Effects Of High Stocking Density Research Articles

Microclimate measuring and fluid‑dynamic simulation in an industrial broiler house: testing of an experimental ventilation system.

The environment in the broiler house is a combination of physical and biological factors generating a complex dynamic system of interactions between birds, husbandry system, light, temperature, and the aerial environment. Ventilation plays a key role in this scenario. It is pivotal to remove carbon dioxide and water vapor from the air of the hen house. Adequate ventilation rates provide the most effective method of controlling temperature within the hen house. They allow for controlling the relative humidity and can play a key role in alleviating the negative effects of high stocking density and of wet litter. In the present study the results of experimental tests performed in a breeding broiler farm are shown. In particular the efficiency of a semi transversal ventilation system was studied against the use of a pure transversal one. In order to verify the efficiency of the systems, fluid dynamic simulations were carried out using the software Comsol multiphysics. The results of this study show that a correct architectural and structural design of the building must be supported by a design of the ventilation system able to maintain the environmental parameters within the limits of the thermo‑neutral and welfare conditions and to achieve the highest levels of productivity.

High stocking density as a predisposing factor for necrotic enteritis in broiler chicks

Stocking density is a management factor which has critical implications for the poultry industry. The aim of the present study was to investigate the effect of high stocking density as a predisposing factor in an experimental model of necrotic enteritis in broiler chicks. The experimental challenge model included an oral inoculation with 10-fold dose of attenuated anticoccidial vaccine and multiple oral inoculations with a specific strain of Clostridium perfringens. Two hundred and forty as hatched day-old broiler chicks were randomly allocated to four treatment groups according to the following experimental design: group N, with normal stocking density (15 birds/m2) and no challenge; group D, with high stocking density (30 birds/m2) and no challenge; group P, with normal stocking density and positive challenge; and group DP, with high stocking density and positive challenge. From each bird, the intestine, gizzard and liver were collected and scored for gross lesions. The intestinal digesta was collected for pH and viscosity determination. One caecum from each bird was taken for microbiological analysis. The statistical analysis and evaluation of the experimental data revealed significant interaction effects between “stocking density” and “challenge”, regarding gross lesion scores in intestine and liver, pH values in jejunum, ileum and caeca as well as C. perfringens counts in the caeca (P ≤ 0.05). High stocking density in challenged birds increased the gross lesion score in the intestine (P ≤ 0.05), contrary to unchallenged birds. It can be concluded that high stocking density affects unfavourably the welfare and gut health of broiler chicks, predisposes to necrotic enteritis in a subclinical experimental model and increases further its importance as a management factor for the poultry industry.

Effect of rearing density on the blood and tissues of mullet (Mugil cephalus L.)

This study evaluated the biological effects of high stocking density on mullet (Mugil cephalus). Fifty fish, caught from Faro lake, were divided into two groups, a low-density control group (n = 15), stocked at 3.4 kg/m3 in an 800 l tank and a high-density experimental group (n = 35), stocked at 8.4 kg/m3 an 800 l tank. The ammonia concentration in the control group tank reached 0.3 mg/l after 2 days while that in the experimental tank reached 5 mg/l. Haematological parameters and serum protein profiles were determined following blood sampling. An Unpaired T-test showed significant differences between the two groups on Red Blood Cell Count, Haematocrit, Haemoglobin, White Blood Cell Count, Mean Corpuscular Haemoglobin, Mean Corpuscular Haemoglobin Concentration, total proteins, albumin and α-globulins. In the experimental group, the disappearance of prealbumin and the γ-globulin fraction was particularly evident. Histopathological changes indicated that mucosal electrolytic failure was the main function compromised. This could eventually lead to death. The findings suggest that mullet is sensitive to stocking density linked to ammonia toxicosis.

