Effects Of High Stocking Density Research Articles

Oregano essential oil and Bacillus subtilis role in enhancing broiler’s growth, stress indicators, intestinal integrity, and gene expression under high stocking density

This study investigates the role of dietary Bacillus subtilis and oregano essential oil in mitigating the effects of high stocking density on growth performance, carcass traits, physiological stress indicators, gene expression, and intestinal integrity in broiler chickens. A total of, 1250 one-day-old Ross 308 male broiler chicks were randomly allocated to five experimental groups, where each group had five replicates of 50 chicks. Group 1 (control, LSD): 15 chicks/m2 fed a basal diet without feed additive, group 2 (HSD): 20 chicks/m2 fed a basal diet without feed additive, group 3 (BHSD): 20 chicks/m2 fed a basal diet supplemented with B. subtilis (500 mg/kg diet), group 4 (OHSD): 20 chicks/m2 fed a basal diet supplemented with oregano essential oil (300 mg/kg diet), group 5 (CHSD): 20 chicks/m2 fed a basal diet supplemented with oregano essential oil and B. subtilis. At 35 days of age, there was a noticeable improvement in the growth performance of broilers fed CHSD under high stocking density through the increase in body weight gain, dressing percentage, and crude protein digestibility with a decrease in feed conversion rate compared to other groups. Adding CHSD enhanced the state of oxidation and immunity through increasing superoxide dismutase, glutathione peroxidase, and the relative weight of bursa of Fabricius, while decreasing malondialdehyde, in addition to increasing plasma triiodothyronine levels. The microbial structure and morphometric parameters improved in the group that received the CHSD compared to the other groups, where villus height and Lactobacillus population increased, whereas Escherichia coli and Clostridium perfringens population decreased. Glucose transporter 2 (GLUT2), fatty acid transporter 1 (FABP1), and amino acid transferase 1 (CAT1) gene expression levels significantly increased when feeding on oregano essential oil with B. subtilis. In conclusion, combining oregano essential oil and B. subtilis supplements mitigated the effects of high stocking density by enhancing growth performance, antioxidative status, and intestinal integrity, in addition to modifying the genetic expression of genes related to nutrient absorption.

Effects of Chronic Stress from High Stocking Density in Mariculture: Evaluations of Growth Performance and Lipid Metabolism of Rainbow Trout (Oncorhychus mykiss).

(1) Background: In aquaculture, chronic stress due to high stocking density impairs animals' welfare and results in declined fishery production with low protein quality. However, most previous studies evaluated the effects of high stocking density on trout in freshwater rather than seawater. (2) Methods: Juvenile trout were reared for 84 days in circular tanks under three stocking densities, including low density ("LD", 9.15 kg/m3), moderate density ("MD", 13.65 kg/m3), and high density ("HD", 27.31 kg/m3) in seawater. The final densities of LD, MD, and HD were 22.00, 32.05 and 52.24 kg/m3, respectively. Growth performance and lipid metabolism were evaluated. (3) Results: Growth performance and feeding efficiency were significantly reduced due to chronic stress under high density in mariculture. The digestive activity of lipids was promoted in the gut of HD fish, while the concentration of triglycerides was decreased in the blood. Furthermore, decreased acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), increased hormone-sensitive lipase (HSL) concentrations, and activated hepatic β-oxidation processes were observed in trout under HD. Redundancy analysis showed that glycerol and HSL can be used as potential markers to evaluate the growth performance of trout in mariculture. (4) Conclusions: We showed that chronic high stocking density led to negative effects on growth performance, reduced de novo synthesis of fatty acids, and enhanced lipolysis.

