Dietary protein requirement for fingerling Channa punctatus (Bloch), based on growth, feed conversion, protein retention and biochemical composition

An 8-week feeding trial was conducted in a flow-through system (1–1.5 L min⁻¹) at 27°C to determine dietary protein requirement for Channa punctatus fingerlings (4.58 ± 0.29 g) by feeding six isocaloric diets (18.39 kJ g⁻¹, gross energy). Diets containing graded levels of protein (300, 350, 400, 450, 500 and 550 g kg⁻¹) were fed to triplicate groups of fish to apparent satiation at 09:00 and 16:00 h. Maximum absolute weight gain (AWG; 8.11 g fish⁻¹), specific growth rate (SGR; 1.82%) and best feed conversion ratio (FCR; 1.48) were recorded in fish fed diet containing 450 g kg⁻¹ protein, whereas protein efficiency ratio (PER; 1.52), protein retention efficiency (PRE; 25%), energy retention efficiency (ERE; 78%) and RNA/DNA ratio (3.01) were maximum for the group fed dietary protein at 400 g kg⁻¹. Second-degree polynomial regression analysis of AWG, SGR and FCR data against varying levels of dietary protein yielded optimum dietary protein requirement of fingerling between 462.24 and 476.72 g kg⁻¹, whereas the regression analysis of PER, PRE, ERE and RNA/DNA ratio data showed a lower protein requirement of 438.28–444.43 g kg⁻¹ of the diet. Considering the PER, PRE, ERE and RNA/DNA ratio as more reliable indicators, this protein requirement is recommended for developing quality protein commercial feeds for C. punctatus fingerlings.     

Influence of poultry meal, meat meal or soybean meal inclusion on weight gain and production characteristics of Australian snapper Pagrus auratus

Two experiments were done to evaluate the effects of poultry meal (PM), meat meal (MM) or solvent-extracted soybean meal (SBM) inclusion on the performance of Australian snapper Pagrus auratus. In each experiment, test feeds were formulated with similar contents of digestible protein (DP) and digestible energy (DE) using previously determined digestibility coefficients for this species. In experiment 1, groups of snapper (initial weight 14 g) were fed 4 feeds containing 360, 480, 610 or 730 g kg⁻¹ PM; 3 feeds containing 345, 320 or 500 g kg⁻¹ MM; 3 feeds containing 420, 600 or 780 g kg⁻¹ SBM. In experiment 2, groups of snapper (initial weight 87 g) were fed 3 extruded test feeds that contained combinations of PM, MM, SBM or blood meal (BM) which replaced all but 600, 250 or 160 g kg⁻¹ of fishmeal in respective diet formulations. Both experiments included a proprietary extruded aquafeed (COM) to benchmark fish performance. In experiment 1, weight gain was highest in snapper fed feeds containing 360, 345 or 420 g kg⁻¹ of PM, MM or SBM, respectively, and was similar (P > 0.05) to snapper fed the COM feed. Nonetheless, weight gain and protein retention efficiency tended to decrease as the amount of each test ingredient was increased. Relative feed intake was not affected by the inclusion level of PM, MM or BM, but declined significantly in snapper fed diets containing 600 or 780 g kg⁻¹ SBM. Feeding behaviour indicated fish found these feeds unpalatable. In experiment 2, the harvest weight of snapper fed the 3 extruded test feeds was similar (P > 0.05), but lower than snapper fed the COM feed (i.e. 234 vs. 256 g). Feed conversion ratio (FCR) was best in snapper fed the COM feed (FCR = 1.53); however, the FCR of snapper fed feeds containing 160 (FCR = 1.66), 250 (FCR = 1.70) or 600 g kg⁻¹ fishmeal (FCR = 1.60) was not different (P > 0.05). Australian snapper will readily accept feeds containing high levels of PM, MM or SBM and feeds containing these ingredients will support rapid weight and protein gain with little affect on whole body composition. In combination, these feed ingredients were able to replace all but 160 g kg⁻¹ of fishmeal in an extruded test feed. As such, they serve as valuable alternatives to fishmeal and extend the manufacturing options available to aquafeed producers.     

