The specific dynamic action of southern catfish, <Emphasis Type="Italic">Silurus meridonalis</Emphasis> Chen,fed diets containing either raw or precooked corn starch or glucose

The growth performance of carnivorous southern catfish (Silurus meridionalis) was lower when fed a diet containing glucose as a carbohydrate source than when fed one containing starch. To test whether this decreased growth performance was partly due to higher metabolic costs induced by the fast assimilation of dietary glucose, the postprandial metabolic responses of southern catfish juvenile (36.7 ± 1.9 g) fed diets containing either raw or pre-cooked corn starch and glucose were investigated at 27.5°C. The peak metabolic rate of fish fed a raw corn starch diet was significantly higher than that of fish fed precooked corn starch and glucose diets (P < 0.05). The specific dynamic action (SDA) coefficients (energy expended on SDA as a percentage of energy content of the meal) of fish fed raw or precooked corn starch diets were significantly higher than that of fish fed a glucose diet (P < 0.05). The postprandial metabolic rate of fish fed a raw starch diet displayed a classic response – increased metabolic rate immediately after feeding, followed by a decreased metabolic rate several hours after feeding – as has been documented earlier in this species. However, the postprandial metabolic rate of fish fed a glucose diet had two alternating cycles of increasing and decreasing metabolic rate, which has not been reported previously. This bimodal pattern of the SDA curve was also found in a subsequent experiment in which purified d-glucose (0.1 g dry mass) was packed into sections of grass carp (Ctenopharyngodon idellus) intestine (0.05 g dry mass). The results suggest that the digestibility and absorption speed of the dietary carbohydrate has a significant effect on postprandial metabolic response in juvenile southern catfish. The results of this study may provide useful data in terms of the utilization of dietary carbohydrates by carnivorous fishes.     

Influence of dietary <Emphasis Type="SmallCaps">l</Emphasis>-selenomethionine exposure on the survival and osmoregulatory capacity of white sturgeon in fresh and brackish water

Near simultaneous exposure to selenium and salinity stress is an environmental reality faced by white sturgeon juveniles in the San Francisco Bay-Delta, having the potential for adverse synergistic impacts on juveniles during seaward migration. White sturgeon juveniles (36–132 g) were transferred into higher salinities (15–20 ppth) after exposure to dietary selenium (0.4, 9.6, 20.5, 41.7, 89.8, or 191.1 μg Se/g diet) in the form of l-selenomethionine (SeMet) for 8 weeks in freshwater (0 ppth). White sturgeon fed above 41.7 μg Se/g diet experienced significant (P < 0.05) declines in survival relative to sturgeon fed between 0.4 and 41.7 μg Se/g diet when transferred into brackish water (15 ppth salinity) for 3 days. Plasma osmolality and ionic concentrations in white sturgeon after abrupt transfer correlated positively with dietary Se concentrations. Transfer of white sturgeon fed above 41.7 μg Se/g diet into 20 ppth brackish water for 1 day resulted in significant declines in survival relative to white sturgeon fed 0.4–41.7 μg Se/g diet. Hematocrit and dehydrational weight loss were significantly correlated with dietary Se concentrations while plasma osmolality and ion concentrations were not. The transfer of sturgeon into 20 ppth water for 3 days resulted in severe survival declines in all treatment groups. The results of this study suggest that the previously established threshold for Se toxicity (10–20 μg Se/g) is sufficient to protect white sturgeon from the adverse interactive affects resulting from increases in dietary Se and ambient water salinity.     