Synergistic interactions of zeolite, stocking density, and water exchange: A holistic approach to optimizing aquaculture performance of juvenile European seabass (Dicentrarchus labrax)

Effective water management is an essential component of sustainable fish farming practices, particularly in the context of global water scarcity. The accumulation of ammonium ions (NH4+) from fish metabolism necessitates frequent water changes, posing a challenge to the sustainability of fish farming operations. Zeolite materials have emerged as a promising solution, offering enhanced ammonium cation removal compared to conventional nitrifying bacteria. This innovative approach alleviates the pressure on water resources and promotes environmental sustainability in fish farming. Over 75 days, this study examined how zeolite, stocking density, and water exchange affected European seabass water quality and growth. 250 kg of seabass, 25.61 ± 2.39 g/fish. Three factors: zeolite levels (Z: 0, 10, and 15 ppt), density (D: 1, 2.5, and 5 kg/m3), and water exchange (W: 10, 25, and 50 %), using 81 hapas with 0.5 m3 vol each (triplicates for each treatment) fixed in concrete ponds, fish were randomly distributed among 81 experimental hapas in 27 ponds. This research illuminates the potential benefits of various therapies. Zeolite in seabass culture improved water quality. It reduced ammonia derivatives, improving water quality. Adjusting seabass stocking density to low or high improved water quality measures. This change kept dissolved oxygen levels within the target range, providing a good home for farmed fish. Zeolite supplements, reduced stocking density, and optimum water exchange improved European seabass growth, along with water quality improvements. These interventions improved feed consumption and growth rates. These approaches promoted fish growth and reduced stress by limiting the negative effects of high stocking density. The study also examined immune-related, hematobiochemical, and plasma biochemical characteristics after the interventions. Zeolite supplementation, to low stocking density, and water exchange improved these characteristics. They strengthened the European seabass' immune system and preserved healthy plasma and hematobiochemical parameters. In conclusion, optimizing European seabass culture with zeolite (15 ppt), stocking density (1 kg/m3), and water exchange (50 %) enhances water quality, growth performance, and physiological parameters. This contributes to improved aquaculture sustainability and efficiency. Further research is required to fully elucidate the molecular mechanisms of those factors that affect fish health and aquaculture practices.

Stress response and oxygen consumption level of vaname shrimp (Litopenaeus vannamei) infested by Ciliata pathogens on culture system with high stocking densities

One of the technology used to increase the production of vaname shrimp is by culture system with high stocking densities. Disease cases that are often reported to attack vaname shrimp in rearing with high stocking densities are derived from ectoparasites Ciliata pathogens such as Vorticella sp., Zoothamnium sp. and Epistylis sp. This study aimed to determine the effect of high stocking density, rearing time and the interaction between high stocking density and rearing time on the stress response (blood glucose level) and oxygen consumption level of vaname shrimp (Litopenaeus vannamei) infested by Ciliata pathogens. This study used an experimental method using a Completely Randomized Design (CRD) with a 3×5 factorial pattern consisting of 3 treatments and 6 replications. Factor A is high stocking density (10 prawns/10L, 15 prawns/10L and 20 prawns/10L) and factor B is rearing time (day-0, 2, 4, 6 and 8). The results of this study showed that high stocking density and rearing time had a significant effect (p<0.05) and there was a significant interaction (p<0,01) with a high stocking density of 20 prawns/10L and rearing time on day-8 of increasing blood glucose level and oxygen consumption level of vaname shrimp infested by Ciliata pathogens.

Effects of high stocking density on growth performance and expression of MyD88, and its temporal expression under the challenge of Vibrio parahaemolyticus in the noble scallop Chlamys nobilis

