Effects of biofloc on growth performance, digestive enzyme activities and liver histology of common carp (Cyprinus carpio L.) fingerlings in zero-water exchange system

Insights into chlorantraniliprole exposure via activating cytochrome P450-mediated xenobiotic metabolism pathway in the Procambarus clarkii: Identification of P450 genes involved in detoxification

To investigate the impact of chlorantraniliprole on Procambarus clarkii, acute toxicity tests were performed. Results indicated that 96 h post-exposure to chlorantraniliprole (60 mg/L) led to the separation of the hepatopancreas basement membrane, causing cell swelling, rupture, and vacuolation. Moreover, acid phosphatase (ACP) and alkaline phosphatase (AKP) activities exhibited divergent trends across four concentrations of chlorantraniliprole (0, 30, 60, and 90 mg/L). Hydrogen peroxide (H2O2) and catalase (CAT) levels significantly increased, while total superoxide dismutase (T-SOD) and malonaldehyde (MDA) activities decreased, indicating oxidative stress in the hepatopancreas. A total of 276 differentially expressed genes (DEGs) were identified, with 204 up-regulated and 72 down-regulated. Out of these, 114 DEGs were successfully annotated and classified into 99 pathways, with a primary focus on the cytochrome P450-mediated xenobiotic metabolism pathway. The DEGs enriched in this pathway, along with transcriptome data, were validated using quantitative-polymerase chain reaction. This study enhances the transcriptome database of P. clarkii and provides fundamental insights into its immune defense and antioxidant mechanisms. Additionally, it lays a theoretical foundation for future research on disease prevention in P. clarkii within rice-shrimp culture systems.

Effects of dietary powdered Ficus deltoidea on the growth and health performance of African catfish, Clarias gariepinus production

Intensive aquaculture causes a decline in the health status of fish, resulting in an increased disease incidence. To counteract this, feed additives have been utilized to improve the growth performance and health of aquaculture species. This work specifically investigates the impact of powdered Ficus deltoidea (FD) on various parameters related to growth, blood parameters, liver and intestine morphology, body proximate analysis, digestive enzymes, antioxidant capacity, and disease resistance to motile Aeromonad Septicemia (MAS) caused by Aeromonas hydrophila infection in African catfish, Clarias gariepinus. Four formulated diets were prepared: T1 (0% FD), T2 (0.5% FD), T3 (0.75% FD), and T4 (1% FD). After 8 weeks, the African catfish's growth performance fed with the T2 diet exhibited a substantial improvement (p < 0.05), along with a remarkably lower (p < 0.05) feed conversion ratio (FCR) when compared to the other treatment groups. Blood parameter analysis revealed notably higher (p < 0.05) levels of white blood cell (WBC), lymphocytosis (LYM), hemoglobin (HGB), albumin (ALB), globulin (GLOB), as well as total protein (TP) in the T2 diet group. While all treatment groups displayed normal intestinal morphology, liver deterioration was observed in groups supplemented with higher FD. The T2 diet group recorded the highest villus length, width, and crypt depth. Protease and lipase levels were also notably improved in the T2 diet group compared to other treatment groups. Additionally, catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were remarkably elevated in all FD diet groups than in the control group. The expression of immune-related genes, including transforming growth factor beta 1, heat shock protein 90, nuclear factor kappa-B gene, and lysozyme G, was upregulated in all treatments. Overall, the results of this study indicate that incorporating dietary FD at 0.5% concentration in the diet of African catfish may enhance their productivity in intensive farming.

Growth and survival of Betta splendens fed microbial aggregates from ex-situ biofloc technology (BFT)

The betta (Betta splendens) is a carnivorous ornamental species that requires live food. In this study, we evaluated the growth and survival of Betta splendens fingerlings fed ex-situ biofloc (BFT). A total of 375 fingerlings (8.3 ± 4.1 mg and 0.8 ± 0.14 cm) were distributed into 15-L plastic tanks (n=25), with five replicates for each of the following treatments: (i) exclusive live food (LF100), (ii) exclusive biofloc (BFT100), (iii) live food supplemented with biofloc (LF100-BFT100), and a reduction of 15% (iv) and 30% (v) in live food with biofloc supplementation (LF85-BFT100 and LF70-BFT100, respectively). The fish were fed newly hatched brine shrimp (Artemia spp. nauplii) and/or fresh biofloc, twice daily, over a 16-day experimental period. Dietary supplementation of Beta splendens with ex-situ BFT (LF100-BFT100, LF85-BFT100, and LF70-BFT100) resulted in a similar final weight (P>0.05) compared to exclusive brine shrimp (LF100). Regarding total length, the fish in the LF100-BFT100 group were superior to those in the LF100 group (P<0.05). The LF100 and LF100-BFT100 groups showed survival rates of 100% and 98.4%, respectively, which were not statistically different (P>0.05). For all analyzed variables, fish exclusively fed biofloc (BFT100) exhibited unfavorable performance. These results indicate that dietary ex-situ biofloc supplementation, without reducing the supply of live food, can be an interesting alternative in the rearing of Betta splendens since biofloc improves growth performance and maintains a good survival rate.

