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1.
The effects of a single oral administration of des-Gly10-[D-Ala6]-luteinizing hormone-releasing hormone (1–9)-ethylamide (LHRHa) in the diet (0.2–2.5 mg/kg body weight) on ovulation and spawning of spotted seatrout (Cynoscion nebulosus) were examined. Oral administration of 1.0–2.5 mg LHRHa/kg to females in four separate experiments resulted in successful spawning 32–38 h later with mean fertilization and hatching success rates of 93.3% and 74.6%, respectively. A lower dose of LHRHa (0.2 mg/kg) was ineffective in two subsequent experiments. The data suggest that oral administration of 1 mg LHRHa/kg is a reliable method of inducing ovulation in spotted seatrout, resulting in predictable spawning within 38 h of feeding. This noninvasive treatment may be particularly useful for induced spawning of teleosts which are susceptible to handling stress.  相似文献   

2.
Aquaculture of Spinibarbus denticulatus (Oshima, 1926), a fish species indigenous to North Vietnam and Eastern China, is constrained by lack of fingerlings for stocking ponds and cages. As these fish do not naturally breed in captivity, carp pituitary extract (CPE), luteinizing hormone-releasing hormone analogue (LHRHa) with domperidone (DOM) and human chorionic gonadotropin (HCG) were administered at various doses to induce ovulation. A first set of experiments evaluated the response to LHRHa (30, 40 and 50 μg kg−1) with or without DOM (10 mg kg−1), CPE (20, 30 and 40 mg kg−1) and HCG (3000, 4000 and 5000 IU kg−1). A second set of experiments evaluated the dose response to LHRHa (30, 35, 40 and 50 μg kg−1) primed with 6 mg kg−1 of CPE, and HCG (3000, 3500, 4000, 5000 IU kg−1) primed with 6 mg kg−1 of CPE. The treatment groups were compared with each other and the control (injected with 0.9% saline solution). Only 25% and 50% ovulation resulted when treated with LHRHa at 40 and 50 μg kg−1, whereas 100% ovulation was achieved with an addition of DOM to LHRHa. Both 30 and 40 mg kg−1 CPE induced 100% ovulation. However, HCG (4000 and 5000 IU kg−1) induced ovulation in only 33% of females. When primed with CPE, the minimum dose of LHRHa required was 35 μg kg−1 to achieve 70% ovulation. Priming HCG with CPE also resulted in 100% ovulation, and the minimum effective dose of HCG to induce ovulation was 3500 IU kg−1 with 60% ovulation. Fertilization and hatch rates observed in this study with different hormonal stimulation were high (80–93%). The results indicate that while the use of combined hormone strategy has no apparent advantage over a single hormone strategy, LHRHa+DOM (40 μg kg−1+10.0 mg kg−1) and CPE (30 mg kg−1) are most effective in consistently inducing ovulation and thus can be used for commercial hatchery production of S. denticulatus larvae.  相似文献   

3.
The effects of a single injection of mammalian superactive analogue [d ‐Ser(tBu)6,Pro9‐NEt]‐LHRHa (20 μg/ kg?1) combined with the dopamine antagonist, haloperidol (HAL, 0.5 mg kg?1), for induction of ovulation in the koi carp broodstocks were determined under routine hatchery conditions. The results were compared with classic carp pituitary extract (CPE, double injection) application (water temperature 22 °C). Physiological saline (0.7% NaCl)‐injected fish were used as a control group and no ovulation occurred in this group. The spawning ratio was high in the LHRHa+HAL treatment group and in the CPE treatment group (6/7 and 5/7 respectively). The latency period was 14–16 h in the LHRHa+HAL treatment group and 12–14 h in the CPE treatment group (after the second injection). There was no difference between the two ovulating groups with respect to the spawning index (the weight of eggs as a percentage of female body weight) and fertilization rate of eggs (P>0.05). As a result, ovulation can be induced successfully in koi carp broodstocks with 20 μg kg?1 [d ‐Ser(tBu)6,Pro9‐NEt]‐LHRHa+0.5 mg kg?1 HAL treatment in a single injection without decreasing the egg quality. Application of this combination can be useful for hatchery and broodstock management in koi carp culture.  相似文献   

