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 results of this study showed that high stocking density produced a chronic stress situation. Plasma cortisol levels increased up to 16.25 ng ml–1 in fish held at high stocking; this value was 4 fold that of fish held at low stocking; density (3.91 ng ml–1 ). As a consequenceof this stressful situation, there was both haemoconcentration and a decrease in alternative complement pathway (ACP), an important component of the immune system of fish (from 167.23 U ml–1 down to 146.37 U ml–1). Haematocrit, haemoglobin concentration and red blood cell count were significantly higher in fish held at high stocking density (43.87%, 10.76 9dl–1 and 3.36 ×106 mm–3, respectively) compared with those fish held at low stocking density (37.21%, 9.32 g/dlg–1 and 2.82 ×106 mm–3, respectively).In addition, high stocking density produced a decrease in hepatosomatic index (from 2.26 down to 2.04) and altered liver fatty acid composition. Oleic acid (18: 1n-9) decreased in liver total lipids of fish held at high stocking density and arachidonic acid (20: 4-n6) and n-3 high unsaturated fatty acids (n-3 HUFA) were reduced in liver polar lipids of those fish. These alterations reflect the effect of stocking density on lipid metabolism to help meet the increased energy demand.     

Effects of cortisol on growth and development in tilapia larvae,Oreochromis mossambicus

Treatment of one-day-old yolksac larvae of tilapia (Oreochromis mossambicus), by immersion in cortisol solution for two weeks, significantly enhanced growth. The standard length, tail length, head width and wet weight showed dose-dependent increases at concentrations of cortisol (hydrocortisone) from 0.05 ppm to 0.5 ppm, with no further increase at 1.0 ppm. However, cortisol at 5.0 ppm retarded the growth of the larvae without causing any morphological abnormality. Yolk absorption and the onset of free-swimming activity in the larvae were also accelerated by cortisol treatment.     

MS-222、丁香油、苯唑卡因对养殖美洲鲥幼鱼的麻醉效果

研究了MS-222、丁香油、苯唑卡因3种麻醉剂对美洲鲥Alosa sapidissima幼鱼的麻醉效果,并运用该3种麻醉剂的适宜剂量对美洲鲥幼鱼进行了运输试验。麻醉试验结果表明:在较高麻醉浓度(MS-222为75 mg/L以上,丁香油为20 mg/L以上,苯唑卡因为40 mg/L以上)下,鱼很快(30 min内)停止鳃盖张合运动,且停止鳃盖运动的鱼在空气中暴露一定时间(10 min内)后也能够复苏;在适宜的麻醉浓度(MS-222为20-30 mg/L,丁香油为8-10 mg/L;苯唑卡因为20-30 mg/L)下,鱼能够进入麻醉状态,且能保持很长时间(12 h);麻醉效果随着水温的升高而增强;在20 mg/L MS-222麻醉剂下,小规格鱼较大规格鱼更容易进入麻醉状态,而在10 mg/L丁香油和20 mg/L苯唑卡因麻醉剂下,小规格鱼却难进入麻醉状态。运输试验结果表明:麻醉运输组和对照组(非麻醉运输组)鱼血清中皮质醇的含量均显著高于基础组(运输前)(P<0.05);麻醉运输后鱼血清中皮质醇的含量虽均有一定程度的升高,但明显低于对照组,其中仅苯唑卡因麻醉运输组鱼血清中皮质醇的含量显著低于对照组(P<0.05)。试验结果表明,苯唑卡因更适合用于运输美洲鲥的麻醉。     

Stress responses and disease resistance in salmonid fish: Effects of chronic elevation of plasma cortisol

