Biochemical parameters of blood plasma and content of microcystins in tissues of common carp (Cyprinus carpio L.) from a hypertrophic pond with cyanobacterial water bloom

The aim of this study was to evaluate the dynamics of the blood plasma parameters and the content of microcystins in the tissues of common carp ( Cyprinus carpio L.) in relation to the toxic cyanobacterial water bloom. Fish (average body mass 2176±697 g) in the hypertrophic pond were exposed to natural water bloom (dominated by Planktothrix agardhii, Pseudanabaena limnetica and Limnothrix redekei ), which contained microcystins (concentration in biomass 20–181 μg g⁻¹ dry wt, concentration in water 0.3–9.5 μg L⁻¹). Biochemical parameters in fish blood plasma were analysed in 89 fish at 14-day intervals during the whole season (nine sampling periods). Our results demonstrated high variability and fluctuations in the investigated parameters. The content of microcystins and density of cyanobacterial cells correlated with some haematological indices as lipase, alanine–aminotransferase, albumin, magnesium and chlorides. The concentrations of microcystins in the muscle and liver of the fish (determined by high-performance liquid chromatography with mass spectrometer) were below the limit of detection during the monitored period [0.31 ng g⁻¹ fresh weight (f.w.) for the liver and 0.13 ng g⁻¹ f.w. for muscle]. Our study demonstrates that although known cyanobacterial toxin microcystins were not detected in the fish tissues, several biochemical parameters important for the fish physiology were modulated by natural cyanobacterial bloom.     

Total sulphur amino acid requirement of the Indian major carp, Labeo rohita (Hamilton)

The quantitative dietary sulphur amino acid requirement of the Indian major carp, Labeo rohita (Hamilton), was determined by conducting a growth study. The experimental diets contained 400 g crude protein kg⁻¹ from casein, gelatine and supplemental crystalline amino acids. Diets containing six graded levels of methionine (3.2, 6.5, 9.0, 11.5, 14 and 16.5 g kg⁻¹) with a constant level of cystine (1.4 g kg⁻¹) were formulated and fed to triplicate groups of Labeo rohita fingerlings twice a day to satiation for 60 days. The optimum dietary requirement for methionine was estimated using the break-point regression analysis at 11.5 g kg⁻¹ of diet or 28.8 g kg⁻¹ of dietary protein. Thus the total sulphur amino acid (Met + Cys) requirement was determined to be 12.9 g kg⁻¹ of diet or 32.3 g kg⁻¹ of protein. Higher survival, specific growth rate and food conversion efficiency values were observed for fish fed the diet containing optimum levels of sulphur amino acids.     

Effect of methionine on intestinal enzymes activities, microflora and humoral immune of juvenile Jian carp (cyprinus carpio var. Jian)

An 8-week feeding experiment was conducted to determine the effect of dietary methionine supplementation on intestinal microflora and humoral immune of juvenile Jian carp (initial weight of 9.9 ± 0.0 g) reared in indoor flow-through and aerated aquaria. Eight amino acid test diets (350 g kg⁻¹ crude protein, CP), using fish meal, soybean-condensed protein and gelatin as intact protein sources supplemented with crystalline amino acids, were formulated to contain graded levels of methionine (0.6–22.0%) at a constant dietary cystine level of 3 g kg⁻¹. Each diet was randomly assigned to three aquaria. Growth performance and feed utilization were significantly influenced by the dietary methionine levels ( P  < 0.05). Maximum weight gain, feed intake occurred at 12 g kg⁻¹ dietary methionine ( P  < 0.05). Methionine supplementation improved hepatopancreas and intestine weight, hepatosomatic and intestine index, intestinal γ-glutamyltransferase and creatine kinase activity, Lactobacillus count, Bacillus count, lysozyme activities, lectin potency, sim-immunoglobulin M content, addiment C3,C4 contents and serum total iron-binding capacity and declined Escherichia coli and Aeromonas counts. Quadratic regression analysis of weight gain against dietary methionine levels indicated that the optimal dietary methionine requirement for maximum growth of juvenile Jian carp is 12 g kg⁻¹ of the dry diet in the presence of 3 g kg⁻¹ cystine.     

