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1.
Used as a traditional Chinese medicine, the high mortality rate and slow growth of Whitmania pigra larvae are the most serious bottlenecks for the scale development of artificial breeding. Firstly, five light colour treatments (white, blue, green, red and yellow) were tested to determine effects of light spectrum on the growth of larval W. pigra at the same intensity of 70.00 μmol m?2 s?1. The experiment lasted for 45 days. Under our experimental conditions, the weight gain (WG) and the specific growth rate (SGR) under blue light condition were significantly higher compared with the other treatments (P ≤ 0.05). It is reasonable to conclude that blue light can promote the leech growth. In addition, reared at five blue light intensity treatments (20.00 ± 3.84, 40.78 ± 4.18, 53.67 ± 5.98, 70.00 ± 7.26 and 87.33 ± 5.77 μmol m?2 s?1), the WG and SGR increased with increasing intensity. Meanwhile, they were significantly higher in the 70.00 and 87.33 μmol m?2 s?1 treatments (P ≤ 0.05). In the higher intensity light treatments, the digestive enzymes were higher and antioxidant enzymes were lower. These results suggest that the optimal light spectrum for the culture of W. pigra during the early life stage was blue and the optimal light intensity was higher light intensity (70.00–87.33 μmol m?2 s?1).  相似文献   

2.
Sporeling and tissue propagation of agarophytic seaweed, Gracilaria fisheri, aimed to investigate the optimal shading colour for the preservation. This study was conducted under different shading colours indoor and outdoor experiments. The indoor experiment: tissues and sporelings of the seaweed were cultured in plastic chambers under fluorescent lights and were wrapped with white, green, blue and red colour PVC sheets of light intensity of 20 ± 1 μmol m?2 s?1. The outdoor tissues were cultured in the plastic tanks under different shadings of Saran sheets: white, green, blue and black covering the hoop‐houses with light intensity of 110 ± 10 μmol m?2 s?1. The results showed that different shading colours strongly influenced growth of G. fisheri sporelings and tissues but little effect on pigmentation. After 40 days, the highest growth rates of G. fisheri tissues and sporelings were found under red light with 1.44 and 1.89% day?1 respectively. There was no significant difference (P > 0.05) on pigment content of tissues indoor, whereas it was found that chlorophyll concentration of the sporelings under green light with 416.8 μg g?1 fresh weight was significantly higher (P < 0.05) than those in other treatments. After 8‐week culture, outdoor tissues showed the highest growth rate with 1.71% day?1 in the green hoop‐house. The study has found that G. fisheri cultivation was less influenced by epiphytes in the back hoop‐house with 15%. This study showed the feasibility of successful cultivation of G. fisheri sporelings and tissues.  相似文献   

3.
Light is a key environmental factor influencing the growth, development and survival of aquatic organisms. We examined the effects of different light qualities (red, orange, white, blue, green or no light) and developmental stage at initial lighting [fertilized egg (FE), trochophore larva (TL), or eye‐spot larva (EL)] on the growth, development, and survival of larvae of the Pacific abalone Haliotis discus hannai Ino. Larva‐hatching success was significantly higher under blue, green, or no light compared with red, orange or white light (P < 0.05). Larval abnormalities were significantly increased under red, orange or white light compared with all other light qualities (P < 0.05). The incidence of metamorphosis in larvae illuminated from the TL stage was significantly higher under blue compared with other light qualities. Irrespective of the stage at initial illumination, the incidence of metamorphosis was lower in larvae cultured under red, orange or no light compared with other light qualities, but the differences were not significant (P > 0.05). Juvenile survival was significantly higher under blue or green compared with other light qualities (P < 0.05), with no significant effect of stage at initial illumination (P > 0.05). Larval size at completion of the shell was unaffected by stage at initial illumination, but was greater under blue or green light, while size at metamorphosis was greatest following illumination with blue or green light since the TL or EL stage (P < 0.05). Metamorphosis time was shortest with blue or green light and in cultures illuminated from the FE or TL stage (P < 0.05). Larval development from the FE to formation of the fourth tubule on the cephalic tentacles was fastest in larvae exposed since the FE or TL stage to blue or green light, compared with other light qualities (P < 0.05). However, there was no difference in terms of the rate of development from the FE to the TL stage between cultures lit or unlit since the FE egg stage (P > 0.05). These results suggest that a blue or green light source applied from the TL stage can increase the hatching and yield of H. discus hannai Ino, with important implications for the development of the aquaculture industry.  相似文献   

