Biofloc Groups Research Articles

Growth performance of critically endangered Hypselobarbus pulchellus in biofloc system: Influence of carbon sources on immune response, enzyme and antioxidant activity

We investigated the effect of various carbon sources on the production performance of critically endangered Hypselobarbus pulchellus in biofloc system. The experimental setup comprised four biofloc treatment groups with various carbon sources (jaggery, tapioca, rice and corn flour) and a control group. Healthy early fry (0.0068 g) was randomly stocked at 100 individuals per m3 into 15 circular fibre reinforced plastic (FRP) tanks (1000 l) and raised for 90 days. All the tested carbon sources significantly influenced weight gain, weight gain (%) and specific growth rate (SGR), with the jaggery treatment displaying the best growth performance (p<0.05). Fingerling survival rates varied from 93 to 95.67% (p>0.05). Compared to the control, the biofloc groups had significantly lower concentrations of nitrogen compounds, specifically total ammonia nitrogen, nitrite and nitrate concentrations were significantly lowered (0.29, 0.35 and 1.32 mg l-1, respectively) in jaggery treatment (p<0.05). In addition, the treatment using jaggery had a higher amount of plankton biomass and an abundance of the Bacillariophyceae group (80%). All biofloc groups displayed enhanced immune and antioxidant activity compared to the control. The jaggery treatment had elevated levels of lysozyme activity than other treatments (p<0.05). Furthermore, fingerlings raised in BFT treatments had significantly higher amylase, protease and lipase activity (p<0.05). Overall, this study’s findings suggest that the addition of various carbon sources significantly improves the production performance, with jaggery as the best carbon source for critically endangered H. pulchellus fingerling production in biofloc system to ensure sustainability. Keywords: Antioxidant activity, Fingerling, Heterotrophic bacteria, Jaggery, Specific growth rate, Sustainability

Effects of bagasse as a carbon source on biofloc formation, water quality, and microbial community structure in shrimp culture system.

As a widely available, low-cost agricultural byproduct, bagasse is a potential solid carbon source and provides microbial attachment as a biofilm carrier. In this study, the effects of bagasse as a carbon source on biofloc formation, water quality, microbial community structure, and nitrogen conversion in a shrimp culture system were explored, and the performance of bagasse bioflocs was assessed. No bagasse was added to the control group (CK), and three bagasse addition groups were set up, with the floc content of the water maintained at 5 mL/L (BF5 group), 10 mL/L (BF10 group), and 15 mL/L (BF15 group). The results showed that bagasse bioflocs formed in the fourth week when bagasse was placed in the culture water, and the surface of bagasse was covered with thick biofilm at that time. The DOC content of the BF15 group was significantly greater than that of the CK group, from 30.31 to 105.06% (P < 0.05), and the DOC increased with increasing bagasse biofloc content. The BF group rapidly converted TAN to NO2--N and then to NO3--N because the accumulation of nitrite nitrogen in the BF15 group occurred 1 week earlier than in the other groups; at the 8th week, the nitrite nitrogen conversion rate of each BF group was close to 100%, which was significantly greater than that of the CK group (P < 0.05). The relative abundances of genes encoding microbial glutamate dehydrogenase and glutamate synthase increased in the bagasse biofloc groups (P < 0.05). The relative abundances of genes from Rhodobacterales and Hyphomicrobiales in each group were greater, but bagasse bioflocs increased the proportion of Hyphomicrobiale. In summary, adding bagasse to the shrimp culture system can form a biofloc system, resulting in the formation of a rich bacterial biofilm on its surface. Bagasse addition not only affects the composition of microbial communities but also accelerates the nitrification process in water. As a result, ammonia and nitrite are converted into nitrate, which is essential for maintaining the stability of the ecosystem balance in aquaculture water.

Effect of dietary protein reduction on growth performance and water quality of the blue streak hap Labidochromis caeruleus (Fryer, 1956) reared in a biofloc system

