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Rearing density is a critical factor for both the productivity and welfare of farmed fish. The present study examined juvenile black sea bream (Acanthopagrus schlegelii) at low (LD), standard (control, CR), moderately high (MD), and high (HD) densities over a 60-day period. The effects of density on physiological aspects of growth, survival, stress response (cortisol), osmosis and ion balance (Na+–K+–ATPase and Ca2+–Mg2+–ATPase), energy metabolism (glucose, lactic acid, and lactic dehydrogenase), digestive enzyme activity (lipase, trypsin, and amylase), antioxidant ability (superoxide dismutase and malondialdehyde), and non-specific immunity (lysozyme) were investigated to evaluate potential physiological improvements in this commercially and ecologically important species under different densities. Both transcriptomic and metabolomics approaches were applied to assess metabolic and transcriptional changes among groups to determine the underlying mechanisms of physiological performance. The results showed that juveniles reared under low density had not only significantly improved growth and survival rate but also significantly reduced energy expense and lower activities of digestive and antioxidant enzymes compared with fish reared under high density. Significantly reduced cortisol and malondialdehyde contents in the LD group indicated less stressful conditions in those fish. Transcriptomic analysis showed that differentially expressed genes (DEGs) were involved in pancreatic secretion, protein digestion and absorption, and protein processing in the endoplasmic reticulum pathway. Metabolomics revealed that significantly different metabolites (SDM) were involved in the biosynthesis of amino acids, ABC transporters, 2-oxocarboxylic acid metabolism, and protein digestion and absorption. A combined analysis of transcriptome and metabolome showed that fish in the LD group exhibited reductions in energy expenditure, osmotic regulation, and antioxidant ability, while fish in the HD group showed higher energy expenditure, digestive ability, and immune regulation. These findings have important implications for the improvement of fish growth and welfare as well as in mechanistic studies of rearing density.

This investigation aimed to assess the impact of rearing biomass on growth, digestive enzyme activity, and hematobiochemical indices of Nile tilapia in a tank-based recirculatory aquaculture system (RAS) for 90 days. Oreochromis niloticus (35.5 ± 0.24 g) were randomly stocked at the following densities: 80 fish/m3 (F80), 120 fish/m3 (F120), and 160 fish/m3 (F160) in triplicate. Ammonia, nitrate, nitrite, and CO2 were increased significantly as density increased and dissolved oxygen decreased (P < 0.05). A significantly increased weight gain, specific growth rate, growth efficiency, and protein efficiency ratio were recorded in F80 groups compared to F160 groups, whereas feed conversion ratio was decreased. Protease, amylase, and lipase activities were significantly lower as fish density increased. An improved (P < 0.05) red blood cell count, hemoglobin, and hematocrit were found in F160 groups. A considerably higher level of glucose, cortisol, triglycerides, total cholesterol, alanine, and aspartate aminotransferase were recorded in high-density tanks (P < 0.05). The crude lipid and carbohydrate contents were significantly lower in F160 groups. Hence, the outcomes of the present study indicated that stocking density 80 fish per m3 would be appropriate as it promotes the growth and health status of Nile tilapia cultured in RAS. [ABSTRACT FROM AUTHOR]

Rearing density has profound effects on life-history decisions for developing organisms because, for example, it can foreshadow the sexual competitive environment potentially experienced in adulthood. Increased sexual competitiveness should favour greater investment in pre- or post-copulatory sexually selected traits such as weaponry or testes, while sexual-signaling traits that attract mates from a long distance should be favoured in low density populations. High density environments should also trigger density-dependent prophylaxis in which individuals increase their investment in immunity. In this study, we experimentally investigated the effect of rearing density on the adult expression of an immunological trait (i.e., melanization response) as well as pre- (i.e., mandible length, harp size) and post-copulatory (i.e., testis size) sexually selected traits in male Gryllus firmus crickets. We found that all morphological traits positively intercorrelated within each environment whereas melanization response was unrelated to any other measured trait. We also found that high-density males produced larger mandibles (weaponry), contrary to expectation, and stronger immunological responses (degree of melanization), in line with expectation, than their low-density counterparts. As predicted, low-density males produced larger harps, a trait involved in sexual signaling. Our results suggest that male G. firmus facultatively partition resources in a manner that maximizes fitness in the environment they expect to encounter as adults. [ABSTRACT FROM AUTHOR]

Population density is an essential factor affecting the life history traits of insects and their trade-off relationships, as increasing density intensifies intraspecific competition. It decreases the average resources available to individuals within a population, affecting their morphology, physiology, behavior, and fitness. The fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), has been an invasive pest of forest trees, ornamental plants, and fruit trees in China for many years. The larvae have a typical aggregation habit before the fourth instar and keep spitting silk to gather the damaged leaves into silk webs. However, the fitness of H. cunea in response to population density remains unclear. In this study, the critical biological parameters, food utilization, and population parameters of H. cunea in response to different rearing densities were investigated. The results showed that under high population density, H. cunea larvae showed better performance, with faster development, higher survival rates, and shorter generation time, but pupal weight and female fecundity decreased as population density increased. In contrast, for larvae raised in low density, the developmental period was prolonged, and mortality was increased, while higher food utilization, greater body size, and female fecundity were observed. Both males and females had similar development strategies in response to the density, but females may be more resistant to crowding than males. In conclusion, H. cunea could adopt different ecological strategies against the stress of density. High population densities result in shorter generation cycles and higher survival rates. Conversely, the low-density generation period becomes longer but with greater fecundity. The results may help determine the possible outbreak mechanism and develop effective population monitoring and forecasting measures for H. cunea.

