The effect of 3,3′,5-triiodo-L-thyronine and 17-α-methyltestosterone on growth and body composition of the glass stage of the eel (Anguilla anguilla L)

This study was undertaken to determine the influence of orally administered 3,3,5-triiodo-L-thyronine (T₃) or 17--methyltestosterone (MT) on growth and body composition of the eel (Anguilla anguilla L.) during the glass stage.Elvers receiving 20 or 40 ppm of T₃ in the food weighed significantly more (P < 0.05) than controls. However, after 61 days of treatment a dosage of 60 ppm was not efficacious.Terminal percentages of body protein were significantly lower (P < 0.05) in elvers that received 20 ppm or 40 ppm T₃ in their diets, than in the control. Crude body fat content was higher (P < 0.05) in elvers receiving 20 ppm (29% fat) or 40 ppm (28% fat), than in the controls (26% fat). Compared to the control, diets containing T₃ at 20 or 40 ppm increased the body glucose concentration.Glass eels fed a diet containing 1 or 10 ppm MT grew significantly more slowly (P < 0.05) than the controls.Total body protein content was higher (P < 0.05), but total body crude fat content was lower (P < 0.05) in elvers fed a diet with 1 or 10 ppm MT compared to the controls. Total body glucose concentration of elvers administered 10 ppm MT was significantly lower (P < 0.05) than that of the control groups.     

Influence of oral administration of estradiol-17β and testosterone on growth,digestion, food conversion and metabolism in the underyearling red sea bream,Chrysophrys major

Estradiol-17 (E2) administered in the diet to the red sea bream Chrysophrys major did not affect appetite, food conversion efficiency, protein efficiency ratio and specific growth rate. Serum concentrations of total protein, albumin, globulin, vitellogenin, -amino acids, total lipid, free fatty acids, cholesterol and calcium were elevated. The hepatosomatic index was also increased. Activities of hepatic enzymes including lactate dehydrogenase, isocitrate dehydrogenase and glutamate-pyruvate transaminase were higher than found in untreated control fish. Intestinal activity of leucine aminopeptidase was augmented. However, there were no changes in muscle water, protein, lipid and glycogen content. In contrast, testosterone (T) given by the same route increased appetite, food conversion efficiency, protein efficiency ratio and specific growth rate. There were no alterations in serum protein and calcium concentrations but serum glucose, ammonia and triglyceride levels were elevated. Hepatic glycogen content was increased. The activities of hepatic fructose- 1,6-diphosphatase, glucose-6-phosphatase and glycogen synthetase and intestinal activities of alkaline phosphatase and -glutamyltransferase were higher than noted on control fish. The results reveal that estradiol-17 and testosterone exerted different metabolic effects in the red sea bream and they suggest that testosterone exerts its anabolic actions by increasing appetite, food conversion efficiency and activities of digestive enzymes.     

Effects of salinity, dietary level of protein and 17α-methyltestosterone on growth hormone (GH) and prolactin (tPRL177 and tPRL188) levels in the tilapia, Oreochromis mossambicus

In the present study, we examined the long-term effects of environmental salinity, diet (35% and 25% crude protein) and 17-methyltestosterone (MT) on corresponding levels of pituitary and serum growth hormone (GH) and prolactins (tPRL₁₇₇ and tPRL₁₈₈) in the tilapia (Oreochromis mossambicus). We observed no discernible patterns in serum GH that would suggest an effect of salinity, diet or MT. However, serum GH levels in all treatments declined at 1 and 3h after first feeding. Serum tPRL₁₇₇ and tPRL₁₈₈ were significantly higher in freshwater (FW) than in seawater (SW) and levels were significantly affected by dietary protein. tPRL₁₇₇ levels were higher in all groups fed a 35% protein diet, but tPRL₁₈₈ levels were higher only in the groups fed the MT-treated 35% protein diet; only serum tPRL₁₈₈ levels were affected by MT. Moreover, serum tPRL₁₇₇ and tPRL₁₈₈ increased throughout the sampling time-course. Subsequent work using fasted tilapia suggests that first feeding is likely to initiate the post-prandial suppression of serum GH levels. In contrast with the picture observed in blood, pituitary glands of SW animals showed higher levels of GH than FW fish. Pituitary GH was elevated by MT in both FW and SW. We also observed that pituitary tPRL₁₇₇ and tPRL₁₈₈ levels were higher in FW fish than in SW fish; tPRL₁₇₇ and tPRL₁₈₈ levels were elevated by MT only in FW animals. To assess the somatomedin activity of plasma from FW- and SW-reared tilapia, we measured [35S]-sulfate incorporation into ceratobranchial cartilage explants in vitro. Plasma from SW-adapted tilapia showed greater activity in this assay than plasma from FW-reared tilapia, suggesting that the GH-dependent IGF bioactivity of plasma is higher in SW-reared tilapia. Collectively, these studies suggest that the growth-promoting actions of SW rearing and of MT administration in tilapia may be linked to elevations in GH and/or prolactin (tPRL₁₇₇ and tPRL₁₈₈)levels.     