4.
To induce synchronized ovulation, migrating wild Caspian brown trout (Salmo trutta caspius) females were treated with two interperitoneal injections of Des‐Gly10, d ‐Ala6 LHRH (LHRHa), given 3 days apart. Two injections of 100 μg kg?1 body weight of this hormone effectively induced ovulation. Within 27 days from the second injection, all fish injected with 100 μg kg?1 LHRHa had ovulated compared with 54.5% of the controls. The mean time to ovulation was reduced significantly (P<0.05) from 31.67±4.84 days in control fish and 28.83±7.31 days in sham‐treated fish to 16.36±1.61 days in fish injected with 100 μg kg?1 LHRHa. The fertilization rate in 50 and 100 μg kg?1 LHRHa‐injected fish was significantly lower than that in the control fish (P<0.05). In fish injected with 50 and 100 μg kg?1 LHRHa, significant (P<0.05) changes in testosterone (T) and 17α‐hydroxyprogestrone (OHP) levels were observed. After the second LHRHa injection, the fish injected with 100 μg kg?1 showed the highest serum levels of testosterone and OHP. These results demonstrate that the use of LHRHa can effectively reduce the mean time to ovulation and induce synchronized ovulation in Caspian brown trout.  相似文献   

5.
This study indicated that the injection of LHRHa was effective for induction of ovulation, and that artificial fertilization should be carried out immediately after ovulation to obtain good results.  相似文献   

6.
This study examined the changes in plasma steroids during natural (Experiment 1) and induced (Experiment 2) final maturation in yellow perch Perca flavescens. In experiment 1, ovulating yellow perch were stripped of eggs and blood samples collected to determine the concentrations of testosterone (T), estradiol-17β (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Eggs from individual females were weighed and fertilized. Fertilization rate was determined at the embryo eyed stage. In experiment 2, females were randomly assigned to one of the following treatment groups: (1) saline (0.7% NaCl), (2) des-Gly10[D-Ala6] LHRH-ethylamide (100 μg LHRHa/kg), and (3) LHRHa plus 17,20βP (100 μg LHRHa/kg + 2 mg 17,20βP/kg). Fish were injected intraperitoneally with two doses at a two-day interval. Blood was collected prior to injections and at the time of ovulation/spawning and concentrations of T, E2, and 17,20βP (free and conjugated) were determined. In experiment 1, low concentrations of 17,20βP were recorded at spawning. In experiment 2, all surviving fish injected with LHRHa (5 of 5) released their eggs spontaneously during the week following injections. None of the surviving control fish (0 of 5) ovulated during this period, whereas only 1 of 3 surviving fish injected with LHRHa + 17,20βP released eggs. In the control group, concentrations of E2 and 17,20βP did not show significant differences over the experimental period, whereas plasma T concentrations increased significantly. In fish injected with LHRHa, the concentrations of T and 17,20βP increased significantly after the first injection but then declined at ovulation/spawning. It also appears that 17,20βP was conjugated to its sulfated form. Mortality reached 62.5% in the group injected with LHRHa + 17,20βP indicating that this treatment was severe. Thus, LHRHa alone appears highly effective in inducing ovulation in yellow perch. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

7.
Abstract.— Control of reproduction in cultured fishes has been improved by the use of gonadotropin releasing hormones (GnRH's) and, in many fishes, the use of dopamine (DA) receptor antagonists. However, little successful use of these treatments has been reported for channel catfish Ictalurus punctatus . This study was conducted to investigate the potential of treatment with a gonadotropin hormone releasing hormone (GnRH) and a dopamine (DA) receptor antagonist to improve cage spawning success in channel catfish. Two and 3-yr-old catfish were selected from ponds. All males were injected with des-Gly10, [D-Ala6]-Leuteinizing hormone releasing hormone ethylamide (LHRHa, 50 μg/kg body weight). Females were randomly assigned to the various injection treatments, control (vehicle injected, C), LHRHa only (L), DA receptor antagonist (pimozide) only (P), and LHRHa and pimozide (LP). After injections, one male and one female were paired and placed into 1 m wide × 1.5 m long × 1.2 m deep spawning cages with a metal spawning can. Spawning cans were checked from 1 to 10 d after injection and successful spawning events were recorded. Five trials were conducted between 13 May and 5 June 1998. The LP treatment yielded significantly more spawns than any other treatment (LP, N = 24, 83% > L, N = 25, 44% > C, N = 23, 43 % > P, N = 11, 36%). The greatest promotion of spawning with LP treatment was in the first two induction trials. In the subsequent three trials, differences between treatments were not significant, although LP tre.ated females tended to spawn more frequently. Percent hatch (60.5 ± 3.4%) did not differ between treatments. Treatment of females with LHRHa + pimozide is a potentially useful method for increasing spawning success, particularly early in the spawning season.  相似文献   