Masculinization of Convict Cichlid (<Emphasis Type="Italic">Cichlasoma nigrofasciatum</Emphasis>) by immersion in <Emphasis Type="Italic">Tribulus terrestris</Emphasis> extract

We have examined the effects of Tribulus terrestris (TT), a non-toxic herb, on sex reversal in the Convict Cichlid Cichlasoma nigrofasciatum with the aim of introducing a new environmentally friendly method for masculinization in C. nigrofasciatum. TT is a natural plant product that elevates the testosterone levels in humans and animals. Different concentrations (0.0, 0.10, 0.20 and 0.30 g/l) of TT extract were tested for their effect on sex reversal in C. nigrofasciatum by immersing newly hatched offspring once weekly for 2 months in TT extract. Of the dosages used in the present study, 0.30 g/l TT was the most effective in terms of masculinization, resulting in a maximum male ratio of 87.23% (P < 0.001). Sex ratios of 79 and 85% at 0.10 and 0.20 g/l TT, respectively, were also significantly different from the expected 1:1 ratio (P < 0.001). Histological examinations revealed that the testes of fish treated with TT extract contained all stages of spermatogenesis, clearly demonstrating that the administration of TT extract to C. nigrofasciatum stimulated spermatogenesis. Total survival rates in all treatments and the control were uniformly high, ranging from 88.57 to 90% (P > 0.05). We concluded that TT had no negative effect on the survival rate of C. nigrofasciatum. In addition, all groups of TT-treated fish exhibited successful growth acceleration compared to the control group, but only the 0.30 g/l TT treatment significantly improved the growth rate of C. nigrofasciatum. (P < 0.01). Sex reversal in C. nigrofasciatum demonstrated that TT-treated 0-day-old larvae showed successful sex reversal, spermatogenesis and a better growth rate than untreated progenies.     

Effect of ration size on growth,body composition,and energy and protein maintenance requirement of fingerling Indian major carp, <Emphasis Type="Italic">Labeo rohita</Emphasis> (Hamilton)

An eight-week feeding trial has been conducted to determine the optimum ration for Indian major carp, Labeo rohita, fingerling (4.10 ± 0.30 cm, 0.55 ± 0.16 g) by feeding a purified diet (40% CP; 3.61 kcal g⁻¹ GE) at six levels, 2, 4, 6, 8, 10, and 12% of body weight per day, at 0800 and 1600 h, in triplicate, to 20 fish per trough fitted with a water flow-through system. Highest weight gain, best feed conversion ratio (FCR), best specific growth rate (SGR%), and highest protein efficiency ratio (PER) were evident for rations of 6–8% body weight. Second-degree polynomial regression analysis for FCR, PER, protein, and energy retention data indicated the break-points occurred at 6.55, 6.75, 6.80, and 6.95% bw per day, respectively. Significant (P < 0.05) differences between body composition were observed for fish fed different rations. Maximum body protein content was recorded for 6% and 8% rations. A linear increase in body fat content was evident with increasing ration. Body moisture and ash content remained non-significantly (P > 0.05) low for higher rations, however. On the basis of these results it is recommended that feeding in the range 6.5–7.0% bw per day corresponding to 2.6–2.8 g protein and 23.49–25.31 kcal energy per 100 g of the diet per day is optimum for growth and efficient feed utilization of Labeo rohita. Results for 2–4% rations (0.8–1.6 g protein and 7.23–14.46 kcal energy) suggest these amounts approximate to the maintenance requirement of this fish.     

Dietary total phosphorus requirement of juvenile yellow catfish <Emphasis Type="Italic">Pelteobagrus fulvidraco</Emphasis>

The present experiment was conducted to determine the dietary total phosphorus requirement of juvenile yellow catfish Pelteobagrus fulvidraco. Six diets with increasing dietary phosphorus concentration (0.43, 0.55, 0.78, 0.90, 1.05 and 1.18% of dry matter, respectively) were fed to triplicate groups of 20 fish each (mean initial body weight, 2.68 ± 0.08 g, mean ± SD) to apparent satiation for 7 weeks. Weight gain and specific growth rate (SGR) increased with increasing dietary phosphorus level from 0.43 to 0.90% and then declined over dietary phosphorus level of 0.90% (P < 0.05). Phosphorus retention increased with increasing dietary phosphorus level from 0.43 to 0.55% and then declined over dietary phosphorus level of 0.55% (P < 0.05). Dietary phosphorus levels significantly influenced whole body crude protein and ash contents (P < 0.05), but not whole body lipid content (P > 0.05). Vertebrae phosphorus content increased with dietary phosphorus level from 0.43 to 0.78% (P < 0.05) and then plateau over the level of 0.78% (P > 0.05). Dietary phosphorus level significantly influenced condition factor, viscerosomatic index and hepatosomatic index (P < 0.05). The relationship between SGR and whole body ash content against dietary phosphorus levels could be expressed as a second-order polynomial equation and the points of 0.89 and 0.85% were considered to be the optimal dietary total phosphorus level, respectively. Based on broken-line analysis of vertebrae phosphorus content, the minimal dietary total phosphorus requirements for maintaining maximum phosphorus storages were estimated to be 0.76% phosphorus.     