Influence of food type,amount, and frequencies on the larviculture of pacamã catfish Lophiosilurus alexandri

This study assessed the performance of L. alexandri postlarvae (2 days after hatching) with different diets (Artemia and Panagrellus redivivus), food amounts (C₃₀₀-C₅₀₀-C₇₀₀), and feeding frequencies (F₁-F₃-F₆) in two experiments lasting 10 days. The best performing food type, Artemia and Artemia with P. redivivus, presented the highest survival rates as well as fish with the greatest weight, length, and specific growth rate (SGR). In the second experiment with Artemia, the weight, length, and SGR presented significant differences, increasing with higher amounts of prey. The best performance was obtained from a daily diet (F₁) with the greatest amount of prey (C₇₀₀).     

Temporal changes in plasma thyroid hormone,growth hormone and free fatty acid concentrations,and hepatic 5′-monodeiodinase activity,lipid and protein content during chronic fasting and re-feeding in rainbow trout (Oncorhynchus mykiss)

Temporal changes in growth, plasma thyroid hormone, cortisol, growth hormone (GH) and non-esterified fatty acid (NEFA) concentrations, hepatic T₃ content and hepatic 5-monodeiodinase activity were measured in rainbow trout (Oncorhynchus mykiss) subjected to a sustained fast for up to eight weeks, and during a four-week re-feeding period. The purpose of the study was to examine aspects of the endocrine control of energy partitioning processes characteristic of short-term (acute; fasting) and long-term (chronic; starvation) food-deprivation states in fish, and to explore the role of the thyroid hormones, cortisol and GH in the energy repartitioning that takes place during an acute anabolic (re-feeding) state following chronic food deprivation.Differences in growth rate between fed and fasted groups were evident after two weeks, but significant weight loss by the fasted groups was not evident until between four and six weeks into the fast. Hepatosomatic indices (HSIs) were significantly reduced in the fasted fish within seven days, and as early as two days in one study; recovery of the HSI in fasted fish was evident within three days of re-feeding. Liver protein content (expressed as % wet weight) was consistently depressed in the fasted fish in only one of the three studies. Liver total lipid content (expressed as % wet weight) was depressed in the fasted fish within two days of food deprivation. Because of the rapid and sustained decrease in the HSI of fasted fish, the hepatic total protein and lipid reserves, when considered on a body weight basis, were markedly lowered within the first few days of the fast. Plasma GH concentrations exhibited a bi-modal pattern of change, with a transient fall in levels, followed by a sustained increase in fasted fish. The indicators of interrenal activity were suggestive of a depressed pituitary-interrenal axis in fasted animals; plasma cortisol levels were elevated to levels of fed animals within one day of re-feeding. The indicators of thyroid hormone economy (plasma thyroid hormone levels, liver triiodothyronine content, hepatic 5-monodeiodinase (MD) activity, thyroid epithelial cell height) were similarly indicative of a depressed pituitary-thyroid axis in fasted animals, with recovery to levels of the fed animals within one week. Despite the compensatory changes in accumulation of reserves (as indicated by a compensatory increase in HSI), there were no apparent compensatory changes in any of the endocrine parameters evident during the re-feeding period.     