8.
Banded morwong (Cheilodactylus spectabilis) are of interest for marine finfish aquaculture in temperate southern Australia. To improve their ovulatory response, adult females were implanted during the autumn spawning season with slow‐release pellets containing 0–400 μg luteinizing‐hormone‐releasing hormone analogue (LHRHa)/kg body weight within 24 h of capture from the wild. Compared to the sham control group, animals treated with LHRHa produced significantly more eggs on each day after implantation for the following 7 d (91 ± 39 and 290 ± 38 mL) and a higher proportion ovulated (8/12 and 27/27). Of fish treated with LHRHa, 93% ovulated 2 d after implantation and 79% ovulated three times at 2‐d intervals, whereas control animals showed no cyclicity of ovulation and few ovulated more than once. Egg production was highest at the first ovulation after LHRHa treatment and declined at subsequent ovulations. In a second experiment investigating the range 100–400 μg LHRHa, there was no effect of dose rate on ovulation parameters, which additionally examined implantation either immediately after capture or after a 5‐d delay. Compared to immediate implantation, a delay resulted in a lower proportion of animals that could be stripped after implantation (100 and 50%, respectively) and the volume of eggs was lower (135 ± 15 and 107 ± 10 mL). The egg quality was poor following delayed implantation, resulting in no fertilization after artificial insemination compared with immediate implantation in which fertilization and hatch rates were higher for eggs collected on Day 2 after implantation (79 ± 8% and 58 ± 9%) than on Day 4 (23 ± 7% and 15 ± 6%). Thus, it is important to implant animals as soon as possible after capture to ensure optimum egg quality. Good‐quality eggs were buoyant and spherical and had a diameter of 1050 ± 25 μm with a single pigmented oil droplet of 190 ± 9 μm. When a separate large batch of eggs collected 2 d after implantation with 100 μg LHRHa was inseminated and cultured at 18 C, larvae hatched after 63 ± 2 h at a standard length of 2.6 ± 0.4 mm. Newly hatched larvae were buoyant and transparent with only a few melanophores, eyes were nonpigmented and jaws were nonfunctional. By the fourth day, jaws were functional and eyes were fully pigmented. Utilization of the endogenous yolk and oil was completed by Day 6, and swimming commenced with exogenous feeding. Larvae, initially fed lipid‐enriched rotifers followed by Artemia, reached 8.9 ± 0.7 mm length on Day 55, after which they metamorphosed to the postlarval paperfish stage of development, 22 ± 0.9 mm on Day 100, and 43 ± 1.0 mm at 6 mo of age. The results show that treatment of wild‐caught females with slow‐release pellets containing LHRHa is effective for the production of eggs for hatchery rearing.  相似文献   

9.
Channel catfish, Ictalurus punctatus, pituitary powder (CP) was prepared and administered to determine the effect of pituitary preparation, head selection criteria, and season of collection on the biological potency of this gonadotropic preparation. Pituitaries were harvested from three catfish processing plants throughout the months of December, February, March, and April to investigate the effect of season on CP potency. Gravid female channel catfish were injected intraperitoneally (IP) with priming (2 mg/kg) and resolving doses (8 mg/kg) of CP treatments, luteinizing hormone‐releasing hormone analog (LHRHa), or saline. Pharmaceutical grade Carbopol 971P resin (CAR) was tested as a 1% aqueous dispersion in physiological saline and administered with CP (10 mg/kg) as a IP single injection at a final volume of 2 mL per kg as a slow‐release vehicle. Individual females were hand‐stripped, and eggs were fertilized with freshly harvested blue catfish, Ictalurus furcatus, spermatozoa. Pituitaries processed with either acetone or ethanol/acetone resulted in significantly different ovulation rates of 35 and 73%, respectively (P≤ 0.01). Ovulation success was not significantly different among CP and LHRHa treatment groups. Ovulation rates were not significantly different among treatment groups of CP collected in April (74%) or December (67%), or collected from male (69%), or small individuals (55%). The shortest latency period among CP treatment was from CP collected in December and from males at 39.1 ± 0.7 and 38.5 ± 0.4 h, respectively. The CAR vehicle treatment performed poorly resulting in an average ovulation rate of 19.0%, with 3.3% viable embryos at 36 h post‐fertilization. Pituitaries collected from channel catfish potentially represent a viable spawning aid for the production of hybrid channel × blue catfish.  相似文献   

