Effects of Nitrite Exposure on Growth and Survival of Sea Bass,Lates calcarifer,Fingerlings in Various Salinities

Sea bass, Lates calcarifer, fingerlings were acclimated to 0. 15, and 32 ppt, and the toxic effects of nitrite exposure were assessed. The 96-hour median lethal concentrations (96-hour LC₅₀ for nitrite were estimated to be 14.5 mg/L at 0 ppt, 105 mg/L at 15 ppt and 93 mg/L at 32 ppt salinity. Chronic exposure to a nitrite concentration equivalent to 10% of the respective 96 hour LC₅₀ resulted in marked growth reduction: growth being reduced in the order of 0 ppt > 32 ppt > 15 ppt. In nitrite-free water, growth rate for fish raised at a salinity of 15 ppt was higher compared to fish raised at salinities of 0 ppt and 32 ppt, a phenomenon which probably reflected the advantage of a reduction in osmoregulatory work in an iso-osmotic environment.     

Production of Spotless Allotriploids from Female Non-Spotted Rainbow Trout (Houraimasu), Oncorhynchus mykiss,and Male Amago Salmon,O. rhodurus

ABSTRACT

A new phenotype, spotless allotriploids, was introduced into the aquaculture industry. Spotless allotriploids were produced from female non-spotted rainbow trout, Oncorhynchus mykiss, and male ama-go salmon, landlocked type of O. rhodurus. These allotriploids combine the favorable characteristics of the good flavor of amago salmon, faster growth (compared to that of amago salmon), and absence of spots, preferred by the market. The relationship between the non-spot character (gene) and the external appearance of the allotriploids was traced by analyzing the erythrocyte major axis, the allozymes, and the progeny test in each maternal genotype. Results indicate that spotless allotriploids can be produced by using female dominant homozygotic (hh) non-spotted rainbow trout. When females are heterozygotic (hn) non-spotted rainbow trout, the offspring produced are both spotted and spotless allotriploids in approximately equal proportions.     

Optimal dietary protein requirement for juvenile ivory shell, Babylonia areolate

A growth experiment was conducted to determine the optimal dietary protein requirement for juvenile ivory shell reared in indoor aerated aquaria. Six isoenergetic experimental diets using fish meal, casein and gelatin as protein sources were formulated to contain graded levels of protein (27, 33, 38, 43, 49 and 54% of dry diet, respectively). Triplicate groups of 40 shells (average weight 93.50 ± 1.70 mg) were stocked in 120-l tanks and fed to apparent satiation twice daily for 8 weeks. The results showed that the growth performance and feed utilization were significantly affected by dietary protein level (P < 0.05). Maximum weight gain, mean protein gain, specific growth rate and soft body to shell ratio occurred at 43% dietary protein level (P < 0.05). There were significant differences in protein, lipid, moisture and ash content in soft body; except that ash content in shell was not significantly affected by dietary protein level. Pepsin activity in soft body tissue significantly increased with dietary protein level up to 43%, and trypsin-like enzyme activity increased with dietary protein level up to 49%. However, lipase activity in soft body decreased with increasing dietary protein level. However, no significant differences (P < 0.05) in survival, calcium, phosphorus concentration in the shell and soft body were found among dietary treatments. Quadratic regression analysis of weight gain against dietary protein level indicated that the optimal dietary protein requirement for maximum growth and feed utilization of juvenile ivory shell is 45% of dry diet.     