Basal levels of plasma cortisol in unstressed salmonid fish are normally in the range 0–5 ng ml⁻¹. An acute stress such as handling or 1 h confinement caused a temporary elevation of the plasma cortisol levels of both brown trout,Salmo trutta L., and rainbow trout,Salmo gairdneri Richardson, in the range 40–200 ng ml⁻¹ with a return to basal levels within 24–48 h. The extent of the cortisol elevation in response to an acute stress was dependent upon both the species and strain of trout. Chronic stresses, such as prolonged confinement or crowding, resulted in an elevation of plasma cortisol levels to approximately 10 ng ml⁻¹. Under these circumstances, blood cortisol levels remained elevated for periods of up to 4 weeks before acclimation finally occurred. It is shown, by means of intraperitoneal implantation of cortisol, that chronic elevation of plasma cortisol levels in the brown trout results in a dose-dependent increase in mortality due to common bacterial and fungal diseases. This effect is apparent at plasma cortisol levels as low as 10 ng ml⁻¹, levels below those often reported as being representative of ‘unstressed’ fish. These findings are discussed in relation to the known immunosuppressive effects of corticosteroids in teleost fish.     

急性拥挤胁迫对鲤血液中皮质醇及几项生化指标的影响

通过对鲤(Cyprinus carpio)3 h急性拥挤胁迫(密度70g/L)实验,并在胁迫开始前(对照)、胁迫结束后的第0至168 h采样测量几项血液指标。实验结果显示在3 h拥挤胁迫结束之时(0 h),鲤血清皮质醇、血糖和乳酸水平均显著高于胁迫前对照值(P<0.05),而游离脂肪酸水平极显著低于对照值(P<0.01)。之后这些指标继续发生波动,但一段时间后均可恢复至对照水平并保持稳定。实验期间血清甘油三酯和胆固醇水平并未出现显著变化(P>0.05)。该结果提示3 h拥挤胁迫可引起鲤体内血清皮质醇水平及部分血液生化指标发生改变,这可能是为了弥补应激期间机体对能量需求的增大。     

Effects of l‐tryptophan on the performance,energy partitioning and endocrine response of Japanese sea cucumber (Apostichopus japonicus Selenka) exposed to crowding stress

The effects of dietary tryptophan on growth performance, energy budget and endocrine response of sea cucumber Apostichopus japonicus (Selenka) were studied, to test whether the tryptophan could mitigate the crowding stress response of the sea cucumber. Four density treatments of the sea cucumber (i.e. 4, 8, 16 and 32 individuals per 40 L water, represented as L, ML, MH and H) were fed with diets containing 0 (control), 1%, 3% and 5% l ‐tryptophan, respectively, for 75 days. The results showed that the specific growth rate (SGR) and feed conversion ratio (FCE) of A. japonicus decreased with increasing in the stocking densities but increased after supplementation of 1% and 3% tryptophan. The energy allocation of the A. japonicus was affected significantly by stocking density and dietary tryptophan treatments (p < .05). In general, the energy consumed (C) and energy used for growth (G) decreased with the increasing in the stocking densities. The highest proportion of energy deposited to growth occurred in each 3% treatment (L, 6.38%; ML, 6.12%; MH, 4.56% and H, 4.14%), which were significantly higher than the controls (p < .05) respectively. Higher cortisol, glucose and lactate levels of A. japonicus were recorded in the control treatments of MH and H, but l ‐tryptophan supplementation could reduce the levels of cortisol, glucose and lactate of the test animals. The present results proved that the growth performance of the sea cucumber was inhibited by high stocking densities, while dietary supplementation of tryptophan could significantly mitigate the crowding stress, and improve the growth of sea cucumber.     

High stocking density induces crowding stress and affects amino acid metabolism in Senegalese sole Solea senegalensis (Kaup 1858) juveniles

Fish held at high stocking densities are generally exposed to chronic stress situations that impose severe energy demands and may predispose the fish to infection. Senegalese sole Solea senegalensis (Kaup) juveniles (78.8±18.9 g body weight) were maintained at low (LSD; 4 kg m^?2 at the end of the experiment), medium (MSD; 9 kg m^?2) and high (HSD; 14 kg m^?2) stocking densities during a period of 63 days. Although disease outbreaks were observed in fish reared at HSD, growth and food consumption did not vary among different treatments. Results from plasma cortisol and free amino acids (FAAs) showed significant differences among different rearing densities pointing to HSD as stressful rearing condition. However, higher plasma glucose and osmolality levels indicated that fish held at MSD may also be under stress. The higher usage of FAAs from the HSD group may be due to the higher demand for energy production in order to cope with stressful rearing conditions, higher rate of protein synthesis or due to synthesis of other important metabolites related to stress response. Therefore, results from the present study point out to HSD as a stressful rearing condition and suggest that crowding stress may affect amino acid requirements.     