10.
Mature black sea bass, Centropristis striata L. (200–800 g), were captured in coastal South Carolina during the spawning season and administered hormones for ovulation induction and strip spawning. During both study years, control groups of females were incorporated into the study design and administered sham injections containing physiological saline solution. In 2004, females received a single intramuscular injection of human chorionic gonadotropin (hCG) (330 IU kg−1) (n=8) or two injections of hCG at 24‐h intervals (n=8). In 2005, females received a single injection of hCG (n=10) or an analogue of luteinizing hormone releasing hormone (LHRHa) (n=10). In 2004, all fish administered a single dose of hCG ovulated at least once. Six fish ovulated on two consecutive days and one fish ovulated on 3 days consecutively. In contrast, six of eight fish receiving two doses of hCG ovulated once, five ovulated on 2 days successively and three fish ovulated 3 days in succession. Of the fish that spawned, no differences were found in any reproductive parameters. In 2005, all fish administered hCG or LHRHa ovulated at least once. Three fish administered hCG ovulated twice, four fish ovulated on three consecutive days and one fish 4 days successively. All fish administered LHRHa spawned at least twice, six fish ovulated thrice and three fish ovulated 4 days, successively. A significant difference in fertility was found between hCG (75.6±11.4%) and LHRHa (55.6±27.4%). The results of this study indicate that both hCG and LHRHa are effective for ovulation induction in prespawning black sea bass.  相似文献   

11.
Effects of pimozide (Pim) and [(D-Ala6, Pro9-NEt) LHRH] (LRH-Aa) on common carp oocytes maturation and ovulationin vivo under laboratory and commercial fisheries farm conditions were investigated.Although injections of Pim and LRH-Aa at the doses of 10 mg and 50 µg/kg body weight respectively, did not increase mGtH levels (66.7–155.8 mg/ml) as much as injections of carp pituitary extract (chh) (382.1 ng/ml), induced GtH levels were high enough to induce ovulation. Changes in the ovary caused by Pim and LRH-Aa were similar to those induced by chh, and Pim injected together with LRH-Aa in a single injection gave the same results concerning ovulation induction as when they were applied separately at 6h interval.  相似文献   

12.
Colisa lalia (Ham.) has been used as a model for the development of techniques for induced spawning that are applicable to small teleosts where ovulation requires prolonged exposure to suitable breeding conditions.Human chorionic gonadotrophin (hCG; 4 IU per fish) induced ovulation within 24 hours, whereas homologous pituitary extracts were relatively ineffective. When administered in saline ( 20 g per fish per injection), des-Gly10,[D-Ala6]- LHRH N-ethylamide (LHRHa) was ineffective, but it stimulated ovulation in a proportion of fish when administered ( 1.6 g per fish) as an emulsion in Freund's incomplete adjuvant (FIA). Together, these results suggest that ovulation requires the synthesis as well as the secretion of gonadotrophin in C. lalia.Long-term treatment with thyroid hormones appeared to enhance the ovulatory response to LHRHa in FIA, possibly by effects on the ovary; whereas the various steroids tested were ineffective at the dosages used  相似文献   

13.
Puffer fishes of the order Tetradontidae exist in both anadromous and non-anadromous seawater resident forms. The obscure puffer akifugu obscurus is an anadromous species whose intensive culture in freshwater has developed rapidly in China. To mass produce larvae for intensive culture, induction of ovulation of 3-year-old obscure puffer cultured entirely in freshwater was attempted by giving the fish multiple injections of LHRHa. Twenty 3-yearold cultured obscure puffers were treated with multiple injections of LHRHa at a constant dosage of 30 g of LHRHa kg-1 of body weight with 36 h interval between injections. Beginning two days after hormonal treatment, abdominal palpation was performed every day to check expansion and hardening of the abdomen of the fish due to hydration of oocytes that indicates the completion of final oocyte maturation. The first four fish ovulated after the second LHRHa injection on day 3, but most females ovulated after the fourth hormone injection. A total of 18 fish (90%) ovulated over a period of 7 days, while no fish ovulated in the control group. The mean fertilization rate and the mean hatch rate was 67.1% and 87.6%, respectively. The viability of newly hatched larvae was very good, with a high survival rate of 98.6% 24 h post-hatch. These results indicate that cultured obscure puffer, which are not allowed to undergo diadromous migration and are entirely cultured in freshwater, could be induced to complete maturation and ovulate by simple multiple injections of LHRHa and that the eggs could be successfully hatched into viable larvae.  相似文献   