The 8-week study evaluated the effect of dietary protein reduction on growth performance and water quality of blue streak hap (Labidochromis caeruleus) using biofloc technology (BFT). Fish averaging 0.67 ± 0.13 g in weight were distributed into 15 polyester tanks, each with a water volume of 60 L within 100 L tanks, accommodating 15 fish per tank. Four isolipidic and isoenergetic diets were formulated with gradually decreasing protein levels (40%, 35%, 30%, and 25%). Four biofloc groups (40P + BF, 35P + BF, 30P + BF, and 25P + BF) and control (C) (40P + without BF) were fed twice daily (09:00 and 17:00) at a rate of 5% of their body weight. Molasses was added to the experimental tanks on a daily basis as an organic carbon source. This ensured that the biofloc tanks had a balanced carbon/nitrogen (C/N) ratio and facilitated control of total ammonia nitrogen (TAN), nitrite-nitrogen (NO2-N), and nitrate-nitrogen (NO3-N) levels. The nutritional composition of the bioflocs obtained from the experimental groups revealed that the crude protein and crude lipid contents were 37.00–38.14% and 1.45–1.52%, respectively (P > 0.05). The best specific growth rate (SGR) (1.68%) and feed conversation ratio (FCR) (2.21) were determined in the 35P group. Based on the overall evaluation of the study’s data, it can be concluded that the dietary protein for the blue streak hap (L. caeruleus) can be reduced from 40 to 35% in a biofloc system without any negative effects on health. Improving water quality and providing additional food to fish through zero water exchange and organic carbon addition (BFT) can be considered a sustainable aquaculture technique that can be used in ornamental fish farming.

Influence of in situ Biofloc Production on Bio Growth Performance, Physiological Immune Response, Digestive Enzyme Activity, Nutrient Composition and Disease Resistance of Etroplus suratensis

Backgroud: The present experiment was conducted to investigate the effects of insitu jaggery based biofloc on biogrowth performance, physiological immuno response, digestive enzyme activity, nutrient composition and disease resistance of Etroplus suratensis. Method: The fingerlings of pearlspot, E. suratensis with an average body weight of 5.67±0.08 g was stocked at the rate of 150/m3 in treatment and control system. The insitu biofloc was produced in 2.4 ton capacity outdoor tanks using jaggery as carbon source at two different C: N ratio of viz, 10: 1 (B1) and 20:1 (B2), where clear brackishwater system and without carbon source as control. Result: The levels of ammonia nitrogen, nitrite–nitrogen and nitrate–nitrogen were reduced in the insitu biofloc compared to control while TSS and TS were increased significantly in all insitu biofloc compared to control. The physiological immuno responses such as Respiratory burst test, Myeloperoxidase, serum lysozyme and antioxidant enzymes activity Superoxide dismutase and catalase were found to be significantly higher in B2 at end of the trial. Stress parameters glucose and cortisol were significantly lower in jaggery based biofloc system especially in (B2) C: N 20:1 compared to control. The fishes from the jaggery based biofloc groups possessed significantly (P less than 0.05) higher immune status as compared to control. The digestive enzymes activity such as amylase protease and lipase, of fish was higher in biofloc treatment and lower in control. Compare to control the nutrient composition of E. suratensis was significantly higher in the treatment groups. Moreover, jaggery based insitu fishes showed the lower cumulative mortality rate and Enhanced relative levels of protectio after experimental challenge with A. hydrophila compared to control.

Biofloc supplementation improves growth performances, nutrient utilization, and histological status of Nile tilapia (Oreochromis niloticus) while enhancing zooplankton diversity, community, and abundance

The present work investigates the effect of biofloc supplementation, as an environmentally clean aqua-feed technique, on water quality, growth performance, feed utilization, and histological status of Nile tilapia (Oreochromis niloticus). Moreover, indicators of zooplankton diversity, community structure, abundance, similarities, and cluster analysis were studied during the experiment. A 60-day growth experiment based on biofloc supplementation was performed to evaluate, in addition to the control group (BF0), the effects of five groups of biofloc supplementation (BF1 = 14.20, BF2 = 28.40, BF3 = 42.60, BF4 = 56.80, and BF5 = 71.0 g L−1, respectively) on Nile tilapia juveniles (initial body weight: 13.30 ± 0.01 g fish−1). During the 15 days of acclimation, the juveniles in all groups were fed twice daily on the same control diet (a commercial diet containing 28% protein). Then, the juveniles were randomly distributed to 18 tanks (each 0.5 m3 with a stocking of 40 fish/tank). The feed rate was 3% of the total fish biomass, adjusted weekly. The water quality indicators were in the ideal range recommended for Nile tilapia culture. The results found that the highest weight gain, specific growth rate and survival rate, and the lowest feed conversion ratio of fish were reported in the BF5 group. Moreover, this group achieved the highest zooplankton abundance (20,706 Ind. L−1) compared to the control group (457 Ind. L−1). The results showed that sections of the muscles in the control group (BF0) revealed fibers arranged into bundles. Comparisons between the muscles in the control group (BF0) and the bioflocs groups (BF1–BF5) showed unclear differences. However, sections of the muscle group BF1 showed increased splitting of muscle fibers and the separation of individual muscle fibers into smaller units. The liver showed multiple pathological lesions in all experimental groups (BF0–BF5). Zooplankton diversity indicators and cluster analysis data also reported a significant difference between the control group (BF0) and the biofloc groups, especially the BF5 group. The present study concluded that the addition of biofloc (71 g L−1) to culture ponds significantly improves the growth, feed utilization, and survival rates of Nile tilapia while enhancing zooplankton diversity, community, and abundance.