Protein requirement of silver barb, Puntius gonionotus fingerlings

Five iso‐energetic (15.05 MJ kg^?1) semi‐purified diets with graded levels of crude protein, i.e. 200 (D‐1), 250 (D‐2), 300 (D‐3), 350 (D‐4) and 400 (D‐5) g kg^?1 diet were fed to Puntius gonionotus fingerlings (average weight 0.88 ± 0.03 g) in triplicate groups (15 healthy fish per replicate) for a period of 90 days to determine the optimum protein requirement of the fish. Fifteen flow‐through cement tanks of 100‐L capacity with a flow rate of 0.5 L min^?1 were used for rearing the fish. Specific growth rate (SGR), food conversion (food gain) ratio (FCR), nutrient digestibility and retention, digestive enzyme activity, RNA : DNA ratio and tissue composition were used as response parameters with respect to dietary protein levels and feed intake. The mean weight gains of fish after 90 days were 10.84 ± 0.27, 11.07 ± 0.12, 14.09 ± 0.20, 11.27 ± 0.12 and 10.91 ± 0.25 g for D‐1, D‐2, D‐3, D‐4 and D‐5, respectively. Maximum SGR (3.13 ± 0.02% per day), RNA : DNA ratio (10.09 ± 0.09), tissue protein content (160 ± 0.1 g kg^?1 wet weight), protease activity (25.27 ± 0.47 μg of leucine liberated mg tissue per protein h^?1 at 37 °C) and minimum FCR (1.60 ± 0.02) was found in D‐3 group fed with 300 g kg^?1 protein level. All these parameters were negatively affected with the further increase in protein level in the diet. Digestibility of protein, lipid and energy was not affected because of variation in dietary protein levels and nitrogen intake of fish. Maximum energy retention (27.68 ± 0.12%) was recorded at 300 g kg^?1 dietary crude protein fed group. However, using broken line regression analysis, the maximum growth was found to be at 317.7 g kg^?1 dietary protein. Hence, it may be concluded that the protein requirement of P. gonionotus fingerling is 317.7 g kg^?1 diet with a resultant P/E ratio of 21.1 g protein MJ^?1.     

Ammonia and pH effects on some metabolic parameters and gill histology of silver catfish, Rhamdia quelen (Heptapteridae)

The aim of the present study was to assess the effect of ammonia exposure at different pH on survivorship and metabolic parameters in the liver, muscle and gill histology of silver catfish (Rhamdia quelen). The 96 h-LC50 of un-ionized ammonia (mg L^− 1) at pH 6.0, 7.5 and 8.2 were: 0.44 (C.I. 0.38–0.49), 1.45 (C.I. 1.25–1.65) and 2.09 (C.I. 1.85–2.36), respectively. Survival of juveniles exposed to different ammonia levels was altered by pH, and fish exposed to all ammonia levels and different pH showed muscle glucose, muscle and liver glycogen reduction. Liver glucose and muscle and liver lactate levels increased in all fish exposed to ammonia as compared to the control. Exposure to waterborne ammonia increased total ammonia levels in both tissues and also induced gill epithelium damages such as lamellar fusion and edema as compared with controls at different pH. Silver catfish exposed to pH 6.0 and different NH₃ levels presented significantly higher hepatic glucose and protein levels when compared to those maintained at low NH₃ levels. Juveniles exposed to NH₃ levels at pH 7.5 and 8.2 showed lower hepatic protein levels compared to those maintained at low NH₃ levels. These parameters are indicative of pH dependence on ammonia toxicity in silver catfish. The metabolic parameters and gill histology may be used as early indicators of ammonia toxicity in silver catfish.     

Dietary energy requirement of piracanjuba fingerlings, Brycon orbignyanus, and relative utilization of dietary carbohydrate and lipid

Ten isonitrogenous casein–gelatin‐based diets were formulated to contain five estimated metabolizable energy concentrations (10.92, 12.29, 13.63, 14.82 and 16.16 kJ g^?1) at two carbohydrate‐to‐lipid ratios (CHO : L, 5.3 and 12.8, g : g) in a 5 × 2 factorial arrangement. Each diet was assigned to triplicate groups of 11 piracanjuba fingerlings (5.25 ± 0.14 g) and fed to apparent satiation twice a day for 90 days. Higher daily weight gain was obtained by fish fed the 13.63 kJ g^?1 diets for both CHO : L ratios. There was a significant reduction of feed consumption when dietary energy concentration increased above 13.63 kJ g^?1. Feed conversion ratio and apparent net energy retention improved as dietary energy increased. Apparent net protein retention tended to be lower in the highest and lowest dietary energy concentrations. The results suggest that dietary lipid energy was more efficiently utilized by piracanjuba fingerlings than carbohydrate energy. Body composition and hepatosomatic index (HSI) were not influenced by dietary CHO : L ratio. However, an increase in dietary energy concentration beyond 13.63 kJ g^?1 resulted in a significant increment in lipid deposition, while body moisture and HSI decreased. Our findings indicate that at 300 g kg^?1 dietary crude protein, a CHO : L ratio of 5.3 is recommended for piracanjuba, and the required energy is either 13.63 kJ g^?1 if raised for aquaculture or 14.82 kJ g^?1 if destined to stock enhancement.     