4.
The aim of this study was to evaluate the effects of hatchery‐tank colours (white, yellow, red, blue, green and black) on the performance of larval culture of Macrobrachium amazonicum. The larvae were fed daily with newly hatched Artemia nauplii. The hatchery‐tank colours affected the light level inside the tanks, the consumption of Artemia nauplii (AN), larval development, survival, mass gain and productivity of postlarvae (PL). The overall consumption of Artemia nauplii per larva during the larval cycle was 30% and 45% higher in the green and red tanks respectively. The significant variation of AN consumption among tank colours (P = 0.0006) indicates that M. amazonicum larvae are visual predators. Survival was higher in the black, blue and green tanks, reaching more than 75%. However, the highest productivity was obtained in the black tanks (80.1 PL L?1). Lighter coloured tanks and excess luminosity (more than 2 μmol s?1 m2 at tank bottom) appear to be important stress factors for larvae, contributing to reduce survival and productivity. The results indicate that rearing M. amazonicum in black tanks will improve larvae condition, ensure greater productivity of postlarvae and lower Artemia consumption, increasing technological and economic viability.  相似文献   

5.
We assessed the effects of light intensity and spectrum on the growth, development and survival of Dicentrarchus labrax larvae from 30 to 96 days after hatching. Twelve lighting regimes were applied using 0.3, 1 and 2 W/m2 full spectrum white, blue, red and green light. By day 66 of exposure, growth performance was significantly better in larvae reared under green or red light compared with white or blue light (p < 0.05), while it was significantly better at 2.0 W/m2 compared with 1.0 or 0.3 W/m2 (p < 0.05). Larvae reared under white or blue light had significantly more deformities (p < 0.05) than did larvae reared under light of other spectra, while larvae reared under 0.3 W/m2 light intensity had a significantly higher proportion of jaw malformations than reared under 1.0 and 2.0 W/m2 (p ? 0.05). Dicentrarchus labrax larvae subjected to green light showed significantly lower survival compared with the other light spectra (p < 0.05). Moreover, light significantly affected brain aanat1a, aanatt1b, mellc, mt1, mt2, gh, tsh and crf mRNA expression. Therefore, the red and green light groups (or under 2.0 W/m2) could improve the growth performance and enhance secretion of melatonin, gh and tsh, and reduce the proportion of jaw malformations.  相似文献   

6.
To provide a specific lighting system to aquaculture, a completely randomized design with five light treatments with three replicates was used to investigate effects of light intensity on juvenile Epinephelus coioides reared in artificial sea water. The weight gain rate (WG, %), specific growth rate (SGR % day?1), protein efficiency ratio (PER) and survival rate (S, %) were significantly higher at the 320–1150‐lx treatments (P ≤ 0.05) compared with the other treatments, but the highest food conversion ratio (FCR) was at the 0‐lx treatment and the lowest at 600–1150 lx. Total protease, amylase and lipase activities in liver, stomach and intestine were significantly higher at 320–1150‐lx conditions and significantly lower at 0 lx (P ≤ 0.05) than in the other treatments. The highest contents of crude protein and crude lipid were observed at 600–1150 lx and 320–550 lx respectively. However, both moisture and ash were highest at 0 lx and lowest at 600–1150 lx. The results indicated that light intensity could significantly affect husbandry parameters, digestive enzymes and whole‐body composition of juvenile E. coioides, with optimal light intensity being at 600–1150 lx.  相似文献   