High‐density fingerling rearing of pengba was conducted for 90 days in biofloc system (BFS) to study the effect of stocking density on growth, feed utilization, water quality, water use efficiency and health of animals. The study was conducted in 12 continuously aerated tanks (50 m3), grouped into four treatments T‐1, T‐2, T‐3 and T‐4, which were stocked with pengba fry (1.25 ± 0.05 g, 4.74 ± 0.70 cm) at 50, 60, 70 and 80 m−3, respectively. Supplementary feed (1 mm floating pellet) was fed twice daily, each time for 30 min duration. Molasses and urea were supplemented to maintain suitable C:N ratio at 15:1. No water exchange was given, except monthly compensation of evaporation loss. While water quality and most of the growth attributes in T‐1 and T‐2 remained similar, T‐3 at 70 m−3 density showed better water quality, higher survival and growth than T‐4. Body composition remained consistent across treatments despite impaired feed digestion and utilization associated with higher densities. The non‐specific immune responses in fingerlings increased from T‐1 to T‐3, but further density rise showed compromised immune in T‐4. Such results suggested 70 m−3 to be an ideal density for production of healthier fingerlings. But T‐4 produced 13.5% more fingerlings than T‐3, and fingerlings (7.56 ± 0.50 cm; 5.43 ± 0.09 g) were within acceptable size range for grow‐out stocking. T‐4 also showed the lowest total water use and the highest water implicating 80 fry m−3 to have more applicability. Thus, the study recommends 70–80 m−3 as ideal range for fingerling rearing of pengba in BFS. [ABSTRACT FROM AUTHOR]

Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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. [ABSTRACT FROM AUTHOR]

Intensive fish farming at high densities results in a wide range of adverse consequences on fish welfare, including pathogen spreading, stress and increased mortality rates. In this work, we have assessed whether the survival of Senegalese sole infected with the nervous necrosis virus (NNV), a pathogen responsible for severe disease outbreaks, is affected by rearing density. Based on the different fish ratios per surface area (g cm−2) and water volume (g L−1), our research showed an earlier mortality onset in the tanks containing NNV‐infected fish reared at medium density (MD: 0.071 g cm−2/5 g L−1) and high density (HD: 0.142 g cm−2/10 g L−1), as well as higher cumulative mortality values. However, transcription analysis of hsp70, gr1 and pepck genes, well‐known stress biomarkers, seems to indicate that none of the challenged fish were under high stress conditions. NNV load was slightly higher both in dead and in sampled fish from MD and HD groups, and especially in the rearing water from these groups, where peaks in mortality seemed to correlate with increasing NNV load in the water. In conclusion, our results suggest that rearing NNV‐infected Senegalese sole at high densities resulted in an earlier mortality onset and higher cumulative values and viral load. [ABSTRACT FROM AUTHOR]

SUMMARY: The Milanino is a heavy Italian chicken breed and represents an important genetic resource for alternative production systems. Due to the absence of standard management guidelines for local chicken breeds, this study aims to determine the space requirement to achieve a good equilibrium between growth performance and stress response in Milanino chickens reared according to a separate-sex free-range program. A total of 140 birds (70M:70F) were reared in outdoor pens from 75 to 235 d of life according to the following experimental groups (35 birds/group): (M2) males in 2 m2/bird; (F2) females in 2 m2/bird; (M10) males in 10 m2/bird; (F10) females in 10 m2/bird. Growth performance and stress condition were recorded. Bird density affected male body weight, that was higher at the lower density of 10 m2/bird. In contrast, females showed a consistent growth rate irrespective of the bird density suggesting lower space requirements. An overall good adaptability of the breed to the separate-sex free-range system was found, irrespective of both sex and bird density. Moreover, the stress markers values assessed at the end of the growing period suggest the ability of Milanino birds to respond well to environmental stressors. The results provided in this report will be implemented into free-range management guidelines for meat production in the Milanino breed: the separate-sex rearing is recommended during the growing period in outdoor pens and the bird density has to be planned according to the sex.

SUMMARY: The Milanino is a heavy Italian chicken breed and represents an important genetic resource for alternative production systems. In order to support its promotion in the market according to consumer expectations on healthy nutrition and animal welfare, this trial aims to study the slaughter performance and the meat quality in male and female Milanino chickens kept at different rearing density in a separate-sex free-range system. A total of 140 birds (70M:70F) were reared in outdoor pens from 75 to 235 d of life according to the following experimental groups (35 birds/group): M2) males in 2 m2/bird; F2) females in 2 m2/bird; M10) males in 10 m2/bird; F10) females in 10 m2/bird. At 235 d of age, 6 birds per group were slaughtered. Slaughter performance and meat quality were assessed. The Milanino chicken is characterized by high carcass weight and carcass yield among local chicken breeds, and a rearing density of 10 m2/bird is recommended for male birds to obtain heavier carcasses. Milanino meat appears bright and intensely colored, and it is characterized by high protein and low fat contents compared with the standard broiler meat. Total lipids of Milanino meat are characterized by a healthy fatty acid composition, corresponding to a high PUFA/SFA ratio. Milanino breast meat is a good supply of nutraceutical PUFA with a positive low n-6/n-3 PUFA ratio. The ability of the Milanino breed either to synthesize or to transfer to tissue a high quantity of PUFA relevant for human health could be a key factor for its economic valorization.