饲料蛋白能量比对红鳍东方鲀幼鱼的生长性能、饲料利用和体组成的影响

为探求红鳍东方鲀(Takifugu rubripes)幼鱼饲料的最适蛋白质能量比,以鱼粉和豆粕作为主要蛋白源,鱼油和豆油作为主要脂肪源,配制粗蛋白含量分别为36％、42％和48％,粗脂肪含量分别为8％、12％和16％,蛋能比为17.06～24.20 mg/kJ的9组饲料.投喂初始体重为14.95 g的红鳍东方鲀幼鱼56...     

Quantifying the dietary niacin requirement of the Indian catfish, Heteropneustes fossilis (Bloch), fingerlings

A growth study was conducted to determine the dietary niacin requirement of the Indian catfish, Heteropneustes fossilis (Bloch), fingerlings (Mean weight 9.41 ± 0.18 g). Semi‐purified diets with five levels (0, 5, 10, 20 and 40 mg kg^?1 diet) of supplemental niacin were fed to H. fossilis for 15 weeks. Each diet was fed to three replicate groups of fish. Results indicated that the highest (P < 0.05) weight gain was for the fish fed the diet supplemented with 20 mg niacin kg^?1, followed by fish fed the diets with 40, 10 and 5 mg niacin kg^?1, and the lowest in fish fed the unsupplemented control diet. Patterns of specific growth rate (SGR) and protein efficiency ratio (PER) were similar to those of the weight gain. Survival of fish fed the control diet and niacin‐supplemented diet was 58% and 91–100% respectively. Niacin deficiency signs such as anaemia, anorexia, lethargy and skin haemorrhage were observed in fish fed the control diet. The haematocrit values (Ht) were higher (P < 0.05) in fish fed the diets supplemented with niacin than in fish fed the control diet. The hepatosomatic indexes (HSI) of fish fed with or without niacin‐supplemented diets were not significantly (P > 0.05) different from each other. Both body protein and lipid content were higher (P < 0.05) in fish fed the diet supplemented with 20 and 40 mg niacin kg^?1, respectively, than those fish fed other diets. The niacin content in liver significantly (P < 0.05) reflected the supplementation level in the diet and ranged from 29.11 to 40.31 mg g^?1 tissue. The associated liver niacin content for growth was about 47 μg g^?1 tissue. Quadratic regression analysis showed that the dietary niacin requirement for maximal growth of H. fossilis under these experimental conditions was about 25 mg kg^?1 diet.     

Estimation of dietary copper requirement of juvenile soft-shelled turtles, Pelodiscus sinensis

Juvenile soft-shelled turtles (Pelodiscus sinensis) were fed diets containing 10 levels (0.8, 3.0, 5.0, 7.8, 9.0, 10.9, 20.4, 41.8, 78.6, 158 mg/kg diet) of copper (Cu) for 16 weeks. Turtles fed 5.0 mg Cu/kg achieved the best growth performance and the highest hematological values among all dietary groups. Growth was reduced significantly when dietary copper exceeded 20 mg/kg. Using the broken-line model with growth and hematological parameters as the dependent variables, the dietary Cu requirement of soft-shelled turtle was estimated to be 4.4–4.8 mg Cu/kg diet. Copper, iron, zinc and selenium concentrations in turtle liver were found to be influenced by dietary Cu level. Thiobarbituric acid-reactive substances in liver tissue of turtles fed diets containing 78.6–158 mg Cu/kg were higher (P < 0.05) than those fed diets containing less copper. Furthermore, diets containing more than 20 mg Cu/kg significantly impaired growth and hematology of soft-shelled turtles, indicating the dietary Cu tolerance above the requirement may be as low as 4 fold (20 vs. 5 mg/kg). Based on the results of this study, a dietary Cu level of 4–5 mg/kg is recommended for soft-shelled turtles.     