The effects of gonadal development and sex steroids on growth hormone secretion in the male tilapia hybrid (Oreochromis niloticus × O. aureus)

Profiles of plasma growth hormone (GH) in male tilapia hybrid (Oreochromis niloticus x O. aureus) were measured and compared at different times of the year. The profiles did not appear to be repetitive, however, differences in their nature were observed at the different seasons; the most erratic profiles were seen in the height of the reproductive season (July), while the peaks were more subdued in the spring and disappeared in the autumn. Peaks in male fish were more prominent than in the females when measured in July. Perifused pituitary fragments from fish with a high GSI responded to salmon gonadotropin-releasing hormone (sGnRH) analog (10 nM-1 M), while those from fish with a low GSI barely responded to even the highest dose. Exposure of perifused pituitary fragments from sexually-regressed fish to carp growth hormone-releasing hormone (cGHRH; 0.1 M) or sGnRH (I M) stimulated GH release only after injection of the fish with methyl testosterone (MT; 3 injections of 0.4 mg kg ¹). The same MT pretreatment did not alter the response to dopamine (DA; 1 or 10 M). GH pituitary content in MT-treated fish was lower than in control fish, which may be explained by the higher circulating GH levels in these fish, but does not account for the increased response to the releasing hormones. Castration abolished the response of cultured pituitary cells to sGnRH (I fM-100 nM) without altering either their basal rate of secretion or circulating GH levels. Addition of steroids to the culture medium (MT or estradiol at 10 nM for 2 days) enabled a GH response to sGnRH stimulation in cells from sexually regressed fish. Pituitary cells which had not been exposed to steroids failed to respond to sGnRH, although their response to forskolin or TPA was similar to that of steroid-exposed cells. It would appear, therefore, that at least one of the effects of the sex steroids on the response to GnRH is exerted proximally to the formation of cAMP, or PKC, presumably at the level of the receptor. An increase in the number of receptors to the GH-releasing hormones, following steroid exposure, would explain also the changing nature of the GH secretory profile in different stages of the reproductive season.     

Oxidative metabolism in a teleost,Anabas testudineus Bloch: effect of testosterone and estradiol-17β on hepatic enzyme activities

Testosterone (T) administration to maleAnabas testudineus significantly stimulated the activities of cytochrome oxidase, -glycerophosphate dehydrogenase (-GPDH) and Mg²⁺ adenosine triphosphatase (Mg²⁺ ATPase) and inhibited lactate dehydrogenase (LDH), cytosolic and mitochondrial malate dehydrogenases (MDH). The activities of succinate dehydrogenase (SDH), glucose-6-phosphate dehydrogenase (G-6-PDH) and catalase were unaffected by testosterone treatment. Administration of estradiol-17 (E2) in female fish, significantly stimulated cytochrome oxidase activity, inhibited Mg²⁺ ATPase, SDH, catalase and cytosolic and mitochondrial MDH activity, and was without effect on other enzymes studied.The simultaneous injections of actinomycin D or chloramphenicol and T or E2 prevented the hormonal influence on hepatic enzyme activities. The present study demonstrates that inA. testudineus sex steroids influence hepatic oxidative metabolism by a mechanism sensitive to the action of inhibitors of protein synthesis.     

Influence of chronic administration of LHRH-analogue and/or 17α-methyltestosterone on maturation in milkfish,Chanos chanos

Five chronic hormone therapies; cholesterol pellets containing 200 μg of LHRH-a (LHRH-a pellet); silastic tubing packed with either 250μg of dissolved 17α-methyltestosterone (liquid 17α-MT capsule) or 10 mg crystalline 17α-methyltestosterone (crystalline 17α-MT capsule); or the combinations of LHRH-a pellets plus a liquid 17α-MT capsule or LHRH-a pellets plus a crystalline 17α-MT capsule, were tested to determine the best treatment for inducing maturation in captive milkfish (Chanos chanos). Experimental groups of 20 milkfish each received one of these five therapies. A sixth control group received placebo implants. LHRH-a pellets were administered monthly; crystalline 17α-MT capsules were administered once, and liquid 17α-MT capsules were administered twice, at the beginning of the experiment and 3 months later.Results show that the combination of LHRH-a pellets plus liquid 17α-MT capsules in the most effective hormone therapy for enhancing the maturation of both sexes. Fifty percent of these fish matured in April, 1 month after implantation, and close to 90% of the fish in this treatment matured by July. The combination of LHRH-a pellets plus crystalline 17α-MT capsules enhanced the maturation of male milkfish but not female. LHRH-a alone was also effective in the maturation of females, but was the least effective of all treatments in maturing males. 17α-MT capsules alone, in either form, did not induce maturation in female milkfish.     