Sustainable aquaculture of the Japanese eel Anguilla japonica requires an understanding of the physiological conditions of the fish under culture conditions. Therefore, we examined the effects of tentative stressors such as background color and rearing density on stress-related hormones in juvenile Japanese eel. In Experiment 1, fish were divided into white- or black-coated tanks and reared for 35 days. Plasma cortisol levels were significantly higher in the white-acclimated fish on day 35. No significant differences were observed between the groups in hypothalamic CRH mRNA levels. In Experiment 2, fish were divided into three rearing density groups (0.5 kg/m2, 1.2 kg/m2, and 2.4 kg/m2) and reared for 28 days. Plasma cortisol levels were significantly lower in the low-density-acclimated fish than in the medium- and high-density-acclimated fish. However, no significant differences were observed in hypothalamic CRH mRNA levels. Evaluation of plasma cortisol levels indicates that a white background and high rearing density induce more stress for juvenile Japanese eel. [ABSTRACT FROM AUTHOR]

With the introduction and advancement of sustainable development in aquaculture, traditional fish farming methods are gradually transitioning to advanced industrial farming models. To explore the occurrence patterns and risks of cryptocaryoniasis in industrialized high-density aquaculture, we used a non-lethal dose of Cryptocaryon irritans theronts (400 theronts/m3) to infect Larimichthys crocea at different rearing densities [low-density group (0.088 kg/m3), medium-density group (0.88 kg/m3), and high-density group (8.80 kg/m3)]. We explored the relationship between L. crocea density and the growth rate of the C. irritans population by observing the differences in growth, feeding, and survival rates of the L. crocea in each group and the changes in water quality and the number of C. irritans tomonts during the rearing process. We also evaluated the risks associated with the occurrence of cryptocaryoniasis in aquaculture. The results showed significant differences in the relative levels of the first round of infection among different density groups of L. crocea , which affected the outbreak speed of cryptocaryoniasis and the maximum relative tomont number (RTN) of L. crocea. Specifically, the outbreak speed of cryptocaryoniasis from fast to slow was as follows: medium-density group>low-density group>high-density group. The RTN when all L. crocea had died in each group was 12.82 (medium-density group), 49.7 (low-density group), and 106.58 (high-density group). The occurrence of cryptocaryoniasis reduced the feeding and growth rates of L. crocea in all groups, and the effect was most pronounced in the second week and the late stages of infection. The occurrence of cryptocaryoniasis caused abnormal swimming behavior in all three density groups. The main manifestations of C. irritans infection in L. crocea included rubbing the snout against the barrel wall, body imbalance, dispersed swimming, and delayed responses. The deterioration of water quality was most pronounced in the high-density group, but the outbreak speed of cryptocaryoniasis was the slowest in the high-density group, suggesting that no significant correlation existed between the deterioration of water quality and the outbreak speed of cryptocaryoniasis. The outbreak speed of cryptocaryoniasis varies depending on the fish-rearing density, and the progression and risk of cryptocaryoniasis are not proportionally correlated with the rearing density of L. crocea. • Cryptocaryon irritans reproduction isn't a simple linear correlation with fish stocking density. • Cryptocaryoniasis causes fish feeding, growth, and behavioral abnormalities. • Poor water quality shows no significant correlation with the outbreak rate of cryptocaryoniasis. [ABSTRACT FROM AUTHOR]

The present study was conducted to test whether a multi-enzyme produced by a fungus would keep performance of broiler chicks receiving a diet with almost 3% less nutrients (energy, protein, amino acids, calcium and phosphor) under two different housing density. In both experiments, positive control received standard broiler diet, negative control received a diet with 3% less nutrients than standard broiler diet and enzyme group received the negative control diet+supplemental enzyme. In the first trial with 1000, day-old chicks housed 10 birds/m2, only 1% improvement in feed conversion efficiency and body growth was achieved with enzyme supplementation in contrast to the negative control at the end of 35 days feeding period. In the second trial with 1200, day-old-chicks accommodated 16 birds/m2. The results showed that enzyme improved broiler performance almost 3.5% in contrast to the performance obtained from the negative control. In conclusion, supplementing broiler diets based on maize/soya with a multi-enzyme produced by a single fungus provides a great potential to gain the gap created by formulating almost 3% nutrients reduction in broilers housed with 16 birds/m2 density. However, providing high comfort and better rearing condition as the birds at 10 birds/m2 density, positive effects of the enzyme was limited.

The teleost zebrafish (Danio rerio), an established model for human skeletal diseases, is reared under controlled conditions with defined parameters for temperature and photoperiod. Studies aimed at defining the proper rearing density have been performed with regard to behavioural and physiological stress response, sex ratio and reproduction. Studies concerning the effect of rearing density on the skeletal phenotype are lacking. This study analyses the response of the skeleton to different rearing densities and describes the skeletal deformities. Wild‐type zebrafish were reared up to 30 dpf (days post‐fertilization) in a common environment. From 30 to 90 dpf, animals were reared at three different densities: high density (HD), 32 fish l–1; medium density (MD), 8 fish l–1 and low density (LD), 2 fish l–1. Animals at 30 and 90 dpf were collected and whole‐mount stained with Alizarin red S to visualize mineralized tissues. The entire skeleton was analysed for meristic counts and 172 types of deformities. The results showed that the rearing density significantly influenced the specimens' average standard length, which decreased with the increase in the rearing density. Differences in meristic counts among the three groups were not observed. Rearing density–independent malformations affected the ribs, neural arches and the spines of the abdominal region, as well as vertebrae of the caudal complex. The HD group showed the highest number of deformities per specimen, the highest number of observed types of deformities and, together with the MD group, the highest frequency of specimens affected by severe deformities. In particular, the HD group showed deformities affecting arches, spines and vertebral centra in the caudal region of the vertebral column. This study provides evidence of an effect of the rearing density on the development of different skeletal phenotypes. [ABSTRACT FROM AUTHOR]

