In vitro effects of plant essential oils on non-specific immune parameters of red drum, Sciaenops ocellatus L.

Phytochemicals such as plant essential oils (EOs) have been reported to favour various activities in the innate immune system of fish. Thus, the aim of this study was to verify the in vitro effect of three different plant EOs (Ocimum americanum, Cymbopogon flexuosus and Melaleuca alternifolia) on non-specific immune parameters and erythrocyte osmotic fragility of red drum, Sciaenops ocellatus. Concentrations of each plant EO evaluated in preparations of head-kidney macrophages, blood leucocytes and blood plasma were as follows: 0.0 (control), 1.0, 2.0, 4.0, 8.0, and 16.0 µg/ml. Red drum head-kidney macrophages significantly increased extracellular superoxide anion production when exposed (20 h) to O. americanum EO (1.0-8.0 µg/ml) and C. flexuosus EO (2.0 and 4.0 µg/ml). The respiratory burst of blood leucocytes (NBT test) significantly increased in all concentrations when compared to the respective control group, for all EOs. At the highest concentration (16.0 µg/ml), C. flexuosus EO significantly inhibited the haemolytic activity of complement system in red drum blood after 1 h exposure. None of the tested concentrations significantly altered plasma lysozyme activity or erythrocyte osmotic fragility after exposing (1 h) red drum whole blood to each EO. This study demonstrated that these plant EOs are capable of triggering superoxide anion production in red drum leucocytes (head-kidney macrophages and/or blood leucocytes). In vivo studies are warranted to address their potential as immunostimulants in the diet of red drum and other aquacultured species.

Dietary arginine requirement of juvenile red drum (Sciaenops ocellatus) based on weight gain and feed efficiency.

Increasing aquacultural production of red drum (Sciaenops ocellatus) has prompted the determination of many of this species' nutritional requirements. However, limited information is available concerning its amino acid requirements, especially for arginine. Therefore, a feeding trial was conducted with juvenile red drum to determine their quantitative dietary requirement for arginine. Experimental diets contained 35 g crude protein/100 g from red drum muscle and crystalline amino acids. Incremental levels of arginine were added to the diets in place of a mixture of glycine and aspartic acid to maintain all diets isonitrogenous. All diets were fed in triplicate to juvenile red drum for 7 wk. Graded levels of arginine significantly (P < 0.05) affected weight gain, feed efficiency, protein efficiency ratio (PER) and plasma arginine levels of the fish. Based on least-squares regression of feed efficiency and PER data, the minimum requirement (+/- SEM) of red drum for arginine was estimated at 1.44 (+/- 0.15) and 1.48 (+/- 0.12) g/100 g diet (4.11 and 4.23 g/100 g dietary protein), respectively. The arginine requirements estimated from weight gain data were 1.75 (+/- 0.18) g/100 g diet or 5.0 g/100 g dietary protein. These values are similar to those reported for other carnivorous fish species.

Metabolic requirements of red drum, Sciaenops ocellatus, for protein and energy based on weight gain and body composition.

Precise formulation of diets that meet but do not greatly exceed nutritional requirements should assist in lowering feed costs for commercial aquaculture of red drum, Sciaenops ocellatus. In this study, protein and energy requirements of red drum for maintenance and maximum gain were determined by feeding a diet containing digestible protein (DP) at 36.5% and 14.2 kJ digestible energy (DE) per gram at various rates for 8 wk in two separate experiments. Changes in weight and whole-body energy and protein were measured and regressed against protein or energy fed using a nonlinear procedure. In the first experiment, juvenile fish [ approximately 3. 4 g initial body weight (BW)] were either starved or fed at one of the following g/(100 g BW.d): 0.5, 1, 2, 4, 6, or 8. The second experiment utilized larger red drum (approximately 5.5 g initial weight), fed 0.75, 1.5, 3, 5, 5.5, 6, 6.5 or 7 g/(100 g BW.d) to confirm and refine results from the first experiment. Based on maintenance of body weight in both experiments, red drum had a protein maintenance requirement of 1.5 and 2.5 g DP/(kg BW.d) whereas estimates based on maintenance of whole-body protein were 0.5 and 2.2 g DP/(kg BW.d). Energy requirements for maintenance of weight and body energy ranged from 58 to 93 and 92 to 97 kJ DE/(kg BW.d), respectively. Protein requirements for maximum weight gain and change in body protein ranged from 20 to 25 g DP/(kg BW.d), whereas energy requirements for maximum weight gain and whole-body deposition ranged from 776 to 958 and 914 to 985 kJ DE/(kg BW.d), respectively. These requirements for maintenance and maximum gain of red drum should assist in formulation of diets for a variety of desired feeding strategies.