Influence of alginic acid and fucoidan on the immune responses of head kidney leukocytes in cod

The present study investigated the immunomodulatory activities of alginic acid and fucoidan, both derived from brown seaweeds, on selected cellular immune responses and antibacterial activity of head kidney (HK) leukocytes of cod, Gadus morhua. Primary cultures of HK leukocytes were incubated with either 10 or 100 μg ml⁻¹ of the substances and the effects on respiratory burst, cellular proliferation, acid and alkaline phosphatase activity and cellular myeloperoxidase were measured at 3- and 24-h post-incubation. The antibacterial activity of the supernatants collected from the cell cultures incubated with 100 μg ml⁻¹ of the substances were tested against Vibrio anguillarum and Aeromonas salmonicida. Respiratory burst was significantly elevated in cells incubated with either alginic acid or fucoidan in a dose-dependent manner. Incubation with a higher dose of alginic acid and fucoidan resulted in lower cellular proliferation at 3- and 24-h, respectively. Both acid and alkaline phosphatase activities of HK leukocytes were not significantly modulated, except for a slight elevation of acid phosphatase in cells incubated with 100 μg ml⁻¹ of alginic acid for 24-h. Fucoidan, but not alginic acid significantly increased cellular myeloperoxidase activity at a concentration of 100 μg ml⁻¹. The growth of the bacteria in both the treated and control supernatants was significantly lower than what was observed in the bacterial culture medium. However, the supernatants from the treated cells had significantly higher bacterial growth compared with supernatants of the control cells. Taken together, these results showed that at the tested concentrations, both alginic acid and fucoidan are able to differentially stimulate some cellular immune responses of cod HK leukocytes in vitro and the respiratory burst activity was significantly stimulated by these brown algal derivatives. These substances could be tested as potential immunostimulants in future in vivo studies.     

Difference Between Tetrodotoxin and Saxitoxins in Accumulation in Puffer Fish Takifugu rubripes Liver Tissue Slices

In vitro accumulation of tetrodotoxin (TTX) and paralytic shellfish toxin (PST) in tiger puffer fish Takifugu rubripes was investigated using liver tissue slices. When T. rubripes liver slices were incubated with Leibovitz’s L-15 medium containing 0.13 mM TTX at 20 °C in air with saturated humidity, they accumulated 21.5 ± 7.3 μg TTX g⁻¹ liver after the incubation for 12 h and increased to 55.3 ± 8.2 μg TTX g⁻¹ liver at 48 h. In the incubation of T. rubripes liver slices with 0.13 mM PST-containing medium, PST was detected 6.3 ± 0.9 μg g⁻¹ liver at 12 h and reached a plateau thereafter. These results reveal the difference between TTX and PST in accumulation in T. rubripes liver tissue slices. To examine the variation in PST accumulation among fish species, the liver tissue slices from tiger puffer fish T. rubripes, parrot-bass Oplegnathus fasciatus and green ling Hexagrammos otakii were incubated at a concentration of 0.027 mM PST. The toxin contents of 3.0 μg g⁻¹ liver were observed at 8 h regardless of fish species but were not increased subsequently, showing no variety among these three species as to accumulation patterns of PST. It is noted that the tiger puffer fish T. rubripes liver specifically accumulate TTX in preference to PST.     

Effects of bifenthrin on some haematological,biochemical and histopathological parameters of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

The aim of this study was to assess the effect of bifenthrin on common carp (Cyprinus carpio L.). The 96-h LC50 value of Talstar EC 10 (active substance 100 g l⁻¹ bifenthrin) was found to be 57.5 μg l⁻¹. Examination of haematological and biochemical profiles and histological tissue examination was performed on common carp after 96 h of exposure to Talstar EC 10 (57.5 μg l⁻¹). The experimental group showed significantly higher (P < 0.01) values of plasma glucose, ammonia, aspartate aminotransferase and creatine kinase as well as the relative and absolute monocyte count, compared with the control group. Histological examination revealed teleangioectasiae of secondary gill lamellae and degeneration of hepatocytes. The bifenthrin-based Talstar EC 10 pesticide preparation was classified as a substance strongly toxic for fish.     

