Effects of dietary <Emphasis Type="Italic">myo</Emphasis>-inositol on growth,chemical composition and plasma chemistry of Amur sturgeon <Emphasis Type="Italic">Acipenser schrenckii</Emphasis>

The present study was conducted to demonstrate the dietary myo-inositol requirement and its effects on the growth, proximate composition and blood chemistry of Amur sturgeon (Acipenser schrenckii). Triplicate groups of 30 fish (initial weight 11.90?±?0.12 g) were fed different diets containing graded levels of myo-inositol (28.75, 127.83, 343.83, 565.81, 738.15 and 936.28 mg kg^?1) until satiation for 56 days. The fish were weighed after a 24-h fast, and six fish were used for whole body composition analysis. Further, the liver and muscle were sampled from another six fish for lipid analysis. The blood and liver were sampled from the remaining six fish for haematology and fatty acid analysis. The weight gain of fish increased with myo-inositol content, from the 28.75- to 343.83-mg kg^?1 myo-inositol treatment groups, and then stabilised. The liver lipid content and hepatosomatic index decreased significantly from 21.91 to 19.14% and from 3.20 to 2.76% with increased dietary myo-inositol supplementation, respectively. The whole body lipid content generally decreased from 6.33 to 5.55%. The content of liver-saturated fatty acids decreased significantly (28.13%) in the 936.28-mg kg^?1 treatment group. The content of plasma non-esterified fatty acids increased with the increase in dietary myo-inositol supplementation from 0.77 to 1.17 mmol L^?1, whereas the content of triglycerides significantly decreased from 4.62 to 3.28 mmol L^?1. In conclusion, the optimum myo-inositol requirement was found to be 336.1 mg kg^?1, based on weight gain in a two-slope quadratic broken-line model.     

Dietary supplementation of yeast (<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>) improves growth,stress tolerance,and disease resistance in juvenile Nile tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>)

The yeast Saccharomyces cerevisiae is one of the commonest probiotics incorporated in aquafeeds. An 84-day feeding trial was conducted to evaluate the effects of varying dietary inclusions of S. cerevisiae, 0% (control), 3% (YF3), 5% (YF5), and 7% (YF7), on growth, stress tolerance, and disease resistance in juvenile (body mass ~?21 g) Nile tilapia (Oreochromis niloticus). Fish were randomly distributed in groups of 20 into 12 1-m³ hapas and fed isoenergetic (~?17 kJ g^?1 gross energy) and isonitrogenous (~?300 g kg^?1 crude protein) diets at 3% of their bulk weight daily. Specific growth rates were significantly higher for the yeast-fed fish (0.77–0.78% day^?1) than for the control fish (0.60% day^?1) and resulted in significantly higher mean final weights for the yeast-treated groups. Protein and lipid retention efficiencies were also significantly higher in the yeast-fed fish than in the control group. In subsequent stress challenge trials, the yeast-fed fish had greater tolerance to acute heat as well as hypoxia exposure than the control fish. Survival rates of the yeast-treated groups following sudden exposure to elevated water temperature (40 °C) ranged from 82.5 to 100% compared to 15% for the control. Mean survival rates following a 24-h hypoxia exposure were also generally significantly higher for the yeast-fed fish. The probiotic groups recorded a relative percent survival (RPS) of 75% after a 14-day Aeromonas hydrophila infection challenge. The results of this study indicate that S. cerevisiae as an additive in Nile tilapia diets has beneficial impacts on growth, stress tolerance, and disease resistance.     

Effect of dietary chitosan on growth performance,hematological parameters,intestinal histology and stress resistance of Caspian kutum (<Emphasis Type="Italic">Rutilus frisii kutum</Emphasis> Kamenskii, 1901) fingerlings