Dietary choline requirement of juvenile red drum (Sciaenops ocellatus).

A 6-wk feeding experiment was conducted to determine the maximal dietary choline requirement of juvenile red drum (Sciaenops ocellatus). Diets were formulated to provide 35 g crude protein/ 100 g dry weight from solvent-extracted lyophilized red drum muscle and an amino acid premix. This premix provided methionine precisely at the minimum requirement determined for red drum so that potential synthesis of choline from methionine would be limited. Menhaden oil and dextrin were added to all diets to provide 13.8 kJ metabolizable energy/g diet as estimated by physiological fuel values. The diets were supplemented with choline chloride to provide 0, 250, 500, 750, 1000 and 1500 mg choline/kg diet. Each diet was fed to triplicate groups of red drum initially averaging 5.5 g/fish in a closed, recirculating system consisting of 110-L glass aquaria. Dietary choline concentration significantly (P < 0.05) affected weight gain, feed efficiency, total lipid in liver and plasma, as well as plasma cholesterol ester, triglyceride, cholesterol and phosphatidylcholine concentrations. Least-squares regression of these responses yielded requirements ranging from 330 to 676 mg choline/kg diet. Based on weight gain data, a maximal requirement estimate (+/- SEM) of 588 (+/- 35) mg choline/kg diet was established. Red drum appear to differ from other animals in regard to the response of total lipid in liver because fish fed choline-deficient diets had reduced liver lipid rather than lipid accumulation. Cultured red drum normally store high levels of lipid in the liver.

Coconut oil and beef tallow, but not tricaprylin, can replace menhaden oil in the diet of red drum (Sciaenops ocellatus) without adversely affecting growth or fatty acid composition.

The ability of juvenile red drum (Sciaenops ocellatus) to utilize medium-chain triglycerides (MCT) and other saturated dietary lipids was investigated in two 6-wk feeding experiments. Diets contained solvent-extracted menhaden fish meal to which menhaden fish oil (control), coconut oil, corn oil, beef tallow or various levels of MCT as tricaprylin (30, 46, 65 and 80% of total lipid) were added. Diets were fed to triplicate groups of juvenile red drum in aquaria containing brackish (6%) water. In the first feeding experiment, red drum fed the control diet had the greatest weight gains and feed efficiencies. Weight gain, but not feed was slightly, of fish fed corn oil and fish fed coconut oil was slightly (P < 0.05) lower. In the second feeding experiment, fish fed coconut oil and those fed beef tallow had significantly higher weight gains and feed efficiencies than did fish fed the control diet. Fish fed the diets containing tricaprylin at all inclusion levels in both feeding experiments had significantly lower weight gains and feed efficiencies and higher levels of beta-hydroxybutyric acid in plasma. Fish fed diets with high levels of MCT also had lower (n-3) and greater (n-6) fatty acid levels in the neutral lipid fraction of muscle tissue compared with fish fed the control diet. Coconut oil and beef tallow consistently resulted in greater liver lipid deposition but had variable effects on other tissue indices. Saturated dietary lipids had variable effects on fatty acid composition of muscle polar and neutral lipid fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dietary lipid and environmental salinity on growth, body composition, and cold tolerance of juvenile red drum (Sciaenops ocellatus).