Rearing density is recognized as a critical consideration in fish husbandry: whereas higher densities may increase productivity and reduce production costs, they also represent a potential source of chronic stress and may negatively affect growth performance and product quality. Accordingly, we investigated the effects of rearing density on growth, physiological responses, and flesh quality of cobia (Rachycentron canadum). Fish (46.32 ± 0.22 g, mean ± SEM) were reared for 42 days in a low salinity (17.6 g/L) recirculation system according to treatments designated as low density (5 fish/tank, 3.30 ± 0.02 kg/m3), medium density (10 fish/tank, 6.67 ± 0.03 kg/m3), or high density (20 fish/tank, 13.15 ± 0.16 kg/m3). Weight gain and specific growth rate were significantly higher among fish reared at low density; however, feed intake, feed conversion ratio, hepatosomatic index, condition factor, and dress‐out were equivalent among treatments. Plasma cortisol, lactate, and osmolality levels were not affected by rearing density, and values were within basal ranges reported for juvenile cobia. Fillet drip‐loss did not vary among treatments, but rigor mortis developed more rapidly among fish reared at high density. Rearing juvenile cobia at high densities may reduce growth performance and may influence the timing of rigor development. [ABSTRACT FROM AUTHOR]

Fish models are essential for research in many biological and medical disciplines. With a typical lifespan of only 6 months, the Turquoise killifish (Nothobranchius furzeri) was recently established as a time‐ and cost‐efficient model to facilitate whole‐life and multigenerational studies in several research fields, including behavioural ecotoxicology. Essential information on the behavioural norm and on how laboratory conditions affect behaviour, however, is deficient. In the current study, we examined the impact of the social and structural environment on a broad spectrum of behavioural endpoints in N. furzeri. While structural enrichment affected only fish boldness and exploratory behaviour, fish rearing density affected the total body length, locomotor activity, boldness, aggressiveness and feeding behaviour of N. furzeri individuals. Overall, these results contribute to compiling a behavioural baseline for N. furzeri that increases the applicability of this new model species. Furthermore, our findings will fuel the development of improved husbandry protocols to maximize the welfare of N. furzeri in a laboratory setting. [ABSTRACT FROM AUTHOR]

Infectious diseases represent an important barrier to sustainable aquaculture development. Rearing density can substantially impact fish productivity, health and welfare in aquaculture, including growth rates, behaviour and, crucially, immune activity. Given the current emphasis on aquaculture diversification, stress-related indicators broadly applicable across species are needed. Utilising an interspecific comparative transcriptomic (RNAseq) approach, we compared gill gene expression responses of Atlantic salmon (Salmo salar) and Nile tilapia (Oreochromis niloticus) to rearing density and Saprolegnia parasitica infection. Salmon reared at high-density showed increased expression of stress-related markers (e.g. c-fos and hsp70), and downregulation of innate immune genes. Upon pathogen challenge, only salmon reared at low density exhibited increased expression of inflammatory interleukins and lymphocyte-related genes. Tilapia immunity, in contrast, was impaired at low-density. Using overlapping gene ontology enrichment and gene ortholog analyses, we found that density-related stress similarly impacted salmon and tilapia in key immune pathways, altering the expression of genes vital to inflammatory and Th 17 responses to pathogen challenge. Given the challenges posed by ectoparasites and gill diseases in fish farms, this study underscores the importance of optimal rearing densities for immunocompetence, particularly for mucosal immunity. Our comparative transcriptomics analyses identified density stress impacted immune markers common across different fish taxa, providing key molecular targets with potential for monitoring and enhancing aquaculture resilience in a wide range of farmed species. Image 1 • Salmo salar reared at high density show higher expression of stress-related markers. • On pathogen challenge, density impacts salmon immune gene expression responses. • Salmon and Nile tilapia have contrasting "stressful" densities. • Density-related stress similarly impacted salmon and tilapia in key immune pathways. • Teleost markers of density-impacted immunity may include inflammatory and Th 17 genes. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Milanino is a heavy Italian chicken breed and represents an important genetic resource for alternative production systems. In order to support its promotion in the market according to consumer expectations on healthy nutrition and animal welfare, this trial aims to study the slaughter performance and the meat quality in male and female Milanino chickens kept at different rearing density in a separate-sex free-range system. A total of 140 birds (70M:70F) were reared in outdoor pens from 75 to 235 d of life according to the following experimental groups (35 birds/group): M2) males in 2 m2/bird; F2) females in 2 m2/bird; M10) males in 10 m2/bird; F10) females in 10 m2/bird. At 235 d of age, 6 birds per group were slaughtered. Slaughter performance and meat quality were assessed. The Milanino chicken is characterized by high carcass weight and carcass yield among local chicken breeds, and a rearing density of 10 m2/bird is recommended for male birds to obtain heavier carcasses. Milanino meat appears bright and intensely colored, and it is characterized by high protein and low fat contents compared with the standard broiler meat. Total lipids of Milanino meat are characterized by a healthy fatty acid composition, corresponding to a high PUFA/SFA ratio. Milanino breast meat is a good supply of nutraceutical PUFA with a positive low n-6/n-3 PUFA ratio. The ability of the Milanino breed either to synthesize or to transfer to tissue a high quantity of PUFA relevant for human health could be a key factor for its economic valorization. [ABSTRACT FROM AUTHOR]