14.
This study addresses rapid methods to identify mature channel catfish, Ictalurus punctatus, females for induced spawning with luteinizing hormone releasing hormone analog (LHRHa) and common carp pituitary extract (CPE) and the effects of stage of maturity, hormone dose, season, and cannulation before hormone injection. Hormonal intervention is the most effective method for inducing maturation and spawning in channel catfish × blue catfish, Ictalurus furcatus, hybrids. A total of 80 mature channel catfish were staged for maturity based on secondary sexual characteristics and 20–30 oocytes cannulated to ascertain their maturation stage based on the position of gonadal vesicle. Twenty females were randomly assigned to one of the four hormone regimes (priming + resolving dose): CPE 2 + 8 mg/kg (CPEC); LHRHa 20 + 40 µg/kg (LHRHaL); LHRHa 20 + 60 µg/kg (LHRHaM); and LHRHa 20 + 80 µg/kg (LHRHaH) and a fifth treatment consisted of 20 females selected based on apparent maturity as evidenced by external appearance were injected with CPE, 2 + 8 mg/kg without cannulation (CPEO). Two trials were conducted in early part of the spawning season and two trials in peak season. External methods to identify maturity correlated (r = 0.63) with that of “germinal vesicle position” method to identify the stage of maturity in females. Mean percent of females that ovulated, hatched, and fry produced per kg body weight did not differ (P > 0.05) among the five hormone treatments. The mean percent females that ovulated was higher (P < 0.05) for CPE‐induced females that were identified as “excellent” females based on external examination. The performance of cannulated females did not differ (P > 0.05) with that of non‐cannulated catfish. The mean egg quality of hormone‐induced females and percent of females ovulated in response to hormone treatment established a weak but significant linear relationship (Y = 3.85 + 0.008 × ovulation, r2 = 0.39, P < 0.05).  相似文献   

15.
Reeves shad Tenualosa reevesii is one of China's best known anadromous fish, but is presently on the verge of extinction. There is an urgent need for conservation of this species through artificial reproduction and culture. In this study, shad broodstock were held in captivity then were induced to spawn with serial injections of luteinizing hormone-releasing hormone analogue (LHRHa) following GtH priming by implantations of 17-methytestosterone (T) combined with environmental manipulations. Induced maturation of 4, 5, and 6-year-old females reached 83.3%, 87.5%, and 100%, respectively, while fish in control treatments remained immature. During the gonadal development priming period, mean serum 17-estradiol levels in the T treatment were significantly higher than the LHRHa treatment and control fish. Gonadal development of females was suppressed when their mesenteric fat index was below 1.5% by April. The effective accumulating temperatures for female and male maturation were 3,995 ± 31.4 C/d and 2,278 ± 8.9 C/d, respectively. Two injections of LHRHa in combination with domperidone (DOM) and environmental regulations were effective in inducing ovulation. About 800,000 fertilized ova were obtained (fertilization 75%) in 1995, and 5,000 fry were hatched in 1996. These results are an important step to develop shad culture and save this endangered species.  相似文献   

16.
Interest in commercial production of black sea bass has increased in recent years, but reliable spawning methods remain problematic. The objective of this study was to evaluate the effects of oocyte size and luteinizing hormone releasing hormone analogue (LHRHa) dosage and delivery systems on ovulatory success for in vitro fertilization. Vitellogenic females with maximum oocyte diameters of 400–625 μm were implanted with a 95% cholesterol–5% cellulose pellet containing 50 μg of LHRHa. Fish with maximum oocyte diameters < 450 μm failed to ovulate. In contrast, 90% of fish with 500 μm oocytes spawned within 36 h and 40% of this group ovulated a second time. All of the females containing oocytes > 550 μm ovulated. In a second experiment, females with uniformly vitellogenic oocytes (> 500 μm) and implanted with 50 μg LHRHa ovulated substantial numbers of eggs (45,000–192,000 eggs/kg body weight (BW), but fertility was consistently low (0–15%). In a third experiment, 19 of 39 females receiving implants containing 6.3–23.6 μg LHRHa/kg BW during the spawning season ovulated, but fecundity (17,000–339,000 eggs/kg) and fertilization (0–98%) were highly variable. When fish were grouped by developmental index, calculated as the number of oocytes with diameters > 400 μm/total number of oocytes measured, there were no statistical differences among groups with respect to the number of spawns, fecundity or fertilization success. In a fourth experiment, 11 of 13 females with a clutch of fully vitellogenic oocytes that were injected with 20 or 100 μg/kg BW LHRHa ovulated between 1 and 2 times on consecutive days. Five of seven given an implant containing 12.5 μg LHRHa ovulated one or more times. Fish implanted with shams or injected with vehicle alone did not ovulate in any of the experiments. No differences were found in the number of spawns, fecundity or fertilization success from fish receiving different doses of injected or implanted LHRHa. Incubation of pooled eggs produced 155,000 larvae (60% hatch) and 95,000 one-gram juveniles. These results demonstrate that injected or implanted LHRHa is effective for inducing ovulation in black sea bass with maximum oocyte diameters > 500 μm.  相似文献   