Simultaneous, 6-week feeding trials were conducted in which diets containing menhaden, corn, coconut and hydrogenated menhaden oil at 7.0%, plus a diet containing 14% menhaden oil, were fed to triplicate groups of juvenile red drum (Sciaenops ocellatus) at two different salinities (5 and 32%.). Weight gain was significantly (p < 0.05) affected by diet and salinity. Fish fed the diet containing 14% menhaden oil had the greatest weight gain; whereas, fish fed the diet containing coconut oil gained the least weight. Fish in brackish water had significantly greater weight gain than fish in full-strength seawater over the 6-week period, although fish fed coconut and saturated menhaden oil in brackish water had reduced survival. Dietary lipid also significantly affected muscle and liver total lipid, hepatosomatic index (HSI), and intraperitoneal fat (IPF) ratio, as fish fed the diets containing 14% menhaden oil had higher values for all of these body condition indices.After the feeding trial, fish were subjected to a chronic cold tolerance assay. In the chronic trial, where temperature was gradually reduced over a 3-week period, fish fed the diets containing menhaden oil had significantly lower median lethal temperatures (MLT) than those fish fed the diets containing coconut, corn and saturated menhaden oils. No significant effects of cold exposure were observed on muscle and liver total lipid. Cold exposure prompted a modification in lipid metabolism by lowering total saturated fatty acids and raising (n - 3) highly unsaturated fatty acids (HUFA) in the neutral lipid of liver. Fish with the lowest MLT in the chronic assay exhibited signs of conserving (n - 3) HUFA and depleting (n - 6) fatty acids [primarily 18:2 (n - 6)], resulting in higher (n - 3)/(n - 6) ratios in the polar lipid of liver. These data suggest that the lower lethal temperature of juvenile red drum can be reduced through dietary manipulation involving the inclusion of high levels of dietary lipid rich in (n - 3) HUFA.

Effects of dietary thyroid hormones on the red drum (Sciaenops ocellatus).

Four separate 8-week feeding trials were conducted to assess the effects of supplementing semipurified diets with either triiodothyronine (T3) or thyroxine (T4) at 0, 2, 10, and 50 mg/kg on growth and body composition of juvenile red drum (Sciaenops ocellatus) held in artificial brackish water (6‰) and artificial seawater (32‰). At both levels of salinity, increasing doses of T3 resulted in fish with reduced weight gain, feed efficiency, condition factor (weight × 100/length(3)), and muscle ratio (muscle weight × 100/body weight), as well as a lighter body color. Significant (p < 0.05) effects of T3 on the proximate composition of whole body, liver, and muscle were variable, generally reflecting decreased lipid and protein storage in liver and muscle, respectively. The two highest doses of T3 given to seawater adapted fish increased survival. Dietary T4 supplementation had no distinctive effects on appearance, growth or proximate body composition. These results indicate that whereas T3 may function to regulate protein and lipid metabolism in red drum, dietary supplementation with T3 leads to a hyperthyroidism-induced catabolic state. The elevated endogenous thyroid hormone levels found in fish fed optimal diets may thus adequately supply tissue needs during juvenile growth.

Responses of channel catfish (Ictalurus punctatus) swim-up fry to dietary calcium in soft and hard water.

1. Responses of channel catfish (Ictalurus punctatus) swim-up fry to dietary calcium in soft (< 1 mg/l as CaCO3) and hard (> 100 mg/l as CaCO3) water were determined by feeding purified egg-white diets containing 0, 0.5, 1.0, or 2.0% calcium from CaCO3 for 8 weeks. 2. Catfish fry fed the basal diet (0.03% Ca) in hard and soft water had lower whole-body ash and whole-body calcium concentrations but higher weight gain and survival than those fed calcium-supplemented diets. 3. Fry in soft water generally had lower whole-body ash, whole-body calcium, and survival, as well as a higher incidence of spinal deformities than fry in hard water. 4. Feeding higher levels of calcium to fry reared in soft water did not increase whole-body calcium levels or decrease spinal deformities to the levels observed for fry reared in hard water and fed supplemental calcium. 5. These data indicate that calcium derived solely from dietary or environmental sources was not sufficient for optimum health of channel catfish fry.

Requirement of hybrid striped bass for dietary (n-3) highly unsaturated fatty acids.