The Milanino is a heavy Italian chicken breed and represents an important genetic resource for alternative production systems. Due to the absence of standard management guidelines for local chicken breeds, this study aims to determine the space requirement to achieve a good equilibrium between growth performance and stress response in Milanino chickens reared according to a separate-sex free-range program. A total of 140 birds (70M:70F) were reared in outdoor pens from 75 to 235 d of life according to the following experimental groups (35 birds/group): (M2) males in 2 m2/bird; (F2) females in 2 m2/bird; (M10) males in 10 m2/bird; (F10) females in 10 m2/bird. Growth performance and stress condition were recorded. Bird density affected male body weight, that was higher at the lower density of 10 m2/bird. In contrast, females showed a consistent growth rate irrespective of the bird density suggesting lower space requirements. An overall good adaptability of the breed to the separate-sex free-range system was found, irrespective of both sex and bird density. Moreover, the stress markers values assessed at the end of the growing period suggest the ability of Milanino birds to respond well to environmental stressors. The results provided in this report will be implemented into free-range management guidelines for meat production in the Milanino breed: the separate-sex rearing is recommended during the growing period in outdoor pens and the bird density has to be planned according to the sex. [ABSTRACT FROM AUTHOR]

Rearing density and disease management are considered as pivotal factors determining shrimp farm productivity and profitability. To systematically investigate the potential mechanisms for density-related differences between disease susceptibility and rearing densities, we conducted comparative transcriptome analysis of the molecular differences between hepatopancreas and intestine of Litopenaeus vannamei under two different rearing densities (800- and 400- shrimp/m3) for 15 d and further analyzed the differences in immune response to Vibrio parahaemolyticus E1 (VPE1) raised under two density conditions. Totally 45 different expression genes (DEGs) were identified in the hepatopancreas under two different rearing densities, the DEGs were grouped into four processes or pathways related to animal immune system. Then, exposure to the VPE1 resulted in 639 DEGs, involved into fourteen immune related processes or pathways. In the intestine, seventeen processes or pathways related to the immune system were identified among the 5470 DEGs under two different rearing densities. 279 DEGs were identified post VPE1 challenge, classified into five processes or pathways associated with the immune system. Meanwhile, the results of growth performance, histopathology and the activities of antioxidant enzymes in the hepatopancreas and intestines of shrimp showed that high density decreased weight gain rate (63.20 ± 1.67% and 18.73 ± 3.35% in the high and low rearing density groups, respectively), severely destroyed the histopathology and inhibited the antioxidant enzymes activities. This study demonstrated that rearing density in L. vannamei significantly impacts susceptibility to the VPE1, via altered transcriptional challenge responses, and thus higher mortality due to disease. • The hepatopancreas and intestinal transcriptome of L. vannamei were constructed. • The mechanisms between disease susceptibility and rearing densities were explored. • HD inhibited growth, destroyed the histopathology and the antioxidant system. • HD disordered the immune system of shrimp, and thus higher mortality due to disease. • HD significantly improved the susceptibility of shrimp to the VPE1. [ABSTRACT FROM AUTHOR]

The ability to mass-rear insects in high densities is a precondition for the edible insect industry but the space requirement has to be determined specifically for each species. Mass-rearing methods for Ruspolia differens Serville (Orthoptera: Tettigoniidae), one of the most consumed edible insect species in East Africa, are currently lacking. Though, these methods are urgently needed to enhance the food security in the region and to reduce the pressure on the wild populations. Here, we experimentally evaluated the effect of rearing density and rearing environment on the survival of R. differens nymphs. We conducted two experiments; in Experiment 1 we used small 0.15-liter rearing containers and in Experiment 2, larger 0.75-liter containers. The rearing densities ranged from 4 to 300 individuals per liter and we used three different rearing environments ('net', 'spikes', and 'oat sprouts'). We found that the survival of R. differens nymphs is strongly density-dependent. The suitable rearing density for young R. differens nymphs should be ≤36 nymphs per liter, as in higher densities the mortality of nymphs increases rapidly over the course of time. With rearing densities ≤36 nymphs per liter, a survival rate of 60% can be expected up to 28 d after rearing. The studied environments only had a minor effect on the survival. These results create the basis for the efforts to upscale the rearing of R. differens in the future. [ABSTRACT FROM AUTHOR]

The present study was conducted to test whether a multi-enzyme produced by a fungus would keep performance of broiler chicks receiving a diet with almost 3% less nutrients (energy, protein, amino acids, calcium and phosphor) under two different housing density. In both experiments, positive control received standard broiler diet, negative control received a diet with 3% less nutrients than standard broiler diet and enzyme group received the negative control diet+supplemental enzyme. In the first trial with 1000, day-old chicks housed 10 birds/m2, only 1% improvement in feed conversion efficiency and body growth was achieved with enzyme supplementation in contrast to the negative control at the end of 35 days feeding period. In the second trial with 1200, day-old-chicks accommodated 16 birds/m2. The results showed that enzyme improved broiler performance almost 3.5% in contrast to the performance obtained from the negative control. In conclusion, supplementing broiler diets based on maize/soya with a multi-enzyme produced by a single fungus provides a great potential to gain the gap created by formulating almost 3% nutrients reduction in broilers housed with 16 birds/m2 density. However, providing high comfort and better rearing condition as the birds at 10 birds/m2 density, positive effects of the enzyme was limited. [ABSTRACT FROM AUTHOR]