Combined effects of high stocking density and Piscirickettsia salmonis treatment on the immune system, metabolism and osmoregulatory responses of the Sub-Antarctic Notothenioid fish Eleginops maclovinus

The aim of this study was to evaluate immunological, metabolic and osmoregulatory secondary stress responses in Eleginops maclovinus specimens submitted to three different stocking densities: i) low (3.1 kg m−3), medium (15 kg m−3) and high (60 kg m−3) during 10 days, alone or in combination with a previous treatment of a protein extract of the pathogen Piscirickettsia salmonis (0.5 μg g weight body−1). Plasma, liver, gill and kidney samples were obtained at the end of both experiments. Plasma cortisol and amino acid levels increased, while plasma glucose, triglyceride and lactate levels decreased at higher stocking densities. However, no effects were observed on serum Immunoglobulin type M (IgM anti P. salmonis level) values. Gill Na+, K+-ATPase activity enhanced under these experimental conditions, suggesting an osmotic imbalance. Energy metabolism changes, assessed by metabolite concentrations and enzyme activities, indicated a reallocation of energetic substrates at higher stocking densities. Specimens inoculated with a protein extract of P. salmonis and maintained at different stocking densities showed primary stress response, as all groups enhanced plasma cortisol concentrations. Serum IgM levels increased after treatment with P. salmonis extract but a negative influence of high stocking density on IgM production was observed when immune system was activated. Furthermore, treatment with P. salmonis protein extract evoked deep changes in the metabolite stores in all tissues tested, indicating a mobilization of energy substrates in response to infection. The results show that stocking density induced immunological, metabolic and osmoregulatory secondary stress responses in E. maclovinus specimens and that previous treatment with P. salmonis compromise these changes.

Effect of stocking density on the expression of glucose transporter protein 1 and other physiological factors in the Lake Victoria Nile tilapia, Oreochromis niloticus (L.)

Fish farmers have a tendency of employing high stocking density (HSD) as a means of increasing productivity. However, HSD is a chronic stressor that is likely to lower profitability of fish farming if not implemented properly. HSD induces stress which in turn elevates sequentially the levels of plasma cortisol and glucose. The resultant glucose is distributed to various tissues by glucose transporter protein (GLUTs) to restore normalcy. GLUT 1, transmembrane protein found in erythrocytes, is responsible for import and export of glucose in red blood cells. However, knowledge on how chronic stress impact glucose and GLUT 1 protein in fish subjected to HSD is still unclear. In this study, effect of HSD on the expression of GLUT 1 in Nile tilapia was investigated in an attempt to elucidate the role of GLUT 1 in glucose metabolism during chronic stress. Fish were reared for 4 weeks at 1.5 and 4.5 kg/m3 for low stocking density (LSD) and HSD, respectively. Four physiological parameters were determined from the blood samples obtained from fish at the end of experiment. At p < 0.05, there were significant differences between fish reared at HSD and LSD in plasma cortisol level (72.1 ± 5.9 ng/ml and 37.5 ± 4.6 ng/ml); blood glucose level (136.00 ± 1.3 mg/dL and 70.2 ± 1.0 mg/dL); erythrocytes count (7.2 ± 0.5 × 106 mm−3 and 2.1 ± 0.4 × 106 mm−3); and plasma GLUT 1 level (1.40 ± 0.17 rbi and 0.81 ± 0.07 rbi), respectively. HSD induced elevation of plasma cortisol level, blood glucose level, erythrocytes count and GLUT 1 level. These elevated physiological factors and particularly GLUT 1 can be used as a cellular stress biomarker in fish farming and aquaculture.

Total egg harvest by the calanoid copepodAcartia tonsa(Dana) in intensive culture - effects of high stocking densities on daily egg harvest and egg quality

Understanding the factors limiting copepod productivity in dense cultures is a prerequisite for the partial or entire replacement of Artemia and rotifers as live feed for finfish larvae. In dense cultures, high encounter rates between individuals may increase stress, cannibalism incidents and potentially trigger resting egg production. We conducted an experiment to evaluate the potential egg production and egg quality of Acartia tonsa stocked at densities ranging from 10 to >5000 ind. L−1. Egg Production (EP), Delayed Hatching Eggs production (DHE), hatching success (HS), egg mortality and water quality were used as end points. In the present system, A. tonsa was raised at >5000 ind. L−1 without affecting the mortality, confirming that attaining this high density in culture is possible. However, egg harvest reached an optimum of 12 000 egg L−1 day−1 at ~2500 ind. L−1 indicating that increasing stocking density above this level is not of practical interest. Calculations showed that the loss in egg harvest at stocking densities <2500 ind. L−1 is of 1.3% for every additional 100 adult copepods L−1. The increasing adult density did not affected the proportion of DHE produced (~10% of harvest) but decreased significantly the HS, though not to a point that would be problematic in a commercial production. Understanding the biology of copepods when stocked at high density is important to improve copepod culture systems and increase egg harvest yields. Technical solutions such as the continuous separation of eggs from adults in the water column, recirculation and the continuous provision of food are seen as potential solutions.