This study was conducted to investigate the effects of dietary chitosan on growth performance, hematological parameters, intestinal histology, stress resistance and body composition in the Caspian kutum (Rutilus frisii kutum, Kamenskii, 1901) fingerlings. Fish (1.7 ± 0.15 g) were fed diets containing chitosan at different levels (0, 0.25, 0.5, 1 and 2 g kg^?1 diet) for a period of 60 days. Results showed that the feed conversion ratio significantly decreased in fish fed diet containing 1 g kg^?1 of chitosan compared to the other groups (P < 0.05), but there were no significant differences between treatments in terms of specific growth rate and condition factor (P > 0.05). Leukocyte increased in fish fed diet containing 2 g kg^?1 of chitosan compared to the other groups (P < 0.05). Lymphocytes, eosinophils and neutrophils did not significantly change among dietary treatments (P > 0.05). Also, the chitosan supplementation did not affect the whole-fish body composition (P > 0.05). Light microscopy demonstrated that the intestinal villus length increased in fish fed diet containing 1 g kg^?1 of chitosan compared to control group (P < 0.05). While 11 and 13 ‰ salinity and 30 °C thermal stress had no effect, 1 g kg^?1 of chitosan (P < 0.05) showed highest survival rate (70 %) in 34 °C thermal stress. The results showed that chitosan in the diet of the Caspian kutum fingerlings could improve feed conversion ratio, the nonspecific defense mechanisms and resistance to some of the environmental stresses.     

Complete replacement of fish meal by other animal protein sources on growth performance of <Emphasis Type="Italic">Clarias gariepinus</Emphasis> fingerlings

To completely replace the fish meal by a mixture of earthworm and maggot meals, experimental diets were tested during 42 days on Clarias gariepinus fingerlings. Five isoproteic and isoenergetic diets (40 % crude protein and 17.9 ± 0.3 kJ g^?1) including the control diet (D1) based on fish meal, were formulated. All these diets satisfied the essential amino acids requirements of C. gariepinus fingerlings. These diets were tested on triplicate groups of 50 fishes (initial body weight: 3 ± 0.1 g) bred in tank (0.5 m³). The approximate ratios 2:5; 1:4; 1:12 and 0:1 between the earthworm meal and the maggot meal were used, respectively, to formulate four diets D2, D3, D4 and D5 without fish meal. After the feeding period, significant differences (P < 0.05) were observed on growth, feed utilization between control diet (D1) and test diets (D2–D5). Fish fed earthworm- and maggot-based diets were grown better than those fed the control diet. Survival and feed utilization were not significantly affected by the ratio between earthworm meal and maggot meal in the test diets. Lipid content was higher in carcass and fillet of fishes fed earthworm- and maggot meals-based diets than that of those fed fish meal-based diet. This study indicates that when the ratio 2:5 between the earthworm meal and the maggot meal is used to entirely replace fish meal and the ratio lysine/arginine of the diet is inferior to 1, the growth performances and feed utilization of Clarias gariepinus fingerlings are improved.     

The immune modulatory effect of oregano (<Emphasis Type="Italic">Origanum vulgare</Emphasis> L.) essential oil on <Emphasis Type="Italic">Tilapia zillii</Emphasis> following intraperitoneal infection with <Emphasis Type="Italic">Vibrio anguillarum</Emphasis>

The current study aimed to evaluate the possible effect of Origanum essential oil on innate immune parameters as well as the hematological profiles of Tilapia zillii following challenge with Vibrio anguillarum. Fifty-four of Tilapia zillii weighing 180?±?10.2 g were randomly distributed into three identical closed recirculating seawater systems. The study included three groups (G1, G2, and G3) repeated in triplicates. Fish of the first two groups were fed on a basal diet without herbs, whereas fish of the last group were fed on a basal diet supplemented with Origanum essential oil at concentration 1 g kg^?1 for 15 days. Subsequently, fish of G2 and G3 subjected to a peritoneal inflammation by intraperitoneally injecting V. anguillarum (5.5?×?10⁵ CFU mL^?1), whereas fish of G1 injected with saline and served as control. Fish of all groups were then sampled at 4, 12, and 24 h post injection. No mortalities were observed in both basal and Origanum fed groups. However, some specimens of fish fed basal diet showed dorsal fin erosions, eroded mouth, and detached skin. Although the kinetics of RBCs, WBCs, Hb, and differential leukocyte values remained unchanged in fish fed different diets at the beginning of the trial, significant increases in those values were observed in fish fed Origanum essential oil at 12 and 24 h post injection. Similarly, an augmentation of plasma proteases, antiproteases, and lysozyme activities were recorded in fish fed Origanum essential oil at the same particular sampling points. A significant enhancement in plasma bactericidal capacity was only recorded in fish fed Origanum essential oil at 12 and 24 h post challenge compared to those fed basal diet. In conclusion, Origanum essential oil had a pronounced influence on the innate immunity and increased the fish resistance to V. anguillarum. These data gave insight into the potential use of Origanum in prophylactic strategies against threatening pathogens.     