High stocking density has been regarded as an adverse factor in bivalve aquaculture. However, its subsequent molecular response to pathogenic bacteria has been little studied. In order to study the question, a novel MyD88 was first cloned using adult noble scallops Chlamys nobilis (CnMyD88), and its tissue distribution was investigated. Then, 1860 juvenile scallops were divided into two groups with two initial densities of high density (200 individuals/layer, HD) and normal density (110 individuals/layer, ND) and in-situ cultured for three months, in which their growth, survival, and the differential expression of CnMyD88 were examined, respectively. Finally, scallops were injected with the Vibrio parahaemolyticus to assess the temporal expression of CnMyD88. As the results show, CnMyD88 cDNA has a full length of 2241 bp and contains an 1107 bp ORF that encodes a 368-derived protein. It was widely expressed in examined tissues with a significantly higher level in hemolymph, intestine, mantle, and gonad than others. Besides, the HD group showed lower growth (0.39 ± 0.05 mm/day) and survival (37.00 ± 8.49%) than the ND group (0.55 ± 0.02 mm/day and 76.82 ± 5.78%). More importantly, the HD group exhibited significantly lower expression levels of CnMyD88 in their examined tissues than the ND group. After V. parahaemolyticus challenging, CnMyD88 had significantly lower expression levels in the scallops from the HD group than that of the scallops from the ND group at 6th, 24th, and 36th. The present results indicated that high stocking density not only made adverse impacts on growth and survival but also may induce immunosuppression in the noble scallop. Therefore, appropriate low stocking density may be worth considering to adopt in scallop aquaculture.

Transcriptome-Based Analysis of the Liver Response Mechanism of Black Porgy (Acanthopagrus schlegelii) to Stocking Density

Long-term high stocking density often brings negative effects such as decreased body weight, decreased immunity, and increased mortality to cultured fish, while the effects of short-term stocking are relatively less studied. In this experiment, we characterized spatial and temporal gene expression in black porgy (Acanthopagrus schlegelii) liver by establishing two stocking density groups—high (H: 26.5 kg/m3) and low (L: 2.95 kg/m3)—and conducting transcriptome sequencing before collecting liver samples at two time points: 6 h (AL and AH) and 60 d (CL and CH) into the culture trial. There were 648 and 550 differentially expressed genes (DEGs) in the AL-vs-AH and CL-vs-CH groups, respectively. The DEGs in the AL-vs-AH group were significantly enriched in steroid biosynthesis, terpenoid backbone biosynthesis, the PPAR signaling pathway, proteasome, aminoacyl-tRNA biosynthesis, and ribosome biogenesis in eukaryotes. The DEGs in the CL-vs-CH group were more significantly enriched in lipid metabolism-related pathways, such as the PPAR signaling pathway, fatty acid metabolism, and cholesterol metabolism. In addition, immune-related pathways such as the phagosome and complement and coagulation cascades were also enriched in the CL-vs-CH group. The expression changes concerning the DEGs in each group were further analyzed. The DEGs related to steroid synthesis, protein synthesis, and the degradation pathways were down-regulated, but immune-related genes were generally up-regulated in the AH group. The DEGs related to lipid synthesis were significantly up-regulated in the CH group, but the DEGs related to lipid consumption and utilization were down-regulated. The expression of immune-related DEGs was also negatively affected in the CH group. These results suggest that acute and chronic crowding stress affects lipid metabolism and immune regulation in the liver of black porgy. Acute stress particularly affected hepatic protein metabolism, while chronic stress showed more effects on hepatic lipid metabolism. The results of this study provide a theoretical basis for understanding the effects of high stocking densities upon black porgy and may also provide a reference for crowding stress regulation studies in other fish species.

Effects of dietary Lactobacillus helveticus ATC 15009 on growth performance, hematology parameters, innate immune responses, and the antioxidant status of rainbow trout (Oncorhynchus mykiss) under high rearing density