7.
In a small‐scale culture experiment, larval haddock, Melanogrammus aeglefinus L., were raised under various combinations of light quality [blue (470 nm), green (530 nm) or full‐spectrum white light] and light intensity [low (0.3–0.4 µmol  s?1  m?2) or high (1.7–1.9 µmol  s?1  m?2)], and in total darkness (both fed, and starved). Larval growth (0.9% day?1 in standard length; 2.4% day?1 in body area) was not significantly different between any combination of coloured light. At the time of total mortality in the starved treatment, survival was significantly reduced under low intensity, full‐spectrum white light (13%) vs. all other coloured light treatments (68%). Larvae raised under both continuous dark treatments (fed and starved) exhibited morphological changes associated with irreversible starvation (point‐of‐no‐return). Lack of a pronounced effect of light quality on larval haddock growth probably results from a combination of plasticity in early larval vision, and enhanced encounter rates between larvae and prey at the relatively high prey densities used in aquaculture.  相似文献   

8.
In order to explore the effects of high temperature (HT) and light on the physiological and biochemical aspects of macroalga Ulva prolifera, we cultured this species under two temperatures (20°C: low temperature, LT; 30°C: HT) and two light intensities (80 μmol m?2 s?1: low light, LL; 400 μmol m?2 s?1: high light, HL) for 5 days. It was found that (a) compared to 20°C, the chlorophyll a (Chl a) content was increased at 30°C under LL conditions, the relative growth rate (RGR) was significantly decreased at 30°C; (b) compared to LL treatment, HL significantly increased RGR but significantly decreased Chl a content; (c) LL‐grown U. prolifera at 30°C showed the highest photosynthetic oxygen evolution rate; however, there were no significant effects of temperature and light on the relative electron transport rate; (d) superoxide dismutase activity was significantly decreased by HL, but no significant effects of temperature were observed; and (e) compared to LL, HL significantly increased the soluble sugar content at 20°C, but significantly reduced at 30°C. These results showed that the inhibitory effects of HT can be offset by HL intensity.  相似文献   

9.
We analysed the effect on production and economic performance of juvenile Litopenaeus vannamei of isoproteic diets substituting fishmeal by 25%, 50%, 75% and 100% with mixtures of wheat, soya bean and cornmeals. In a laboratory trial, 10 juveniles m?2 (1.1 ± 0.1 g) were reared in 60‐L plastic containers using a recirculation system for 90 days. Three replicates were used to test each diet. A commercial diet serving as a reference and the diet with the highest content of essential amino acids (50% substitution, 6.46 ± 1.1 g) produced significantly higher shrimp final weight (7.12 ± 0.9 g, P < 0.05). There were not significant differences in specific growth rate and mean survival (85.9 ± 0.2%, P > 0.05). In a pond trial, 10 shrimp m?2 (1.08 ± 0.3 g) were cultivated in 1.5 m?3 cages for 35 days, testing the diets in triplicate. Final weight was significantly higher (P < 0.05) when 100% substitution was used (10.89 ± 0.24 g), while survival did not differ significantly among diets (P > 0.05). The optimal level of substitution was estimated at 86.0%. Apparently, nutrients contained in the diets combined well with natural feed available in the pond, up to a point where 7.3% of fishmeal inclusion is recommended. An economic analysis showed that 100% substitution produced the best results. We conclude that mixtures of wheat, corn and soya meals are potential alternatives to replace fishmeal effectively in diets for L. vannamei.  相似文献   

10.
Present experiment was conducted to determine the effect of different feeds with varying protein levels on the growth, survival and reproductive performance of zebrafish, Danio rerio. The control diet (T1) was wild‐collected zooplankton from local fish ponds, while test diets with 350 g kg?1 protein (T2), 400 g kg?1 protein (T3) and 450 g kg?1 protein (T4) were formulated and fed to fish for a period of 210 days. The significantly (P < 0.05) highest mean weight gain and specific growth rate were observed in T1, which were similar with T3 and T4. The significantly (P < 0.05) highest number of egg production per female and relative fecundity were found in T1, followed by T4 and T3 while T2 produced lowest number of eggs. No significant (P > 0.05) differences were observed in brood survival rate, fertilization and hatching rate among the dietary treatments. The highest (P < 0.05) fry survival rate was recorded in T1, followed by T3 and T4. Thus, it is suggested that control diet i.e. mixed zooplankton exhibited better growth, reproductive performance and fry survival rate. However, diet containing 400 g kg?1 crude protein also gave comparable results in terms of growth, survival and reproductive performance of zebrafish.  相似文献   