<Emphasis Type="Italic">Curcuma longa</Emphasis> as additive in the diet for <Emphasis Type="Italic">Astyanax aff. bimaculatus</Emphasis>

The aim of the present study was to evaluate the effect of turmeric (Curcuma longa) as additive in the diet for Astyanax aff. bimaculatus. Fish (0.83 ± 0.04 g) were fed, for 60 days, with six diets containing 0.0, 20.0, 40.0, 60.0, 80.0, and 100.0 g turmeric kg^?1 feed. There was an increasing linear effect of turmeric on the thickness of the muscular layer, and height and width of the folds of the intestine. In the liver, a quadratic effect was observed of turmeric on the percentage of hepatocyte cytoplasm and a decreasing linear effect on the percentage of sinusoid capillaries. A quadratic effect was also observed of turmeric on the liver glycogen. There was no effect of turmeric on the antioxidant activity in the liver, carcass composition or productive performance of the fish. Thus, we concluded that Curcuma longa has trophic effects on the epithelium and the muscular layer of the intestine of A. aff. bimaculatus. Additionally, low levels of Curcuma longa cause increased deposition of liver glycogen and high levels cause reduction.     

Growth,hematological and biochemical indices of common carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis> fed diets containing corn gluten meal

The effects of replacing fish meal (FM) with corn gluten meal (CGM) on growth and physiological performance were evaluated in common carp (Cyprinus carpio). Six experimental diets were formulated by substituting 0 (control), 20, 40, 60, 80, and 100% CGM protein for FM protein. The concentrations of dietary protein in the experimental diets were 27.8–29% and the P:E ratios were 14.7–15.46 mg/kJ. Eighteen fish with an initial weight of 13.5?±?0.1 g were allocated to each of 18 circular tanks (450 L) to give triplicate groups for each dietary treatment. The fish were fed to satiation for 8 weeks. At the end of the feeding trial, growth indices, body proximate composition, and hematological and biochemical parameters were measured. Blood samples were taken from six fish in each tank. Final weight and total length were significantly higher in fish fed 100% CGM (27.8?±?1.2 g and 11.9?±?0.3 cm) than for those fed the control (22.7?±?1.4 g and 10.9?±?0.5 cm) or 20% CGM (22.3?±?1.2 g and 11?±?0.4 cm) diets. No effect of FM replacement by CGM was observed for condition factor or hepatosomatic index (P?>?0.05). The highest value of protein productive value (14.31?±?0.65) was observed in fish fed 20% CGM (P?<?0.05). There were no significant differences in percentage body moisture and fat, but percentages of protein and ash were significantly different among experimental groups; the highest values of protein (15.6?±?0.24%) and ash (3.01?±?0.26%) were recorded in fish fed 40% CGM. For hematological parameters, the highest number of white blood cells (4.1?±?0.1?×?10³ mm^?3) was observed in fish fed 100% CGM (P?<?0.05). In addition, the highest hematocrit (42.1?±?0.7%) and triglyceride (294.11?±?23.82 mg dl^?1) were seen in fish fed the diet containing 40% CGM, while 80% CGM gave the highest cholesterol level (204.44?±?9.0 mg dl^?1; P?<?0.05). Replacement of FM with CGM had no negative effects on growth and physiological parameters of common carp fingerlings in this short (8 weeks) trial, suggesting that it may be feasible to replace FM with CGM in diets formulated for juvenile common carp.     

Wheat grains fermented by fungal mycelia (<Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> or <Emphasis Type="Italic">Lentinus edodes</Emphasis>) as alternative feed ingredients for juvenile rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

