Identification of haematological markers in shrimp health assessment from the immune profile of Fenneropenaeus indicus on β-1,3-glucan administration and white spot syndrome virus challenge

Haematological alterations in Fenneropenaeus indicus fed marine yeast glucan-incorporated diet and challenged with white spot syndrome virus were analysed. Adult F. indicus 16.45 ± 2.12 g (mean ± SD) were reared in 25 ‰ sea water and allowed to acclimate for a period of 7 days. Diet was prepared incorporating glucan (0.2 %) extracted from marine yeast, Debaryomyces hansenii S169. The shrimps were reared on experimental diet for 28 days and then challenged with white spot syndrome virus through oral administration. Random sampling was done (n = 6 shrimps) on 1st, 15th and 28th day of the experiment and on post-challenge day 2 (PCD 2) and PCD 7 for haematological analysis. The immune parameters viz. plasma protein, total haemocyte count, phenoloxidase activity, superoxide anion production, alkaline phosphatase and acid phosphatase activities were estimated in the haemolymph. Superoxide dismutase, catalase, glutathione peroxidase, hydroperoxide, conjugated dienes and malondialdehyde concentrations in the haemolymph of shrimps were also analysed. Analysis of variance showed that there are significant differences (p < 0.05) in the immune and antioxidant parameters in different treatment groups of F. indicus. The shrimps fed glucan-incorporated diet showed higher survival rate with comparatively lower accumulation of lipid peroxidation products. Correlation coefficients showed that all haematological variables except hydroperoxides and conjugated dienes exhibited positive correlation with the survival rate. The immune variables and antioxidant parameters exhibited a greater degree of correlation with each other. When multiple regression of survival rate on all immune parameters was considered, the amount of variability explained was 93 % (R Square = 0.932). When significant regression coefficients among the immune parameters were taken into account, it was found that total haemocyte count (p < 0.001), phenoloxidase activity (p < 0.05), alkaline phosphatase activity (p < 0.05) and plasma protein concentration (p < 0.05) together are explaining 84 % (R ² = 0.842) of the variability, indicating that these four parameters are mainly supporting the survival. The amount of variability explained by the antioxidant parameters was 94 % (R ² = 0.938). When significant regression coefficients among the antioxidant parameters were taken into account, it was found that superoxide dismutase activity (p < 0.01) and catalase activity (p < 0.05) together are explaining 87.4 % (R ² = 0.874) of the variability, indicating that these two antioxidants act as the major immune effectors supporting the survival in shrimps.     

Effect of brewer’s yeast on immune response of giant freshwater prawn, Macrobrachium rosenbergii, and its resistance to white muscle disease

The present study was conducted to find the effect of dietary brewer’s yeast on growth, survival, immune response, and resistance to white muscle disease in giant freshwater prawn, Macrobrachium rosenbergii. The brewer’s yeast was supplemented at graded levels 0, 5, 10, and 20?g per kg diet, and the experiment was conducted for 75?days. After the feeding trials, growth, survival, immune parameters like prophenoloxidase activity, respiratory burst, and total hemocyte count were assessed. The growth, specific growth rate, and survival were not found significantly different among the treatment and control groups “prophenoloxidase activity and respiratory burst” were found significantly different (p?<?0.05) among the treatment and control groups. The total hemocyte count was significantly different (p?<?0.05) among control and treatment groups. Cumulative percent survival was higher in M rosenbergii fed 1?% brewer’s yeast-supplemented diet when they were challenged with white muscle disease virus (MrNV (Macrobrachium rosenbergii nodavirus) and XSV (extra small virus)). The present work revealed that the incorporation of brewer’s yeast in the diet is effective in enhancing immune response and controlling the white muscle disease in M rosenbergii.     

Effect of dietary ω3 and ω6 fatty acids on growth and feed conversion efficiency of coho salmon (Oncorhynchus kisutch)

Sixteen isocaloric diets varying only in the levels of ω3 and ω6 fatty acids were prepared. Each diet was fed to duplicate groups of coho salmon for 14 weeks. At termination, the final weight of each diet group fish was determined. The optimum level of dietary ω3 fatty acid ranged from 1% to 2.5%. Dietary ω6 fatty acid higher than 1% depressed fish growth. Fish growth, feed conversion efficiency, fish mortality and fatty acid composition of fish phospholipids were determined.     