Biofloc Technology (BFT) in Aquaculture: What Goes Right, What Goes Wrong? A Scientific-Based Snapshot

Aquaculture is a crucial industry that can help meet the increasing demand for aquatic protein products and provide employment opportunities in coastal areas and beyond. If incorrectly manage, traditional aquaculture methods can have negative impacts on the environment and natural resources, including water pollution and overuse of wild fish stocks as aquafeed ingredients. Biofloc technology (BFT) may offer a promising solution to some of these challenges by promoting a cleaner and sustainable production system. BFT converts waste into bioflocs, which serve as a natural food source for fish and shrimp within the culture system, reducing the need for external inputs, such as feed and chemicals. Moreover, BFT has the potential to improve yields and economic performance while promoting efficient resource utilization, such as water and energy. Despite its numerous advantages, BFT presents several challenges, such as high energy demand, high initial/running costs, waste (effluent, suspended solids, and sludge) management, opportunistic pathogens (vibrio) spread, and a lack of understanding of operational/aquatic/microbial dynamics. However, with further training, research, and innovation, these challenges can be overcome, and BFT can become a more widely understood and adopted technique, acting as an effective method for sustainable aquaculture. In summary, BFT offers a cleaner production option that promotes circularity practices while enhancing performance and economic benefits. This technique has the potential to address several challenges faced by the aquaculture industry while ensuring its continued growth and protecting the environment. A more broad BFT adoption can contribute to meeting the increasing demand for aquaculture products while reducing the industry's negative impact on the environment and natural resources. In this context, this review provides an overview of the advantages and challenges of BFT and highlights key technical, biological, and economic aspects to optimize its application, promote further adoption, and overcome the current challenges.

Health Risk Assessment and Comparative Studies on Some Fish Species Cultured in Traditional and Biofloc Fish Farms

The present study aimed at (a) determining the concentration of macro-minerals and toxic metals in fish species collected from biofloc and traditional fish farms; (b) assessing the contribution of macro-minerals to our daily diet; and (c) evaluating the health risks of children and adults based on the US Environmental Protection Agency (USEPA) deterministic model. Significantly higher concentrations of macro-minerals and significantly lower levels of toxic metals (at < 0.05 level) were found in most of the biofloc fish species compared to the market fish samples. The values of the target hazard quotient (THQ) were less than 1.0 for all individual trace metals in all species, which indicated that there were no noncarcinogenic health risks. Furthermore, the value of the hazard index (HI) in three samples of Tilapia from the market exceeded the recommended value of 1.0, while all samples from the biofloc fish tank were within the maximum tolerable limit, which suggested that the daily consumption of Tilapia fishes from the market may result in considerable harmful effects. Target cancer risk (TCR) for Pb in all of the studied samples was within the range of 10^-6 and 10^-4, hence the adults and children would not experience any kinds of carcinogenic effects. The result obtained from this comparative study revealed that the consumption of fish species from both local market and biofloc fish farms was almost safe, but the value of TCR in Pb was higher in traditional fish samples than that of biofloc tanks, hence fish samples from biofloc farms were more suitable for consumption.