Effects of Different Carbon Sources on Growth and Some Innate Immune Responses of Russian Sturgeon (Acipenser gueldenstaedtii) in Biofloc Systems

The Russian sturgeon (Acipenser gueldenstaedtii) species is in high demand owing to its valuable caviar. Therefore, it is in danger of extinction. Since the Russian sturgeon reaches sexual maturity late in its life cycle, this species has a high economic cost for farmers. However, this high cost can be reduced with an environmentally friendly system called biofloc technology. This study compared the growth performance and health indicators of biofloc groups using different carbon sources such as starch (BS), molasses (BM) and dextrose (BD). In the 60-day study, fish with an average initial weight of 106.44±5.79 g were stocked in tanks at a density of 21 fish/tank (0.4 m3/tank). The water temperature was set at 19 ℃ degrees throughout the study. On the 30th and 60th days of the experiment, fish were weighted to measure the growth parameters and sampled for immune indices. No mortality was observed in any group throughout the study. A between group comparison of weight gain revealed that BS and BM (105.51±2.26; 100.50±2.18) performed better than the control (BC, without external carbon sources) and BD groups (95.90±2.09; 87.36±2.18) (P&amp;lt;0.05). Furthermore, FCR and SGR were calculated from the data obtained at the end of the experiment, and the data shows that the BS and BM groups were statistically more effective than the other groups. Moreover, a comparison of NBT, lysozyme and myeloperoxidase enzyme activities indicated that all BFT groups had a stronger immune system than the control group (P&amp;lt;0.05). According to the results, the immune-enhancing effect of BFT for sturgeon was determined, and it was reported that BS and BM are more suitable for use in this species in terms of FCR and SGR, as they result an economic and environmentally friendly production.

Influence of the biofloc bacterial community on the digestive activity of Nile tilapia (Oreochromis niloticus)

High-throughput sequencing was performed to study the diversity of bacterial communities in the water of an aquaculture production system using Biofloc technology (BFT) and its effect on the activity of digestive enzymes in Nile tilapia, Oreochromis niloticus. Sex-reversed juveniles were reared in six circular indoor tanks (1 m3) for 12 weeks. The following treatments were performed: biofloc with 0% protein restriction in the diet (BFTH = high protein diet); biofloc with 11% dietary protein restriction (BFTL = low protein diet), and clear water control with 0% dietary protein restriction (CW). Biofloc groups showed a higher bacterial diversity and a completely different composition compared to CW, with significant increase of Actinobacteria and Planctomycetes and a decrease in Verrumicrobia and Fusobacteria. At the genus level, Flavobacterium, Thermomonas, Comamonas, Microbacterium, and Intestinibacter present in BFT significantly correlated with the activity of trypsin, aminopeptidase, and alkaline proteases. Twenty percent of the difference between the biofloc groups was due to the higher activity of acid proteases and aminopeptidases. The metagenome prediction revealed metabolic pathways differentially expressed in BFTH and BFTL. Most were similarly expressed in both treatments; except for the CoA degradation pathway I, which was expressed in BFTL, and the biosynthesis of isoprene II and mevalonate II in BFTH. The biofloc microbiota provided enzymes that, in synergy with the endogenous digestive enzymes of the fish, improved digestion and nutrient assimilation. The study provides knowledge on the exogenous enzymatic contribution and diversity of the bacterial groups present in the biofloc; the contribution of these microorganisms in digestive metabolism and fish performance is also highlighted.

Effect of Stocking Density and Dietary Protein Level in Biofloc System on the Growth, Digestive and Antioxidant Enzyme Activities, Health, and Resistance to Acute Crowding Stress in Juvenile Common Carp (Cyprinus carpio).

This study is aimed at evaluating the effects of stocking densities and dietary protein levels in the biofloc system on the performance of common carp. Fish (12.09 ± 0.99 g) were transferred to 15 tanks: fish reared at 10 kg/m3 as medium density and fed 35% (MD35) or 25% (MD25) protein and fish reared at 20 kg/m3 as high density and fed 35% (HD35) or 25% (HD25) protein in the biofloc system and control fish reared at MD and fed 35% protein in clear water. After 60 days, fish were subjected to crowding stress (80 kg/m3) for 24 h. The growth of fish was highest in MD35. The feed conversion ratio was lower in MD35 compared to the control and HD groups. The amylase, lipase, protease, and superoxide dismutase and glutathione peroxidase activities in the biofloc groups were significantly higher than in the control. After crowding stress, cortisol and glucose levels in biofloc treatments were significantly decreased compared to the control. After 12 and 24 h stress, lysozyme activity in MD35 was significantly lower than in the HD treatments. Overall, the biofloc system with MD could improve growth and robustness against acute stress in fish. Also, biofloc could compensate 10% reduction of protein in common carp juvenile diet when reared in MD.