11.
Abalones were reared in a laboratory to determine the percentage response rate, response time, average crawling speed and the time taken to recover an upright posture under nine light‐emitting diode light quality treatments (red, orange, yellow, green, cyan, blue, purple, white and grey) and a dark environment. Animals were placed in the centre of an experimental device, and the tropism of each animal was continuously monitored by video. The highest percentage response rate (80% in dark adapted abalones, 60% in light adapted abalones) was observed in the dark environment, followed by red and orange light (27% and 30% in dark adapted abalones, respectively, 22% and 24% in light adapted abalones). Two induction materials (substrate and brown algae Laminaria japonica) were used to assess the effect of light quality on the tropism of abalones, with the highest percentage response rate (76% in the L. japonica treatment, 22% in the substrate treatment) also observed in the dark environment, followed by red and orange light (both 25% in the L. japonica treatment, and 26% and 32%, respectively, in the substrate treatment). The tropism order of the abalones under dark, red, orange and yellow light was as follows: dark > orange > red, yellow, but fewer abalones chose to stay in blue, green, cyan and purple light. The response time (about 700 s) in the dark environment was significantly longer than for the other light quality treatments. Compared with the average crawling speed in the other light quality treatments, abalones were relatively slower (about 3.8 mm s?1) in red and orange light, and the dark environment. The mean time required for the recovery of an upright posture in red light and the dark environment was longer than in the other light quality treatments, with the average recovery time reaching a maximum of 60 s in the dark environment. The results demonstrate the phototaxis and locomotion behaviour of abalones, as well as confirming the necessity of a dark, orange or red environment for their management and aquaculture.  相似文献   

12.
A 12‐week growth trial was conducted in a flow‐through system to determine dietary selenium (Se) requirement for on‐growing gibel carp (initial body weight: 76.2 ± 0.05 g, mean ± SEM). Selenomethionine was supplemented to the basal diet to formulate seven semi‐purified diets containing 0.26, 0.58, 0.72, 1.14, 1.34, 1.73 and 2.09 mg Se kg?1 diet. The results showed that plasma superoxide dismutase (SOD) activity significantly increased when fish were fed with 0.58 mg Se kg?1 diet (P < 0.05) and then decreased at 2.09 mg Se kg?1 diet (P < 0.05). Plasma T‐AOC activity was higher in fish fed with 0.72 mg Se kg?1 diet (P < 0.05) and plasma malondialdehyde (MDA) was higher in fish fed with 0.26 mg Se kg?1 diet (P < 0.05). When fish were fed 1.14 mg Se kg?1 diet, hepatic GSH‐Px, T‐AOC, GSH and CAT activities were significantly higher than those fed with 0.26 mg Se kg?1 diet (P < 0.05). Hepatic superoxide dismutase (SOD) activity was higher at 1.34 mg Se kg?1 diet (P < 0.05). Fish liver Se concentrations were significantly higher when fed with 0.72 mg Se kg?1 diet (P < 0.05) and then kept constant when Se ≥ 0.72 mg kg?1 (P > 0.05). Whole‐body and muscle Se concentrations were higher when fed with 1.34 mg Se kg?1 diet (P < 0.05) and kept a plateau when Se ≥ 1.34 mg kg?1 (P > 0.05). In conclusion, based on broken‐line regression of hepatic Se concentrations, hepatic SOD activity and hepatic T‐AOC activity, dietary Se requirements for on‐growing gibel carp was 0.73 mg kg?1, 1.12 mg kg?1 and 1.19 mg kg?1 diet respectively.  相似文献   