We investigated the effects of replacing non-fermented wheat grains with wheat grains fermented by fungal mycelia in the diet of juvenile rainbow trout (Oncorhynchus mykiss). We assessed growth performance, feeding parameters, and body composition in three experimental groups (0.33?±?0.01 g, in triplicates of 50 individuals each). The diets for all the groups contained ca. 43% protein and 19% lipids. Experimental diets were made by replacing the 100 g kg^?1 of wheat grains present in the basal diet (CTRL) with the same proportion of wheat grains fermented by Pleurotus ostreatus (PWD) or Lentinus edodes (LWD) mycelium. Fish were fed to apparent satiation twice a day for 56 days. Both, PWD and LWD, significantly increased fish body weight from day 28 onwards. Final body weight was 2.37?±?0.04 g (CTRL), 4.29?±?0.02 g (PWD), and 3.50?±?0.05 g (LWD), and feeding efficiency (%) was increased from 64.5?±?0.7 (CTRL) to 92.5?±?0.5 (PWD) and 84.8?±?1.5 (LWD). The experimental diets also improved nutrient retention efficiency (%): 30.0?±?0.5 (PWD), 27.7?±?1.1 (LWD), and 21.0?±?0.1 (CTRL), for crude protein; 40.3?±?0.6 (PWD), 31.0?±?1.8 (LWD), and 16.1?±?0.7 (CTRL), for ether extract; and 16.1?±?0.1 (PWD), 14.0?±?0.3 (LWD), and 11.6?±?0.6 (CTRL), for phosphorus. Body lipid content was highest for PWD followed by LWD and CTRL (81.4?±?1.4, 63.2?±?2.5, 42.3?±?2.6 g kg^?1, respectively), while viscerosomatic index was lowest for PWD (p?<?0.05). Liver glycogen in LWD and PWD fish (0.62?±?0.10 and 0.21?±?0.08% liver weight) was significantly higher than in CTRL fish (0.05?±?0.01% liver weight). Wheat-mycelium meals appear to be suitable dietary ingredients for improving juvenile rainbow trout growth and nutritional performance. These benefits vary according to the mushroom species used.     

Comparative evaluation of fermented and non-fermented de-oiled rice bran with or without exogenous enzymes supplementation in the diet of <Emphasis Type="Italic">Labeo rohita</Emphasis> (Hamilton, 1822)

A 60-day feeding trial was conducted to study the effect of exogenous enzymes (xylanase and phytase) supplementation in the non-fermented and fermented de-oiled rice bran (DORB)-based diet of Labeo rohita. Four test diets (T1-DORB-based diet, T2-fermented DORB-based diet, T3-phytase and xylanase supplemented DORB-based diet, and T4-phytase and xylanase supplemented fermented DORB-based diet) were formulated and fed to the respective groups. Test diets T3 and T4 were supplemented with 0.01% xylanase (16,000 U kg^?1) and 0.01% phytase (500 U kg^?1) enzymes. One hundred twenty juveniles of L. rohita, with an average weight 5.01?±?0.02 g, were stocked in 12 uniform size plastic rectangular tanks in triplicate with 10 fishes per tank following a completely randomized design (CRD). Exogenous enzyme supplementation to the T3 group significantly improved the growth performance of L. rohita (p?<?0.05). Fermented DORB fed groups registered significantly lower growth irrespective of the supplementation of exogenous enzymes. The carcass composition (except CP %), enzyme activities (except amylase activity), globulin, and A/G ratio did not vary significantly (p?>?0.05). Based on the results of the present study, it is concluded that exogenous enzyme supplementation significantly increases the growth of fish fed with DORB-based diet.     

Physiological response,blood chemistry profile and mucus secretion of red sea bream (<Emphasis Type="Italic">Pagrus major</Emphasis>) fed diets supplemented with <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> under low salinity stress

Environmental stressors caused by inadequate aquaculture management strategies suppress the immune response of fish and make them more susceptible to diseases. Therefore, efforts have been made to relieve stress in fish by using various functional feed additives in the diet, including probiotics. The present work evaluates the effects of Lactobacillus rhamnosus (LR) on physiological stress response, blood chemistry and mucus secretion of red sea bream (Pagrus major) under low salinity stress. Fish were fed four diets supplemented with LR at [0 (LR0), 1 × 10² (LR1), 1 × 10⁴ (LR2) and 1 × 10⁶ (LR3) cells g^?1] for 56 days. Before stress, blood cortisol, urea nitrogen (BUN) and total bilirubin (T-BIL) showed no significant difference (P > 0.05), whereas plasma glucose and triglyceride (TG) of fish-fed LR2 and LR3 diets were significantly lower (P < 0.05) than those of the other groups. Plasma total cholesterol (T-CHO) of fish-fed LR3 diet was significantly (P < 0.05) lower than that of the other groups. Furthermore, total plasma protein, mucus myeloperoxidase activity and the amount of mucus secretion were significantly enhanced in LR-supplemented groups when compared with the control group (P < 0.05). After the application of the low salinity stress test, plasma cortisol, glucose, T-CHO and TG contents in all groups showed an increased trend significantly (P < 0.01) compared to the fish before the stress challenge. However, plasma total protein and the amount of secreted mucus showed a decreased trend in all groups. On the other hand, BUN, T-BIL and mucus myeloperoxidase activity showed no significant difference after exposure to the low salinity stress (P > 0.05). In addition, the fish that received LR-supplemented diets showed significantly higher tolerance against low salinity stress than the fish-fed LR-free diet (P < 0.05). The physiological status and the detected immune responses, including total plasma protein and mucus myeloperoxidase activity in red sea bream, will provide a more comprehensive outlook of the effects of probiotics to relieve stress in fish.     