Abstract This study aimed to evaluate the effects of dietary probiotic supplementation of Lactobacillus helveticus on growth, digestive enzymes, and hematological, biochemical, immune, and antioxidant parameters, as well as intestinal microbiota of rainbow trout (Oncorhynchus mykiss). Fish (35.46±0.9 g) were fed with different levels of dietary L. helveticus: control, 1 × 106, 1 × 107, 1 × 108, and 1 × 109 at high stocking density (80 kg m−3) for 60 days. Results indicated that growth performance significantly improved in probiotic supplemented fish (P&lt;0.05). Digestive enzyme parameters revealed that supplementation could significantly increase amylase, protease, and lipase (P&lt;0.05). The treated groups showed significant improvements in serum immune parameters including lysozyme (LYZ), alternative complement (ACH50), respiratory burst activity (RBA), and myeloperoxidase (MPO) (P&lt;0.05). Total protein (TP), albumin (ALB), and globulin (GLO) increased in fish fed experimental diets (P&lt;0.05). Lactate dehydrogenase (LDH) activity was significantly lower in fish fed dietary additives (P&lt;0.05) while white blood cells (WBC), lymphocytes, neutrophils, hematocrit (Hct), red blood cells (RBC) were significantly enhanced (P&lt;0.05). Fish fed with supplemented diets showed significantly enhanced antioxidant status, catalase (CAT) and superoxide dismutase (SOD). Malondialdehyde (MDA) content was significantly lower in fish fed dietary additives (P&lt;0.05). Lactic acid bacteria (LAB) in the treatment groups were significantly increased (P&lt;0.05). In conclusion, dietary supplementation of L. helveticus reduced detrimental effects of high stocking density on growth performance and immune response. It appears that L. helveticus can be recommended as a beneficial probiotic feed additive for rainbow trout.

Body Tactile Stimulation Reduces the Effects of High Stocking Density on the Welfare of Nile Tilapia (Oreochromis niloticus)

High stocking density is used in aquaculture to optimize farming. However, such strategies can stress territorial fish by increasing aggression, thus harming the fish welfare and productive performance. Here, we tested the effect of long-term tactile body stimulation (TS) on alleviating the impact of high stocking density in Nile tilapia (Oreochromis niloticus). Ten males were grouped for 21 days into four treatments (10 replicates each one) combining TS with high (1.2 kg·m³) or low (0.6 kg·m³) densities: (1) without TS and high density; (2) without TS and low density; (3) with TS and high density; and (4) with TS and low density. A rectangular PVC frame fitted with vertical plastic sticks sided with silicone bristles was placed in the center of aquarium. The fish receive TS when passing through the bristles. An apparatus without bristles was used as control. We found higher cortisol levels under TS conditions. All parameters of productive performance (growth, food efficiency, and condition factor) were higher in the treatment with TS and low density, lower in the treatment without TS and high density, and similar between treatments high density with TS and low density without TS. The results suggest that TS improves productive performance of Nile tilapia, counteracting the negative effects of high stocking density.

Effects of different stocking density and various phytogenic feed additives dosage levels on growing-finishing pigs.

This study was to investigate the effects of different phytogenic feed additives (PFA) dosage levels in growing- finishing pigs stressed by high stocking density. A total of 72 mix sexed 12 weeks growing pigs ([Landrace × Yorkshire] × Duroc) with initial body weight (BW) of 49.28 ± 4.58 kg were used for 8 weeks. There were 3 replicate pens in each treatment group, with 3 pigs per pen. The dietary treatment groups consisted of basal diets in animal welfare density (negative control [NC]), basal diet in high stocking density (positive control [PC]), PC + 0.04% essential oil (ES1), PC + 0.08% essential oil (ES2), PC + 0.10% bitter citrus extract & essential oil (CES1), PC + 0.20% bitter citrus extract & essential oil (CES2), PC + 0.05% grape pomace extract (GP1), PC + 0.10% grape pomace extract (GP2). The reduction of space allowance decreased (p < 0.05) average daily gain, feed efficiency, and digestibility of dry matter, crude protein, and gross energy. Also, the fecal score of PC groups increased (p < 0.05) compared with other groups. Basic behaviors (feed intake, standing, lying) were inactive (p < 0.05) and singularity behavior (biting) was increased (p < 0.10) under high stocking density. There was no difference in blood profile. However, the supplementation of PFA alleviated the negative effects such as reduced growth performance, nutrient digestibility, and some increasing stress indicators in th blood (cortisol) and animal behavior (biting). In conclusion, the negative effect of high stocking density was most effectively mitigated by the normal dosage of the mixture of bitter citrus extract and essential oil additive (CES1).