A detailed look at the impacts of biofloc on immunological and hematological parameters and improving resistance to diseases

The innate immunity of invertebrates serves as a critical trait that provides a valuable foundation for studying the common biological responses to environmental changes. With the exponential growth of the human population, the demand for protein has soared, leading to the intensification of aquaculture. Regrettably, this intensification has resulted in the overuse of antibiotics and chemotherapeutics, which have led to the emergence of resistant microbes or superbugs. In this regard, biofloc technology (BFT) emerges as a promising strategy for disease management in aquaculture. By harnessing the power of antibiotics, probiotics, and prebiotics, BFT offers a sustainable and eco-friendly approach that can help mitigate the negative impacts of harmful chemicals. By adopting this innovative technology, we can enhance the immunity and promote the health of aquatic organisms, thereby ensuring the long-term viability of the aquaculture industry. Using a proper carbon to nitrogen ratio, normally adding an external carbon source, BFT recycles waste in culture system with no water exchange. Heterotrophic bacteria grow along with other key microbes in the culture water. Heterotrophs play a major role in assimilating ammonia from feed and fecal waste, crucial pathway to form suspended microbial aggregates (known as 'biofloc'); while chemoautotrophs (e.g. nitrifying bacteria) oxidize ammonia into nitrite, and nitrite into nitrate promoting a healthy farming conditions. By using a highly aerated media and an organic substrates that contain carbon and nitrogen, protein-rich microbes are able to flocculate in culture water. Several types of microorganisms and their cell components have been studied and applied to aquatic animals as probiotics or immunostimulants (lipopolysaccharide, peptidoglycan, and 1-glucans) to enhance their innate immunity and antioxidant status, thereby enhancing their resistance to disease. In recent years, many studies have been conducted on the application of BFT for different farmed aquatic species and it has been observed as a promising method for the development of sustainable aquaculture, especially due to less use of water, increased productivity and biosecurity, but also an enhancement of the health status of several aquaculture species. This review analyses the immune status, antioxidant activity, blood and biochemical parameters, and level of resistance against pathogenic agents of aquatic animals farmed in BFT systems. This manuscript aims to gather and showcase the scientific evidences related to biofloc as a 'health promoter' in a unique document for the industry and academia.

Biofloc Technology in Fish Aquaculture: A Review

The application of biofloc to fish species has several advantages, including the enhancement of production by increasing growth performance and survival rate and the improvement of fish aquaculture physiological activity. There has been a recent increase in biofloc addition to fish culture, and this review examines changes this causes to the survival and growth rate of fish and its economic feasibility. Physiological activity and disease resistance of biofloc-fed fish is being extensively studied. The hematological parameters and antioxidant and immune responses of fish fed biofloc were reviewed in this study, as well as their disease resistance by testing them for major specific diseases. Standards for effectively applying biofloc to fish aquaculture are also suggested.

Effects of high fat in the diet on growth, antioxidant, immunity and fat deposition of Macrobrachium rosenbergii post-larvae

Lipids are essential nutrients for organisms, and high-fat feeds for shrimp may cause oxidative stress. This study evaluated the effects of feeding high fat in the diet on the growth, antioxidant, immunity, and liver fat accumulation of Macrobrachium rosenbergii post-larvae. Five groups with an initial body weight of 0.0084 ± 0.001 g were fed five isonitrogenous and isoenergetic diets (47.01% crude protein and 18.40 kJ/g gross energy) containing 8%, 10%, 12%, 14% and 16% (named L8, L10, L12, L14 and L16) lipid for 8 weeks, respectively. The results showed that the weight gain rate (WGR) and specific growth rate (SGR) of L8 group were significantly higher than those of L10, L12, L14 and L16 group (P < 0.05), and the feed coefficient (FCR) of L8 group was significantly lower than that of other groups (P < 0.05). With the increase of dietary fat level, the content of MDA and the activity of SOD increased significantly, and the activities of T-AOC and CAT decreased significantly (P < 0.05). H&E staining clearly revealed the occurrence of hepatocyte swelling, hepatocyte vacuolization and nucleus displacement to the peripheral cell vacuolization in the L16 group, and hepatic lipid accumulation was further observed in the L14 and L16 group by Oil red O staining. In addition, high-fat diet significantly upregulated the expression of Dorsal, Relish and IκBα mRNA, and also upregulated the expression of fat synthesis-related genes FAS, ACC, DGAT and fat transport-related gene FABP (P < 0.05), and significantly downregulated the expression of fat metabolism-related genes AMPK and CPT-1 (P < 0.05) compared to that of the L8 group. In conclusion, this study showed that feeding a high-fat diet could induce oxidative stress, inhibit growth performance, alter antioxidant capacity, cause hepatic fat deposition and affect the immune system of M. rosenbergii post-larvae.

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.