Effect of oxidation–reduction potential on performance of European sea bass (Dicentrarchus labrax) in recirculating aquaculture systems

The direct impact of oxidation–reduction potential (ORP) on fish welfare and water quality in marine recirculating aquaculture systems (RAS) is poorly documented. In this study, the effects of the fish size (S₁, S₂, S₃) and ORP level (normal, four successive levels) on the performance of European sea bass (Dicentrarchus labrax) were investigated. Three size fish were distributed into two RAS (RAS and RAS O₃). Ozone was injected into RAS O₃ to increase the ORP level. The ORP was stabilized to four successive levels: 260–300, 300–320, 320–350, and 300–320 mV in fish tanks during four periods (P_1–4). At the last day of each period, the hematological parameters, plasma protein and mortality of sea bass were analyzed. Two-way ANOVA revealed that several hematological parameters, including pH, hematocrit, concentrations of oxygen, carbon dioxide, glucose (Glu), ionized calcium, kalium, and hemoglobin, were significantly influenced by the increased ORP levels over the experimental period. The alteration in blood Glu and plasma protein concentration showed that ORP around 300–320 mV started to stress sea bass. Once the ORP exceeded 320 mV in the tanks during the P₃ period, mortality occurred even when total residual oxidants/ozone-produced oxidants was only 0.03–0.05 mg L^?1 in the fish tanks. At the same time, plasma protein decreased notably due to appetite depression. After the decrease in ORP during the P₄ period, mortality continued. In conclusion, the results strongly suggest that for European sea bass in RAS, the ORP should not exceed 320 mV in the tanks. Once ozonation damaged fish, the effect seemed to be irreversible. However, how ORP affected related hematological parameters still need the further investigations.     

The effects of hairtail protein hydrolysate–Fe<Superscript>2+</Superscript> complexes on growth and non-specific immune response of red swamp crayfish (<Emphasis Type="Italic">Procambarus clarkii</Emphasis>)

The experiment was conducted to investigate the effects of prepared hairtail protein hydrolysate–Fe²⁺ (PH–Fe²⁺) complexes on growth and non-specific immune responses of crayfish (Procambarus clarkii). The diets with five different levels of PH–Fe²⁺ (200, 400, 600, 800, and 1000 mg/kg) were fed to crayfish for 60 days. The results indicated that the survival rate, weight gain percentage, specific growth rate, and muscle index of crayfish with 400–1000 mg/kg of PH–Fe²⁺ feeding were significantly higher, 9.94–10.10, 8.55–8.72, 0.24–0.29 %/day, and 2.39–3.05 %, respectively, than the control values after 60 days of feeding. Additionally, after 30 days of feeding, 200–400 mg/kg of PH–Fe²⁺ showed no significant (P > 0.05) improvement effect on activities of superoxide dismutase (SOD), phenoloxidase (PO), lysozyme (LSZ), and acid phosphatase (ACP) in serum or hepatopancreas of crayfish. However, significant improvement effects were observed in 800–1000 mg/kg groups. After 60 days of feeding, 400–600 mg/kg of PH–Fe²⁺ significantly (P < 0.05) improved the activity of SOD and LSZ, but did not affect the activity of PO and ACP significantly (P > 0.05). Moreover, the activities of SOD, PO, LSZ, and ACP in serum and hepatopancreas were all significantly enhanced upon treatment with 800–1000 mg/kg of PH–Fe²⁺. For these reasons, PH–Fe²⁺ can be recommended as a supplement in crayfish feed to increase the growth and immunity.     

Daily rhythms of cortisol and glucose and the influence of the light/dark cycle on anaesthesia in Nile tilapia (Oreochromis niloticus): Does the timing of anaesthetic administration affect the stress response?