Impact of Prebiotic Supplementation on Productive Performance, Carcass Traits, and Physiological Parameters of Broiler Chickens under High Stocking Density Condition

The present study was performed to investigate the effect of increasing stocking density, prebiotic supplementation, and the interactions on broiler chicken performance and some physiological parameters. A total of 912 one-day-old chickens were used in this study, and they were randomly divided into six groups with 4 replicates each. The experiment included three levels of stocking densities (10, 13, and 15 broiler chicken/m2) in 6 groups. Groups 1, 3, and 5 were maintained without prebiotic supplementation, while groups 2, 4, and 6 received a diet supplemented with prebiotics in water (1cm/liter). Reducing stocking densities and adding prebiotics improved body weight, feed consumption, feed conversion ratio, hemoglobin, packed cell volume, oxidative stress parameters (total antioxidant capacity), and European production efficiency factor, while decreasing malondialdehyde levels. On the other hand, stocking density and prebiotic supplementation did not affect dressing percentage, the relative weight of giblet parts, hind part, front part, and lymphoid organs (thymus and bursa of Fabricius). In conclusion, adding prebiotics at 1 cm/liter (Mannan-oligo saccharide and B-Glucan) can partially mitigate the negative effects of high stocking density on production performance, physiological and oxidative stress parameters, and European production efficiency factor. Keywords: Antioxidant biomarkers, Broiler chicken, β-glucan, Mannan oligosaccharide, Oxidant, Prebiotic, Stocking density

The Effect of High Stocking Density and Dietary Protein Levels on Blood Profiles, Intestinal Bacteria, Some Immunological Parameters, Status Antioxidant, and Performance in Native Chickens

The Effect of High Stocking Density and Dietary Protein Levels on Blood Profiles, Intestinal Bacteria, Some Immunological Parameters, Status Antioxidant, and Performance in Native Chickens

Response of zebrafish to royal jelly supplementation and differences in stocking density

Dietary supplementation with royal jelly (RJ) may improve growth, antioxidant gene expression, and intestinal antioxidant capacity, and possibly mitigate effects of stress induced by high stocking density (HSD) in zebrafish (Danio rerio). Effects of HSD and RJ supplementation on growth performance, antioxidant gene expression, and intestinal antioxidant capacity in zebrafish were investigated. A total of 240 four-month-old zebrafish were used in a 2 x 2 factorial design, with four treatments and three replications. The treatments consisted of normal stocking density (NSD) (1 fish/L) and high stocking density (HSD) (3 fish/L) and an unsupplemented commercial diet (0RJ) and commercial diet supplemented with 10% RJ (10RJ). The experiment lasted 25 days. Daily weight gain, final body length, specific growth rate, and survival were recorded. On day 25, six fish per treatment were euthanised and their intestines analysed for antioxidant capacity, and superoxide dismutase 2 (SOD2) and catalase (CAT) gene expression. There were no effects of diet or SD and diet interaction on growth. High stocking density decreased daily weight gain by 25.31%, body length by 2.70%, and survival by 16.85%. Stocking density (SD) and diet interaction influenced intestinal SOD2 and CAT expression and antioxidant capacity. The HSD/0RJ group had lower antioxidant gene expression and antioxidant capacity than the HSD/10RJ and NSD/0RJ groups. Supplementation with RJ did not mitigate the harmful effects of stocking stress. These results indicate that HSD promotes transcriptional suppression of gene encoding enzymes that form the first line of antioxidant defence, resulting in reduced elimination of toxic substances and occurrence of intestinal oxidative stress.

Dietary Artemisia, Artemisia annua , supplementation improves common carp welfare under high stocking density