Preliminary investigations on the effects of dietary lipid on the spawning performance and egg quality of black sea bass Centropristis striata L

Adult black sea bass Centropristis striata broodstock ( N =162) were fed three different dietary treatments: two commercially prepared diets with 45% protein and two different lipid levels (12% and 20%) (diets 1 and 2), and a diet of frozen Atlantic silversides Menidia menidia (SS, diet 3). Broodstock were held under controlled photothermal conditions and induced to spawn with an LHRHa pellet (72 μg kg⁻¹ bw). Dietary lipid had pronounced effects on spawning performance and egg quality. Diet 3 (SS) produced a significantly ( P <0.05) higher fertilization success (22.4%) than diets 1 (0.6%) and 2 (4.8%). The hatching success of fertilized eggs was similar in all diets (range=40–58.6%), but only two spawns from diet 1 (12% lipid) yielded viable yolk-sac larvae (YSL). Diet 3 (SS) also produced significantly more YSL per female (21.8 × 10³) than the diet 1 (0.3 × 10³). Eggs from diet 3 (SS) contained a significantly greater proportion of n-3 series fatty acids, with docosahexaenoic acid (DHA) as the largest fraction. Eggs from commercially prepared dietary treatments contained significantly more n-6 fatty acids. The poor spawning performance of fish fed diet 1 (12% lipid) may be related to higher levels of linoleic acid and lower levels of DHA in the diet.     

池塘和稻田养殖模式对金边鲤和建鲤肌肉品质的影响

分析了稻田和池塘养殖模式下金边鲤和建鲤肌肉营养成分、理化特性和质构特性,并进行营养价值评价,评估金边鲤的肌肉品质,为开发和推广金边鲤稻田养殖提供数据依据。结果显示,稻田金边鲤的粗脂肪、粗灰分和系水力均显著高于池塘金边鲤;稻田建鲤和池塘建鲤的基本营养成分除水分外差异均不显著;稻田金边鲤肌肉的硬度、弹性、咀嚼性显著高于池塘建鲤和稻田建鲤,硬度和恢复性显著高于池塘金边鲤,而内聚性显著低于池塘金边鲤、池塘建鲤和稻田建鲤;测定的17种氨基酸中,4组鱼肉的Lys含量均高于WHO/FAO标准和鸡蛋蛋白标准,稻田金边鲤的∑TAA、∑EAA、∑DAA和∑NEAA均高于池塘建鲤和稻田建鲤,且EAA/TAA比值更接近FAO/WHO要求的40%的标准;稻田和池塘金边鲤的EAAI均超过100分,高于稻田和池塘建鲤(82.31～83.36分);测定出的24种脂肪酸中,稻田金边鲤的∑SFA、∑MUFA和DHA+LA+油酸总量均高于其他3组。研究表明,金边鲤和建鲤鱼肉可作为人体优质的赖氨酸源,稻田金边鲤肌肉比建鲤和池塘金边鲤肌肉更富有嚼劲,其肌肉必需氨基酸、不饱和脂肪酸及高度不饱和脂肪酸含量更高,且组成比例更符合人体需求。稻田养殖金边鲤的肌肉品质优势明显,具有较高的产业开发潜力。     