The paper defines the methods for maintenance of maximum density ( N ) in respect of the freshwater crayfish ( Astacus leptodactylus) fingerlings (larvae/juveniles), a prospective model organism for aquaculture. The question of optimal maintenance of the fingerlings has been addressed in the present study, considering the following parameters: (1) the ratio between the total area on which the fingerlings are being grown, and the area occupied by one individual, and (2) the planting density dependence on the specific growth rate of differently aged individuals ( C ). Analysis of our results shows that the N values decrease significantly with the growth of individuals (4167, 2222 and 617 ind. m for 30, 65 and 120 days old fingerlings, respectively). The values of C for individuals at the age of 30 days, however, do not depend on rearing density within the range of 300-1500 ind. m. A linear decrease in C is observed in density gradient for older ages. The density at which C becomes equal to zero is 3553 ind. m for 65 days old fingerlings, and 1307 ind. m for the 120 days old ones. The revealed differences (with respect to growth rates and planting densities in different age groups) may presumably be caused by the influence of the specific mechanisms of an intra-populational regulation, tenable with the conditions of high densities of fingerlings. [ABSTRACT FROM AUTHOR]

Lowered rearing density has repeatedly been shown to increase the performance of hatchery-reared salmonids stocked into natural environments. One possible mechanism for this pattern could be that lower densities enhance brain development, which has been shown to be the case in other hatchery enhancement strategies, like environmental enrichment. Here, we investigated the size of the brain in hatchery-reared Atlantic salmon Salmo salar kept at standard (high) and reduced (low) tank densities. In contrast to our predictions, we found that fish reared at high density had larger dry mass of cerebellum and telencephalon, correcting for body size. No differences were detected for total brain mass. Furthermore, we found that the relative size of both telencephalon and cerebellum, in relation to total brain mass, changed with body size. Cerebellum increased in relative size with increased body size, while the opposite pattern was observed for telencephalon. Overall, these results reveal substantial brain plasticity depending on the surrounding environment as well as ontogenetic adaptive changes in the brain of the Atlantic salmon. [ABSTRACT FROM AUTHOR]

Lymantria dispar caterpillars were reared under two different rearing densities for the first three days of the 4th larval instar: 5 larvae that were kept in a Petri dish (V = 80 ml) belonged to the intense stress (D1 group); 5 larvae that were kept in a plastic cup (V = 300ml) belonged to the group exposed to less intense stress (D2 group). In the control group, single larvae were reared in a Petri dish. Morphometric changes in L1, L2 and L2’ dorsolateral neurosecretory neurons (nsn) were analyzed. After keeping 5 larvae in a Petri dish, the size of L2 neurosecretory neurons (nsn) significantly increased. Rearing 5 larvae in a plastic cup significantly increased the size of L1 nsn nuclei and the number of L2’nsn. A decrease in relative band densities in the region of molecular masses (11-15 kD) that correspond to prothoracicotropic hormones in the gypsy moth was observed in the electrophoretic profiles that were obtained after both treatments in comparison to the control group. [Acknowledgments. This study was supported by the Serbian Ministry of Education and Science (Grant No. 173027).]

Morphometric changes of A1, A1' and A2 protocerebral dorsomedial neurosecretory neurons, total brain protein content and brain protein profiles were analyzed in 4th instar Lymantria dispar larvae under elevated rearing density, i.e. under intense stress when 5 larvae were kept in a petri dish (V = 80 ml), less intense stress when 5 larvae were kept in a plastic cup (V = 300 ml). In the control samples the larvae were reared in isolated conditions. Protein pattern changes in the brain were observed. Proteins with the following molecular masses: 30, 14, 10 and 3.4-2.5 kD were detected in the experimental groups. The size and cytological characteristics of protocerebral dorsomedial neurosecretory neurons were changed under elevated rearing density.

Sharpsnout seabream Diplodus puntazzo has been successfully introduced in Mediterranean aquaculture for reasons of species diversification. However, there is limited information related to specific rearing conditions that the species may require for production optimization in land-based aquaculture. The aim of the present study was to investigate the combined effects of rearing density and background colour on growth performance of sharpsnout sea bream D. puntazzo reared in a recirculating water system. Juveniles (4.0 ± 0.03 g) were reared (duplicated groups) under low (D 16 fish tank or 1 kg m) and high (3D 48 fish tank or 3 kg m) density in white, light blue and black tanks for 88 days. During the first 53 days of rearing, fish under low density presented better growth than fish under high density. However, in the following period (days 53-88) SGR in 3D-reared fish was significantly higher than in D-reared fish, resulting in no mass differences on day 88. Regardless of rearing density effects, black tanks had a negative effect on growth and should be avoided in sharpsnout sea bream rearing. Within the life stage studied, present growth results, along with those of fish groups homogeneity (coefficient of mass variation, frequency distribution of mass), indicate a change in social interactions according to body size. It is suggested that juvenile sharpsnout seabream should be stocked at low density until they reach approximately 16 g. Afterwards, a higher density seems more appropriate for this species while it also ensures a higher productivity. [ABSTRACT FROM AUTHOR]

The river pufferfish T akifugu obscurus is one of the most valuable aquaculture species in South Korea and China. To analyse the effect of rearing densities in the aquaculture of this species, we performed an experiment where T. obscurus was reared for 3 months after hatching at different initial rearing densities (10 fish L−1, 20 fish L−1, and 25 fish L−1) which are similar to rearing densities in aquaculture (10-15 fish L−1). The growth of the high density group (25 fish L−1) was significantly slower than that of the low density group. To determine biomarkers for stress under conditions of high rearing density, we chose six stress-related genes (heat shock proteins ( HSP s) 70 and 90β, metallothionein ( MT), cytochrome P450 1A ( CYP 1A), glucocorticoid receptor ( GCR) and phosphoenolpyruvate carboxykinase ( PEPCK) and evaluated their expression by real-time reverse transcript polymerase chain reaction (real-time RT- PCR). In the high density group, we observed significant up-regulation of genes encoding HSP s 70 and 90β, MT, CYP 1A, and PEPCK in liver and brain, but no up-regulation of the GCR. In particular, expression of HSP 70, MT and CYP 1A was up-regulated in a tissue-specific pattern. Our results demonstrate that growth retardation at high initial rearing densities is associated with stress-induced gene expression. These findings further indicate that molecular biomarkers can be useful to determine the optimal rearing conditions with respect to densities of pufferfish culture. [ABSTRACT FROM AUTHOR]