Effects of triploidy on the Caspian salmon <Emphasis Type="Italic">Salmo trutta caspius</Emphasis> haematology

The aim of this study was a comparison of key haematological features of diploid (2n) and triploid (3n) Caspian salmon (Salmo trutta caspius). Morphometric indices of erythrocytes were determined on blood smears by light microscopy. Triploidy significantly (P < 0.001) increased all morphometric indices measured in the erythrocytes including cell size, cell surface area, and cell volume. The increase in cell size was larger for the major (27%) axis than for the minor (22%) axis, thus making erythrocytes of 3n Caspian salmon more ellipsoidal. The estimated increase in erythrocyte nuclear volume (87%) was bigger than the theoretical expected 50% increase. Haematological indices were measured manually by hemocytometry. Triploids had lower numbers of red blood cells (RBC: 1,120,000 cells/mL in 2n vs. 700,000 cells/mL in 3n; P < 0.001) but they were larger in size (mean erythrocytic volume [MEV]: 363.1 nm³ in 2n vs. 483.3 nm³ in 3n; P < 0.001). The decrease in RBC number was not compensated by the increase in MEV and, thus, triploidy affected the haematocrit (Hct: 38.8% in 2n vs. 33.06% in 3n; P < 0.05). Total blood hemoglobin concentration was lower in triploid fish (Hb: 9.9 g/dL in 2n vs. 8.9 g/dL in 3n; P < 0.05). In contrast, mean erythrocytic hemoglobin (MEH: 95 μg in 2n vs. 133.2 μg in 3n; P < 0.001) was higher for 3n Caspian salmon as a result of their larger erythrocytes, although MEH concentration (MEHC: 0.26 g/dL in 2n vs. 0.27 g/dL in 3n) did not significantly differ (P > 0.05). White blood cell (WBC) counts (lymphocytes and neutrophiles) were measured and WBC/RBC ratios were calculated. There were no significant differences in WBC (15,710 cells/mL in 2n vs. 12,683 cells/mL in 3n; P > 0.05), lymphocytes, and neutrophils as %WBC as well as WBC/RBC ratios between two ploidy levels (P > 0.05). Triploid Caspian salmon showed higher erythrocyte abnormalities such as ‘twisted’, ‘tailed’, and ‘anucleated’ cells as well as high portions of immature RBC in blood smears in comparison with diploids (P < 0.001).     

Replacement of fishmeal in cobia (<Emphasis Type="Italic">Rachycentron canadum</Emphasis>) diets using poultry by-product meal

An 8-week feeding trial was conducted to evaluate the use of local poultry by-product meal (PBM) in replacement of imported fishmeal in the diets of cobia, Rachycentron canadum. Six isolipidic (12%) and isoproteic (45%) experimental diets were formulated using PBM to replace fishmeal at 20, 40, 60, 80 and 100% dietary protein. Eleven juvenile cobia (initial mean weight of 30.7 ± 0.78 g) were randomly stocked in 300-L circular fibreglass tanks and hand-fed based on the total biomass of each tank, twice a day at 0900 h and 1500 h. The fish were group weighed at 2-week intervals to monitor their growth performance in order to adjust the feeding ratio. At the end of the feeding trial, weight gains (WGs) ranging from 221 to 322% were obtained. The specific growth rate (SGR), WG and protein efficiency ratio (PER) for fish fed with PBM-based diets were not significantly different (P > 0.05) when compared to fish fed the control diet. The best SGR was recorded for fish fed with 60PBM diet, which was significantly higher (P < 0.05) than those fed the control diet with values at 2.40 ± 0.01 and 1.97 ± 0.26%/day, respectively. The FCR of 1.83 ± 0.05 for fish fed the 60PBM diet was not significantly different (P > 0.05) when compared to those fed the control diet. The PBM source and dietary level did not significantly (P > 0.05) affect the hepatosomatic index of the fish. The results from this study suggested that PBM could replace 100% dietary fishmeal without adversely affecting the growth performance, but an optimal replacement level at approximately 60% was recommended for better growth performance and efficient feed utilization.     