Effect of dietary pantothenic acid supplement on growth, body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A 9-week feeding trial was carried out with juvenile Jian carp to study the effect of dietary pantothenic acid (PA) on growth, body composition and intestinal enzyme activities. Semi-purified diets with seven levels (4.0, 15.5, 25.6, 36.1, 45.9, 56.1 and 65.9 mg PA kg⁻¹) of supplemental calcium d -pantothenate were fed to Jian carp (13.0 ± 0.0 g). PA improved specific growth rate (SGR), protein productive value (PPV), protein efficiency ratio (PER) and lipid production value (LPV) ( P <  0.05). Fish fed the control diet had significantly lower feed efficiency (FE) than that in any other group ( P <  0.05). Body protein content increased with increasing PA levels ( P <  0.05), but moisture, lipid and ash of fish carcasses were negatively related to the graded PA levels ( P <  0.05). Intestine protein content (IPC), hepatopancreas protein content (HPC) and activity of α-amylase, lipase, trypsin, Na⁺,K⁺-ATPase, alkaline phosphatase (AKP) and gamma-glutamyl transpeptidase (γ-GT) were all positively affected by the dietary PA levels ( P <  0.05), while intestine index (ISI) and hepatopancreas index (HSI) decreased with the increment of supplemental levels of PA ( P <  0.05). These results suggested that PA could enhance fish growth and intestinal enzyme activities. The dietary PA requirement of juvenile Jian carp, Cyprinus carpio var . Jian (13.0–73.0 g), for optimal growth estimated by the broken-line analysis was 23.0 mg PA kg⁻¹ diet.     

Myo-inositol prevents oxidative damage, inhibits oxygen radical generation and increases antioxidant enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to evaluate the effects of dietary myo -inositol (MI) on the antioxidant status of juvenile Jian carp ( Cyprinus carpio var. Jian). A total of 1050 Jian carp (22.28±0.07 g) were randomly distributed into seven groups of three replicates each, feeding diets containing graded levels of MI (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg kg⁻¹ diet) for 60 days. Results indicated that the malondialdehyde content was the lowest for fish fed diets containing ≥384.2 mg MI kg⁻¹, and the highest for fish fed the MI-unsupplemented basal diet ( P <0.05). The protein carbonyl content was decreased with increasing dietary MI levels up to 535.8 mg kg⁻¹ diet, and no differences were found with a further increase in the MI concentration. The anti-superoxide anion capacity (ASA) and anti-hydroxyl radical capacity (AHR) were increased with increasing MI levels up to 535.8 mg kg⁻¹ diet, and plateaued thereafter. The superoxide dismutase and glutathione- S -transferase activities showed the same tendency with the ASA capacity. Catalase, glutathione peroxidase and glutathione reducase activities were improved with increasing MI levels up to 838.8, 384.2 and 687.3 mg kg⁻¹ diet, respectively, and remained nearly constant thereafter. These results suggested that MI could inhibit oxygen radical generation, increase enzymatic antioxidant capacity and prevent oxidative damage of carp. Dietary MI requirements for ASA and AHR activities of juvenile Jian carp were 567.94 and 517.22 mg MI kg⁻¹ diet respectively.     

Evaluation of carbohydrate rich diets through common carp culture in manured tanks

Four diets (T₀–T₃) were formulated reducing the fishmeal (Indian) component by 100 g kg^–1 from 300 to 0 g kg^–1 and including proportionately increasing quantities of maize. Diets were fed for 120 days at 50 g kg^–1 body weight to triplicate groups of common carp (av. wt. 2.11–2.18 g) stocked at 1 m^–2 in mud bottomed cement tanks (18 m²), fertilized with poultry manure. Fish growth, SGR and FCR in the different treatments were statistically not significantly different ( P  > 0.05). PER was lowest for the 300 g fishmeal kg^–1 diet treatment (diet T₀), increasing with decrease in dietary fishmeal content (diets T₁–T₃). Fish survival ranged from 96.29 to 100%. Diets influenced carcass composition and digestive enzyme activity. A significant increase in lipid deposition was recorded with increasing dietary carbohydrate content. Amylase, protease and lipase activities were higher in fish fed with diets T₂ and T₃. The protein sparing effect of dietary carbohydrate and the economic implication of eliminating fishmeal from the diet are discussed.     