Phytoplankton uptake and growth rate in the Japanese egg cockle Fulvia mutica

To clarify the relationship between the quantity of food ingested by and the growth rate of the Japanese egg cockle Fulvia mutica (Reeve), we conducted a laboratory breeding experiment for 2 weeks and estimated the chlorophyll a (chl-a) concentrations in water and the increments in shell length and soft-body weight of this species under five chl-a concentrations. Moreover, we compared the relationship between cockle growth (changes in soft-body weight and shell length) and their feeding environment observed in the laboratory experiment with the results of a field investigation conducted at two sites in the Sea of Japan, Kumihama Bay (35°38′5″ N, 134°54′00″ E) and Kunda Bay (35°33′30″ N, 135°15′4″ E). The changes in soft-body weight were similar in both laboratory and field investigations, but those in shell length were not. We, therefore, considered shell length changes as unsuitable for evaluating the relationship between growth and feeding in F. mutica. Based on the changes in soft-body weight, it was possible to classify the feeding environment of this species into the following three types: (1) < 1.52 μg chl-a L−1, negative feeding environment for cockle growth; (2) 1.52–5.71 μg chl-a L−1, neutral feeding environment for cockle growth; (3) > 5.71 μg chl-a L−1, positive feeding environment for cockle growth (growth increased with increasing chl-a concentration up to about 11 μg chl-a L−1). These results indicate that maintaining chl-a concentration in the breeding water within 5.71–11 μg chl-a L−1 is desirable for rearing Japanese egg cockle.     

Protein-sparing effect of dietary lipid in practical diets for blunt snout bream (Megalobrama amblycephala) fingerlings: effects on digestive and metabolic responses

This study aimed to evaluate the protein-sparing effect of dietary lipid on digestive and metabolic responses of fingerling Megalobrama amblycephala. Fish were fed nine practical diets with three protein levels (270, 310 and 350 g kg⁻¹) and three lipid levels (40, 70 and 100 g kg⁻¹) for 8 weeks. Weight gain was significantly affected only by dietary lipid levels with the highest found in fish fed 70 g kg⁻¹ lipid. Relative feed intake and whole-body protein content showed little difference among all the treatments. Activities of intestine lipase and amylase increased significantly as dietary lipid levels increased, whereas little difference was observed in protease activities. Liver lipid content was significantly affected only by protein levels with the lowest found in fish fed 310 g kg⁻¹ protein. Liver aspartate aminotransferase (GOT) activities increased significantly with decreasing lipid levels, whereas the highest GOT activity was obtained in fish fed 310 g kg⁻¹ protein in terms of dietary protein levels. Activities of liver lipoprotein lipase, total lipase and plasma cholesterol concentration of fish fed 350 g kg⁻¹ protein were significantly lower than that of the other groups, whereas the same was true for plasma 3, 5, 3′-triiodothyronine level of fish fed 270 g kg⁻¹ protein. The results indicated that an increase of dietary lipid content from 40 to 70 g kg⁻¹ can enhance the growth and digestive enzyme activities of this species and reduce the proportion of dietary protein catabolized for energy without inducing hepatic steatosis; meanwhile, decreasing protein level from 350 to 310 g kg⁻¹ leads to the increase of lipase activities both in intestine and liver coupled with the reduced liver lipid content.     

Effect of light intensity and photoperiod on biomass and fatty acid composition of the microalgae, Chlorella vulgaris

The effects of irradiance and photoperiod on the biomass and fatty acid (FA) composition of Chlorella vulgaris were examined in the exponential growth phase. Results indicated significant differences in biomass and FA at different intensities and photoperiods. Maximum biomass (2.05 ± 0.1 g l⁻¹) was at 62.5 μmol photons m⁻² s⁻¹ and 16:8 h light/dark photoperiod. FA composition changed considerably in different light regimes; the maximum percentage of total saturated (SFA) (33.38%) was recorded at 100 μmol photons m⁻² s⁻¹ and 16:8 h photoperiod, while monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids decreased with increasing irradiance and light duration. The maximum percentage of total MUFA (15.93%) and PUFA (27.40%) was recorded at 37.5 μmol photons m⁻² s⁻¹ and 8:16 h photoperiod.     