Dietary protein and carbohydrate requirement of juvenile Hawaiian limpet (<Emphasis Type="Italic">Cellana sandwicensis</Emphasis> Pease, 1861) fed practical diet

This study was conducted to evaluate dietary protein and carbohydrate requirement of juvenile Hawaiian limpets Cellana sandwincensis. A total of 64 juvenile limpets (3.12 ± 0.86 g) were fed five different dietary protein levels ranging from 270 to 470 g kg^?1 for 90 days. Carbohydrate and lipid levels were held constant at 180 and 49.7 g kg^?1, respectively. Weight gain and growth rates of the animals did not differ significantly (P > 0.05) among the protein levels ranging from 270 g kg^?1 (0.30 % day^?1) to 470 g kg^?1 (0.23 % day^?1). Next, opihi were fed four diets with protein levels from 210 to 500 g kg^?1 with a constant carbohydrate level at 120 g kg^?1. Weight gain and specific growth rates of opihi increased with increasing dietary protein from 210 to 350 g kg^?1, and significantly (P < 0.05) decreased at the 500 g kg^?1 diet. Highest weight gain, growth rates, and protein efficiency ratio were achieved at 350 g kg^?1. Elevated carbohydrate levels (180–370 g kg^?1) produced a significant difference (P < 0.05) in growth. The fastest growth rates of animals were obtained with 270 g kg^?1 (0.27 % day^?1) and 320 g kg^?1 (0.26 % day^?1). The weight gain of animals fed 180 and 370 g kg^?1 carbohydrate diets were significantly (P < 0.05) lower than those of animals fed 270 and 320 g kg^?1. We conclude that about 350 g kg^?1 protein and 320 g kg^?1 carbohydrate levels could be used for opihi.     

Influence of the dietary inclusion of <Emphasis Type="Italic">Gracilaria cornea</Emphasis> and <Emphasis Type="Italic">Ulva rigida</Emphasis> on the biodiversity of the intestinal microbiota of <Emphasis Type="Italic">Sparus aurata</Emphasis> juveniles

Partial substitutions of fish meal by 5, 15, or 25 % of Gracilaria cornea or Ulva rigida in experimental diets were evaluated to study their effects on biodiversity of intestinal microbiota composition in gilthead seabream (Sparus aurata) juveniles. The diets were offered to duplicate groups of 15 juvenile fish (14.0 ± 0.5 g) for 70 days, and at the end of the experiment the intestinal microbiota from four specimens of each treatment was analysed by denaturing gel gradient electrophoresis. Results showed that the substitution of fish meal by algae meal induced important modifications in the intestinal microbiota community, as a big reduction of the biodiversity when the highest percentage (25 %) of U. rigida was included. On the contrary, an increase on the number of species was detected when a 15 % of algae was included. Various Lactobacillus delbrueckii subspecies were selectively stimulated when G. cornea was included in the feed, and other bacterial species, such as those included in the Vibrio genus, were reduced.     