Oxidized Palm Oil Diet Affects Fatty Acid Profiles, Apparent Digestibility Coefficients and Liver of Hybrid Grouper Juvenile (Epinephelus fuscoguttatus × Epinephelus lanceolatus)

Vegetable oil is progressively replacing fish oil (FO) in aquafeed production. However, the effect of oxidized vegetable oil is less reported. This study was done to investigate the effects of oxidized refined palm oil (RPO) on the growth performance, feed utilization, proximate and fatty acid profiles, apparent digestibility coefficients and oxidative stress of hybrid grouper juvenile (Epinephelus fuscoguttatus × E. lanceolatus). RPO was force-oxidized and introduced into diets at three oxidative levels to replace 50% of FO. Diets with FO and fresh RPO were served as controls. The peroxide value of the oxidized diets was measured as 14.73, 24.50, and 36.10 meq/kg for diets OxL, OxM, and OxH, respectively. These diets were fed to triplicate groups of hybrid grouper (initial body weight 9.91 ± 0.01 g) for 8 weeks. There was no significant difference in terms of growth performance, survival, feed utilization, and whole-body protein proximate composition in all treatments (p &gt; 0.05). However, different dietary treatments affected the body fatty acids profile and fish-fed OxM diet achieved the highest body weight gain without significant difference (p &gt; 0.05). In terms of hepaticsomatic index (HSI), fish-fed OxH showed a significantly lower value compared to other treatments. Similarly, the lowest apparent digestibility coefficients (ADC) of nutrients were observed in fish fed OxH diet. The oxidized diets caused significant lower blood cholesterol and high-density lipoprotein cholesterol (HDL) (p &lt; 0.05). The oxidative stress in the liver as indicated by the significantly higher thiobarbituric acid-reactive substance (TBARS) value in fish fed all the oxidized diets while no significant changes on the muscle TBARS values. In conclusion, the oxidized RPO diets significantly affected the liver, the nutrient digestibility, and the blood total cholesterol and HDL. Furthermore, hybrid grouper can tolerate up to 20 meq/kg of oxidized RPO in the diet without compromising the growth.

Effects of different carbon sources on water quality, biofloc quality, and the productivity of Nile tilapia reared in biofloc-based ponds

The present study evaluated the effects of different carbohydrates materials used as carbon sources on water quality, biofloc quality, and growth and productive performance of Nile tilapia (Oreochromis niloticus) reared in biofloc (BFT)-based cement ponds (25 m x 10 m x 1.2 m; with 250 m3 volume). Nile tilapia fingerlings (44.9±1.9 g) were distributed into nine ponds at a density of 40 fish per 1 m3 (10000 fish/pond) to represent three treatments in triplicates. The control ponds received no carbon source addition; meanwhile sugarcane molasses (MO) and wheat flour (WF) were added to ponds. A commercial diet (30% crude protein) was offered to fish in each pond at levels of 3% and 2% of live body weight of fish in the control and BFT-based ponds, respectively, for 12 weeks. The amounts of feed were divided equally to three equal portions and offered to fish at 9:00, 13:00, and 17:00 h. The control ponds’ water was replaced by 50% every day with new water; meanwhile in MO and WF ponds, water loss via evaporation or leakage was compensated to reach the 1.0 m depth only. The pH value as well as unionized ammonia and nitrite levels, in the present study, were significantly lower, meanwhile nitrate and total suspended solids levels were significantly higher in MO and WF-treated ponds than the control one. The WF treatment resulted in significantly larger biofloc volume and higher total bacterial count compared to the MO treatment. The highest growth and production indices of Nile tilapia were observed in the BFT-based treatments as compared with the control group; particularly at the WF treatment followed by the MO treatment. In conclusion, the WF addition to cement fishponds is a more beneficial carbonaceous source for the efficient water quality, biofloc biomass, and growth and productivity of Nile tilapia reared in BFT-based system.

A Solution for Sustainable Utilization of Aquaculture Waste: A Comprehensive Review of Biofloc Technology and Aquamimicry

Biofloc technology (BFT) is gaining traction as a strategic aquaculture tool for boosting feed conversions, biosecurity, and wastewater recycling. The significant aspect of BFT is aquaculture with highest stocking density and minimal water exchange. It not only improves the water quality of a system by removing inorganic nitrogen from wastewater but also serves as a suitable feed supplement and probiotic source for cultured species. This technology is commonly used for shrimp and tilapia culture and can be used for both semi-intensive and intensive culture systems. Biofloc, when combined with formulated diets, forms a balanced food chain that improves growth performance. Nutrients in this system are continuously recycled and reused and form an efficient alternative system in aquaculture. In addition to the reduction in water exchange, it is also considered as a bio-security measure, since it prevents entry of disease from outside sources. Aquamimicry is an innovative concept that simulates natural estuarine conditions by developing copepods that act as supplementary nutrition especially for shrimp culture. The review highlights the process, significance, and development of BFT, its microbial interactions, nutritional value, transition from biofloc to copefloc, and concept of aquamimicry to sustainably improve aquaculture production.