13.
The effect of the different dietary carbohydrate types and levels on growth performance, haematological indices and hepatic hexokinase (HK) and glucokinase (GK) genes expression involved in control of glucose metabolism, was studied in juvenile mirror carp (Cyprinus carpio). Two carbohydrates (glucose and starch) diets with two levels (250 and 500 g kg?1) were fed to triplicate groups of 35 fish for 60 days. The best weight gain rate and specific growth rate were observed in fish fed with 250 g kg?1 glucose diet and 500 g kg?1 starch diet (P < 0.05). Fish fed with 500 g kg?1 glucose showed low feed utilization, with the highest food conversion ratio and the lowest protein efficiency ratio (P < 0.05). Hepatosomatic index was significantly higher in fish fed with glucose diets and the 500 g kg?1 starch diet compared to 250 g kg?1 starch. CHOL, HDL‐C and LDL‐C were significantly highest in fish fed with 500 g kg?1 starch than all other diets (P < 0.05). Hepatic GK mRNA expression level and activity were positively related to glucose and starch levels (P < 0.05). Correlation analysis showed that hepatic glycogen concentration was increased by dietary carbohydrate content (P < 0.05). These results suggest that GK may play a major role in the postprandial glucose utilization in juvenile mirror carp.  相似文献   

14.
Two 8‐week growth trials were conducted in indoor recirculation system to evaluate the protein requirements for juvenile (3.70 ± 0.20 g) and pre‐adult (85.2 ± 0.70 g) gibel carp, Carassius auratus gibelio var. CAS III. Six isoenergetic diets were formulated for each trial using fish meal and casein as protein sources, and protein level was 250–450 g kg?1 in Trial 1 and 200–450 g kg?1 in Trial 2. With the increasing dietary protein, feeding rate (FR) and feed conversion ratio (FCR) significantly decreased (P < 0.05). Weight gain (WG) increased first and then reached a plateau in 330–450 g kg?1 in Trial 1 (P > 0.05), while decreased after the maximum value in 350 g kg?1 in Trial 2 (P < 0.05). Productive protein values (PPVs) were lower in 370–450 g kg?1 in Trial 1 and 400–450 g kg?1 in Trial 2 (P < 0.05). Increasing dietary protein level increased protein content and decreased lipid content in whole fish body and white muscle (P < 0.05). Apparent digestibility coefficient of dry matters (ADCd) decreased, while apparent digestibility coefficient of protein (ADCp) increased in 370–450 g kg?1 in Trial 1 and 250–450 g kg?1 in Trial 2 (P < 0.05). Trypsin activity significantly increased in 370–450 g kg?1 in Trial 1 (P < 0.05) and was not affected in Trial 2 (P > 0.05). Hepatic alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in both trials increased when dietary protein was above 400 g kg?1 (P < 0.05). Based on quadratic regression of WG, it was estimated that dietary protein requirement for maximum growth was 414 g kg?1 (digestible protein of 376 g kg?1) and 365 g kg?1 (digestible protein of 324 g kg?1) for juvenile (3.70 g) and pre‐adult gibel carp (85.2 g).  相似文献   

15.
Effects of light intensities on growth, survival, reproductive and life span traits of Artemia urmiana were investigated under laboratory conditions. Nauplii of A. urmiana were hatched and raised in 100 g L?1 at four illuminations including 0, 100, 2000 and 5000 lx with 14:10 (light:dark) photoperiod. Mating pairs of mature animals were randomly isolated and reared continuously under similar conditions. The mode and potential of reproduction as well as adult survival shown by each pair were determined throughout their life span. Results showed that percentages of nauplii survival were significantly (P ≤ 0.05) different at 5000 and 0 lx (76.50% compared with 26.25%) respectively. Total number of offspring was highly correlated with the light intensities showing increased numbers at higher light intensities compared with darkness or 100 lx. Reproduction mode was relatively affected by various light intensities. Significant (P ≤ 0.05) differences were found both in reproductive period and life span at different illuminations. Maximum and minimum offspring productions per reproductive day were found at 5000 and 100 lx respectively. The relative degree of oviparity increased as the illumination decreased (57.92% compared with 22.65% at 0 and 5000 lx respectively). The optimum light intensities appear to be between 2000 lx and 5000 lx in this study. These findings could probably be useful for mass culture of A. urmiana in indoor or recirculating systems as well as in outdoor systems for intensive cyst and biomass production.  相似文献   