Demographic and competition studies on <Emphasis Type="Italic">Brachionus ibericus</Emphasis> and <Emphasis Type="Italic">Proales similis</Emphasis> in relation to salinity and algal (<Emphasis Type="Italic">Nannochloropsis oculata</Emphasis>) density

We isolated the rotifers Brachionus ibericus and Proales similis from the sediment of shrimp tanks and studied their individual demographic characters and competition between them at two food levels (0.25?×?10⁶, 1.00?×?10⁶ cells ml^?1 of Nannochloropsis oculata at 25 °C) and salinities ranging from 10 to 30‰. Our hypothesis was that growth rates would be higher with increasing food levels and salinities. Observations were taken twice a day for life table studies and daily once for population growth experiments. Using survivorship and fecundity data, we derived various life history variables. Although the average life span (7.6?±?0.4 days) and gross reproductive rate (33.8?±?2.9 neonate female^?1 day^?1) of B. ibericus were higher than those of P. similis (average life span 5.4?±?0.6 days and gross reproductive rate 13.0?±?0.6 neonate female^?1 day^?1), the population growth experiments showed that P. similis had higher r values (0.32?±?0.005 day^?1) than B. ibericus (0.23?±?0.002 day^?1) at 1.0?×?10⁶ cells ml^?1 of N. oculata. The rotifer P. similis was more adversely affected due to the presence of B. ibericus than vice versa. The data are important for developing techniques for a large-scale culture of these rotifers as food in aquaculture.     

Effects of potential probiotic <Emphasis Type="Italic">Lactococcus lactis</Emphasis> subsp. <Emphasis Type="Italic">lactis</Emphasis> on digestive enzymatic activities of live feed <Emphasis Type="Italic">Artemia franciscana</Emphasis>

In the present study, cellulase, protease, lipase and amylase activities were performed to investigate the effects of Lactococcus lactis subsp. lactis CF4MRS bioencapsulation of Artemia franciscana. Our results show that cellulase activities (total cellulase—FPase activity, exoglucanase and endoglucanase—CMCase activity) were significantly higher (P < 0.05) in A. franciscana tissue homogenates compared to those in the control group after 8 h of L. lactic bioencapsulation. Notably, an exception case was found in β-D-glucosidase activity, whereby the cellulase activity was not significantly different (P > 0.05) compared to the control group. Administrations of L. lactis at cell concentration of 10⁸ CFU mL^?1 showed considerable improvement of other important enzymatic activities such as amylase, protease and lipase in A. franciscana. The amylase/protease ratio in probiotic-treated A. franciscana was recorded at 0.343, approximately two times higher than those without probiotic administration (0.184). In contrary, amylase/lipase ratio showed half of a reduction (0.330) in L. lactis-administrated A. franciscana compared to the control (0.614). Our study suggests that important digestive enzymes, e.g., cellulase, amylase, protease and lipase, can be enhanced through bioencapsulation of A. franciscana with L. lactis subsp. lactis, which could in turn lead to further stimulation of endogenous enzymes in the fish and shrimp larvae.     

Effects of exogenous non-starch polysaccharide-degrading enzymes in diets containing <Emphasis Type="Italic">Gracilaria lemaneiformis</Emphasis> on white-spotted snapper <Emphasis Type="Italic">Lutjanus stellatus</Emphasis> Akazaki

A feeding experiment was conducted to investigate the effects of exogenous non-starch polysaccharide (NSP)-degrading enzymes in diets containing Gracilaria lemaneiformis (GL) on growth performance and digestive enzyme activities of white-spotted snapper Lutjanus stellatus Akazaki (initial mass 8.0 ± 0.1 g). A basal diet (D0) containing a mixed protein source (fish meal, soybean meal and GL meal) was used as the control. Two diets supplemented with 0.5 g (D1) and 1 g (D2) exogenous NSP-degrading enzymes per kilogram of diet were formulated. Each diet was assigned to triplicate groups of fish in a total of nine floating sea cages (270 fish, 30 fish per cage). After a 60-day feeding trail, significantly higher weight gain, specific growth ratio and feed efficiency ratio were observed in fish fed D2 diet compared to those of control (P < 0.05). Body lipid, moisture and ash contents were not significantly affected by NSP-degrading enzyme supplementation, but significantly higher protein content was noticed in fish fed D2 diet compared to that of control (P < 0.05). The amylase activity in the stomach and intestine was significantly higher in fish fed D2 diet (P < 0.05), but no significant differences were observed in pepsin and lipase activities in the stomach or trypsin and lipase activities in the intestine between all treatments. The results suggested that addition of 1 g kg^?1 NSP-degrading enzymes in diet could efficiently improve seaweed feed utilization and growth performance of white-spotted snapper fish.     