Influence of dietary C: N: P ratios on Nile tilapia Oreochromis niloticus growth performance and formation of water biotic communities within a biofloc system containment

The present study conducted to evaluate the impact of dietary C: N: P ratios on Nile tilapia, growth induces in biofloc system and formation of water biotic communities. Five isonitrogenous, 30% crude protein and isocaloric 23.35 MJ/kg gross energy were formulated. Diets were equal but with variation of mono ammonium phosphate, NH₄H₂PO₄ levels to obtain different Carbon/Nitrogen/ Phosphorus (C/N/P) dietary ratios. The basal diet had no NH₄H₂PO₄ added (Co) and contain 12:1 N/P ratio. Diets 2–5 each contained NH₄H₂PO₄ at levels of 1.2 (NP10), 3.3 (NP8), 6.8 (NP6) and 13.7 (NP4) g/kg diet, respectively to provide 10:1, 8:1, 6:1 and 4:1 N/P ratios, respectively. Phytoplankton was collected every two weeks during 70 days using 10 L water samples that were sieved via a 10 µm mesh plankton net. The result revealed that the highest growth performance parameters, best nutrients utilization include FCR and PER values were recorded for Nile tilapia fed NP10 diet compared to control treatment. The poorest FCR value was recorded for fish fed the NP6 diet. The phytoplankton community increased with the increasing of dietary phosphate level associated with increasing N: P ratios. On the vice versa, zooplankton showed a remarkable decrease with the increase of phosphate concentrations. The density of aerobic plate count, total Diazotroph, spore forming Diazotroph and lactic acid bacteria increased as the N/P ratio increased to 8:1. The present findings revealed that the fish in the biofloc groups had the best performance and nutrients utilization than the basal diet. However, the positive impacts of BFT technology on growth and feed utilization efficiency of Nile tilapia have been stated.

Application of bioflocculating agent in inoculum enhances quality of biofloc and influences growth, feed utilization and stress responses of GIFT tilapia reared in-situ

An experiment was conducted for in-situ rearing of GIFT tilapia to evaluate the efficacy of bioflocculating agent chitosan at various dosages in the inoculum. Growth and physiological responses of GIFT Tilapia was studied in a biofloc system developed with a bioflocculating agent based inoculum. A dose optimization study was carried out to determine the optimum dose of chitosan in the inoculum using 3 different doses viz. 30, 60 and 90 ppm. Based on the results of dose optimization, the second experiment was conducted using 10, 20 and 30 ppm of chitosan dosage in the inoculum designated as T1, T2, T3, respectively, and one control (without chitosan) with in-situ rearing of tilapia. The tanks (12 Nos) were stocked randomly with an equal number of fishes of initial mean weight (1.70 ± 0.36 g) at 50 numbers per 250 L of water and C: N ratio was maintained at 15:1 using tapioca flour as carbon source. The biofloc developed with the inoculum using 30 ppm (T3) chitosan showed highest floc volume, highest flocculation activity (83.82 ± 1.84%) and highest total suspended solids level (550.67 ± 32.23 mg L - 1). Higher body weight gain (11 g), specific growth rate, feed conversion ratio (1.5) and feed efficiency ratio were observed to be significantly similar for 20 and 30 ppm chitosan supplemented biofloc groups, where as they indicated higher response compared to 10 ppm (T1) and 0 ppm (C) chitosan supplemented group. The activities of amylase was increased in T2 and T3 groups, while the activities of hepatic and gill superoxide dismutase (SOD) and lactate dehydrogenase (LDH) were significantly lower in T1, T2 and T3 groups compared to control. However, activities of protease, lipase and catalase, serum cortisol and glucose were non-significant. The study concluded that the introduction of bioflocculating agent chitosan at a dosage of 20–30 ppm in the inoculum for in-situ biofloc technology can enhance growth, feed utilization, amylase activity and ameliorating stress in GIFT tilapia.

