to the system based on high daily exchange rate.     

Evaluation of carbohydrate‐to‐lipid ratio in diets supplemented with Bacillus subtilis probiotic strain on growth performance,body composition and digestibility in juvenile white seabass (Atractoscion nobilis,Ayres 1860)

This study aimed to evaluate the effect of increasing the carbohydrate to lipid ratio in diets supplemented with Bacillus subtilis in white seabass (Atractoscion nobilis) juveniles on digestibility, growth performance, feed utilization efficiency and tissue composition. Four experimental isoenergetic and isoproteic diets supplemented with B. subtilis were formulated with increasing starch to lipid ratios (g/g) of 10:19; 14:17; 18:15 and 22:13 (diets PD10, PD14, PD18 and PD22 respectively). A negative control diet for B. subtilis supplementation was also formulated to be similar to diet PD10 (diet CD10). Each experimental diet was fed to triplicate groups of 20 fish per tank (IBW: 9.5 g), three times a day, to apparent satiation, for 60 days. Supplementation with B. subtilis, of the low starch‐high lipid diet (10:19), significantly enhanced the overall growth performance, digestibility and feed efficiency. Moreover, the increase in starch to lipid ratio, in supplemented probiotic diets, significantly increased growth performance, feed intake, feed utilization efficiency and protein and energy digestibility, being maximum for the highest dietary starch to lipid level. Lipid content of whole body, muscle and liver and hepatosomatic index significantly increased with the increase in starch to lipid ratio. The results of this study indicate that B. subtilis supplementation significantly enhanced growth performance, digestibility and feed utilization of low starch‐high lipid diet. However, further improvement of growth performance and feed utilization efficiency may be achieved combining B. subtilis supplementation with increased dietary starch to lipid ratio to 22:13.