Effects of dietary protein levels on growth,feed utilization,protein retention efficiency and body composition of young <Emphasis Type="Italic">Heteropneustes fossilis</Emphasis> (Bloch)

An 8-week growth trial was conducted to assess the effect of dietary protein on growth, feed utilization, protein retention efficiency, and body composition of young Heteropneustes fossilis (10.02 ± 0.09 g; 9.93 ± 0.07 cm). Isocaloric (4.15 kcal g⁻¹, GE) diets with varying levels of protein (25, 30, 35, 40, 45, and 50% of the diet) were fed near to satiation to triplicate groups of fish. Optimum dietary protein was determined by analyzing live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR%), and protein retention efficiency (PRE%) data. Maximum LWG% (167), best FCR (1.42), PER (1.75), SGR (1.76), and PRE (31.7%) were evident in fish fed 40% protein diet (Diet 4). Body protein data also supported the above level. However, second-degree polynomial regression analysis of the above data indicated that inclusion of dietary protein in the range of 40–43% is optimum for the growth of young H. fossilis.     

Growth,feed conversion and body composition of fingerling stinging catfish Heteropneustes fossilis (Bloch) fed varying levels of dietary l‐threonine

An 8‐week feeding trial was conducted to assess the effects of dietary l ‐threonine on growth, protein utilization, threonine retention efficiencies, nucleic acid indices and body composition of fingerling Heteropneustes fossilis (6.6 ± 0.1 g; 10.9 ± 0.2 cm). Casein–gelatin based isonitrogenous (38% crude protein; CP) and isocaloric (15.3 kJ g^?1 digestible energy; DE) amino acid test diets with six levels of dietary l ‐threonine (0.75%; 1.0%; 1.25%; 1.5%; 1.75%; 2.0% dry diet) were prepared and hand‐fed to quadruplicate groups of fingerling to apparent visual satiation twice daily. Weight gain (WG; 46.3 g fish^?1), feed conversion ratio (FCR; 1.98), protein utilization efficiency (PUE; 0.25), threonine retention efficiency (TRE; 0.69), lipid productive value (LPV; 0.45), body protein (18.2%) and RNA/DNA ratio (3.6) of fish fed graded levels of dietary threonine increased significantly (P < 0.05) up to 1.49% threonine of dry diet. To generate precise information, the WG, RNA/DNA and LPV data were subjected to broken‐line and quadratic regression analyses. The two models were superimposed and requirement was determined by establishing the point, where the quadratic curve first intersected the plateau of broken‐line. Based on the above mathematical analyses, optimum dietary threonine requirement of fingerling H. fossilis was estimated to range between 1.62% and 1.69% of the diet, corresponding to 4.26–4.44% protein.     

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.     

Effect of dietary lipid level on growth performance,feed utilization and body composition of grouper <Emphasis Type="Italic">Epinephelus coioides</Emphasis> juveniles fed isonitrogenous diets in floating netcages