Growth and fatty acid composition of <Emphasis Type="Italic">Octopus vulgaris</Emphasis> paralarvae fed with enriched <Emphasis Type="Italic">Artemia</Emphasis> or co-fed with an inert diet

The rearing of Octopus vulgaris paralarvae during its planktonic life stage is a major challenge, as mortality is currently very high and unpredictable. In this study, we examined the survival and growth rates, as well as the fatty acid composition, of O. vulgaris paralarvae fed on three different dietary treatments: group ArDHA was offered juvenile Artemia enriched with a lipid emulsion (Easy DHA-Selco^®); group ArMA was fed with juvenile Artemia enriched with a mixture of microalgae (Rhodomonas lens and Isochrysis galbana); and group ArMA+ID received the same Artemia as group ArMA complemented with an inert diet. Dietary treatments were tested in triplicate with homogenous groups of paralarvae (25 individuals l^?1) established in 50-l tanks, and the experiment was conducted for 15 days. The survival rate of 15-day post-hatch (-dph) paralarvae from groups ArMA (20 ± 8%) and ArMA+ID (17 ± 4%) tended to be higher than in group ArDHA (13 ± 5%), though these differences were not statistically different. The dry weight (DW) of 15-dph paralarvae increased by almost 60% in groups ArMA and ArMA+ID, and nearly 40% in group ArDHA, with respect to hatchlings. The fatty acid (FA) composition of paralarvae revealed a remarkable drop of docosahexaenoic acid (22:6n-3, DHA) from hatchlings to 15-dph paralarvae of all groups (P < 0.05). However, paralarvae from group ArDHA contained higher levels of DHA than those from ArMA and ArMA+ID (P < 0.05). Despite Artemia enriched with DHA-Selco^® contained three-times more DHA than Artemia enriched with microalgae, no beneficial effects of this dietary treatment were observed on the performance of paralarvae.     

Aflatoxin B<Subscript>1</Subscript> (AFB<Subscript>1</Subscript>) reduces growth performance,physiological response,and disease resistance in Tra catfish (<Emphasis Type="Italic">Pangasius hypophthalmus</Emphasis>)

Triplicate groups of one hundred Tra catfish (8 g?±?0.2) were fed seven test diets containing increasing levels of AFB₁ (0, 50, 100, 250, 500, and 1000 μg AFB₁ kg^?1). Additionally Mycofix® Secure was added at 1.5% to one diet containing 500 μg AFB₁ kg^?1. Results showed that Tra catfish are sensitive to AFB₁. Reduction in weight gain (P?<?0.05) was observed for fish fed 50 μg AFB₁ kg^?1 and declined further with increasing levels of AFB₁ in the diets. Fish fed diets contaminated with 500 and 1000 μg AFB₁ kg^?1 showed increased (P?>?0.05) hepatosomatic index (HIS), while an increase in adipose somatic index (ASI) was observed in fish fed 50 μg AFB₁ kg^?1 and above when compared to the control and Mycofix® diets. After 12 weeks, blood serum analysis revealed higher alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in fish fed the 50, 100, and 250 μg AFB₁ kg^?1 suggesting occurrence of liver damage. Disease resistance of fish exposed to Edwardsiella ictaluri was also compromised by the presence of AFB₁ in the feed and was directly related to the contamination level. Seven days after Edwardsiella ictaluri exposure, survival rates were 50, 41.7, 31.7, and 8.3% for fish fed control, 50, 100, and 250 μg AFB₁ kg^?1, respectively. This trial shows that AFB₁ at a level of 50 μg AFB₁ kg^?1 and above can affect fish performance and disease resistance. Application of an effective mycotoxin management in the feed seems to be useful to prevent the negative effects of AFB₁.     