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

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

Influence of Ulva meal on growth, feed utilization, and body composition of juvenile Nile tilapia (Oreochromis niloticus) at two levels of dietary lipid

A nutrition trial was conducted to investigate the effects of dietary lipid levels and supplemental Ulva meal on growth performance, feed efficiency, nutrient utilization, and body composition of juvenile Nile tilapia, Oreochromis niloticus. Four isonitrogenous (CP 40%) diets containing 0% and 5% Ulva meal were formulated to contain 10% (low-lipid; LL) and 20% (high-lipid; HL) crude lipid. Triplicate groups of fish (~10 g) were fed to apparent satiation three times daily for 16 weeks. Fish fed 5% Ulva meal showed an increased growth performance (P < 0.05) compared with fish fed non-Ulva supplemented diets, irrespective of dietary lipid level. In particular, the incorporation of Ulva meal improved specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER). Feeding fish 5% Ulva meal diets resulted in significantly lower carcass lipid content. The results indicate that 5% inclusion of Ulva meal at both dietary lipid levels improves growth performance, feed efficiency, nutrient utilization, and body composition of Nile tilapia.     

Studies on activity, distribution, and zymogram of protease, α-amylase, and lipase in the paddlefish Polyodon spathula

A series of biochemical determination and electrophoretic observations have been conducted to analyze the activities and characteristics of protease, α-amylase, and lipase of paddlefish Polyodon spathula. The results obtained have been compared with those of bighead carp (Aristichthys nobilis) and hybrid sturgeon (Huso dauricus ♀?×?Acipenser schrenki Brandt ♂), in order to increase available knowledge of the physiological characteristics of this sturgeon species and to gain information with regard to its nutrition. Further, a comparative study of enzymatic activity, distribution, and characterization between commercial feed-reared paddlefish (CG) and natural live food-reared (NG) paddlefish was conducted. Results showed that higher proteolytic activity was observed in the pH range 2.5-3.0 and at a pH of 7.0 for paddlefish. Levels of acid protease activity of paddlefish were similar to that of hybrid sturgeon, and significantly higher than that of bighead carp. The inhibition assay of paddlefish showed that the rate of inhibition of tosyl-phenylalanine chloromethyl ketone was approximately 2.6-fold that of tosyl-lysine chloromethyl ketone. There was no significant difference observed for acid protease activity between PG and CG groups, whereas the activity of alkaline protease, α-amylase, and lipase in the PG group were significantly lower than those in the CG group. The substrate sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis further showed that there were certain types of enzymes, especially α-amylase, with similar molecular mass in the paddlefish and hybrid sturgeon. It can be inferred that acid digestion was main mechanism for protein hydrolysis in paddlefish, as reported for other fishes with a stomach. This indicates that the paddlefish requires higher alkaline protease, α-amylase, and lipase activity to digest natural live food.     

Influence of 11-ketotestosterone, 17β-estradiol, and 3,5,3′-triiodo-L-thyronine on distribution and metabolism of carotenoids in Arctic charr, Salvelinus alpinus L.*

This investigation examines the influence of implants containing 11-ketotestosterone (11KT), 17-estradiol (E₂), and 3,5,3-triiodo-l-thyronine (T₃) on astaxanthin metabolism in sexually immature individually tagged Arctic charr. The fish (initial average weight 427 g) were maintained in freshwater for 40 days, and weekly implanted intraperitoneally with oil-based injections containing either 11 KT, E₂ or T₃ at levels of 0.1, 1.0 and 0.1 mg (100 g body weight (BW))^–1, respectively. The control fish were given the oil medium alone (0.2 ml 100 g BW^–1). The diet contained ca. 50 mg astaxanthin kg^–1. Carotenoid composition was monitored in plasma, fillet, liver and skin, and 11 KT, E₂ and testosterone (T) levels in plasma. All hormone treatments reduced plasma T compared to the control. E₂-treated fish had a higher (p<0.05) hepatosomatic index (HSI) than the other treatments. Hormone treatment did not influence gonadosomatic index (GSI). T₃ administration induced a silvery skin appearance. The fillet and plasma carotenoid content decreased during the experiment. 11 KT implantation reduced astaxanthin and idoxanthin concentrations of plasma and fillets, and increased the amount in liver and skin, compared to the other treatments. The relative proportion of astaxanthin to idoxanthin was higher in the control fish and T₃ implanted fish, than in fish implanted with 11 KT or E₂ (p<0.05). Fish treated with E₂ had the highest skin carotenoid concentration. Male fish had significantly higher carotenoid content in plasma, fillet and skin than female fish. This study reveals that sex hormones affect carotenoid metabolism and partitioning among body compartments of Arctic charr, effects differently displayed by the sexes.     