An experiment was conducted to determine the effect of dietary lipid levels on growth performance and body composition of grouper Epinephelus coioides juveniles cultured in floating netcages (1.5 m × 1 m × 1.5 m). Six isonitrogenous diets (53% dietary protein) with increasing dietary lipid concentration (5.16, 7.38, 9.73, 12.36, 14.13, 16.04% of dry material, DM) were fed to satiation to triplicate groups of 20 fish (mean weight: 10.9 ± 0.1 g) for 56 days. Dietary energy levels were 300, 322, 340, 371, 382, 400 kcal/100 g DM, respectively. Fish fed the 9L diet had the highest weight gain (WG) and specific growth rate (SGR), but they were not significantly different from that of fish fed the 7L or 12L diet (p > 0.05). FI varied inversely with dietary lipid levels. The poorest FCR and the lowest PER were observed in fish fed the 5L diet but these parameters showed no significant differences (p > 0.05) for fish fed the dietary lipid level ranging from 9 to 16%. Nitrogen intake decreased with dietary lipid levels. Fish fed the 7L diet showed the highest N gain, which was not markedly different from that of fish fed the 9L and 12L diets (p > 0.05). N retention was significantly lower in fish fed the 5L diet than in the other groups. Lipid intake and lipid gain increased with dietary lipid levels. Lipid retention (%) of the 7L diet was lowest but showed no significant differences among other treatments (p > 0.05). Proximate composition of fish body was significantly affected by dietary lipid level (p < 0.05). Body lipid content increased in direct proportion to dietary lipid levels. In contrast, moisture content of whole-body was correlated negatively to dietary lipid level. Dietary lipid content had no significant effect on protein content in whole-body and white muscle (p > 0.05). Condition factor (CF), hepatosomatic index (HSI) and viscerosomatic index (VSI) increased with increasing dietary lipid level. Based on second-order polynomial regression analysis of WG against dietary lipid level, a breakpoint of 10.0% was indicated to be the optimal dietary lipid concentration for maximum growth for grouper Epinephelus coioides juveniles cultured in floating netcages.     

Haemato-biochemical responses and induction of HSP70 to dietary phosphorus in <Emphasis Type="Italic">Catla catla</Emphasis> (Hamilton) fingerlings

A feeding trial of 120 days was conducted to study the effect of graded levels of dietary phosphorus on haematology, serum protein concentrations and HSP70 expression in fingerlings of the Indian major carp, Catla (Catla catla). Eight isonitrogenous and isoenergetic purified diets were formulated to contain graded levels of dietary phosphorus (dP), i.e., T₁, 0.1%; T₂, 0.3%; T₃, 0.5%; T₄, 0.7%; T₅, 0.9%; T₆, 1.1%; T₇, 1.3%; or T₈, 1.5%. Four hundred and eighty fish (average weight 4.23 ± 0.016 g) were equally distributed into 24 tanks forming eight treatments with three replicates each. The fish were fed daily at the rate of 3.5% body weight in two instalments. At the end of feeding trial fish were sampled to study total RBC and WBC count, haemoglobin, serum lysozyme activity, serum total protein, albumin (A), globulin (G) concentration and HSP70 expression. Total RBC count, haemoglobin concentration and serum lysozyme activity did not vary significantly in response to different dietary phosphorus concentrations. Total WBC count was found to be significantly (P < 0.05) higher in T₁ relative to all other treatments. Serum albumin and A/G ratio was found to be significantly lower in fish of T₁ and T₂ in relation to T₇ group (P < 0.05). Serum globulin and total protein levels remained unaffected by variations in dietary phosphorus. HSP70 expression was observed in T₁ group (0.1% dP) in gills and brain tissue, but not in liver and muscle tissues. No HSP70 expression was observed in fish of T₄ (0.7% dP) and T₈ (1.5% dP) treatments. These prima facie results suggest that dietary phosphorus had only minor influence on the haemato-biochemical parameters studied; however dietary phosphorus deficiency caused organ specific induction of HSP70 in catla fingerlings.     