Effects of nucleotides on growth performance,immune response,disease resistance and intestinal morphology in shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> fed with a low fish meal diet

Nucleotides (NT) are widely used as an immunostimulant in aquaculture. A 10-week feeding trial was conducted to evaluate the effects of dietary NT on the growth performance, immune response, disease resistance and intestinal morphology of the Pacific white shrimp Litopenaeus vannamei (initial mean body weight: 0.39 ± 0.00 g). Five isolipidic (about 7 % crude lipid) and isonitrogenous (about 39 % crude protein) practical diets were supplemented with graded levels of NT (0, 60, 90, 120 and 1200 mg kg^?1), respectively. These diets were named as N1, N2, N3, N4 and N5. Each diet was randomly fed to six tanks of shrimps, and each tank contained 40 shrimps. The shrimps were fed four times daily (07:00, 11:00, 16:00 and 21:00 h). The results showed that there were no significant differences in survival, final weight, specific growth rate, feed intake, feed conversion ratio and whole-body compositions among all the treatments (P > 0.05). Shrimps fed the control diet had the significantly lowest activities of superoxide dismutase, total nitric oxide synthase and lysozyme (P < 0.05). However, those parameters increased when dietary NT increased from 60 to 120 mg kg^?1 and decreased as inclusion level increased to 1200 mg kg^?1 (P < 0.05). The cumulative mortality of the shrimps challenged with Vibrio parahaemolyticus was significantly higher in the treatments without dietary NT supplementation than those in treatments with dietary NT (≥90 mg kg^?1) (P < 0.05). The jejunum wall thickness in shrimps fed the control diet was significantly lower than that in the treatments of N2, N3 and N4 (P < 0.05). For the villus height, the highest value (49.29 µm) was found in N3. In summary, the present study showed that 90 mg kg^?1 of dietary NT is the optimum dietary level for good gut health, immune response and disease resistance of Pacific white shrimp fed a diet with 18 % fish meal.     

Pre-sedation and transport of <Emphasis Type="Italic">Rhamdia quelen</Emphasis> in water containing essential oil of <Emphasis Type="Italic">Lippia alba</Emphasis>: metabolic and physiological responses

The effects of transporting silver catfish (Rhamdia quelen) for 6 h in plastic bags containing 0 (control), 30 or 40 µL/L of essential oil (EO) from Lippia alba leaves were investigated. Prior to transport, the fish in the two experimental groups were sedated with 200 µL/L of EO for 3 min. After transport, dissolved oxygen, carbon dioxide, alkalinity, water hardness, pH, temperature and un-ionized ammonia levels in the transport water did not differ significantly among the groups. However, total ammonia nitrogen levels and net Na⁺, Cl^? and K⁺ effluxes were significantly lower in the groups transported with EO of L. alba than those in the control group. PvO₂, PvCO₂ and HCO₃ ^? were higher after transporting fish in 40 µL/L of EO of L. alba, but there were no significant differences between groups regarding blood pH or hematocrit. Cortisol levels were significantly higher in fish transported in 30 µL/L of EO of L. alba compared to those of the control group. The metabolic parameters (glycogen, lactate, total amino acid, total ammonia and total protein) showed different responses after adding EO to the transport water. In conclusion, while the EO of L. alba is recommended for fish transport in the conditions tested in the present study because it was effective in reducing waterborne total ammonia levels and net ion loss, the higher hepatic oxidative stress in this species with the same EO concentrations reported by a previous study led us to conclude that the 10–20 µL/L concentration range of EO and lack of pre-sedation before transport are more effective.     

In vitro and in vivo evaluation of probiotic properties of <Emphasis Type="Italic">Enterobacter cloacae</Emphasis> in Kenyi cichlid, <Emphasis Type="Italic">Maylandia lombardoi</Emphasis>

In this study, Enterobacter cloacae bacterium was isolated from curd and its antibacterial potential against the pathogen Plesiomonas shigelloides was evaluated using the freshwater ornamental fish Kenyi cichlid (Maylandia lombardoi). Among the bacterial isolates, E. cloacae exhibited tolerance to acidic pH 2 and demonstrated the highest antibacterial activity against P. shigelloides in various in vitro assays. Dietary supplementation of E. cloacae with prebiotic supplement 2% mannan oligosaccharide improved the growth performance and reduced the toxic metabolites such as nitrite in culture tank water of Kenyi cichlid. In vivo application of E. cloacae with mannan oligosaccharide significantly elevated (p?<?0.05) white blood cell counts (88.47?±?2.15 10³ mm^?3) and respiratory burst activity (0.243?±?0.007) of Kenyi cichlid when challenged with P. shigelloides. Intestinal morphology of Kenyi cichlid fish treated with probiotic and prebiotic combinations showed improved intestinal architectures. The present findings confirm that the isolated bacterium E. cloacae is a potential probiotic and can be used effectively to prevent infection of P. shigelloides in freshwater ornamental fish culture.