Inclusion of β-1,3/1,6-glucan in the ornamental fish,Jewel tetra (Hyphessobrycon eques), and its effects on growth,blood glucose,and intestinal histology

The effects of β-1,3/1,6-glucan on Hyphessobrycon eques were assessed after 42 days of feeding diets containing 0 (control group given commercial feed), 0.5, 1, or 2 g β-glucan/kg diet. In total, 180 fish, with an initial weight of 0.43?±?0.03 g, were used. There were 15 fish in each of twelve 42-L aquariums, and there were 3 aquariums of fish for each dietary treatment. The fish were fed until apparent satiety. Performance parameters (final weight, total length, standard length, feed intake, survival rate, weight gain, feed conversion, specific growth rate, and condition factor) and plasma glucose concentration were measured. Histological analysis of the proximal portion of the intestine (width and height of the villi, depth of the crypts, height of the enterocytes, thickness of the muscle layer, and number of goblet cells) was performed. Different levels of the additive did not influence fish performance (for example, final weight: control: 0.63 g, 0.5: 0.60, 1: 0.58, and 2: 0.61). Likewise, there was no influence on the plasma glucose concentration (control: 81.80 mg/dL, 0.5: 75.33, 1: 85.00, and 2: 81.00) and intestinal morphometry of the animals. However, the results showed that 2.0 g/kg of β-1,3/1,6-glucan provided a greater abundance of goblet cells secreting acidic and neutral mucus present in the epithelium (periodic acid-Schiff: 66.67 cells, Alcian blue pH 1.0: 72,67 cells, and Alcian blue pH 2.5: 95.00 cells), showing significant differences when compared to animals in the control group, which may represent better protection of the intestinal epithelium of H. eques.

     

Effect of long-term administration of dietary β-1,3-glucan on growth, physiological, and immune responses in Litopenaeus vannamei (Boone, 1931)

β-1,3-Glucan at different dietary doses was administered to enhance the growth, immunity, and survival against nitrite stress in Pacific white shrimp, Litopenaeus vannamei. Four different diets supplemented with 0, 250, 500, or 1,000 mg of β-1,3-glucan kg⁻¹ diets were fed to L. vannamei. Growth performance (weight gain and survival rate), physiological conditions (blood total protein, glucose, lactate, triacylglycerols, cholesterol levels) and immunological responses (superoxide dismutase, catalase, lysozyme, acid phosphatase, and alkaline phosphatase activities) of shrimp were recorded after 84-day feeding and 120 h after exposed to nitrite-N. After 84-day feeding, 250 mg kg⁻¹ β-1,3-glucan diet resulted in better weight gain (P < 0.05). Before the nitrite stress, blood lactate, triacylglycerols, and cholesterol level in shrimp fed with 250 mg kg⁻¹ β-1,3-glucan diet were significantly higher than those observed in shrimp fed with other diets (P < 0.05). Higher activities of catalase, lysozyme, and alkaline phosphatase were observed in shrimp fed with 500 or 1,000 mg kg⁻¹ β-1,3-glucan diet as compared to those obtained in shrimp fed with other diets (P < 0.05). After 120-h nitrite stress, blood protein, lactate, superoxide dismutase, catalase, and alkaline phosphatase activities in shrimp fed with 500 or 1,000 mg kg⁻¹ β-1,3-glucan were significantly higher than those observed in shrimp fed with other diets (P < 0.05). Glucose and triacylglycerol levels of shrimp fed with 500 or 1,000 mg kg⁻¹ β-1,3-glucan were significantly lower than those observed in other diets (P < 0.05). In shrimp fed with 500 and 1,000 mg kg⁻¹ β-1,3-glucan and 120-h after nitrite stress, the mortality was significantly lower than that observed in shrimp of control. Together, in this 84-day feeding trial, 250 mg kg⁻¹ β-1,3-glucan improved growth, whereas 500 mg kg⁻¹ β-1,3-glucan preferentially improved nitrite resistance, probably through accelerating energy metabolism and activating immune system.