Effect of different dietary raw to pre-gelatinized starch ratios on growth performance,feed utilization and body composition of juvenile yellowfin seabream (<Emphasis Type="Italic">Sparus latus</Emphasis>)

The effects of different ratios of dietary raw to pre-gelatinized starch on the growth performance, feed utilization and body composition of juvenile yellowfin seabream (Sparus latus) were evaluated during a 10-week growth trial. Five isonitrogenous, semi-purified diets containing 200 g kg⁻¹ starch comprising different ratios of raw to pre-gelatinized starch [(in g kg⁻¹)100:100 (diet 1), 150:50 (diet 2), 50:150 (diet 3), 200:0 (diet 4), 0:200 (diet 5), raw:pre-gelatinized] were prepared and fed to triplicate groups of juvenile S. latus. Our results showed that fish fed diet 4 (200 g kg⁻¹ raw starch) had the highest weight gain and specific growth rate, followed by those fed diet 2, diet 1, diet 3 and diet 5. Feed efficiency, protein efficiency ratio and protein productive value in the fish on diets 4 and diet 2, respectively, were significantly higher than those on diets 3 and diet 5, respectively. Body and muscle compositions were unaffected by the different dietary raw to pre-gelatinized starch ratios. Values of hepatosomatic index, intraperitoneal fat ratio, viscerosomatic index and condition factor did not vary among experimental treatments. Plasma indices showed variations, but these were not relative to dietary treatments. In conclusion, the partial or total replacement of raw starch by pre-gelatinized starch in diets for yellowfin seabream did not improve its growth performance and feed utilization.     

Effects of dietary thiamin on the physiological status of the grouper <Emphasis Type="Italic">Epinephelus coioides</Emphasis>

This study was conducted to evaluate the effects of dietary thiamin on the physiological status of the juvenile grouper, Epinephelus coioides. Graded levels of thiamin (0.08, 0.50, 2.12, 3.15, 4.63, 12.37 mg thiamin kg⁻¹ diet) were fed to grouper juveniles (mean weight: 16.97 ± 0.14 g) for 10 weeks. Although fish fed the thiamin-deficient (TD) diet showed no obvious symptoms of thiamin deficiency or increased mortality, those fed the lowest doses of thiamin (0.08 and 0.50 mg thiamin kg⁻¹ diet) had significantly decreased transketolase activity in the liver. In addition, the level of liver thiobarbituric acid reactive substances in fish fed the TD diet was 33–67% higher than that in fish with the thiamin-supplemented diet. There were no significant differences in superoxide dismutase activity between the different groups of fish.     

Haemato-immunology and histo-architectural changes in <Emphasis Type="Italic">Labeo rohita</Emphasis> fingerlings: effect of dietary aflatoxin and mould inhibitor

A feeding trail of 60 days was conducted for delineating the effect of dietary aflatoxin (AFB1) with or without supplementation of a mixture of mould inhibitor (0.25% clove oil + 0.32% sodium propionate) on haematology, respiratory burst activity and histology of Labeo rohita fingerlings. Three hundred and sixty fishes (avg. wt. 1.48–1.54 g) were randomly distributed into eight treatment groups. Eight experimental diets with four different levels of aflatoxin (0, 10, 20 and 40 ppb) with or without mould inhibitor were prepared. Haematological parameters like total serum protein, albumin, globulin and A:G ratio were significantly (P < 0.05) reduced with increasing levels of aflatoxin in the diet. However, supplementation of mould inhibitor showed enhanced values when compared to non-supplemented counter parts suggesting ameliorating effects of mould inhibitor on aflatoxin. Total leucocyte count was higher in aflatoxin-treated groups. Histological observations were complementary to haematological parameters. Respiratory burst activity was significantly (P < 0.05) decreased in higher aflatoxin-treated groups but not affected significantly (P > 0.05) due to inclusion of inhibitor alone and/or interaction of aflatoxin level and inhibitor in the diet. From this study, it was concluded that up to 20 ppb aflatoxin level in the diet the haemato-immunological parameters are protected.     