Changes in enzymatic and structural properties of grass carp fast skeletal myosin induced by the laboratory-conditioned thermal acclimation and seasonal acclimatization

ABSTRACT:   Myosins were prepared from fast skeletal muscles of grass carp thermally acclimated to 10, 20 and 30°C in the laboratory as well as from those seasonally acclimatized and collected in January (winter) 2003 and May (spring), August (summer) and November (autumn) 2002. The maximal initial velocities ( V _max) of actin-activated Mg²⁺-ATPase activity for myosins from the 10°C-acclimated and winter grass carp were 1.7–1.8-fold as high as those from the 30°C-acclimated and summer fish. The inactivation rate constant ( K _D) of Ca²⁺-ATPase for myosin from the 10°C-acclimated grass carp was three to fourfold higher than those for myosins from the fish acclimated to 20°C and 30°C, whereas myosin from winter grass carp was about sevenfold as high as that for myosin from summer fish. Myosins from spring and autumn fish showed K _D values comparable to those of the fish acclimated to 30°C and 10°C, respectively. In differential scanning calorimetry analysis, the transition temperature ( T _m) was observed near 38°C and 45–46°C with most myosins. However, the lowest T _m at 32–33°C was given as one of the major endotherms in myosins from the 10°C-acclimated, autumn and winter fish. These responses of grass carp to changed environmental temperatures were almost similar to those for common carp reported previously.     

Evaluation of indigenous marine periphytic Amphora, Navicula and Cymbella grown on substrate as feed supplement in Penaeus monodon postlarval hatchery system

Three isolated marine diatoms ( Amphora , Navicula and Cymbella ) grown on substrate were evaluated as feed supplement for Penaeus monodon postlarvae (PL) in hatchery system for a period of 19 days without changing water. Specific growth rate (day⁻¹) (0.27 ± 0.0) and survival (%) (56.3 ± 1.8) of PLs were significantly higher ( P  < 0.05) in treatment tanks when compared with the control (0.20 ± 0.0; 36.0 ± 1.5, respectively). Shrimp PLs reared in substrate-based tanks had significantly higher ( P  < 0.05) levels of protein, lipid (521.0 ± 7.0; 304.0 ± 2 g kg⁻¹ dry weight, respectively), ecosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (189.0 ± 2.0; 176.0 ± 2 g kg⁻¹ of total fatty acid, respectively) than the control (435.0 ± 22.0; 258.0 ± 22 g kg⁻¹ dry weight; 172.0 ± 5.0; 152 ± 2 g kg⁻¹ total fatty acid, respectively). The periphytic diatoms contained protein and lipid (430–490; 230–260 g kg⁻¹ dry weight, respectively), EPA (30–150 g kg⁻¹ of total fatty acids), DHA (20–30 g kg⁻¹ of total fatty acids) and nine essential amino acids. The results showed that isolated marine periphytic diatoms grown on substrate could be used as feed supplement in enhancing the growth and survival of P. monodon postlarvae.     

Comparative Nile tilapia and silver carp filtration rates of Partitioned Aquaculture System phytoplankton

Nile tilapia (Oreochromis niloticus) and silver carp (Hypophthalmichthys molitrix) held in timed-pulse feeding chambers were provided water dominated either by green algae (Scenedesmus, Ankistrodesmus and Tetraedron) or by cyanobacteria (Microcystis) to compare filtration rates (FRs). FRs were expressed as suspended particulate organic carbon (POC)/kg wet fish weight/h and as phytoplankton units filtered based on counts. Nile tilapia and silver carp filtration significantly reduced phytoplankton number of both taxonomic groups with the larger phytoplankton being filtered proportionally more than the smaller phytoplankton. Nile tilapia FR of green algae was significantly higher than silver carp; however, silver carp FR of cyanobacteria was higher than Nile tilapia. Ivlev's 90% saturation FRs (FR₉₀) in green-algal and cyanobacterial water sources were 702 and 812 mgC/kg/h for Nile tilapia and 414 and 1028 mgC/kg/h for silver carp, respectively. Silver carp were observed to reach these FR₉₀ values at lower POC concentrations than Nile tilapia with both green algae and cyanobacteria.     