A feeding trial was conducted to quantify the requirement of hybrid striped bass (Morone chrysops female x M. saxatilis male) for dietary (n-3) highly unsaturated fatty acids (HUFA), specifically eicosapentaenoic [20:5(n-3)] and docosahexaenoic [22:6(n-3)] acids. Graded levels of (n-3) HUFA as ethyl esters were substituted for part or all of the 5 g olive oil/100 g diet in the semipurified basal diet. Total amount of 20:5(n-3) plus 22:6(n-3) in the experimental diets was 0.5, 1.1, 1.5, 2.0 or 3.2 g/100 g dry wt. Control fish received a diet containing menhaden fish oil at 5 g/100 g. Each diet was fed to triplicate groups of hybrids (with an initial average weight of 13.0 g/fish) in aquaria for 10 wk. Significantly (P < 0.05) higher relative weight gain as well as more efficient food and protein utilization were observed for fish fed the diets with 0.5, 1.1, 1.5 or 2.0% (n-3) HUFA or 5% menhaden fish oil as compared with those fed the basal diet. These responses generally reached a plateau between 1.1 and 1.5% (n-3) HUFA, but the lowest values were observed for fish fed the diet with 3.2% (n-3) HUFA. Fatty acid composition of body lipids (total lipid of intraperitoneal fat and polar lipids of muscle and liver) was affected by diet and indicated some elongation and desaturation of octadecatetraenoic acid [18:4(n-3)] and 20:5 (n-3) to 22:6(n-3). These data indicated that 20:5(n-3) and 22:6(n-3) are essential for hybrid striped bass, and the minimum requirement is approximately 1% of diet or 20% of dietary lipid.

Dietary effects on thyroid hormones in the red drum, Sciaenops ocellatus.

Juvenile red drum (Sciaenops ocellatus) were cultured at 25°C on a variety of diets and blood sampled over eight weeks to examine the relationship between growth and plasma thyroid hormone levels. Maximum growth rates were achieved on formulated experimental diets and a simulated natural shrimp diet. Associated with these maximal rates was a significant increase in triidothyronine (T3), but no consistent change in thyroxine (T4). Reduced rations of diets resulted in low growth rates associated with significantly lowered levels of T3 but not T4. To determine whether weight gain could be increased by application of exogeneous hormone, diets were supplemented with T3 or T4 at 2, 10, and 50 mg hormone/kg diet. Significantly elevated T3 was induced by supplementation with 10 and 50 mg T3/kg diet, although there were no indications of an anabolic effect of T3 incorporation, and 50 mg T3/kg diet was in fact associated with decreased weight gain. Incorporation of T4 into diets had no effect on growth or T3, and had effects on T4 which were small and inconsistent, indicating that T4 may not be effectively absorbed from the gut. No difference was found in response to hormone feeding between low (6 ppt) or high (35 ppt) water salinity. T3 levels thus appear to closely parallel growth in fish on unsupplemented diets, whereas T4 which were small and manipulation. Supplementation with T3 is not an effective means of stimulating growth in red drum fed optimum diets. Whereas thyroid hormones may function to regulate intermediary metabolism in red drum, elevated endogenous thyroid hormone levels appear adequate to supply tissue needs during juvenile growth in culture.

Essential fatty acid requirement of juvenile red drum (Sciaenops ocellatus).

Feeding experiments and laboratory analyses were conducted to establish the essential fatty acid (EFA) requirement of red drum (Sciaenops ocellatus). Juvenile red drum were maintained in aquaria containing brackish water (5 ± 2‰ total dissolved solids) for two 6-week experiments. Semipurified diets contained a total of 70% lipid consisting of different combinations of tristearin [predominantly 18:0] and the following fatty acid ethyl esters: oleate, linoleate, linolenate, and a mixture of highly unsaturated fatty acids (HUFA) containing approximately 60% eicosapentaenoate plus docosahexaenoate. EFA-deficient diets (containing only tristearin or oleate) rapidly reduced fish growth and feed efficiency, and increased mortality. Fin erosion and a "shock syndrome" also occurred in association with EFA deficiency. Of the diets containing fatty acid ethyl esters, those with 0.5-1% (n-3) HUFA (0.3-0.6% eicosapentaenoate plus docosahexaenoate) promoted the best growth, survival, and feed efficiency; however, the control diet containing 7% menhaden fish oil provided the best performance. Excess (n-3) HUFA suppressed fish weight gain; suppression became evident at 1.5% (n-3) HUFA, and was pronounced at 2.5%. Fatty acid compositions of whole-body, muscle and liver tissues from red drum fed the various diets generally reflected dietary fatty acids, but modifications of these patterns also were evident. Levels of saturated fatty acids appeared to be regulated independent of diet. In fish fed EFA-deficient diets (containing only tristearin or oleate), monoenes increased and (n-3) HUFA were preferentially conserved in polar lipid fractions. Eicosatrienoic acid [20:3(n-9)] was not elevated in EFA-deficient red drum, apparently due to their limited ability to transform fatty acids. Red drum exhibited some limited ability to elongate and desaturate linoleic acid [18:2(n-6)] and linolenic acid [18:3(n-3)]; however, metabolism of 18:3(n-3) did not generally result in increased tissue levels of (n-3) HUFA. Based on these responses, the red drum required approximately 0.5% (n-3) HUFA in the diet (approximately 7% of dietary lipid) for proper growth and health.