Chronic stress due to high stocking density in open sea cage farming induces variation in biochemical and immunological functions in Asian seabass (Lates calcarifer, Bloch)

Stocking density is an important factor in cage aquaculture of finfish. Effects of high stocking density (35 fishcubicm(-1)) on a range of biochemical and immunological parameters in Asian seabass reared in open sea floating net cages were compared to fish held in relatively low density (15 fishcubicm(-1)). The results revealed that chronic stress due to high stocking density induced variations in most of the parameters studied as evidenced by increased cortisol and glucose levels and decreased activity of lysozyme, myeloperoxidase and complement. Production of reactive oxygen species, total leucocyte count and total serum protein were also decreased, whereas anti-protease, alkaline phosphatase and acid phosphatase activities were increased in high stocking-density group when compared to low stocking-density group. Effects of chronic stress due to high stocking density were discussed in relation to variations in these parameters.

The effect of lycopene on antioxidant status in rainbow trout (Oncorhynchus mykiss) reared under high stocking density

Lycopene, the major carotenoid found in tomato, exhibits health beneficial effects by virtue of its antioxidant activity. As stocking density is known as a stress factor in fish, the effects of dietary lycopene supplementation (0, 200 or 400mgkg−1) on growth performance and antioxidant status in rainbow trout under normal (20kgm3−1) and high (100kgm3−1) stocking density were studied. Glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities were evaluated, as well as lipid peroxidation measured as malondialdehyde (MDA). Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), erythroid-derived 2-like 2 (Nrf2) and heme-oxygenase 1 (HO-1) levels were also assayed as an indicator of detoxifying/antioxidant defense mechanisms to cope with oxidative stress. Results showed that exposure to high stocking density depressed feed intake by 6.8% and body weight gain by 12.1%, increased plasma and hepatic MDA level by 88.5 and 124.3% and decreased hepatic SOD, CAT and GSH-Px activities by 22.1, 43.4 and 51.7%, respectively. In fish under crowded conditions, an expression of hepatic NF-κB was increased by 71.5%, being suppressed in Nrf2 and HO-1 by 40.6 and 42.7%, respectively. Lycopene supplementation increased linearly fish growth performance and antioxidant enzyme activity, and decreased linearly MDA concentration in both low and high stocking densities. NF-κB levels decreased hepatic Nrf2 and HO-1 levels increased linearly with lycopene supplementation at a greater extent in fish under low stocking condition. In conclusion, dietary supplementation of lycopene to fish reduces the detrimental effects of high stocking density on growth performance and modulates oxidative status via activating host defense system at cellular level. It appears that lycopene can be added up to 400mgkg−1 to rainbow trout diets to improve meat quality.