Haematological, serum biochemical and anti‐oxidative enzymes responses of sutchi catfish ( Pangasianodon hypophthalmus ) against Aeromonas hydrophila using various carbon sources in biofloc system

A 90-day experiment was conducted to study haematological, serum biochemical and anti-oxidative enzymes responses of sutchi catfish (Pangasianodon hypophthalmus) fingerlings in biofloc system using various carbon sources. The experiment consisted of four treatments and control (clearwater) having three replicates using three hundred sutchi catfish fingerlings (6.40 ± 0.05 g) in 15 tanks (20 in 100 L). Various carbon sources viz. tapioca, sorghum, pearl millet, and finger millet were assigned as BFT-T, BFT-S, BFT-PM and BFT-FM, respectively. Post-rearing, sutchi catfish were challenged with Aeromonas hydrophila (1 × 107 cfu/ml), and blood and serum parameters were analysed. During pre-challenge condition, significantly (p < 0.05) higher haemoglobin concentration (7.69 ± 0.13 g/dl), total erythrocytes count (1.62 ± 0.02 106 cells/mm3), total leucocytes count (137.34 ± 4.37 103 cells/mm3), packed cell volume (23.93 ± 1.84%) and mean corpuscular volume (142.33 ± 6.80 fL) were observed in BFT-FM as compared to control. The mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration did not differ significantly among the treatments. The serum biochemical parameters were significantly higher in BFT-FM compared to other treatments. The serum glucose (59.44 ± 2.04 mg/dl) and cortisol (50.82 ± 2.21 ng/ml) were significantly lower in BFT-FM than other treatments and control. Serum superoxide dismutase and catalase values increased significantly in biofloc groups when compared with control. The haematological and biochemical values did not differ significantly between the pre- and post-challenge conditions, and stimulated immune response was observed in sutchi catfish against A. hydrophila. The results reveal that finger millet-based biofloc application acts as an immunostimulator; and thereby, reducing the stress and improving haematology and biochemical status of P. hypophthalmus fingerlings.

Effects of Probiotics on Growth, Survival, Water Quality and Disease Resistance of Red Hybrid Tilapia (Oreochromis spp.) Fingerlings in a Biofloc System.

Simple SummaryStreptococcosis, a warm-water pathogenic bacteria, has greatly affected red hybrid tilapia production in Malaysia over the years, causing mass mortality in various culture systems. Probiotics have been used to treat and prevent bacterial diseases, including streptococcosis, yet they require constant application to ensure that their concentration is adequate. Incorporating probiotics in a biofloc system may reduce this issue as the effective microorganism may further flourish and be utilized by the fish. The objectives of this study were to evaluate the influence of probiotic addition on the growth performance and water quality of red hybrid tilapia. From the study, it was observed that a probiotic mix was able to inhibit Streptococcus spp., improve red hybrid tilapia performance and disease resistance against streptococcosis. Providing a beneficial mix of probiotics can effectively improve biofloc culture in red hybrid tilapia culture.Biofloc technology has shown positive effects in aquaculture, especially on the growth performance of cultured animals. The aims of this study were to evaluate the effects of adding different probiotic strains in a biofloc system on the growth performance and disease resistance of red hybrid tilapia (Oreochromis spp.). Three different probiotics (Lysinibacillus fusiformis SPS11, Bacillus amyloliquefaciens L9, and Enterococcus hirae LAB3), commercial probiotics (MG1) and a mixed probiotics (MP) combining all three strains were used in this study. The in vitro assay results showed that the mixed probiotic (MP) was able to inhibit the growth of Streptococcus agalactiae and Streptococcus iniae significantly compared to the single and commercial probiotic. The efficacy of MP was further tested in in vivo tilapia culture challenged with S. agalactiae. The best specific growth rate (3.73 ± 0.23% day−1) and feed conversion ratio (0.76 ± 0.04) were recorded in the group of biofloc with addition of MP. After being challenged with S. agalactiae, the group of biofloc with MP had significantly higher survival (83 ± 1.43%) compared to the other groups. Furthermore, the nitrogen concentration (NO2-N and NH4-N) was significantly lower in all the biofloc groups compared to the control. Hence, the addition of probiotics was able to provide beneficial effects to red hybrid tilapia culture in the biofloc system.

Cellular and molecular immune response and production performance of Indian white shrimp Penaeus indicus (H. Milne-Edwards, 1837), reared in a biofloc-based system with different protein levels of feed