Research Progress on Hair Cortisol as Evaluation Indicators of Chronic Stress

Making hair cortisol as the gold standard of reflecting chronic stress level is prospective and innovative.Hair cortisol not only can be used in detecting and estimating the chronic stress level of animals, but also can be benefit for understanding the body's physiological and pathological process and making effective health management strategy in time.Blood, saliva, urine and milk cortisol concentrations can be regarded as matrices for reflecting acute stress level as well, they have been used in detecting and establishing the diurnal profile of circulating cortisol studying.But hair which is a good supplementary matric can reflect the chronic stress level retrospectively.Hair cortisol as a reflection of the biochemical markers of chronic stress has the advantages of no invasive, relatively sensitive detection and convenient sampling stress, and hair cortisol is a heritable trait (h²=0.31).The utility of hair cortisol as a maker for HPA activity, and a useful tool for identifying genetic variation influences on long term individual differences in HPA activity.This article summarized the relationship between the cortisol and animal's healthy, the regulating mechanism and genetic adaptation change under chronic stress and the research progress of evaluation indicators during chronic stress, the research progress of hair as a matric of cortisol, the limitations and challenge of regarding hair cortisol as the biochemical marker to reflect the chronic stress level in the future.     

Effect of Long-distance Road Transport on Thyroid and Adrenal Function and Haematocrit Values in Limousin Cattle: Influence of Body Weight Decrease

The purpose of this study was to evaluate the effect of long-distance road transport as a relevant stressor on total and free iodothyronines, cortisol levels and haematocrit values in 10 male Limousin cattle. Serum T₃,T₄,fT₃,fT₄ and cortisol concentrations were analysed by immunoenzymatic assays. Serum cortisol levels and haematocrit modifications were also evaluated on the basis of percentage body weight decrease. The results showed a general increase of total and free iodothyronines and cortisol levels after short-and long-distance road transport and a decrease 15 days after transport, as compared to basal values. Significant positive correlations between T₃ and T₄, between T₃ and fT₃, and between T₄ and fT₄ were found. These results suggest that transport stress induces an increase in the activity of thyroid and adrenal function in Limousin cattle that is evident after even a short-distance road transport and continues to increase after long-distance transport.     

Measurement of Cortisol Metabolites in Faeces of Ruminants

Twenty-one metabolites were detected in faecal samples collected after infusion of (¹⁴C)cortisol into the jugular vein of sheep, using high-performance liquid chromatography/radiometric analysis plus mass spectrometry. One group of metabolites had molecular weights of between 302 and 308, and another group of 350, which indicates that the substances have a C₁₉O₃ or a C₂₁O₄ structure. Therefore, an enzyme immunoassay against 5-androstane-3-o1-11,17-dione-17-CMO:BSA was established. Faecal samples were collected from 10 cows immediately after transport and then during a course in which non-invasive diagnostic procedures were being taught (course 1). For comparison, faeces were sampled from another 5 cows that were being used for teaching invasive procedures (course 2). Six cows from a university farm served as controls. In the animals used in course 1, the highest concentrations of cortisol metabolites were measured immediately after transport to the university (median value: 2.2 mol/kg faeces). During the first 5 days at the university, the concentrations decreased to 0.52 mol/kg (median) and remained at this level during the rest of the course. The median concentration in the samples that were taken during course 2 (collected about 2 months after transport) was 0.48 mol/kg. There was no significant difference in the excretion of cortisol metabolites between these cows and the controls. We conclude from these data that, using the enzyme immunoassay against 5-androstane-3-o1-11,17-dione-17-CMO, we were able to detect transport/novel environment stress but not the potential disturbance that cows experience during diagnostic procedures.