닭의 고밀도 사양체계가 스트레스 및 지방대사 연관 유전자 발현에 미치는 영향

본 연구는 육계에서 고밀도 사양체계가 간의 지놈 전사체, 특히 스트레스 및 지방대사 연관 유전자들의 발현에 어떤 영향을 미치는지 알아보기 위하여 실시하였다. 공시된 시험동물의 대조군 사육밀도는 <TEX>$495cm^2$</TEX>/수, 고밀도군은 <TEX>$245cm^2$</TEX>/수를 35일령까지 유지하였다. 대조구와 비교하여 고밀도 사양 육계에서 체중, 증체량, 사료섭취량이 유의적(p<0.05)으로 감소되는 것으로 나타났다. 폐사율은 고밀도군에서 15.7%로서 대조군(3.7%)에 비해 폐사율이 4.2배 높았다. 육계의 사육밀도에 따른 스트레스관련 유전자 HMGCR, <TEX>$HSP90{\alpha}$</TEX>, HSPA5 (GRP78/Bip), DNAJC3, ATF4 등의 발현이 증가하였으며, interferon-<TEX>${\gamma}$</TEX>, PDCD4 등의 발현은 감소하였다. Endoplasmic reticulum (ER) stress 관련 HSPA5 (GRP78/Bip), DNAJC3 그리고 ATF4은 유전자들은 고밀도 사양계에서 유전자의 발현이 2-3배 증가함을 보였다. 고밀도 사양은 지방산 합성에 관여하는 효소들(ACSL5, TMEM195, ELOVL6)의 유전자 발현증가와 지방산산화(<TEX>${\beta}$</TEX>-oxidatin)에 관여하는 효소들(ACAA1, ACOX1, EHHADH, LOC423347, CPT1A)의 RNA 발현 증가를 유도하였다. 본 연구는 밀사에 의한 스트레스가 닭의 간에서 지방을 합성하기 위한 유전자들의 발현을 증가시키고, 합성된 지방산을 분해하여 에너지를 생산하기 위한 지방산의 산화도 높게 유지하고 있음을 보여주었다. 닭의 주요 지방대사기관인 간에서 외부적 환경인자(사육환경)에 의한 스트레스와 생리적 대사(지방대사 및 소포체 스트레스)가 서로 밀접한 관계가 있음을 분자생물학적 수준에서 확인하였다. 따라서 스트레스저감 사육환경제공 및 친환경 사육방법 도입 등 동물복지를 고려한 가금사양체계가 필요한 것으로 사료된다. The effect of high stocking density (HSD) on the expression of stress and lipid metabolism associated genes in the liver of broiler chickens was examined by chicken genome array analysis. The chickens in a control group were randomly assigned to a <TEX>$495cm^2/bird$</TEX> stocking density, whereas the chickens in a HSD group were arranged in a <TEX>$245cm^2/bird$</TEX> stocking density with feeding ad libitum for 35 days. The chickens assigned to the HSD group had a significantly lower body weight, weight gain, and feed intake compared with those of the control group (p<0.05). The mortality of chickens was higher in the HSD group than in the control group. The microarray analysis indicated up-regulation of stress associated genes such as HMGCR, <TEX>$HSP90{\alpha}$</TEX>, HSPA5 (GRP78/Bip), DNAJC3 and ATF4, and down-regulation of interferon-<TEX>${\gamma}$</TEX> and PDCD4 genes. The endoplasmic reticulum stress associated genes, HSPA5 (GRP78/Bip), DNAJC3 and ATF4, were highly expressed in the HSD group. The genes, ACSL5, TMEM195 and ELOVL6, involved in fatty acid synthesis, were elevated in the HSD group. The genes, ACAA1, ACOX1, EHHADH, LOC423347 and CPT1A, related to fatty acid oxidation, were also activated in the HSD group. These results suggest that a HSD rearing system stimulates the genes associated with fatty acid synthesis as well as fatty acid oxidation in the liver of broiler chickens.

Stocking density affects the growth performance of broilers in a sex-dependent fashion

The effects of stocking density, sex, and dietary ME concentration on live performance, footpad burns, and leg weakness of broilers were investigated. A total of 876 male and 1,020 female 1-d-old chicks were placed in 24 pens to simulate final stocking density treatments of 26 kg (LSD; 10 males or 12 females/m(2)) and 42 kg (HSD; 16 males or 18 females/m(2)) of BW/m(2) floor space. Two series of experimental diets with a 150 kcal/kg difference in ME concentration (2,800, 2,900, and 3,000 or 2,950, 3,050, and 3,150 kcal of ME/kg) were compared in a 3-phase feeding program. The HSD treatment significantly decreased BW gain and feed conversion ratio (FCR). The HSD chickens consumed less feed by 35 d of age; thereafter, the reverse was true. Male chickens had significantly higher feed intake (FI), BW gain, and FCR compared with females. A significant interaction was found of stocking density and age for FI, BW gain, and FCR. Compared with LSD treatment, HSD broilers had a higher FI and a lower FCR from 36 to 42 d of age. Stocking density, sex, and age had a significant interaction for BW gain and FCR. Female broilers had worse BW gain and FCR when stocked at high density from 36 to 42 d of age. Stocking density had no significant influence on breast, thigh, or abdominal fat yield. Female broilers had significantly higher breast yield and abdominal fat. Male broilers and HSD treatment had high footpad burn and gait scores. A low ME diet increased footpad burn score but had no effect on gait score. The result indicated that stocking density had a more severe effect on the growth of male broilers before 35 d of age. Female broilers need more space than males at similar BW per square meter near marketing age. The incidence and severity of leg weakness are associated with sex, diet, and stocking density. This result suggests that the deteriorated effect of high stocking density is sex and age dependent.