Fatty acid and lipid content of Oreochromis niloticus L. in Ethiopian lakes — dietary effects of phytoplankton

Abstract— Herbivorous tilapia fish, Oreochrornis niloticus L. (Cichlidae), collected from five Ethiopian lakes were analyzed for lipid and fatty acid contents of the dorsal muscle using spectrophotometry and gas-liquid chromatography. The results showed remarkable variation between the lakes in both the lipid and total fatty acid content of the fish, 1.7–21 and 1.6–9.3% of dry weight (DW), respectively. Most fish from Lakes Haiq and Chamo contained higher levels of fat (≥ 10% DW) compared to fish from Lakes Ziway, Langeno and Awassa which contained ≤ 5% DW fat. A total of 28 fatty acids were identified. The saturated fatty acids ranged from 5.3–30 mg. gg⁻¹ DW, monounsaturated Fatty acids from 1.3–30 and polyunsaturated fatty acids from 6.8–29 mg. g⁻¹ DW. The most abundant fatty acids were palmitic acid, docosahexaenoic acid (DHA), oleic acid, stearic acid, palmitoleic acid, arachidonic acid and eicosapentaenoic acid (EPA). EPA and DHA alone amounted to 2.6–15 mg. g⁻¹ DW. The ω3/ω6 ratios ranged from 1.3–7.6 and L. Haiq fish showed the highest ratios, 5.1–7.6, indicating that the fat was of high nutritional quality. The reason for such variation is probably the varied diet available to the fish in the various lakes, This study, along with previous reports, confirms that the phytoplankton flora constituting the diet of O. niloticus varies greatly between the study lakes. The variation in phytoplankton is also reflected by the fatty acid pattern of net samples taken from the study lakes.     

Dietary formic acid enhances apparent digestibility of minerals in rainbow trout, Oncorhynchus mykiss (Walbaum)

The effect of dietary formic acid on the availability of phosphorus (P) from a fishmeal-based diet by rainbow trout, Oncorhynchus mykiss (Walbaum), reared in brackish water (5–6 g L⁻¹) was determined. Diets containing a low amount of P (6.0 mg P g⁻¹ dry matter) were acidified with 0, 4 and 10 mL kg⁻¹ formic acid and fed to trout (average weight, 520 g) for 4 weeks. The measured pH of the diets were 6.3, 5.8 and 5.3, respectively. The intestinal solubility of P and the digestibility of P were measured by stripping the faecal matter from the fish. The apparent digestibility coefficient (ADC) of P significantly ( P < 0.05) increased from 69.5% to 75.0% of the basal diet in fish fed diets containing 10 mL kg⁻¹ formic acid. The solubility of P in the intestine was highly variable within each treatment, and the differences were not significant. The pH of intestinal content increased with the increase in dietary formic acid concentration. The ADC of magnesium and calcium also showed a significant ( P < 0.05) increase with the acidification of diet by formic acid.     

Enzyme-linked immunosorbent assay (ELISA) for the detection of spring viraemia of carp virus (SVCV) in tissue homogenates of the carp, Cyprinus carpio L.

Abstract. An enzyme-linked immunosorbent assay (ELISA) for the demonstration of the virus of spring viraemia of carp (SVCV) in liver, kidney and spleen homogenates, and in infected cell cultures is described. The sensitivity of the method is 10^2·8–10^3·5 TCID₅₀ 0·lml⁻¹ of the examined fluid. The specificity has been confirmed by the ELISA inhibition test and by results of virological examinations. Contamination with bacteria or fungi of samples taken from dead fish had no effect on the results of ELISA. Specific anti-SVCV sera were used successfully for the production of conjugates for the direct immunoperoxidase and immunofluorescence detection of SVCV in infected cell cultures.     