16.
Based on Box–Behnken experimental design and response surface method, the joint effect of temperature (16–36°C), salinity (0–22 ppt) and rearing density (200–1000 fish.m?3) on the specific growth rate (SGR) and feed conversion rate (FCR) of Nile tilapia juveniles were studied under laboratory conditions. The entire experiment lasted for 1 month (30 days). Results showed that the linear and quadratic effects of temperature, salinity on both growth and feed utilization were highly statistically significant (P < 0.01). The linear and quadratic effect of rearing density on the growth was highly significant (P < 0.01); the linear effect of rearing density on feed utilization was significant (P < 0.05), but the quadratic effect nonsignificant (P > 0.05). Interactions between temperature and salinity, and between salinity and rearing density on the growth statistically differed from zero (P < 0.05). Interactions between temperature and salinity, between temperature and density on feed utilization was significant (P < 0.05). Model equations of the growth and feed utilization on temperature, salinity and density were established, with the coefficient of determination being 98.34% for growth and 98.11% for feed utilization, and could be applied to projection. The optimal temperature/salinity/density combination was obtained utilizing statistical optimization approach: 29°C/6 ppt/500 fish.m?3, at which the maximal specific growth and feed utilization reached 4.228%.d?1 and 0.520 respectively, with the desirability being 0.989.  相似文献   

17.
Light intensity has been shown to influence the foraging success of larval fish. However, the effect of light intensity on larval foraging is likely variable and influenced by both the density and characteristics of planktonic prey. In this study we examined the influence of light intensity of 0.1, 2.0, and 60 μmol·s?1·m?2 Photosynthetically Active Radiation (PAR) on foraging of yellow perch (Perca flavescens) larvae at two prey densities. We fed them with a mixture of zooplankton taxa common to lakes inhabited by yellow perch. In addition to light intensity and prey density, the effect of larval yellow perch size was examined by using fish ranging from 9 to 15 mm. The results of our study indicated that yellow perch larvae are well adapted to feed at a wide range of light intensities, as there was no difference in foraging success at investigated light intensities. Increasing prey density from 25 to 150 (zooplankton·l?1) significantly improved the foraging success of larval yellow perch. However, the influence of prey density on foraging success was dependent on fish length. Improved foraging success at increased prey densities occurred only for individuals with a total length >10 mm. Overall, prey selection by fish larvae was influenced by light intensity, prey density, and fish length. However, the factors that influenced selection for specific prey types differed. Our study, combined with evidence from other field and laboratory work, highlight the need for a better understanding of the influence of prey density on foraging throughout ontogeny.  相似文献   

18.
A growth experiment was conducted to determine the optimum dietary protein‐to‐energy (P/E) ratio of juvenile Chinese mitten crab Eriocheir sinensis. Six practical diets were formulated with P/E ratios ranging from 15.94 to 21.25 g protein MJ?1 gross energy (g MJ?1). Results showed that specific growth rates related with molting were significantly affected by dietary P/E ratio (P < 0.05). The specific growth rates both in body weight (SGRw) and carapace width (SGRcw) for the entire experimental period were not significantly affected by dietary P/E ratio (P > 0.05). Molting frequency, survival rate and crab body composition were also significantly affected by dietary P/E ratio (P < 0.05). Rate of precocity displayed negative trends with growth rate, and the trend with SGRcw was significant (P < 0.01). The activities of alkaline phosphatase, trypsinase and steapsin were significantly affected by dietary P/E ratio (P < 0.05). Molting frequency (P < 0.001), SGRw1‐2 (P < 0.05) and SGRw0‐2 (P < 0.05) were positively and significantly related to alkaline phosphatase activity. We recommend 18.13–19.20 g MJ?1 as the optimum dietary P/E ratio for juvenile E. sinensis, based on growth performance, rate of precocity and digestive enzyme activities.  相似文献   