Effects of artificial substrates on the growth, survival and spatial distribution of Litopenaeus vannamei in the intensive culture condition

In order to investigate the effects of artificial substrates (vertical surface of polypropylene fabrics) on cultured shrimp, we reared 28-day old Litopenaeus vannamei post-larvae (PL28) intensively for 90 days at a density of 510 shrimp/m 2 in each of 8 tanks. Two tanks containing no artificial substrate were a control group, and 1, 3 and 5 artificial substrates were present in other 6 tanks. The volume of each tank was 100 L. In the tanks with artificial substrates, the percentage of shrimp distribution on the bottom was less significant (P<0.05) than that in the control tanks. The percentage of shrimps attached to the artificial substrates increased and fewer shrimp occupied the tank bottom as more artificial substrates were added to the tanks. Moreover the trends were more significant as rearing days increased. These results showed that artificial substrates could disperse the shrimp from the tank bottom onto the artificial substrates and thus alleviate the negative effect of high stocking density on shrimp growth in the tanks. Both the average weight and survival in the tanks with artificial substrates were significantly higher (P<0.05) than those in the control tanks. Furthermore, weight and survival increased when more artificial substrates were added. Because the shrimps in all tanks were supplied with suitable water quality and adequate nutritional food, we suggest that the differences of growth and survival were affected mainly by living space added with the addition of artificial substrates.

Biological viability of producing white shrimp Litopenaeus vannamei in seawater floating cages

In the last few years, in an attempt to foment the controlled culture of penaeid shrimp by artisanal fishermen communities, an innovative culture technology using floating cages have been developed in Brazil. In this work, we assessed the biological viability of culturing the Pacific white shrimp Litopenaeus vannamei in floating cages at different stocking densities in Santa María's Bay, México. Additionally, the influence of artificial substrates on growth performance of the shrimp was analyzed. Cages made of PVC-coated polyester mesh supported by wooden poles and PVC tubes were used for this study. Post larvae (PL) were stocked in four nursery cages at 700 PL per m 2. After 30 days of nursery culture, shrimp had reached an average weight of 0.5 g and were then transferred to grow out cages at densities of 100, 150, and 200 shrimp per m 2, with and without the addition of artificial substrates. Survival rate was neither affected by stocking density nor by the presence of added artificial substrates. In contrast, final shrimp weight was higher for those reared at low densities (100 shrimp per m 2) and the use of artificial substrates showed a positive effect on final shrimp weight. After 2 months of culture survival rate was above 90%, the shrimp weight ranged from 6.94 ± 1.51 g to 9.33 ± 1.48 g and yields varying from 818 to 1297 g/m 2 were recorded. The high shrimp production in floating cages was probably due to optimum environmental and rearing conditions provided to the shrimp. The present results confirmed the deleterious effect of high stocking density on shrimp growth, demonstrated the benefits of adding artificial food substrates to the cages, and proved the biological viability of culturing L. vannamei in seawater floating cages in México.

Growth performance, feed utilization, survival and body composition of rabbitfish Siganus canaliculatus raised at two different stocking densities in sea net cages

Over a period of 213-day, the effect of two stocking densities (8 and 12 fish/m3) on the performance of the rabbitfish, Siganus canaliculatus (3.38g ±0.14) in floating cage nets was tested. The results of the study revealed no differences (p < 0.05) in the growth performance and survival of the two groups. Comparatively, the fish group under the higher stocking density (12 fish/m3) exhibited a lower survival rate. The values of feed intake, feed utilization efficiency and final body composition for both treatments did not differ significantly (p < 0.05). In conclusion, the study suggested the possibility of applying higher stocking density in commercial rabbitfish farming. However, more studies are needed on the effects of high stocking densities on fish survival.