Quantitative dietary threonine requirement of juvenile Pacific white shrimp, Litopenaeus vannamei (Boone) reared in low-salinity water

An 8-week feeding trial was conducted to determine the threonine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low-salinity water (0.50–1.50 g L⁻¹). Diets 1–6 were formulated to contain 360 g kg⁻¹ crude protein with fish meal, wheat gluten and pre-coated crystalline amino acids with six graded levels of l -threonine (9.9–19.0 g kg⁻¹ dry diet). Diet 7, which was served as a reference, contained only intact proteins (fish meal and wheat gluten). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.48±0.01 g), each four times daily. Shrimps fed the reference diet had similar growth performance and feed utilization efficiency compared with shrimps fed the diets containing 13.3 g kg⁻¹ or higher threonine. Maximum specific growth rate (SGR) and protein efficiency ratio were obtained at 14.6 g kg⁻¹ dietary threonine, and increasing threonine beyond this level did not result in a better performance. Body compositions, triacyglycerol and total protein concentrations in haemolymph were significantly affected by the threonine level; however, the threonine contents in muscle, aspartate aminotransferase and alanine aminotransferase activities in haemolymph were not influenced by the dietary threonine levels. Broken-line regression analysis on SGR indicated that optimal dietary threonine requirement for L. vannamei was 13.6 g kg⁻¹ dry diet (37.8 g kg⁻¹ dietary protein).     

Effect of the protein/energy ratio on the growth of Mediterranean yellowtail (Seriola dumerili)

Yellowtails weighing 490 g were fed five experimental diets with different protein/energy ratios, 24.6, 26.9, 28.9, 31.8 and 35.8 g MJ⁻¹, for 152 days. The energy content was similar in all the diets and the protein and lipid levels were 40/26, 45/26, 50/18, 50/26 and 55/18 %CP/%CL respectively. The final weight and SGR were lower in fish fed diets with a lower PD/ED ratio (24.6 and 26.9 g MJ⁻¹), and the mortality of fish fed diet 24.6 g MJ⁻¹ was higher. In fact, only fish that consumed diet 35.8 g MJ⁻¹ had a haematocrit and a normal erythrocyte number similar to that in healthy yellowtail. No differences appeared in feed intake and feed conversion ratio. Digestible energy ingestion was similar for all the diets and digestible protein intake was also low for 24.6 compared with 35.8 g MJ⁻¹. The meat composition was similar for fish fed all the diets, but the profiles of muscle fatty acids indicated an increasing content of saturates and n-3 HUFA, while the levels of monounsaturates decreased, corresponding to an increase in the PD/ED relation. The economic conversion ratio and economic profit index were not different for fish fed the experimental diets.     

Dietary threonine requirement of juvenile hybrid striped bass (Morone chrysops♀×M. saxatilis♂)

Two growth studies were conducted to determine the dietary threonine requirement of reciprocal cross hybrid striped (sunshine) bass. Semipurified diets were prepared with crystalline amino acids and lyophilized fish muscle to supply 350 g crude protein kg⁻¹ diet. The basal diet contained 4.9 g threonine kg⁻¹ from fish muscle, and test diets were supplemented with graded levels of L-threonine. In the first experiment, fish initially averaging ≊ 9.8 g each were fed diets containing threonine levels of 4.9, 7.5, 10.0, 12.5, 15.0 and 17.5 g kg⁻¹ dry diet for 7 weeks. Weight gain, feed efficiency and protein efficiency ratio (PER) were significantly ( P < 0.01) influenced by dietary threonine level. Based on weight-gain responses, a threonine requirement (± SE) of 8.4 (± 0.8) g kg⁻¹ dry diet was determined, and dietary threonine levels of 10.0 g kg⁻¹ diet or greater resulted in the highest levels of free threonine in plasma.
Based on the results of the first experiment, a second feeding trial was conducted with diets containing threonine levels of 4.9, 6.5, 8.0, 9.5, 11.0 and 12.5 g kg⁻¹ dry diet. Fish initially averaging ≊ 3.0 g each were fed each diet for 8 weeks. Weight gain, feed efficiency and PER values of fish were markedly improved, with increases in dietary threonine up to 8.0 g kg⁻¹ dry diet. Regression analysis of weight gain, feed efficiency and PER data using the broken-line model resulted in threonine requirement estimates of 9.7, 8.5 and 8.6 g kg⁻¹ dry diet, respectively. Based on these data, the threonine requirement of juvenile sunshine bass was determined to be ≊ 9.0 g kg⁻¹ dry diet or 26 g kg⁻¹ of dietary protein.     