The present study focuses on the immunity and growth of Penaeus indicus fed with varying protein levels (25%, 30%, and 35%) in a biofloc based rearing system. A 120 days growth trial was carried out using juvenile Penaeus indicus (0.71 ± 0.01) with dietary protein level, 25% (LP), 30% (MP), and 35% (HP), and a control diet-fed with 35% acted as control group resulting in 4 treatments each with four replicates and were randomly assigned 16 tank units (7500 L each). A combination of different carbon sources (molasses, wheat flour, and rice bran in 2:1:1 ratio), yeast and a probiotic (Bacillus sp.) consortium were used for the development of biofloc. At the end of the trial, the growth parameters of shrimps viz., initial weight, feed conversion ratio (FCR), and daily growth coefficient (DGC) were computed. The results indicated that shrimp fed with medium (30%) protein (MP) diet recorded significantly (P < 0.05) improved growth performance compared to high protein fed group (35%) and low protein (25%) fed group (LP) in a biofloc system and control group (35%). The immunological parameters such as hemagglutination activity (HA) assay, serum protein, lysozyme, phenol oxidase (PO), and inhibition of superoxide dismutase (SOD) activity were observed in serum, plasma, and hemocyte lysate supernatant (HLS). The HA activity, PO activity in plasma was found to be higher in high protein fed animals, whereas medium protein resulted in enhanced PO activity in serum. Similarly, lysozyme and SOD were inhibited well in high protein fed animals compared to the low protein fed group. The vital immune genes's mRNA profiling showed a potential rise in the expressional pattern in MP and HP treatments compared to LP and control. BGBP (beta-1,3-glucan binding protein) and hemocyanin mRNA transcript levels were highly upregulated in the HP (5 fold) and moderately expressed in MP (2 fold) and LP (1–2 fold). The transcripts of peroxinectin, antimicrobial peptides like crustin showed significant upregulation in HP followed by in MP and LP and control. Likewise, other immune genes, such as SOD, prophenoloxidase (proPO), showed a similar trend in a marginal way, indicating immunomodulation in the biofloc groups. This study suggested that biofloc with high protein (35%) supplementation can substantially enhance the immune response of shrimps, although medium protein level (30%) is optimum for improving the survival, growth, and in turn economic return in Indian white shrimp.

Effect of biofloc technology on growth performance, digestive enzyme activity, proximate composition, and hematological parameters of Asian stinging catfish (Heteropneustes fossilis)

ABSTRACT This investigation aimed to evaluate the effects of the biofloc system on growth, digestive activity, proximate composition, and hematology of Asian stinging catfish for 120 days. Fingerlings (n = 2,700; 4.40 ± 0.10 g) were randomly distributed in six outdoor circular tanks (3,000 L) with supplementary aeration and hand-fed with a commercial diet (35% CP) at 5%–2% of the biomass in the control group and 2%–1% in the biofloc group (sugarcane molasses) to establish a (C/N) ratio 10:1. Ammonia, nitrate, nitrite, and total suspended solids were significantly lower in the BFT than in the control (P < 0.05). Suspended floc significantly ameliorates mean weight gain, percent weight gain, mean total biomass, specific growth rate, and feed utilization compared to the control (P < 0.05). Protease and amylase activity in the intestine and liver lipase activity of fish were found to be significantly higher in the biofloc group (P < 0.05). An improved hematological profile was observed in the biofloc groups (P < 0.05). The crude protein and lipid content was also higher in the biofloc system than in the control. This study indicates that biofloc would be the best alternative approach for sustainable aquaculture production of Asian singing catfish.

Effects of restricted feeding levels and stocking densities on water quality, growth performance, body composition and mucosal innate immunity of Nile tilapia (Oreochromis niloticus) fry in a biofloc system

In aquaculture feed accounts for more than 50% of current costs. Biofloc has the potential to compensate for food reduction, so restricted feeding levels should be investigated to decrease food consumption. The present study conducted to evaluate the effect of restricted feeding levels and stocking densities on water quality, growth performance, body composition and mucosal innate immunity of Nile tilapia (Oreochromis niloticus) fry in biofloc system (BFT). A 5*2 factorial experimental design was used with five restricted feeding levels (0, 15, 30, 45 and 100) and 2 stocking densities(500 fish/m3 and 1000fish/m3) comprising 10 treatments for BFT and for each density there were clear water (CW) system as control with three replicates. Fry with initial weight of 3.2 ± 0.05 g were stocked in tank(40 L), fed three times a day at 8:00, 12:00 and 16:00. Molasses was added to BFT treatments as organic carbon source at a C/N ratio of 15. Results showed that, growth indices (WG, DGR, SGR, FCR), water quality parameters (TAN, NO2, NO3, settled solids and total suspended solids), as well as innate immunity (Total immunoglobulin, Lysozyme and Catalase activity) were improved in biofloc system compared to the CW system. The reduction of feeding rate resulted in significantly decreasing growth performances and immunity among biofloc groups (p < 0.05) except for the group with 15% feed reduction in stocking density of 500/m3. Stocking density had significantly (p < 0.05) reverse effect on growth indices except for the biofloc treatment 1000/m3 without feed reduction. Proximate analysis revealed that by reduction of feeding rate, protein, ash and moisture contents increased, whereas lipid contents decreased significantly (p < 0.05). Survival rate was high (94.8–100%), and no significant differences were seen among treatments (p > 0.05) except for the non-feeding biofloc treatment with stocking density of 1000/m3 (67/9%). Innate immunity was significantly decreased by reduction of feeding rates while, Liver enzyme activity showed an increasing trend by reduction in feeding rate and increasing the stocking density (p > 0.05). These results indicate that the BFT improved water quality, growth performance and immune function of Nile tilapia fry compared to CW system. Also it is possible to decrease 15% daily feeding rate in BFT system. In conclusion, the study suggests the stocking density of 1000/m3 for larviculture of tilapia in BFT to use water and equipment more efficiently.