Interactive effects of high stocking density and food deprivation on carbohydrate metabolism in several tissues of gilthead sea breamSparus auratus

The influence of high stocking density (HSD) and food deprivation was assessed on carbohydrate metabolism of several tissues of gilthead sea bream Sparus auratus for 14 days. Fish were randomly assigned to one of four treatments: (1) fed fish under normal stocking density (NSD) (4 kg m(-3)); (2) fed fish under HSD (70 kg m(-3)); (3) food-deprived fish under NSD; and (4) food-deprived fish under HSD. After 14 days, samples were taken from the plasma, liver, gills, kidney and brain for the assessment of plasma cortisol, levels of metabolites and the activity of several enzymes involved in carbohydrate metabolism. HSD conditions alone elicited important changes in energy metabolism of several tissues that in some cases were confirmatory (5-fold increase in plama cortisol, 20% increase in plasma glucose, 60% decrease in liver glycogen and 20% increase in gluconeogenic potential in the liver) whereas in others provided new information regarding metabolic adjustments to cope with HSD in the liver (100% increase in glucose phosphorylating capacity), gills (30% decrease in capacity for phosphorylating glucose), kidney (80% increase in the capacity of phosphorylating glucose) and brain (2.5-fold increase in ATP levels). On the other hand, food deprivation alone resulted in increased plasma cortisol, and metabolic changes in the liver (enhanced gluconeogenic and glycogenolytic potential of 13% and 18%, respectively) and brain (10% increase in glycolytic capacity), confirmatory of previous studies, whereas new information regarding metabolic adjustments during food deprivation was obtained in the gills and kidney (decreased lactate levels in both tissues of 45% and 55%, respectively). Furthermore, the results obtained provided, for the first time in fish, information indicating that food deprivation increased the sensitivity of gilthead sea bream to the stress induced by HSD compared with the fed controls, as demonstrated by increased plasma cortisol levels (50% increase vs. fed fish) and a further increase in the capacity to export glucose mobilized from liver glycogen stores (70% decrease vs. fed fish). These results lend support for a cumulative effect of both stressors on plasma cortisol and parameters assessed on carbohydrate metabolism in the present experiments, and provide information regarding reallocation of metabolic energy to cope with simultaneous stressors in fish.

Effects of Artificial Substrate and Stocking Density on the Nursery Production of Pacific White Shrimp Litopenaeus vannamei

AbstractNursery production may be enhanced by the addition of artificial substrate to increase the surface area upon which shrimp graze and to serve as refuge. The objective of this study was to assess the effects of the artificial substrate, AquaMatsTM, on the performance of postlarval Pacific white shrimp Litopenaeus vannamei stocked at three densities. Eighteen 230‐L tanks were stocked with 10‐d postlarvae (mean weight &lt; 0.01 g). Six treatments were evaluated and consisted of shrimp stocked at three densities (778 shrimp/m2, 1,167 shrimp/ m2, and 1,556 shrimp/m2) with and without access to artificial substrate. Shrimp in all treatments received a commercial diet ad libitum. After 6 wk, shrimp were harvested from each nursery tank, counted, and batch weighed. Mean final weight, survival, production, feed conversion ratio, and water quality parameters were analyzed by 2‐way ANOVA. There were highly significant (P &lt; 0.001) density and substrate effects on final weight, but there was no significant interaction effect. Final weight was 26.0, 17.4, and 34.5% greater in treatments with substrate than without substrate when stocked at 778, 1,167, and 1,556 shrimp/m2, respectively. There was no significant density, substrate, or interaction effect on survival or water quality. Mean survival was ± 89.1% for all treatments. Increased shrimp growth in the presence of added substrate was likely due to the availability of attached particulate organic matter on the AquaMatsTM that served as an additional food source. Results from this study indicate that artificial substrate can be used to mitigate the potential negative effects of high stocking density on growth of L. vannamei in nursery systems.