19.
Female northern whitefish were treated with salmon [D‐Arg6Pro9Net]‐sGnRHa emulsified in Freund′s incomplete adjuvant as a sustained release treatment (sGnRHa‐FIA) or with [D‐Arg6Pro9Net]‐sGnRHa dissolved in physiological saline as acute release treatment (sGnRHa‐PS). Females in four experimental groups (A, B, C, D) and one control group (E) were injected intraperitoneally as follows: A and B – sGnRHa‐FIA at doses of 50 and 25 μg kg?1, respectively; C – double injection (DI) of sGnRHa‐PS at 25 μg kg?1 administered 3 days apart; D – single injection (SI) of sGnRHa‐PS at 25 μg kg?1; and E – control group receiving a 1:1 mixture of FIA and physiological saline. All treatments induced and synchronized ovulation. Mean time to ovulation was significantly reduced (P < 0.05) in GnRHa‐treated groups compared with control. Hormone treatments did not affect the relative fecundity. Slight differences were found in ovarian fluid pH between group A and D (P < 0.05). Except for group C, egg size was significantly reduced (P < 0.01) in hormonally synchronized groups compared with the control. Survival to the eyed stage of eggs from females in groups A, B and C was significantly lower (P < 0.01) than in groups D and E. Per cent hatched alevins was lower (P < 0.01) in groups A, B and C than in groups D and E. We conclude that synchronization of ovulation in northern whitefish can be induced by a single acute injection of [D‐Arg6Pro9NEt]‐sGnRHa at 25 μg kg?1 BW if given near the natural spawning time determined by water temperature below 2°C.  相似文献   

20.
An 8‐week feeding trial was conducted to determine the optimum dietary methionine (Met) requirement of juvenile Pseudobagrus ussuriensis with an initial average weight of 0.60 g reared in indoor flow‐through and aerated aquaria. Six isonitrogenous (430 g kg?1 protein) and isolipidic (50 g kg?1 lipid) test diets were formulated to contain graded levels of crystalline L‐methionine (4.9, 9.0, 11.8, 14.2, 18.1 and 20.8 g kg?1 dry diets, respectively) at a constant dietary cystine level of 2.5 g kg?1 dry diets. Equal amino acid nitrogen was maintained by replacing methionine with non‐essential amino acid mixture. Fish were randomly allotted to 18 aquaria (1.0 × 0.5 × 0.8 m) with 50 fish to each glass aquarium. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. No significant difference was observed in survival of fish (84.67–91.33%). Specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), protein productive value (PPV) and protein efficiency ratio (PER) were significantly affected by different dietary methionine levels (P < 0.05). WG, SGR PPV and PER increased, while FCR decreased with increasing dietary methionine level from 4.9 to 11.8 g kg?1 (P < 0.05). However, with further increase from 11.8 to 20.8 g kg?1, WG, SGR PPV and PER significantly decreased, FCR increased (P < 0.05). The whole body and muscle composition were affected by different dietary methionine levels (P < 0.05). Condition factor (CF) increased with increasing dietary methionine levels up to 11.8 g kg?1 (P < 0.05) and after 11.8 g kg?1 methionine diet, but not significant, declines were observed (P > 0.05). Hepatosomatic index (HSI) of the 4.9, 9.0, 11.8 and 14.2 g kg?1 Met diets was significantly higher than that of fish fed diets 18.1 and 20.8 g kg?1 Met diets (P < 0.05). Viscerosomatic index (VSI) of the 4.9, 9.0 and 11.8 g kg?1 Met diets was significantly higher than that of fish fed diets 14.2, 18.1 and 20.8 g kg?1 Met diets (P < 0.05). Quadratic regression analysis of WG and PER against dietary methionine levels indicated that the optimal dietary methionine requirement for maximum growth and feed utilization of juvenile Pseudobagrus ussuriensis was 14.3 and 14.1 g kg?1 dry diet (35.3 and 34.8 g kg?1 dietary protein), respectively, in the presence of 2.5 g kg?1 dry diets cystine.  相似文献   

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