Intensive aquaculture supports higher production per unit of area, but it may be associated by stress and health problems in fish. Thus, researches are continuing to find applicable methods for suppressing such negative effects. Dietary supplementation with medicinal plant is known as a promising method in this field. Accordingly, the present study aimed at assessing the benefits of dietary Artemisia, Artemisia annua, supplementation (0, 2.5, 5 and 10 g/kg) on growth performance, stress, antioxidant and immunological responses of common carp, Cyprinus carpio, held at a high stocking density (10 g/L vs. 3 g/L) for 70 days. Increase in fish stocking density significantly (p < 0.05) reduced growth performance, haematological parameters (red blood cell, haematocrit, haemoglobin, leukocyte and lymphocyte) and immune responses (total protein, complement and total immunoglobulin), but increased neutrophil, lysozyme, stress responses (cortisol, glucose, aspartate aminotransferase and lactate dehydrogenase), antioxidant enzymes’ activities (superoxide dismutase, catalase and glutathione peroxidase) and lipid peroxidation. Artemisia supplementation significantly (p < 0.05) restored haematological parameters, leukocyte count and mitigated the changes in lymphocyte, neutrophil, stress and immunological parameters, antioxidant enzymes’ activities and lipid peroxidation. Based on the results, dietary Artemisia supplementation is not capable to restore growth retardation of common carp under high stocking density; however, it mitigates the adverse effects of high stocking density on haematological, antioxidant and immunological parameters. Supplementation at 5 g/kg is recommended for carp feed formulation.

The use of mirrors to alleviate the detrimental effects of high stocking density in broiler chickens

Abstract A study was conducted to investigate whether providing mirrors as environmental enrichment to broiler chickens housed at two different stocking densities affects growth performance, behaviour and physiological stress responses. The experiment was conducted in a completely randomized design with a 2 × 2 factorial arrangement consisting of two stocking densities and two environmental enrichment regimens. A total of 208 day-old male broiler chicks were assigned to one of the four subgroups with eight replicates. Within each enrichment regimen [provision of mirrors (ME) or no-mirror (NM)], birds were raised at two stocking densities of low, 0.1000 m 2/bird (5 birds/cage; LD) or high, 0.0625 m 2/bird (8 birds/cage; HD) density from day 1 onward. On day 35, the HD-birds had a significantly lower feed intake and body weight than their LD counterparts. On day 34, the HD-broilers showed significantly more resting behaviour than those of the LD-group. Neither stocking density nor environmental enrichment had significant effects on other activities throughout the study. There were significant interactions between stocking density and environmental enrichment for serum levels of corticosterone (CORT) and ceruloplasmin (CPN) at day 35. Provision of mirrors resulted in similar CORT and CPN among the LD- and HD-chickens on day 35. However, the HD-NM birds had significantly higher CORT and CPN than the LD-NM group. Overall, the results suggest that the provision of mirrors has a negligible effect on growth performance, but can reduce the physiological stress response in broiler chickens with a higher stocking density.

Effect of high stocking density and dietary nano-zinc on growth performance, carcass yield, meat quality, feathering score, and footpad dermatitis in broiler chickens

In this study, effect of dietary nano-Zn and stocking density on performance, carcass yield, meat quality, and feathering score of broiler chickens was assessed at 42 d of age. Experimental treatments consisted of a 2 × 2 factorial arrangement of stocking density (low = 12 broiler/m2 and high = 18 broiler/m2) and dietary Zn form (inorganic or nano). Four hundred eighty 1-d-old male broiler chickens were randomly assigned to 4 treatments with 8 pens in each treatment having 15 chickens per pen. Corn-soybean meal diets were formulated for starter, grower, and finisher phases. The high stocking density (HSD) negatively affected body weight gain (BWG) and feed intake (FI) of broiler chickens at 24 to 42 and 0 to 42 d of experiment (P < 0.05) but did not affect feed conversion ratio (FCR). The BWG (d 10 to 24, d 24 to 42, and d 0 to 42) and FI (d 10 to 24 and d 0 to 42) were negatively affected by dietary nano-Zn whereas, FCR was poor at 10 to 24 d only (P < 0.05). Dietary nano-Zn lowered the BWG at d 24 to 42 (P = 0.028), and FI of LSD and HSD treatments at d 24 to 42 and 0 to 42 (P = 0.019 and P = 0.028, respectively) compared to broiler chickens of LSD group fed inorganic Zn. Neither HSD nor nano-Zn had any effect on the relative yields of carcass, breast, and thigh. Meat quality traits were not affected by either HSD or nano-Zn. There were no differences between groups about back feathering score. However, HSD negatively affected wing feathering score (P < 0.05), and the worst score was observed in HSD dietary inorganic Zn group (P < 0.01). The HSD increased the footpad dermatitis (FPD) scores of chickens at d 24 and 42 (P < 0.01). Dietary nano-Zn reduced the FPD scores on d 24 (P < 0.05) but did not affect FPD on d 42. In conclusion, HSD negatively affected growth performance, wing feathering score, and FPD score in broiler chickens. Dietary nano-Zn suppressed the growth performance of broiler chickens subjected to HSD and did not affect the feathering, however, reduced the FPD score in broiler chickens.