Effects of Age and Stocking Density on Leg Weakness in Broiler Chickens

The effects of stocking density (STD) on leg weakness in broiler chickens was assessed in two trials. The interaction between age and STD on leg weakness was further evaluated in one trial. In Trial 1, walking ability was assessed at 28, 42, and 49 d of age. Birds were stocked at 833, 625, or 435 cm2 per bird. In Trial 2, birds were stocked at 625 or 455 cm2 per bird and assessed for tibial dyschondroplasia (TD) by radiographic examination at 28 d and walking ability at 35 d. Foot pad burn, hock burn, and angulation of the hock joint were also assessed at slaughter on Day 42. Body weight was measured during both trials. At 4 wk of age, leg weakness was a relatively minor problem; few severely lame birds had a gait score (GS) of 4 or 5 at any density. However, 2 wk later, the birds had substantially poorer walking ability. Further deterioration had occurred by 7 wk of age. At all ages, males exhibited greater leg weakness than did females, and the proportion of severely lame birds increased with age of assessment. The effect of STD was consistent across both trials; higher STD were associated with poorer walking ability and reduced live weights. In Trial 2, higher STD resulted in more foot and hock burns. Females were more sensitive to STD than were males However, there was no effect of STD on the prevalence of TD or angulation of the hock joint. The effect of high STD on walking ability was apparent even at 4 wk of age. Adjusting the observations for differences in BW did not alter the findings. It was concluded that the lower STD substantially reduced the prevalence of leg weakness.

High stocking density produces crowding stress altering some physiological and biochemical parameters in gilthead seabream, Sparus aurata, juveniles

High stocking density has been shown to produce a wide variety of effects on cultured fish populations, such as alterations in behavior and poor feed utilization, resulting in mortality and poor growth. High stocking density has also been reported to produce chronic stress and mobilization of energy sources in fish. There are few studies focusing on the effect of high stocking density on one of the most important marine fish species for Mediterranean aquaculture, gilthead seabream (Sparus aurata). Consequently, this study investigates the effect of high stocking density on juveniles of this species, focusing on effects of stocking density on growth, biochemical composition, immune status and hematology.

The effect of high stocking density of fish and duck on pond community structure

The effect of high stocking density of fish and duck on pond community structure

Interactive effects of high stocking density and triiodothyronine-administration on aspects of the in vivo intermediary metabolism and in vitro hepatic response to catecholamine and pancreatic hormone stimulation in brook charr, Salvelinus fontinalis.

Brook charr (Salvelinus fontinalis) were maintained at one of two stocking densities (SD) (30 or 120 kg/m3) and fed either a control or a T3-supplemented (20 mg/kg) diet for 30 days in order to investigate possible interactive effects of SD and T3-administration on growth, feeding rate, food conversion efficiency, and hepatic and dark muscle enzyme activity. In addition, liver slices were incubated in vitro for 6 h with epinephrine, norepinephrine, isoproterenol, propranolol, insulin, glucagon, or somatostatin to evaluate possible SD-T3 interactive effects on hepatic responses to hormonal stimulation. Maintaining the fish at high SD appeared to increase the clearance rate of T3 from the T3-supplemented group. There was no clear evidence of SD-T3 interactive effects on growth rate, feeding rate, or food conversion efficiency, although T3-administration decreased food conversion efficiency, and high SD decreased growth and feeding rates. Of the hepatic enzymes studied, HOAD, malic enzyme, G6PDH, CS, PFK, HK, and GDH activities all showed changes suggestive of interactive SD-T3 effects. Although hepatic FBPase was stimulated by both high SD and T3-administration, there was no evidence of interactive SD-T3 effects. Dark muscle HOAD, CS, and PFK also showed SD-T3-related responses; dark muscle malic enzyme, G6PDH, HK, and GDH were unaffected by either altered SD or T3-administration. Prior treatment of the fish with T3 and high SD had significant effects on free fatty acid (ffa) release to the medium and on hepatic lipid content, but had no effect on the responses to the various endocrine agents used. Glucose release from liver slices of fish stocked at high density (both T3-supplemented and controls) was higher than that of the fish stocked at low density; with the exception of insulin and glucagon, glucose release was similar in all pre-treatment groups. The insulin- and glucagon-stimulated changes in glucose release seen in the fish fed non-supplemented diets were not found in the two groups of fish fed the T3-supplemented diets. High SD and/or T3-administration induced significant lowering of hepatic glycogen content, but there was no effect of pre-treatment on the response to any of the endocrine agents used. The data show a marked effect of SD on energy partitioning processes in brook charr and the animal's ability to respond to T3-stimulation, but provided no evidence of such effects on the liver response to the various agents used.