Although daily variations in drug pharmacokinetics have been reported for a variety of teleost species, the influence of this daily variation on the cortisol response following anaesthesia remains poorly understood. To address this, two experiments were performed. The first experiment described the daily patterns of cortisol and glucose secretion in tilapia (Oreochromis niloticus). The second experiment investigated how the timing of anaesthetic administration (specifically at mid‐light [ML] or at mid‐dark [MD]) affects the induction and recovery times and plasma cortisol and glucose levels of juvenile Nile tilapia exposed to benzocaine, clove oil or tricaine methanesulphonate (MS‐222). The results revealed that the effect on the stress response associated with the moment when anaesthesia took place (ML or MD) varied according to the treatment (p < 0.05). Cortisol levels were significantly higher at ML for MS‐222 (ML = 116.23 ± 25.55; MD = 48.25 ± 22.33 ng/dl) (p < 0.05) and clove oil (ML 59.73 ± 14.27; MD 38.26 ± 12.07 ng/dl) (p < 0.05), whereas no significant differences were found between ML and MD cortisol levels for the control treatment (ML = 72.91 ± 18.42; MD = 64.80 ± 10.68 ng/dl) (p > 0.05) or in the benzocaine‐treated group (ML = 38.7 ± 4.90; MD = 38.60 ± 3.69 ng/dl) (p > 0.05). The highest plasma cortisol level in ML was found in the MS‐222‐treated group. All the tested anaesthetics had similar cortisol levels at MD (p > 0.05).     

The impact of net-isolated polyculture of tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) on plankton community in saline–alkaline pond of shrimp (<Emphasis Type="Italic">Penaeus vannamei</Emphasis>)

We used 12 land-based experimental enclosures (6 m × 5 m) in a saline–alkaline pond of shrimp (Penaeus vannamei) to determine the impact of net-isolated polyculture of tilapia (Oreochromis niloticus) on plankton communities for 40 days. Tilapias were stocked in net cages suspended in enclosures, in polyculture ponds including tilapia and shrimp. Four tilapia biomass were tested: 0, 39, 115 and 227 g m⁻². Shrimp stocking biomass were 0.7 g m⁻² in all treatments. There were three replicates in each treatment. Our results showed that the presence of tilapia significantly reduced phytoplankton biomass directly through predation and indirectly through top-down effect. The stocking of tilapia reduced zooplankton biomass, particularly rotifer biomass. However, copepod biomass was not been significantly affected. So, net-isolated polyculture of tilapia can thus have a strong impact on phytoplankton allowing the co-existence of large numbers of copepods with planktivorous fish and improving the water quality of shrimp ponds.     

Impact of phased harvesting on population structure,feed intake pattern and growth performance of <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> DeMan (giant freshwater prawn) in polyculture with carps in concurrent rice–fish culture

This study was carried out to study the impact of phased harvesting on the population structure, feed intake pattern and growth performance of Macrobrachium rosenbergii in polyculture with carps in a deepwater rice–fish system. There were two experimental conditions—rice–fish culture with phased harvesting (T₁) and rice–fish culture without phased harvesting (T₂)— and a control, which consisted of rice monoculture without fish (T₃). In the T₁ trial, 61% of the population had a mean body weight (MBW) <20 g 120 days after stocking (DAS), which fell significantly to 7.3% at 210 DAS. However, in the T₂ trial, 62% of the population had a MBW <20 g at 120 DAS, which only fell to 23.7% at 210 DAS. Similarly, at 210 DAS, 12.5% of the population attained a MBW >80 g in the T₁ trial, while none of the population reached a MBW >80 g in the T₂ trial. The removal of fast-growing individuals in T₁ improved the prospects of other smaller individuals to achieve their individual growth potential. This step also disrupted the continuation of the socially induced differential growth rates, resulting in a wide variation in size within the population over time. The matrix of dietary overlap(s) of cultured species revealed that the degree of food preference was more similar between Cyprinus carpio and M. rosenbergii (0.9), while it overlapped poorly between Catla catla and M. rosenbergii (0.42). This high similarity index between bottom dwellers is evidence of the strong possibility that these bottom dweller compete for food. Natural and supplemental feed together with phased harvesting boosted the production of freshwater prawns (550 kg ha⁻¹) in the T₁ trial, while a 11.3% reduction in production was recorded in the T₂ trial.