Effect of prebiotic xylooligosaccharides on growth performances and digestive enzyme activities of allogynogenetic crucian carp (<Emphasis Type="Italic">Carassius auratus gibelio</Emphasis>)

The effect of prebiotic xylooligosaccharides (XOS) on the growth performance and digestive enzyme activities of the allogynogenetic crucian carp, Carassius auratus gibelio, was investigated. XOS was added to fish basal semi-purified diets at three concentrations by dry feed weight: diet 1, 50 mg kg⁻¹; diet 2, 100 mg kg⁻¹; diet 3, 200 mg kg⁻¹, respectively. Twelve aquaria (n = 20) with three replicates for each treatment group (diets 1–3) and control treated without XOS were used. Weights of all collected carp from each aquarium were determined at the initial phase and at the end of the experiment, and the carp survival was also determined by counting the individuals in each aquarium. After 45 days, there were significant differences (P < 0.05) in the relative gain rate (RGR), and daily weight gain (DWG) of diets 1–3 were compared with the control. However, the survival rate was not affected (P > 0.05) by the dietary treatments. For enzymatic analysis, dissection produced a crude mixture of intestine and hepatopancreas of each segment to measure. The protease activity in the intestine and hepatopancreas content of fish in diet 2 (487.37 ± 20.58 U g⁻¹ and 20.52 ± 1.93 U g⁻¹) were significantly different (P < 0.05) from that in the control (428.13 ± 23.26 U g⁻¹ and 12.81 ± 1.52 U g⁻¹) and diet 3 (428.00 ± 23.78 U g⁻¹ and 14.04 ± 1.59 U g⁻¹). Amylase activity in the intestine was significantly higher for diet 2 compared to diet 1 and the control. As for amylase in the hepatopancreas, assays showed higher activity in diet 2 (P < 0.05) compared to the rest.     

Gastrointestinal and hepatic enzyme activities in juvenile silvery-black porgy (<Emphasis Type="Italic">Sparidentex hasta</Emphasis>) fed essential amino acid-deficient diets

As amino acids (AAs) are vital molecules in the metabolism of all living organisms and are the building blocks of enzymes, a 6-week feeding trial was conducted for determining the influence of dietary essential amino acid (EAA) deficiencies on pancreatic, plasma, and hepatic enzyme activities in silvery-black porgy (initial weight 4.7?±?0.01 g) juveniles. Eleven isoproteic (ca. 47%) and isoenergetic (ca. 20.5 MJ kg^?1) diets were formulated including a control diet, in which 60% of dietary nitrogen were provided by intact protein (fish meal, gelatin, and wheat meal) and 40% by crystalline AA. The other 10 diets were formulated by 40% reduction in each EAA from the control diet. At the end of the experiment, fish fed with threonine-deficient diet showed the lowest survival rate (P?<?0.05), whereas growth performance decreased in fish fed all EAA-deficient diets, although the reduction in body growth varied depending on the EAA considered. Pancreatic enzymes (trypsin, lipase, α-amylase, and carboxypeptidase A) activities significantly decreased in fish fed the EAA-deficient diets in comparison with fish fed the control diet (P?<?0.05). Fish fed with the arginine-deficient diet had the highest plasma and liver alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels (P?<?0.05). Plasma and liver lactate dehydrogenase and superoxide dismutase showed the highest and lowest values, respectively, in fish fed the arginine and lysine-deficient diets (P?<?0.05). Plasma metabolites were significantly affected by dietary EAA deficiencies (P?<?0.05). The results of this study suggesting dietary EAA deficiencies led to reduction in growth performance as well as pancreatic and liver malfunction. Furthermore, arginine and lysine are the most limited EAA for digestive enzyme activities and liver health in silvery-black porgy.     

Effect of a mannan oligosaccharide on the growth performance and immune status of rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

The objective of these experimental trials was to determine the effect of a mannan oligosaccharide (MOS) derived from the outer cell wall of Saccharomyces cerevisiae strain 1026 on the growth performance and immune status of rainbow trout. Two experiments were conducted, one with eight net cages and the other with eight raceways. The net cage experiment (42 days) involved 14,400 fish with an initial average weight of 30 g. The raceway experiment (90 days) was conduced with 40,000 fish with an initial average weight of 101 g. Both experiments compared a commercial extruded diet with and without 2,000 ppm MOS supplementation. The calculated daily feed was supplied in six equal rations. Body weight, feed intake, and mortality were recorded and samples were taken for analysis of indicators of immune status. All data were subjected to ANOVA, with a net cage or raceway regarded as an experimental unit. Significantly improved performance and immune status were observed in the net cage trial—improved weight gain of 13.7% (P < 0.01), reduced feed conversion ratio (FCR) (P < 0.05), reduced mortality (P < 0.01), and improved indicators of immune status (P < 0.01) for fish fed the MOS supplement compared with controls. Similar significantly improved performance was observed for the MOS-treated groups in the raceway trial—9.97% improved weight gain (P < 0.01), lower FCR (P < 0.01), and reduced mortality compared with the control treatment. In the raceway trials, however, only the indicators of immune status lysozyme concentration, APCA, and CPCA were significantly improved by MOS treatment (P < 0.05). These experimental trials demonstrated the ability of MOS to improve the growth performance, survival, and immune status of rainbow trout produced in net cages or raceways.     