Replacement of by-catch fishmeal with dried chicken viscera meal in extruded feeds: effect on growth,nutrient utilisation and carcass composition of catfish <Emphasis Type="Italic">Clarias batrachus</Emphasis> (Linn.) fingerlings

An 84-day feeding trial was conducted to study the effect of replacing dietary fishmeal with dried chicken viscera meal (CVM) on the growth (net biomass gain, specific growth rate, SGR), feed acceptability, feed conversion ratio (FCR), protein efficiency ratio (PER) and carcass composition of Clarias batrachus fingerlings. Triplicate groups of fingerlings with mean initial body weight of 13.35 g were fed on six iso-nitrogenous and iso-lipidic diets. The control diet (CVM0) used marine by-catch fishmeal as the sole source of animal protein. In the other five diets (CVM100–CVM500), 20–100% of fishmeal was substituted by dried CVM at 20% increments. The highest body weight gain, SGR and PER, and the lowest FCR were observed in fish fed a diet containing 300–500 g CVM kg⁻¹. The fish accumulated increasing quantities of lipids and decreasing levels of ash in their carcasses with increasing levels of dietary CVM.     

Effects of Haematococcus pluvialis supplementation on antioxidant system and metabolism in rainbow trout (Oncorhynchus mykiss)

Effects of commercial source for astaxanthin (Haematococcus pluvialis) (H.p) on antioxidant power, specific marker enzymes, and some metabolites were examined in rainbow trout (Oncorhynchus mykiss). Fish were fed on diets containing 1, 3, and 10 g microalga kg⁻¹ feed for 30 days. Serum total antioxidant activity and lipid peroxidation product, indicated by malondialdehyde (MDA), significantly enhanced with different doses of administration, indicating the elevated antioxidant status in all treatment groups. In group fed with high dose of alga, significantly elevated aspartate aminotransferase activity (AST) was noted, indicating damage of normal liver function in this group. Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were not affected in all groups. Although serum total protein remained unaffected, serum glucose level was decreased significantly in lower doses of administration. Furthermore, triglyceride and cholesterol levels showed significant decrease in 3 g kg⁻¹ microalga group by modulation of lipid metabolism in this group. On the other hand, in highest dose, significant increase in lipids was observed, indicating the slight dysfunction in lipid metabolism in this treatment group. The present study suggests that Haematococcus pluvialis especially in dose of 3 g kg⁻¹ feed administration may effectively enhance the antioxidant system and some biochemical parameters in rainbow trout.     

Evaluation of Nile tilapia in monoculture and polyculture with giant freshwater prawn in biofloc technology system and in recirculation aquaculture system

Biofloc technology system (BFT), recirculation aquaculture system (RAS) and polyculture promote efficient use of water, area and nutrient recycling, which are essential practices for sustainable aquaculture development. The aim of this study was to evaluate the growth, feed efficiency, biofloc composition and water quality of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in monoculture and polyculture with giant freshwater prawn Macrobrachium rosenbergii (De Man, 1906) in BFT and RAS, over a period of 30 days. Fish (n = 128; 7.29 ± 0.67 g) were distributed randomly in 16 experimental tanks (8 fish/tank). Prawn (n = 96; 0.50 ± 0.09 g) were allocated in 8 experimental tanks (12 prawn/tank) in a polyculture. The experimental design was completely randomized with four treatments with four replicates each, in a factorial design 2 × 2 (BFT and RAS vs. monoculture and polyculture). The experimental diet (28% of digestible protein; 3100 kcal kg−1 of digestible energy) was used both to fish and prawn in BFT and RAS. There was significant effect (p < 0.01) of the system and the culture for weight gain, apparent feed conversion and protein efficiency ratio. The average weight gain and apparent feed conversion of tilapia in monoculture (30.04 g and 1.39) and in polyculture (36.44 g and 1.27) were superior (p < 0.01) in BFT than in monoculture (23.64 g and 1.74) and in polyculture (24.14 g and 1.61) in RAS. Weight gain and survival of giant freshwater prawn was superior (p < 0.01) in BFT (0.43 g and 87%) compared to RAS (0.26 g and 79%). The data showed that BFT provides better growth performance responses in monoculture for Nile tilapia and in polyculture with giant freshwater prawn compared to RAS.     