Dietary rutin has limited synergistic effects on vitamin C nutrition of fingerling channel catfish (Ictalurus punctatus).

A study was conducted to determine the possible synergistic effects between dietary rutin (a bioflavonoid) and vitamin C, and to evaluate their antioxidant effects in fingerling channel catfish. Purified casein/gelatin diets containing two levels of rutin (0 and 1000 mg/kg diet) and three levels of L-ascorbic acid (0, 1500 and 3000 mg/kg diet) in a factorial arrangement were fed to fingerling channel catfish for 16 weeks. Fish fed the diets without supplemental vitamin C showed deformed spinal columns, external hemorrhages and fin erosion after 10 to 12 weeks. Also these fish had significantly (p < 0.05) depressed body weight gain, feed efficiency, hematocrit, hepatosomatic index (% liver weight), as well as reduced liver, fillet and plasma vitamin concentrations after 16 weeks. Liver, fillet and plasma vitamin C concentrations were correlated with dietary vitamin C levels. Forced oxidation of fillet samples significantly (p < 0.05) increased 2-thiobarbituric acid (TBA) values of fillets from fish fed diets without vitamin C and rutin. However, results from the present study indicated only limited synergistic effects of dietary rutin on vitamin C nutrition of channel catfish.

Protein and energy requirements of fingerling channel catfish for maintenance and maximum growth.

In two separate experiments, purified diets containing 25% crude protein and 2.85 kcal/g and 35% crude protein and 3.99 kcal/g were fed at incremental rates [0-5% of body weight (BW)/d] to fingerling channel catfish (Ictalurus punctatus) in aquaria for 8 wk. Linear (r2 = 0.95) increases in growth rate were observed in each experiment with increases in feeding rate up to 8.75 g protein/(kg BW X d) and 99.75 kcal energy/(kg BW X d). Regressing growth rate back to zero resulted in maintenance requirement values of 1.32 g protein/(kg BW X d) and 15.06 kcal energy/(kg BW X d) for experiment 1 and 1.32 g protein/(kg BW X d) and 15.08 kcal energy/(kg BW X d) for experiment 2. Net gains in body protein and energy also increased linearly (r2 = 0.93) with increasing feeding rates up to 8.75 g protein/(kg BW X d) and 99.75 kcal energy/(kg BW X d) in both experiments. Regression equations from these data predicted 1.07 g protein/(kg BW X d) and 17.00 kcal energy/(kg BW X d) in experiment 1 and 1.00 g protein/(kg BW X d) and 17.33 kcal energy/(kg BW X d) in experiment 2 was required to maintain a constant amount of protein and energy in catfish tissue. These requirement values for maintenance and maximum gain agree closely with those predicted from growth data.

Effects of singular and combined dietary deficiencies of selenium and vitamin E on fingerling channel catfish (Ictalurus punctatus).

Selenium and vitamin E interrelationships in the nutrition of channel catfish (Ictalurus punctatus) were investigated in a 26-wk experiment. A purified basal diet alone or supplemented with 0.2 mg/kg selenium, 50 mg/kg vitamin E or both was fed to fingerling channel catfish in aquaria. Combined deficiencies of selenium and vitamin E caused suppressed growth, anemia, severe myopathy, exudative diathesis and death. Singular deficiencies of either selenium or vitamin E did not produce any of these deficiency signs. Catfish fed selenium-deficient diets with or without supplemental vitamin E had reduced glutathione peroxidase activity and elevated glutathione transferase activity in liver. Vitamin E deficiency in catfish caused elevated ascorbic acid-stimulated lipid peroxidation of hepatic microsomes, which was unaffected by selenium supplementation. The results indicate that there is a significant interaction between selenium and vitamin E in the nutrition of the channel catfish.