Bioencapsulation of erythromycin using adult brine shrimp, Artemia franciscana (Latreille)

Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL⁻¹) relative to Artemia fed the direct suspension (> 100 μg mL⁻¹) over the same time period. When enriched with suspensions up to 1 g erythromycin L⁻¹ sea water for 14 h, Artemia survival was not significantly affected ( P > 0.05) relative to controls. Using a suspension of 1 g L⁻¹, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL⁻¹  Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL⁻¹ were obtained using suspensions of 2–5 g L⁻¹, but Artemia survival significantly ( P < 0.05) decreased.     

Growth efficiency, body composition, survival and haematological changes in great sturgeon (Huso huso Linnaeus, 1758) juveniles fed diets supplemented with different levels of Ergosan

Growth performance, carcass quality, survival and haematological responses were determined when Huso huso juvenile (41.7±1.8 g) fed diets containing Ergosan (an algal product) at 0, 2.0, 4.0 and 6.0 g kg⁻¹ for 60 days. Each diet was fed to triplicate groups of fish at 10-day intervals (1–10, 20–30 and 40–50 with non-supplemented diets and 10–20, 30–40 and 50–60 with supplemented diets). Results showed that fish fed diets containing Ergosan had significantly higher growth than the control group ( P <0.05). Survival was not different among all dietary treatments ( P >0.05). Food conversion ratio in the fish fed a diet containing 4.0 and 6.0 g kg⁻¹ Ergosan was significantly better than the other treatments ( P <0.05), whereas protein efficiency ratio was not different between experimental diets. Lymphocyte count in the fish fed diets containing Ergosan was higher than the other treatments. Haematocrit, haemoglobin (Hb) concentration, number of erythrocytes, total leucocytes, monocyte, eosinophil, myelocyte, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration were not different between treatments. Neutrophil count in the control group was higher than the fish fed supplemented diets. Furthermore, whole body lipid, moisture and fibre were not different among dietary treatments ( P >0.05) but body protein in the fish fed a diet containing Ergosan at the level of 2.0 and 4.0 g kg⁻¹ was higher than the other treatments. Whole body ash content was higher in the control group. It was concluded that dietary administration of Ergosan can influence some growth and haematological parameters in great sturgeon, H. huso juveniles.     

Comparative sensitivity of carp, Cyprinus carpio L. and rainbow trout, Salmo gairdneri Richardson, to Renibacterium salmoninarum

Abstract. The pathogenicity of Renibacterium salmoninarum to carp, Cyprinus carpio L., and rainbow trout, Salmo gairdneri Richardson, was investigated. All carp injected with 4·8 × 10⁸ cells/fish, or 4·8 × 10⁷ cells/fish survived for 38 days. R. salmoninarum was isolated from all moribund fish, but not from the kidney of surviving fish, although R. salmoninarum antigen was detected in several of these fish by the dot blot assay. On the other hand, mortality in rainbow trout was 95% in the fish injected with 4·8 × 10⁸ cells/fish, and 15% in those which received 4·8 × 10⁷ cells/fish. R. salmoninarum antigen was detected by the dot blot assay in all surviving rainbow trout. The number of R. salmoninarum cells was immediately decreased by carp or rainbow trout serum, and the serum bactericidal activity of carp was higher than that of rainbow trout. Carp blood leucocytes had higher phagocytic activity than those of rainbow trout.