Acute effects of cadmium on liver phase I and phase II enzymes and metallothionein accumulation on sea bream Sparus aurata

This research was designed to study Sparus aurata (sea bream) biotransformation and detoxification responses to acute exposure to cadmium (Cd). Sexually immature gilthead sea bream were treated by intraperitoneal injection of Cd chloride (200 μg kg⁻¹) for 6, 12, 24 and 48 h. Cd accumulation was quantified in sea bream liver by graphite furnace atomic absorption spectroscopy after the various exposure periods. The following biological responses were measured: (1) ethoxyresorufin-O-deethylase (EROD) activity as phase I biotransformation parameter, (2) liver glutathione-S-transferase (GST) activity as a phase II conjugation enzyme and metallothionein (MT) content as specific response to Cd contamination. Cd bioaccumulation in the liver resulted in an increasing uptake up to 10.3 μg g⁻¹ wet weight after 48 h of exposure. EROD showed a significant activation only after 6 h exposure and a return to control levels after 12 h. GST revealed significant activation starting from 12 h exposure. MT accumulation in liver showed the same behavior as GST activation.     

Cultivation of <Emphasis Type="Italic">Chondrus canaliculatus</Emphasis> (C. Agardh) Greville (Gigartinales,Rhodophyta) in controlled environments

Increased market demand for algal raw materials has stimulated research and development into new cultivation technologies, particularly in countries with economically important seaweed industries. Chondrus canaliculatus is a red alga endemic to the temperate Pacific coast of South America and produces a complex carrageenan. In Chile, this potential marine resource has been underutilized since the early 1990s, after it was replaced mainly by imports of Kappaphycus and Eucheum from Asia. The study of the cultivation of C. canaliculatus in outdoor tanks demonstrates the potential to produce large quantities of algal material due to the high productivity observed. The material produced may be important in Chile as feed for cultured algal herbivores such as Haliotis spp. Data were obtained on the key factors affecting the growth of this alga, including light, temperature, and nutrient concentrations. The results showed that, on a dry weight basis, productivity varied seasonally between 40 g m⁻³ wk⁻¹ in autumn and 200 g m⁻³ wk⁻¹ in spring, and the optimal stocking density in our experiments was 8 kg m⁻³. Effects of self-shading were among the most important limiting factors in the culture. Discussion is presented on the interactions between temperature, pH, salinity, enrichment with N and P, and water exchange on the maximal growth of C. canaliculatus in this culture.     

Application of synthetic hormone LHRH-A<Subscript>2</Subscript> on the artificial propagation of Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis>

For studying the effect of LHRH-A₂ hormone on the induction of final maturation and ovulation of Persian sturgeon, 71 matured females and 20 matured males were used. Five groups of breeders were injected with sturgeon pituitary gland hormone (50 mg per fish) and LHRH-A₂ in dosages of 3.5, 7, 8 and 10 μg kg⁻¹ for females and 3 and 5 μg kg⁻¹ for males. Results showed that LHRH-A₂ successfully induced final maturation and ovulation in females, and there was no significant difference between five groups of breeders in ovulation proportion, fertilization rate, survival rate of incubation, survival of yolk-sac absorption period and active feeding period of larvae. It can be concluded that the LHRH-A₂ is a proper alternative for pituitary gland hormone in artificial propagation of Persian sturgeon.     

Effect of feed colour on growth and feed utilization of Nile tilapia (Oreochromis niloticus L.) larvae and fingerlings