The Effect of Adding Molasses in Different Times on Performance of Nile Tilapia (Oreochromis niloticus) Raised in a Low-Salinity Biofloc System

This study aimed to evaluate the effect of adding molasses in different times on water quality, growth performance, body biochemical composition, digestive and hepatic enzymes of Nile tilapia in the biofloc system. Tilapia fingerlings (1.53 ± 0.14 g) were distributed in five treatments including control, BFT24 (adding molasses to the tanks every 24 h), BFT48 (48 h), BFT72 (72 h), and BFT96 (96 h) and reared for 37 days in fiberglass tanks (130 L), with a stocking density of one fish per litre. The results showed that highest increases in biomass (740.12 g) and survival (98.97%) were obtained in BFT24 treatment (P<0.05). The body composition was affected by the experimental treatments so that the highest protein content was obtained in the BFT72 (P<0.05). Digestive enzymes activities were significantly (P<0.05) higher in BFT treatments than the control group. The current study showed higher biomass and survival ratio for Nile tilapia were observed in BFT24 treatment. The liver and digestive enzymes of Nile tilapia were affected by the different addition times of molasses to the rearing tanks.

Dietary Lactobacillus casei K17 Improves Lipid Metabolism, Antioxidant Response, and Fillet Quality of Micropterus salmoides

Simple Summary

In order to find effective antioxidants to improve the fleshy degeneration and liver tissue lesions of Micropterus salmoides that were fed artificial mixed feed, Lactobacillus casei K17, which displayed a high level of antioxidant activity in vitro and in vivo was selected in this study. The results indicated that after a trial for 69 days, live bacteria (LB), live bacteria protected by skim milk powder (MB), and dead bacteria were able to improve hemal and hepatic lipid metabolism and antioxidant response, reduce reactive oxygen species production, and protect Micropterus salmoides hepatic cells from injury, while LB and MB were also able to improve fillet quality. Therefore, Lactobacillus casei K17 might be a good alternative source of improving fillet quality and liver health in Micropterus salmoides.

Abstract

We previously demonstrated that Lactobacillus casei K17, isolated from Korean kimchi, has high antioxidant levels in vitro and in vivo. However, its effect on Micropterus salmoides is unknown. In this study, we investigated the impact of L. casei K17 supplementation on the lipid metabolism, antioxidant response, liver histology, and fillet quality of M. salmoides. We randomly assigned 450 M. salmoides (33.0 ± 0.5 g) to six diet groups for 69 days. The diets were as follows: 0.85% normal saline; 10% skim milk powder; 1 × 10⁸ CFU/g live L. casei K17 (LB); 1 × 10⁸ live L. casei K17 protected by skim milk powder (MB); 1 × 10⁸ dead L. casei K17 (DB); and L. casei K17 fermentation supernatant. MB significantly improved the crude protein, total collagen, alkaline-insoluble collagen, fiber numbers, hardness, chewiness, and gumminess of M. salmoides fillets (p < 0.05). LB significantly improved crude protein and fiber numbers (p < 0.05). Furthermore, dietary supplementation with LB, MB, and DB maintained normal liver histology, preserved liver function, and increased hepatic and hemal antioxidant status by enhancing antioxidant enzyme activities. Meanwhile, the three diets also promoted lipid metabolism by increasing HDL-C effectiveness and reducing total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels in serum and liver tissues, indicating that dietary supplementation with DB, LB, and MB had hypolipidemic effects on M. salmoides. MB and LB significantly improved fillet quality and LB, MB, and DB improved hemal and hepatic lipid metabolism and antioxidant response and reduced reactive oxygen species production, protecting M. salmoides hepatic cells from injury.