The enrichment of diet with beneficial bacteria (single- or multi- strain) in biofloc system enhanced the water quality, growth performance, immune responses, and disease resistance of Nile tilapia (Oreochromis niloticus)

The present study examined the influences of dietary single strain (SSP; Lactobacillus plantarum) or multi-strain (MSP; Bacillus subtilis, L. plantarum, L. rhamnosus, L. acidophilus, L. delbrueckii) potential probiotics on Nile tilapia (Oreochromis niloticus) in biofloc (BF) and stagnant-renewal (SR) culture systems. Fish (8.63 ± 3.35 g) were allotted in six groups: T1, SR control; T2, SR + SSP; T3, SR + MSP; T4, BF + MSP; T5, BF + SSP; T6, BF control. After 112 days, water dissolved oxygen (O2), pH, electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), total ammonia nitrogen (TAN), un-ionized ammonia (NH3), and nitrite (NO2) levels were significantly increased while nitrate (NO3) concentrations were decreased under BF condition. Also, bacterial supplements showed significant effects on EC, TAN, NH3, NO2, and NO3 levels. The BF availability remarkably enhanced the activities of digestive enzymes and fish fed SSP-containing diet presented significantly superior weight gain and average daily growth over other diets. A significant effect on amylase activity was detected by probiotic and culture system interactions. Meanwhile, serum total protein, albumin, globulin, total immunoglobulin, superoxide dismutase (SOD), myeloperoxidase (MPO), and respiratory burst activity (RBA) were significantly higher and malondialdehyde and endotoxin were lower for fish stocked in BF system. Additionally, MSP-containing diet significantly promoted serum protease, SOD, catalase (CAT), alkaline phosphatase (AP), MPO, and RBA activities compared to other tested diets. Interestingly, serum alternative complement (ACH50) and lysozyme activities were merely affected by the main effect of probiotics. However, probiotics and culture system found to have individual or combined effects on the intestinal antioxidant enzymes, AP, and pro-inflammatory cytokines (tumor necrosis factor alpha and interleukin-1 beta). Further, tilapia challenged with Aeromonas hydrophila showed reduced mortality in BF groups fed probiotics. The results suggested that the effect of probiotics greatly differed upon the culture condition and the application of multiple strains probiotics had higher efficiency toward immunity than single strain probiotic.

The Effect of Stocking Density and Carbon Sources on the Oxidative Status, and Nonspecific Immunity of Nile tilapia (Oreochromis niloticus) Reared under Biofloc Conditions

Simple SummaryThe present study investigated the effect of stocking density and dietary carbon sources on the water quality, oxidative status and immune-related of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions (BFT). Eight groups were established at two levels of stocking densities (140 fish per m3: low stocking density, LSD) and (280 fish per m3: high stocking density, HSD) (5.15 ± 1.12 g) and kept in eight biofloc units containing water without carbon sources (control groups) or with glycerol, molasses, or starch. Overall, this study has reported that immune response gene expression is better in LSD than HSD and improved by carbon addition. More specifically, based on the overall performances of tilapia reared under LSD or HSD, using molasses is recommended as a carbon source to promote the performances and health status of Nile tilapia cultured in a biofloc system.The present study investigated the effect of stocking density and dietary carbon sources on the water quality, oxidative status, and immune-related genes of Nile tilapia (Oreochromis niloticus) reared under biofloc conditions (BFT). Eight groups were established at two levels of stocking densities (140 fish per m3: low stocking density, LSD) and (280 fish per m3: high stocking density, HSD) (5.15 ± 1.12 g) and kept in eight biofloc units containing water without carbon sources (control groups) or with glycerol, molasses, or starch. Red blood cells count, hemoglobin, and hematocrit values were reduced in fish stocked in control groups at LSD and HSD than biofloc groups. Control fish groups reared at both LSD and HSD have the highest significant (p < 0.05) white blood cells number than other fish groups. Meanwhile, fish groups that received glycerol, molasses, and starch maintained in both LSD and HSD presented a higher significant (p < 0.05) monocyte % than in the control group reared at both LSD and HSD. The fish group reared in biofloc conditions (BFT) using starch carbon source and reared at the HSD presented a significantly higher (p < 0.05) increase in total serum protein and albumin levels as well as globulin value than the control fish group reared at both LSD and HSD. The highest glucose and cortisol levels were showed in the control fish group reared at both LSD and HSD. Fish maintained in glycerol-based biofloc at LSD attained the highest (p < 0.05) serum superoxide dismutase (SOD), glutathione reductase (GR), and catalase than other experimental groups. Regarding the nonspecific immune status, significantly increased expression of CC-chemokines, CXC-chemokines, TLR7 and IL-8 genes was found in molasses based biofloc groups. The data of the present study revealed that using molasses promotes health status of Nile tilapia cultured in a biofloc system.