Two experiments were conducted to investigate the effects of feed colour on the performance of Nile tilapia (Oreochromis niloticus) larvae and fingerlings. In the first experiment, triplicate groups of newly hatched larvae (0.01 g fish⁻¹) were stocked in 40 L glass aquaria at a density of 2 fish L⁻¹. The fish were fed a test diet (400 g kg⁻¹ crude protein) with six different colours (dark blue, dark green, red, dark brown, yellow and light brown) for 60 days. The best performance and survival were achieved in fish fed on dark‐coloured diets, while light‐coloured diets (yellow and light brown) resulted in inferior performance. Dark diets also produced higher body protein than light diets. Body water, lipids and ash showed irregular trends. In the second experiment, triplicate groups of Nile tilapia fingerlings (5.30 g fish⁻¹) were stocked in 140‐L aquaria, in a recirculating indoor system. The fish were fed a test diet (350 g kg⁻¹ crude protein) with the same colours used in the larval trial, for 60 days. Growth rates, feed efficiency, survival and body composition were not significantly affected by feed colours. These results suggest that Nile tilapia larvae are visual feeders, and they prefer dark‐coloured diets to light‐coloured diets, while fingerling fish showed no preference to diet colours.     

The effect of stocking density on yield,growth, and survival of Asian river catfish (<Emphasis Type="Italic">Pangasius</Emphasis><Emphasis Type="Italic">bocourti</Emphasis> Sauvage, 1880) cultured in cages

Asian river catfish (Pangasius bocourti Sauvage, 1880) were cultured at five different stocking densities in cages (submerged volume 1 m³) suspended in a dugout pond from August to November 2009. Pangasius bocourti fingerlings (mean weight 27.09 ± 0.54 g) were stocked at densities of 12, 25, 50, 100, and 200 fish m⁻³. At the end of 3 months, the harvest weights (gross yields) were, respectively, 2.05 ± 0.30, 5.20 ± 0.31, 10.60 ± 0.42, 19.98 ± 0.78, and 42.37 ± 0.41 kg m⁻³. The mean fish weights among the stocking densities of 25, 50, 100, and 200 fish m⁻³ were not significantly different, but were significantly higher than that of the 12 fish m⁻³ density. The specific growth rates among high stocking densities of 50, 100, and 200 fish m⁻³ were not significantly different; however, they were significantly higher than those of the low stocking densities of 12 and 25 fish m⁻³. Asian river catfish performed poorly at the lowest density. The results indicate an initial lower stocking threshold for Asian river catfish of above 5.20 kg m⁻³. The Asian river catfish cultured in small cages placed in a pond reached the desirable market size (>200 g) within a 90-day grow-out period. The results show that the maximum yield for Asian river catfish during a 3-month production cycle was not reached.     

Evaluation of three phytoplankton species as food for the pearl oyster <Emphasis Type="Italic">Pinctada fucata</Emphasis>

In the pearl cultivation farms of the Ehime Prefecture, Japan, mass mortalities of the pearl oyster Pinctada fucata have occurred since 1994. The occurrences of mass mortality roughly coincided with a shift of the dominant phytoplankton from Skeletonema and Chaetoceros to Chaetoceros and Nitzschia all of which belong to Bacillariophyceae. Hence, we evaluated Nitzschia, together with Chaetoceros and Isocrysis, as food for the oyster. Wet weights, lengths, widths, glycogen contents, and growth rates in terms of wet weight of the oysters in all the feeding treatments were significantly higher than those in the non-feeding treatment. The highest glycogen content (2.34%) and growth rate (2.21 g month⁻¹) were found in the Chaetoceros treatment. Growth rate in the Isocrysis treatment (1.63 g month⁻¹) was also high, although glycogen content in this treatment (0.41%) was low. In the Nitzschia treatment, growth rate of the oyster (0.94 g month⁻¹) was the lowest and glycogen content (0.83%) was also low relative to that in the Chaetoceros treatment. Chlorophyll a concentration in fecal pellets was lowest in the Nitzschia treatment (<2.7 μg mg⁻¹), suggesting more complete digestion of Nitzschia by the oyster. Thus, Nitzschia was edible and digestible but not assimilated by P. fucata. We propose the following scenario for the relationship between Nitzschia dominance and mass mortality. When Nitzschia dominates in a culture area, the physiological condition of P. fucata deteriorates due to low assimilation of Nitzschia by the oyster, followed by susceptibility of the oyster to infection by agents lethal to the oyster.     