Effects of dietary Lactobacillus plantarum (KC426951) in biofloc and stagnant-renewal culture systems on growth performance, mucosal parameters, and serum innate responses of Nile tilapia Oreochromis niloticus

Effects of dietary Lactobacillus plantarum (KC426951) on growth and innate responses of Nile tilapia Oreochromis niloticus were evaluated in biofloc technology system and stagnant-renewal culture system (SRCS). The 90-day-long experiment contained four treatments: SRCS without probiotic (T1), SRCS with probiotic (T2), biofloc without probiotic (T3), and biofloc with probiotic (T4). The administration dose of probiotic was 2 × 10⁸ CFU kg^-1 diet. At the end of experiment, the mean final weights, specific growth rates, feed conversion ratios, and total biomass were significantly (P < 0.05) better in BFT treatments, with no significant effect of probiotic on these parameters in both culture systems. Meanwhile, skin mucosal parameters including total protein (TP), lysozyme (LYZ), alkaline phosphatase (ALP), and protease (PRO) activity were significantly enhanced following probiotic supplementation. T4 treatment displayed a significantly higher LYZ and ALP activity in mucus versus other treatments. Also, serum alternative complement activity was significantly heightened in probiotic-supplemented fish. Superoxide dismutase activity in T4 was detected higher than that of SRCS groups. The results of the current study demonstrated the enhancement of some mucosal and serum innate responses of Nile tilapia in both culture systems upon L. plantarum (KC426951) supplementation.

Biofloc technology improves growth, innate immune responses, oxidative status, and resistance to acute stress in common carp (Cyprinus carpio) under high stocking density

This study aimed to evaluate the effects of biofloc technology (BFT) on the performance of common carp under high stocking density. Fish (8.41 ± 0.44 g) were stocked into 12 tanks (70 L) in a 2 × 2 factorial design consisting of clear water (CW) and BFT systems at two stocking densities. Fish were divided into four groups according to culture system and stocking density: CW6 (clear water, 6 kg m^-3), CW12 (clear water, 12 kg m^-3), BFT6 (biofloc, 6 kg m^-3), and BFT12 (biofloc, 12 kg m^-3). After 49 days, the fish were exposed to acute crowding stress (40 kg m^-3) for 7 days to evaluate the fish performance to additional stressors. Total ammonia nitrogen (TAN) concentration was significantly lower in BFT groups at the end of the trial. The growth of fish was significantly higher and the feed conversion ratio was lower in BFT groups. The final density of fish was highest in BFT12 group (25.41 ± 0.48 kg m^-3). The amylase and protease activities in BFT groups were significantly higher than the CW12 group. The highest serum catalase, superoxide dismutase, and glutathione peroxidase activities, and malondialdehyde content (3.07 ± 0.16 nmol mg^-1 protein) were observed in CW12 group. Serum LDL, cholesterol, triglyceride, total protein, and albumin levels were significantly higher in CW6 and BFT6 groups, followed by BFT12 group, and lowest in CW12 group. Serum globulin level was lowest in CW12 group (0.68 ± 0.06 g dL^-1). After 49 days, serum lysozyme, alternative complement (ACH₅₀) and ALP activities were significantly higher and serum cortisol and glucose levels and ALT and AST activities were lower in BFT groups than the CW12 group. After 7 days of acute stress, serum lysozyme activities were significantly lower and ACH₅₀ and ALP activities were higher in BFT groups than the CW12 group. Also, fish in CW12 group were more sensitive to the acute stressor, showing higher cortisol and lower glucose levels. Overall, biofloc had the anti-stress effect, and the culture of common carp in the biofloc system at a stocking density of 12 kg m^-3 could be recommended. BFT can also exert beneficial effects on the welfare of fish subjected to acute stress.

Serum biochemistry, liver histology and transcriptome profiling of bighead carp Aristichthys nobilis following different dietary protein levels

Dietary protein plays a major role in determining the rate of fish growth and overall health. Given that the liver is an important organ for metabolism and detoxification, we hypothesized that optimal dietary protein levels may benefit liver function. Herein, we investigated the effects of dietary protein level on serum biochemistry, liver histology and transcriptome profiling of juvenile bighead carp Aristichthys nobilis fed for 8 weeks on a diet supplemented with high protein (HP, 40%), low protein (LP, 24%) or optimal protein (OP, 32%; controls). The results revealed a significant change in liver morphology in LP and HP groups compared with the OP group, coupled with increased serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity. RNA sequencing (RNA-Seq) analysis of the liver transcriptome yielded 47 million high-quality reads using an Illumina platform, which were de novo assembled into 80,777 unique transcript fragments (unigenes) with an average length of 1021 bp. Subsequent bioinformatics analysis identified 878 and 733 differentially expressed unigenes (DEGs) in liver in response to LP and HP diets, respectively. KEGG enrichment analysis of DEGs identified immune and metabolism-related pathways, including Toll-like receptor signaling, PI3K-Akt signaling, NF-κB signaling, complement and coagulation, peroxisome, nitrogen metabolism, PPAR signaling, and glycolysis and gluconeogenesis pathways. Transcriptome profiling results were validated by quantitative real-time PCR for 16 selected DEGs. The findings expand our understanding of the molecular mechanisms underlying the effects of dietary protein level on liver function in bighead carp.