17.
Induced spawning in perch, Perca fluviatilis L., was studied using follicle stimulating hormone and lutenizing hormone (FSH + LH) with the addition of pimozide or metoclopramide. The doses administered to fish were: 75 IU kg?1 of FSH + LH with 5 or 10mgkg?1 of pimozide (P) or metoclopramide (M) in females, and 25 IU kg?1 of FSH + LH with 2.5 or 5 mg kg?1 of P or M in males. Hormonal injections in males (except the injection of FSH + LH with 10 mg kg?1 of M) did not influence the quantity of milt obtained. All females treated in this experiment had oocytes at the same stage of nucleus migration, so the time of ovulation was very synchronous, i.e. 16-24 h after injection. The relationship between the quality of the eggs, expressed as a survival to eyed-egg stage, and latency was inverse. Spawning success, expressed as a spawning effectiveness coefficient (Se), was highest in the fish that had been treated with FSH + LH with a higher dose of M.  相似文献   

18.
The effects of intraperitoneal injections of [D-Ala6, Pro9-N-ethylaminde]-luteinizing hormone releasing hormone (LHRH-A) and pimozide (PIM), a dopamine receptor antagonist, on ovulation in loach were investigated. LHRH-A and PIM administered separately were ineffective in inducing ovulation. However, injections of PIM and LHRH-A simultaneously or the injection of PIM 2.5–3 h prior to LHRH-A were highly effective means of inducing ovulation. The simultaneous injection of PIM (1.0 μg/g body wt) and LHRH-A (0.05 μg/g body wt) resulted in a greater ovulatory response than injection of carp pituitary extract (1 pituitary/fish).  相似文献   

19.
Abstract. The effect of two GnRH-As – des Gly10 (D-Ala)6 LHRH and des Gly10 (D-Tle)6 GnRH in total doses 10–249mu;g/kg – and four neuroleptics – pimozide, sulpiride, metoclopramide and isofloxythepin in total doses 1–50mg/kg - and environmental temperatures on the development of final stages of Pacific mullet oogenesis was investigated. The best technique of those used by us for spawning stimulation of Pacific mullet, Mugil so-iuy Bas., females is shown to be administration of neuroleptics in doses of l-8mg/kg with posterior injections on GnRH-A in doses of 25 and 50mu; g/kg applied 4 and 28h respectively after the neuroleptic injection. At water temperatures below 17°C, ovulation does not occur unless the optimal stimulation is applied.  相似文献   

20.
The effect of treating immature, masculinized, Atlantic salmon, Salmo salar, with testosterone or [Des-Gly10] D-Ala6-LHRH ethylamide (LHRHa), either alone or in combination, over an 81 day period was evaluated as a method for accelerating maturation. Two sustained-release LHRHa implants were compared: ethylene vinyl acetate copolymer (EVAC) and silicone elastomer. Animals primed with testosterone did not express advanced spermatogenesis when compared against control salmon (p > 0.05). However, fish primed with testosterone, followed by sham, LHRHa EVAC, or LHRHa silicone elastomer implants expressed increased (p < 0.05) gonadosomatic index (GSI) when compared with values derived from day 0 of the study. Neither spermatogenesis nor GSI were affected when salmon were treated with LHRHa alone, irrespective of the vehicle employed. In contrast, spermatogenesis was significantly (p < 0.05) advanced in testosterone-treated fish, which were administered LHRHa by EVAC, when compared with groups that received individual treatment only. © Rapid Science Ltd. 1998  相似文献   

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