Transcriptomic analysis to elucidate the effects of high stocking density on grass carp (Ctenopharyngodon idella)

BackgroundGrass carp (Ctenopharyngodon idella) is one of the most widely cultivated fishes in China. High stocking density can reportedly affect fish growth and immunity. Herein we performed PacBio long-read single-molecule real-time (SMRT) sequencing and Illumina RNA sequencing to evaluate the effects of high stocking density on grass carp transcriptome.ResultsSMRT sequencing led to the identification of 33,773 genes (14,946 known and 18,827 new genes). From the structure analysis, 8,009 genes were detected with alternative splicing events, 10,219 genes showed alternative polyadenylation sites and 15,521 long noncoding RNAs. Further, 1,235, 962, and 213 differentially expressed genes (DEGs) were identified in the intestine, muscle, and brain tissues, respectively. We performed functional enrichment analyses of DEGs, and they were identified to be significantly enriched in nutrient metabolism and immune function. The expression levels of several genes encoding apolipoproteins and activities of enzymes involved in carbohydrate enzymolysis were found to be upregulated in the high stocking density group, indicating that lipid metabolism and carbohydrate decomposition were accelerated. Besides, four isoforms of grass carp major histocompatibility complex class II antigen alpha and beta chains in the aforementioned three tissue was showed at least a 4-fold decrease.ConclusionsThe results suggesting that fish farmed at high stocking densities face issues associated with the metabolism and immune system. To conclude, our results emphasize the importance of maintaining reasonable density in grass carp aquaculture.

Effects of eliminating interactions in multi-layer culture on survival, food utilization and growth of small sea urchins Strongylocentrotus intermedius at high temperatures

Poor growth and disease transmission of small sea urchins Strongylocentrotus intermedius in summer greatly hamper the production efficiency of the longline culture. Reducing the adverse effects of high stocking density while maintaining high biomass is essential to address these problems. Here, we conducted a laboratory experiment to simulate the multi-layer culture for sea urchins at ambient high temperatures (from 22.2 to 24.5 °C) in summer for ~ 7 weeks. Survival, body size, lantern growth, gut weight, food consumption, Aristotle's lantern reflex, 5-hydroxytryptamine concentration, pepsin activity and gut morphology were subsequently evaluated. The present study found that multi-layer culture led to significantly larger body size than those without multi-layer culture (the control group). This was probably because of the greater feeding capacity (indicated by lantern growth and Aristotle's lantern reflex) and food digestion (indicated by morphology and pepsin activity of gut) in the multi-layer cultured sea urchins. These results indicate that multi-layer is an effective approach to improving the growth efficiency of sea urchins at high temperatures. We assessed whether eliminating interaction further improve these commercially important traits of sea urchins in multi-layer culture. This study found that eliminating interactions displayed greater body size and Aristotle's lantern reflex than those not separated in the multi-layer culture. This approach also significantly reduced the morbidity compared with the control group. These novel findings indicate that eliminating interactions in multi-layer culture greatly contributes to the growth and disease prevention of sea urchins at high temperatures. The present study establishes a new technique for the longline culture of sea urchins in summer and provides valuable information into the longline culture management of other commercially important species (e.g. scallops, abalones and oysters).