Effects of dietary phospholipid level in cobia (<Emphasis Type="Italic">Rachycentron canadum</Emphasis>) larvae: growth,survival, plasma lipids and enzymes of lipid metabolism

A study was conducted to determine the effects of dietary phospholipid (PL) levels in cobia (Rachycentron canadum) larvae with regard to growth, survival, plasma lipids and enzymes of lipid metabolism. Fish with an average weight of 0.4 g were fed diets containing four levels of PL (0, 20, 40 and 80 g kg⁻¹dry matter: purity 97%) for 42 days. Final body weight (FBW), weight gain (WG) and survival ratio were highest in the 8% PL diet group and mortality was highest in PL-free diet group. We examined the activities of lipoprotein lipase (LPL) and hepatic lipase (HL) in liver, lecithin-cholesterolacyltransferase (LCAT) in plasma as well as plasma lipids and lipoprotein. LCAT activity showed a decrease of more than two-fold in PL-supplemented diet groups compared with the PL-free diet group. HL activity was highest in the 8% PL diet group and the other three groups showed no difference. LPL activity was significantly higher in the PL-supplemented diet groups than in the PL-free diet group. The dietary intervention significantly increased plasma phospholipids and total cholesterol (TC) levels, and the higher free cholesterol (FC) level contributed to the TC level. However, the fish fed PL exhibited a significantly decreased plasma triglyceride (TG) level. The lipoprotein fractions were also affected significantly by the PL. The PL-supplemented diet groups had significantly higher high-density lipoprotein (HDL) compared with the PL-free diet group, but showed a marked decrease in very low-density lipoprotein (VLDL). The results suggested that PL could modify plasma lipoprotein metabolism and lipid profile, and that the optimal dietary PL level may well exceed 80 g kg⁻¹ for cobia larvae according to growth and survival.     

Effects of dietary protein and lipid levels and protein to energy ratios on growth performance and feed utilization of hatchery-reared juvenile spotted babylon (<Emphasis Type="Italic">Babylonia areolata</Emphasis>)

A 120-day feeding trial was designed to determine the effects of different dietary protein and lipid levels and protein to energy ratio (P:E) on growth performance and feed utilization of hatchery-reared juvenile spotted babylon, Babylonia areolata, cultured under a flow-through seawater system. Six diets were formulated to contain three protein levels (18, 28, and 36%) and two lipid levels (10 and 15%) in a 3 × 2 factorial design with three replicates to provide six different dietary P:E ratios (50.17, 49.09, 68.50, 65.85, 88.66, and 85.36 mg protein/kcal). Each replicate was stocked with 50 snails (0.12 + 0.01 g, initial weight) and fed to satiation once daily. The results showed that survival was above 96% at the end of the feeding trial in all groups and was not affected by either dietary protein level or dietary lipid level. The highest significant (P < 0.05) growth and feed utilization were observed for juveniles fed diet with a P:E ratio of 88.66 kcal g⁻¹ diet. With respect to dietary protein and lipid levels, the highest (P < 0.05) values for growth and feed efficiency were observed for snails fed a diet containing 36% protein level and the same trend was observed for snails fed a diet with 10% lipid level. This results indicated that the diet containing 36% protein and 10% lipid level with a dietary P:E ratio of 88.66 mg protein/kcal would be suitable for optimum growth and feed utilization of B. areolata juveniles.