Abstract: The effect of stocking density on indicators of welfare has been investigated by several studies on farmed rainbow trout Oncorhynchus mykiss. However, the densities at which welfare are compromised remain ambiguous. Here three different stocking density treatments were selected based on the results of a previous study, where levels of crowding where determined using the spatial distribution of fish in two-tank systems. An un-crowded low density of 25kgm−3, the highest density accepted by the fish without showing indications of crowding stress of 80kgm−3 as the intermediate density, and the highest density accepted by the fish showing indications of crowding stress of 140kgm−3 as the high density were investigated. The aim of the present study was to examine the effect of being held at these densities on indicators of welfare. This was achieved through oxygen consumption measurements using automated respirometry, recording fin erosion, determining scale loss and analysing plasma cortisol and brain serotonergic activity levels. The results obtained in the present study indicated that at the lowest density the fish had the space and opportunity to display their natural aggressive behaviour and that the fish held at the highest density were exposed to a situation of confinement. [Copyright &y& Elsevier]

We evaluated growth and survival of spring Chinook salmon Oncorhynchus tshawytscha reared at varying densities at Warm Springs National Fish Hatchery, Oregon. For three consecutive brood years, density treatments consisted of low, medium, and high groups in 57.8-m3 raceways with approximately 16,000, 24,000, and 32,000 fish/raceway, respectively. Fish were volitionally released in both the autumn and spring to mimic the downstream migration timing of the endemic wild spring Chinook salmon stock. Just prior to the autumn release, the rearing density estimate was 4.24 kg/m3 for the low-density group, 6.27 kg/m3 for the medium-density group, and 8.42 kg/m3 for the high-density group. While weight gain did not differ among density treatments (P = 0.72), significant differences were found in median fork length (P < 0.001) for fish reared at different densities. Fish reared at high density exhibited the highest on-hatchery mortality rate during two brood years; however, differences in mortality rate among densities were not significant (P = 0.20). In one brood year, adult recovery rates appeared to support the hypothesis that lower initial densities improved postrelease survival (P < 0.01). All rearing densities utilized in this evaluation were relatively low and may partially explain why more differences were not readily apparent among density groups. In addition, the volitional release was a confounding factor in our study because we were unable to quantify the number of fish released in the autumn. [ABSTRACT FROM AUTHOR]

Abstract: A 9week growth trial was performed at two rearing densities; low (~25kgm−3) and high (~100kgm−3), in combination with either static water or a water current corresponding to 0.9body lengthss−1, to investigate the effects of density and exercise on the bioenergetics of rainbow trout reared at 19°C, particularly routine metabolic rate (RMR), specific growth rate (SGR), and feed conversion ratio (FCR). The growth trial showed that high rearing density resulted in significantly lower SGR and increased FCR, with no significant alleviating effects of a water current, although slight improvement in both parameters were observed at low density. A significant linear relationship between SGR and FCR suggested that increased energy expenditure was the primary cause of reduced growth. Hourly measurements of instantaneous oxygen uptake, during a period of similar growth (200–350g), revealed clear effects of the experimental conditions. Energetic budgets were calculated from feed intake and routine metabolic rate (RMR) and revealed that whilst feed intake was similar for all groups, a higher RMR in the high density groups resulted in a higher daily rate of energy utilization for routine activity, leading to slower growth. However, a lower RMR in fish subjected to a current resulted in a greater proportion of energy being retained, leading to significantly higher SGR for the selected period, at both low and high density. Furthermore, the presence of a water current was observed to induce schooling behaviour, which is known to reduce aggression and stress. It is thereby likely that the presence of a current had a positive effect on welfare in addition to its effect on energy metabolism. We conclude that the presence of a water current to some extent could alleviate the negative effects of high density at 19°C, a relatively high temperature experienced in farming of rainbow trout during hot seasons. [Copyright &y& Elsevier]

Effects of rearing density, adult density and sex ratio in the flight chamber, adult age, sex, presence or absence of food, and duration of food deprivation on rate of and time to flight initiation of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), were studied in the laboratory. Rates of flight initiation were slightly lower at lower rearing densities, but they did not differ with age or sex of adults, presence or absence of food in the flight chamber, or duration of food deprivation. Focal adults were less likely to fly when individuals of the opposite sex were present in flight chambers. Presence of the same sex or mixed sexes and numbers of individuals in flight chambers did not affect tendency to fly of focal individuals. Mean time to flight of older beetles (7-20 d old) was less than that of younger beetles (1-4 d old). No young beetles flew during the first 24 h of flight tests. Mean time to flight did not differ with rearing density, sex, presence or absence of food, or duration of food deprivation. Our results indicate that this species is highly dispersive during the adult stage and that flight does not seem to be associated with just prereproductive or postreproductive dispersal phases, high rearing density, or short to medium periods of food deprivation. Therefore, T. castaneum level of flight activity does not seem to be associated with factors that have been shown in the literature to increase dispersal by walking for this species and to increase flight initiation in other stored-product species. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that fish vision and spectrum perception are strongly related to each species natural habitat and living ethology. Recent research data clearly indicate that light spectrum affects farmed fish stress response, physiological status, behaviour, and consequently growth performance. This study aimed to investigate the effects of white (full-spectrum), red (605nm) and blue (480nm) light on common carp reared in a recirculating water system. Two experiments were conducted. The first (Experiment 1) was performed on scaled carp (14.68±0.14g, duration 158 days) combining light treatment with two stocking densities (low: 10specimenstank−1 or 1.22kgm−3 and high: 40specimenstank−1 or 4.89kgm−3). The second (Experiment 2) investigated the effects of light spectrum in mirror carp (51.88±0.46g, duration 143 days) combined with two light intensities (150 and 300lx). Within the fish life stage examined and duration of present experiments, it is indicated that scaled common carp should be reared under red illumination when at low stocking density and blue illumination when at high stocking density. For the rearing of mirror carp, blue or red light should be avoided since they induced an increase in size heterogeneity. Present results also underline the importance of lighting conditions on reared common carp physiological status. Changing light spectrum in indoor recirculating water systems is easy, cost efficient and appropriate manipulation could befit reared fish welfare. [Copyright &y& Elsevier]