Chitosan vitamin E nanocomposite ameliorates the growth, redox, and immune status of Nile tilapia (Oreochromis niloticus) reared under different stocking densities

A 70-days feeding investigation was undertaken to highlight the influence of dietary incorporation with the conventional form of vitamin E (VE) and chitosan vitamin E nanocomposite (CVEN) on different health aspects of Oreochromis niloticus (O. niloticus) reared under different stocking densities. Growth performance, antioxidant status, and immune response were assessed. Fish (n = 405, average weight: 14.74 ± 0.06 g) were randomly assigned into six groups in triplicates. Three experimental diets were used; 1) basal diet with no additives, 2) basal diet +300 mg/kg VE, 3) basal diet +300 mg/kg CVEN, with two stocking densities for each; standard stocking density (SSD) (15 fish/ aquaria) and high stocking density (HSD) (30 fish/ aquaria). Furthermore, a subsequent challenge with pathogenic Aeromonas sobria (A. sobria) was performed at the end of the feeding period. A significant improvement in the final body weight, total weight gain, feed intake, specific growth rate, and average daily weight gain was found in the CVEN group raised under SSD. Vitamin E supplementation, especially the nano form (CVEN), ameliorates the bad effect of high stocking density on fish growth. Marked elevation in the serum level of vitamin E and growth hormone and decreased AST and ALT levels were observed in the CVEN group reared under SSD compared with other groups. An improvement in the serum and hepatic antioxidant activities and the immunological indicators (lysozyme activity, nitric oxide, phagocytic index, and IL-10) was observed in Vitamin E supplemented groups reared under SSD. Supplementation of vitamin E, especially the nano form, improved the serum and hepatic antioxidant enzymes and decreased lipid peroxidation of fish reared under HSD. Increased survivability of fish reared under HSD by CVEN supplementation. Vitamin E supplementation counteracts the negative impact of HSD on the histoarchitecture of the liver. This study suggested that; supplementation of the fish diet with CVEN (300 mg/kg) could promote the growth performance, antioxidant status, immune response, and increase fish tolerance to rearing under HSD. Moreover, dietary supplementation with CVEN enhanced fish resistance to A. sobria infection.

Effects of high stocking density on survival and growth of Sabaki tilapia Oreochromis spilurus

This study's main objective was to estimate the survival rate and growth performance of grow-out Sabaki tilapia (Oreochromis spilurus, Günther, 1894) at different high stocking density levels: 50, 100, 150, 200 and 250 fish per m3. The experiments were conducted in triplicate and monitored for survival rate and growth performance for an experimental period of 16 weeks. Results indicated that the survival rate was significantly different in higher stocking density groups. The growth performance was not significantly different in each group. Overall, the results indicate that the Sabaki tilapia farming is feasible in high stocking density conditions.

Can thyme (Thymbraspicata L. var. spicata) volatile oil alleviate the detrimental effects of high stocking densities in Japanese quail?

This study was conducted to observe the effects of thyme plant (Thymbra spicata L.var. spicata) volatile oil on quails and intestinal microbiota in high stocking density. For this purpose, 300 7-day-old Japanese quails (Coturnix coturnix Japonica) were used in the study. The quails were selected on the basis of body weight and divided into 6 groups, each consisting of 5 replications that contained 50 quail chicks according to the following experimental design: positive control group (NSD - CONT), with normal stocking density and no additive; negative control group (HSD - CONT), with high stocking density (HSD) and no additive; group HSD - ANT, with HSD and 10 mg/kg of avilamycin additive, and other groups named HSD - T1, T2, and T3, with HSD and 200, 400, and 600 mg/kg of volatile oil additive respectively. In the study, a stocking density of 160 cm2/quail was chosen, while the high stocking density (HSD) was 90 cm2/quail. A statistically significant difference was found in terms of improvements in feed intake and feed conversion ratio (P &lt; 0.01), and the highest total bacteria count (cfu/g) was observed in HSD - CONT group (P &lt; 0.01). The addition of zahter-thyme volatile oil in the diet of quails kept in high stocking density provided improvements at various levels with regard to intestinal microbiota and animal performance. It was observed that the inclusion of zahter-thyme volatile oil, in particular at 600 mg per kg level, reduced the detrimental effects of stress generated by high stocking density.