Guanylyl cyclase stimulation by homologous and heterologous natriuretic peptides in salmonids

A range of homologous (trout ANP, trout CNP, trout VNP) and heterologous (eel ANP, eel ANP-NH₂, rat ANP, porcine CNP) NPs were tested for their effect on guanylyl cyclase in gill and kidney membrane preparations from freshwater and seawater-acclimated rainbow trout and Atlantic salmon. All NPs stimulated guanylyl cyclase at 1 μmol l⁻¹in all preparations. ANP was the most potent stimulator of kidney guanylyl cyclase and CNP the most potent stimulator of guanylyl cyclase in gills. Some differences were apparent between the potencies of homologous and heterologous peptides at 1 μmol l⁻¹: tANP was more potent than rANP in the SW trout kidney and tCNP was more potent than pCNP in FW salmon tissues. While eANP was more potent than tANP in trout gills, it was less potent than tANP in FW salmon gills. However, there was no significant difference between the potencies of eANP and eANP-NH₂ in trout or salmon gills. Salinity did not affect guanylyl cyclase activity with the exception that trout ANP at 1 μmol l⁻¹was more potent in SW trout kidneys than in FW trout kidneys. These results suggest a predomination of NPR-A in the kidney and NPR-B in the gill. It appears that salmonid NPR-A and NPR-B are relatively promiscuous in their ligand affinity, with few differences in the potencies of trout and mammalian NPs and only small differences in cGMP production where these differences do occur. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of ethanolic extract of propolis on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss)

This study was conducted to evaluate the effect of ethanolic extract of propolis (EEP) on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss). Graded levels of EEP [0 (control), 1, 2, and 4 g kg⁻¹ diet] were fed to trout juveniles (mean weight 7.73 ± 0.17 g) for 10 weeks. Dietary EEP supplementation regardless of inclusion level significantly improved the specific growth rate of fish. Similarly, supplemental EEP generally improved the feed efficiency ratio and protein efficiency ratio, but no significant differences were observed between the 1 g kg⁻¹ EEP group and the control group. In addition, dietary EEP supplementation generally increased the plasma superoxide dismutase, lysozyme, total antioxidant capacity, glutathione peroxidase, and catalase activities, but decreased the plasma malondialdehyde level. The plasma triglycerides level was significantly lower in the 1 or 4 g kg⁻¹ EEP group as compared with the control group. Dietary EEP supplementation generally decreased the plasma aspartate aminotransferase and alanine aminotransferase activities, but increased the hepatic aspartate aminotransferase and alanine aminotransferase activities. These results indicate the potential to use the EEP as a growth promoter, hepatoprotective agent, and immunostimulant for rainbow trout.     

Comparative growth of Pacific oyster (Crassostrea gigas) postlarvae with microfeed and microalgal diets

Two trials were carried out in the laboratory in order to assess the effect of microparticulated feed (F) and live (Thalassiosira pseudonana, M) diets on the growth of recently set (396 ± 13 μm shell height) and 2 mm Crassostrea gigas postlarvae. Different proportions of M and F (100:0, 75:25, 50:50; 25:75, 0:100) were delivered in a single dose of 3 h d⁻¹ in trial 1. Dietary M:F proportions of 100:0, 50:50, and 0:100 were delivered as a single pulse of 8 h d⁻¹ (P1) or two pulses of 4 h⁻¹ (P2) in trial 2. Maximal daily M ration was 296 cells μl⁻¹ d⁻¹ (trial 1), 150 M cells μl⁻¹ d⁻¹ (trial 2), or their equivalent F dry weight. Shell height (SH), dry (DW), and organic weight (AFDW) were evaluated weekly. Oysters from trial 1 significantly increased their size after 28 days, and exhibited no significant dietary differences in terms of DW (1.21 ± 0.15 to 2.01 ± 0.28 mg) or AFDW (0.091 ± 0.022 to 0.166 ± 0.029 mg). Newly set postlarvae (trial 2) also exhibited significant growth after 25 days. No dietary differences were observed in trial 2, yet P2 oysters attained significantly higher shell heights (825–912 μm) than P1 oysters (730–766 μm) after 25 d. Pulse effects were marginally not significant in terms of AFDW and growth rate. Together, these findings showed that balanced microfeeds have a practical potential for the culture of early C. gigas postlarvae, when they are delivered in pulse-feeding schemes