Dietary selenium requirement of fingerling channel catfish.

Two experiments were conducted in aquaria to determine the minimum dietary selenium requirement of fingerling channel catfish (Ictalurus punctatus). Casein-gelatin diets containing graded levels of supplemental selenium (as Na2SeO3) ranging from 0 to 15 mg/kg were fed to catfish for 15 weeks in experiment 1 to broadly define their selenium requirement and toxicity levels. Although growth of catfish was affected by dietary selenium level, significant differences in weight gain were not easily discernible due to variability among the groups of fish. Weight gain data generally indicated that the basal diet containing 0.06 mg Se/kg diet caused growth depression, and a supplemental selenium level of 15 mg/kg also caused a reduced growth response, which indicated selenium toxicity. Selenium concentrations in edible muscle tissue increased almost linearly with increasing dietary selenium levels. Liver and plasma selenium-dependent glutathione peroxidase (Se GSH-Px) activities indicated the selenium requirement of fingerling channel catfish was between 0.1 and 0.5 mg Se/kg diet. In experiment 2, casein-gelatin diets containing incremental levels of supplemental selenium were fed to catfish for 14 weeks to more precisely determine their minimum dietary selenium requirement. Growth data and liver and plasma Se GSH-Px activities indicated that the minimum selenium requirement of fingerling channel catfish fed adequate vitamin E was 0.25 mg Se/kg dry diet. Based on these data, it appears that selenium supplementation of commercial catfish feeds is warranted.

Dietary zinc requirement of fingerling channel catfish.

Two experiments were conducted in order to establish the essentiality of zinc for fingerling channel catfish (Ictalurus punctatus) and to determine their dietary zinc requirement. Purified egg white diets with and without supplemental zinc were fed to channel catfish fingerlings for 12 weeks in the essentiality experiment. Catfish fed the basal diet containing 1.0 - 1.5 mg Zn/kg diet developed deficiency signs such as anorexia and suppressed growth. After week 8 of this experiment, two groups of fish fed the basal diet were converted to the zinc-supplemented diet, which contained 28 mg Zn/kg diet. Deficiency signs in these fish were alleviated after consumption of the zinc-supplemented diet. In the requirement experiment, graded levels of a zinc premix were added to egg white diets and fed to fingerling channel catfish for 14 weeks. Serum alkaline phosphatase, serum zinc, bone zinc and bone calcium data indicated that the minimum zinc requirement of fingerling channel catfish was 20 mg Zn/kg dry diet.

Dietary phosphorus requirement of channel catfish.

Two experiments were conducted to reevaluate the dietary phosphorus requirement of fingerling channel catfish. Basal diets containing either casein with supplemental inorganic phosphorus and 0.5% total calcium or egg albumin with supplemental inorganic phosphorus and 0.75% total calcium yielded similar requirement data. Eleven-week growth, feed efficiency, serum phosphorus, bone ash, bone calcium and bon phosphorus data indicate that 0.33% apparent available dietary phosphorus is adequate for maximum growth and bone mineralization. Based on these data and previous findings, we would suggest a value of 0.4% apparent available phosphorus be used in formulating catfish feeds. The apparent availability of phosphorus from soybean meal, as determined by the chromic oxide indicator method, was 29% for channel catfish.

Magnesium requirement of fingerling channel catfish and signs of magnesium deficiency.

Purified casein diets with and without supplemental magnesium were fed to fingerling channel catfish (Ictalurus punctatus) in order to establish the essentially of this mineral. Fish fed the basal diet containing 0.004% magnesium developed deficiency signs such as poor growth, anorexia, sluggishness, muscle flaccidity and high mortality. After 3 weeks, two groups of fish fed the basal diet were converted to the supplemental diet containing 0.057% magnesium. Deficiency signs in these fish were alleviated almost immediately. In a second experiment, graded levels of magnesium sulfate were added to casein-based diets and fed to channel catfish fingerlings to determine their dietary requirement for magnesium. Results indicated that a minimum magnesium level of 0.04% of the dry diet was required to maintain normal growth, serum and bone magnesium levels in channel catfish fingerlings.