Influence of Biofloc technology on economic evaluation of culturing Oreochromis niloticus reared at different stocking densities and feeding rates.

The present work aimed to investigate the effect of Biofloc technology at different densities (60 &80 fish/m3) and feeding rates (2% & 3%) of Oreochromis niloticus vs control clear water groups on growth performance and protein utilization, then the estimation of economic evaluation on production scale (3000 m3) based on the output of the present work. A 20-week study was performed from June to October 2019. Triplicate four Biofloc groups vs four control once were used. All Biofloc groups had additional carbohydrates diets composed of molasses and rice brane (1:1) Circular 250 Liter tanks with 200 Liter were used. Results of growth and feed conversion ratio in the present study were used to estimate economic evaluation of production scale (Feddan composed of 3000 m3 net volume). Generally, Biofloc improved growth performance, protein utilization and achieved more estimated net income than clear water groups net income with 9/1 provide of water consumption.

Mannanoligosaccharides as a Carbon Source in Biofloc Boost Dietary Plant Protein and Water Quality, Growth, Immunity and Aeromonas hydrophila Resistance in Nile Tilapia (Oreochromis niloticus).

The aim of the present study was to evaluate mannan oligosaccharides (MOS) or glycerol (GLY) as a carbon source on biofloc systems of Nile tilapia (O. niloticus) juveniles. Fish (n = 750) were reared in open flow (Controls) or biofloc systems (B-GLY and B-MOS) fed with a plant or fish protein source over a period of twelve weeks. Total ammonia nitrogen and nitrate decreased in the biofloc groups, while biofloc volume increased in B-MOS. Compared to the controls, B-MOS and B-GLY exhibited higher weight gain and improved feed conversion, irrespectively of the diet. Serum level of C-reactive protein was reduced, while IgM and lysozyme activity was higher in the B-MOS fish, compared to other groups. Intestinal Bacillus spp. count was increased, whereas Vibrio, Aeromonas and Pseudomonas spp. counts decreased in B-MOS reared groups, compared to the other groups. The proinflammatory cytokine (IL-8 and IFN-γ) transcript expression was upregulated in B-MOS more than B-GLY reared groups. Compared to the controls, the virulence of Aeromonas hydrophila was decreased in the B-MOS and B-GLY groups. The results indicate several benefits of using MOS as a carbon source in a biofloc Nile tilapia system; a cost benefit analysis is required to assess the economic viability of this.

Evaluation of hemato-immunological parameters and stress indicators of common carp (Cyprinus carpio) in different C/N ratio of biofloc system

In spite of various advantages of biofloc technology in aquaculture, few studies have focused on the health status of fish in biofloc system. In this survey, the effect of cane molasses as a carbon source of biofloc system on hemato-immunological parameters, antioxidant status, and stress indicators of common carp (Cyprinus carpio) was investigated. Four hundred and twenty juvenile common carp (40.2 ± 5.76 g) were randomly divided into four equal groups in triplicates as follows: groups A, B, and C were reared in biofloc system with molasses as a carbon source with C/N ratio of 15, 20, and 25, respectively, whereas control group (D) was reared in similar intensity without biofloc system. Fish were reared for 90 days and samples were taken on days 0, 30, 60, and 90 of the experiment. Immunological parameters including serum lysozyme and bactericidal activity, serum complement and IgM level, and NBT reduction and resistance to bacterial challenge as well as hematological parameters (RBC, WBC, hematocrit, hemoglobin) were assessed in experimental groups. Meanwhile, antioxidative enzyme activity (glutathione and superoxide dismutase, catalase) and stress indicators (glucose and cortisol level) were measured and compared among the groups. Water quality parameters were evaluated in all groups. Results showed that most of the immunological parameters as well as resistance against bacterial infection increased in biofloc groups (particularly in C/N = 20 groups) (P < 0.05). Hematological parameters and antioxidative enzyme activity were not affected by biofloc systems. Stress indicators showed a significant decrease in biofloc system, particularly in C/N = 20 group compared with control (P < 0.05). The results indicated that biofloc system (particularly C/N ratio = 20 groups) could not only improve immunological parameters, antioxidative status, and water quality but it decreased stress statues of common carp.