Effects of waterborne nitrite on hematological parameters and stress indicators in olive flounders, Paralichthys olivaceus, raised in bio-floc and seawater

Juvenile olive flounders, Paralichthys olivaceus (mean weight 2.69 ± 0.31 g), were raised in bio-floc and seawater for six months, these P. olivaceus (mean weight 280.1 ± 10.5 g, mean length 28.37 ± 2.3 cm) were exposed to different concentrations of waterborne nitrite (0, 25, 50, 100, and 200 mg NO₂^-/L) for 7 days. None of the P. olivaceus individuals exposed to bio-floc and seawater containing waterborne nitrite concentrations of 200 mg/L for 7 days survived. Hematological parameters (hemoglobin and hematocrit) were significantly reduced by nitrite exposure. Regarding plasma components, the concentrations of glucose, glutamic oxalate transaminase (GOT), and glutamic pyruvate transaminase (GPT) increased significantly in response to nitrite exposure, whereas cholesterol concentrations significantly decreased. Stress indicators, including concentrations of plasma glucose, cortisol, and liver and gill concentrations of heat shock protein 70 (HSP70) were significantly increased by nitrite exposure. The results of the study indicate that nitrite exposure affected the hematological parameters and stress indicators of P. olivaceus raised in bio-floc and seawater, and these changes were more prominent in the P. olivaceus raised in seawater than those raised in bio-floc.

Effects of dietary ginkgo biloba leaf extract on growth performance, plasma biochemical parameters, fish composition, immune responses, liver histology, and immune and apoptosis-related genes expression of hybrid grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀) fed high lipid diets

For thousands of years, leaves from the Ginkgo biloba tree have been a common treatment in Chinese medicine. The present study was conducted to investigate the effects of dietary ginkgo biloba leaf extract (GBE) supplementation on growth performance, plasma biochemical parameters, fish composition, immune responses, liver histology, and immune and apoptosis-related genes expression of hybrid grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀) fed high lipid diets. A basal diet supplemented with GBE at 0, 0.50, 1.00, 2.00, 4.00 and 10.00 g kg^-1 was fed to hybrid grouper for 8 weeks. The study indicated that dietary GBE did not improve growth performance and feed utilization but it reduced intraperitoneal fat rate. There were no significant differences in condition factor, viscerosomatic index, hepatosomatic index, spleen index, relative gut length, food intake, protein deposit rate and survival among all groups (P > 0.05). Dietary supplementation with 0.50-4.00 g GBE kg^-1 diets effectively increased plasma HDL content and decreased plasma GLU, LDL and TG content in fish. Furthermore, dietary GBE had a significant effect on moisture, crude protein and lipid in the liver, and protein in the whole body of fish (P < 0.05). Dietary supplementation with 0.50-1.00 g GBE kg^-1 diets effectively decreased occurrence rates of the hepatocyte swelling, hepatocyte vacuolization, and nuclei shifting to the cellular periphery cytoplasmic vacuolization, meanwhile hepatic antioxidant enzymes (SOD, CAT and T-AOC) activities significantly increased whereas MDA content significantly decreased in fish fed diets supplemented with GBE (P < 0.05). Moreover, dietary GBE up-regulated the expression of antioxidant genes (CAT, GPx and GR), immune-related genes (MHC2 and TLR3) and anti-inflammatory cytokines (IL-10 and TGF-β1), while dietary supplementation with 0.50-4.00 g GBE kg^-1 diets down-regulated apoptosis-related genes (p53, caspase-9, caspase-8 and caspase-3) expression in the head kidney of hybrid grouper. These results indicated that hybrid grouper fed diets supplemented with GBE did not improve growth performance and feed utilization but it had hypolipidemic effects, improved hepatic antioxidant status, maintained normal liver histology and preserved liver function, increased immune-related genes expression and decreased apoptosis-related genes expression in the head kidney of hybrid grouper.