This study examined breed-specific stress-related hormonal and gene expression profiles in three Italian chicken breeds (Valdarnese Bianca, Bionda Piemontese, Robusta Maculata) reared in controlled conditions. Glucocorticoids work through the glucocorticoid receptor (GR), which modulates target genes transcription. We investigated breed-specific changes in corticosterone (ELISA) and GR expression. GR mRNA levels were analyzed using one-tube, two-temperature real-time PCR for absolute quantification of the gene expression by the standard curve method. Our results show high expression of GR in hepatic tissue. Significant effect of the breed was recorded for plasma corticosterone concentration: Valdarnese Bianca 3.35 ng/mL, Bionda Piemontese 1.73 ng/mL, Robusta Maculata 2.02 ng/mL. Breed specific gene expression has been recorded with a GR ranging from 1.12E+04 (Robusta Maculata) to 1.00E+05 (Bionda Piemontese) mRNA copy number/100 ng total RNA. Negative correlation was found between gene expression and blood corticosterone level. [ABSTRACT FROM AUTHOR]

Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) vectors Xylella fastidiosa, a bacterium causing Pierce's disease in grapevine. The development and reproductive biology of this economically important insect species were studied under greenhouse and laboratory conditions during the spring-summer and fall-winter and at different rearing densities. The greenhouse was heated during the cool months to match summer temperatures and photoperiods were enhanced artificially. Longevity was affected by sex and season, with winter individuals living significantly longer than summer males (6.5-fold) and females (two-fold). Vitellogenesis was delayed in fall female H. vitripennis and a higher variability in lifetime fecundities was also observed. Longevity and the factors influencing it such as environmental conditions and availability of food sources are key factors determining fecundity in H. vitripennis. Offspring performance (developmental time, survival) was moderate during the cool months, although development of nymphs to adulthood was ≈=13% greater. Rearing densities affected developmental time, survival, and egg production. Egg production per capita was higher in winter adults and the largest egg output was obtained at a rearing density of 100 nymphs per cage. Data presented herein suggest that nymph and adult H. vitripennis have evolved to ensure that only resistant stages are exposed to seasonal hazards. Captive adult females entered reproductive diapause in the fall as wild females would and despite warm greenhouse temperatures and long photoperiods and nymphal development decreased three- to six-fold during the fall-winter depending on rearing densities. These traits may be critical for the species to perpetuate in its native range. [ABSTRACT FROM AUTHOR]

During 84 days, the effects of density on juvenile sea bass (Dicentrarchus labrax) (76± 16 g) were studied in an experimental tank-based flow through system. Performance, stress response and resistance to virus infection were analysed under five stabilized rearing densities: 10, 20, 40, 70 and 100 kg m-3. Water quality parameters (CO2, total ammonia nitrogen and O2) were measured and maintained close to the recommended values for farmed sea bass by adjusting water renewal exchange. No significant differences were observed between density treatments, neither on stress response (cortisol) nor susceptibility to nodavirus. With regards to biological performances, the daily feed intake and specific growth rate were significantly lower in fish reared at the 100 kg m-3 density. Results on the effects of density in sea bass reared in flow through (present study) and in recirculating aquaculture systems (RAS) (Sammouth et al. 2009) were compared as a contribution to the identification of density not affecting health and welfare in farmed sea bass. [ABSTRACT FROM AUTHOR]

Blue king crab ( Paralithodes platypus) larvae were cultivated to test the effects of diet, temperature and rearing density. Dietary treatments included no feeding (unfed), Artemia nauplii enriched with diatoms Thalassiosira nordenskioeldii (THAL), unenriched Artemia fed in addition to Thalassiosira (A+THAL) and a control diet of Artemia enriched with frozen Isochrysis paste (ISO 6). Trials were conducted at 6 °C, and a rearing density of 10 zoea L−1, with six replicates per treatment. The ISO 6 diet was also tested at 3 °C (ISO 3) and 9 °C (ISO 9), and at densities of 20 (ISO 20) and 40 (ISO 40) zoea L−1. Survival of zoea larvae fed the A+THAL diet (91.7%) was significantly higher than all others, whereas unfed zoea larvae died within 2 weeks. Temperature and rearing density had no significant effects on survival. Time required to reach stage C1 was significantly greater at 3 °C (109 days) than at 6 °C (70 days), but did not decrease further at 9 °C. After reaching the postlarval (glaucothoe) stage, half of the replicates in the ISO 20 and ISO 40 treatments were fed continuously, but survival did not differ significantly from unfed glaucothoe. We conclude that blue king crab larvae are not lecithotrophic and can be cultivated with high survival using the proper diet. These techniques can be used to produce large numbers of juvenile crab for laboratory research, or could be modified for use in stock-enhancement programmes. [ABSTRACT FROM AUTHOR]