Effect of dietary protein:energy ratio on intake, growth and metabolism of juvenile green abalone Haliotis fulgens

Juvenile green abalone Haliotis rufescens were grown under laboratory conditions at 21±1 °C and fed formulated diets consisting of different protein:energy ratios (mg protein/kcal), 62, 74, 85, 100, 108, for 60 days. The level of crude protein ranged from approximately 26% to 44% while the energy content remained constant at about 4.1 kcal g⁻¹. Growth ranged from 3.63 to 12.33 mg day⁻¹. The growth of abalone fed the 100 and 108 diets was significantly greater than that of each of the other diets. Protein efficiency ratio increased as the dietary protein content increased except for the T108 diet (44% crude protein). Abalone apparently consume food to satisfy an energy requirement. Caloric expenditure due to metabolism was estimated for abalone fed diets with protein ratios of 62, 85, 100. Energy loss due to respiration did not vary appreciably among abalone fed the different diets. The proportional distribution of dietary energy into fecal, digestible, growth, and metabolic energy was estimated for abalone fed these diets. Apparent dry matter digestibility was among the lowest for abalone fed the 100 P:E diet, but growth of abalone fed this diet was significantly higher than that of each of the other treatments except the 108 diet. Unexplained energy loss to achieve balance ranged from 7% to 28.5%, some of which is probably due to differential mucus and ammonia production. Results suggest a potential for the reduction of both dietary protein and lipid without causing any adverse effects on the growth response.     

Effects of dietary starch and energy levels on maximum feed intake, growth and metabolism of Nile tilapia, Oreochromis niloticus

The aim of this study was to gain insight into how Nile tilapia (Oreochromis niloticus) regulate feed and energy intake in response to diets low and high in starch and cellulose. It was hypothesized that high-starch diets would reduce feed intake due to the effect of high blood glucose level, and that stomach volume may limit feed intake of fish fed diets low in energy. Four experimental diets, low starch–no cellulose inclusion, high starch–no cellulose inclusion, low starch–with cellulose inclusion, and high starch–with cellulose inclusion, were formulated. The high-starch diets and diets with cellulose inclusion were 17.5% more energy-diluted than the low-starch diets and diets without cellulose inclusion, respectively. Male tilapia were fed to apparent satiation for six weeks. Feed and digestible energy intake of fish fed diets with cellulose inclusion increased and decreased by 8.3% and 5.5%, respectively, compared to fish fed diets without cellulose inclusion. This suggests the role of stomach volume in restricting feed consumption. Fish fed high-starch diets achieved only 0.5% more feed intake and 13.9% less digestible energy intake than fish fed low-starch diets. The lower increase in feed intake and higher decrease in digestible energy intake of fish fed high-starch diets than of fish fed diets with cellulose inclusion suggests that high blood glucose suppresses feed intake in Nile tilapia. An alternative explanation for the differences in feed and digestible energy intake of fish fed different diets was based on the fact that heat production was not influenced by starch nor cellulose-inclusion levels. Thus, under satiation feeding, oxygen uptake capacity may determine feed and digestible energy intake in fish rather than blood glucose or stomach volume.     

花(鱼骨)对饲料中磷的营养需求

以酪蛋白-明胶为蛋白源,磷酸二氢钾为磷源配制6个磷水平(0.32%、0.58%、0.83%、1.09%、1.35%和1.59%)的等氮等能的精制饲料,饱食投喂花(鱼骨)[初始体质量为(7.97±0.07)g]8周,探讨饲料磷水平对花(鱼骨)生长、饲料利用、骨组织无机物含量、血清磷的影响,确定花(鱼骨)对饲料磷的需要量.试验结果表明:(1)当饲料磷水平从0.32%上升到0.83%时,增重、饲料效率随之而提高,但超过此水平后各组差异不显著(P0.05),折线模型分析饲料磷水平与相对增重率之间的关系,花(鱼骨)获得最大增重时饲料磷的最低需求为0.91%.(2)脊椎骨、鳃盖骨和鳞片的矿物组成受到饲料磷水平的显著影响(P<0.05),二次曲线回归方程拟合饲料磷水平与脊椎骨灰分率的关系,花(鱼骨)脊椎骨达到最大矿化时饲料磷为1.17%.(3)血清磷水平随饲料磷的增加而升高,饲料磷对血清钙没有显著影响.综合分析体增重、磷存留率、骨灰分含量、血清磷浓度等多项生物学指标,花(鱼骨)对饲料磷的需要量为0.91%～1.17%.     

Effects of dietary protein to energy ratios on growth and body composition of juvenile Japanese seabass, Lateolabrax japonicus

A growth experiment was conducted to determine the optimal dietary protein to energy (P/E) ratio for juvenile Japanese seabass (initial average weight 6.26±0.10 g). Nine practical diets were formulated to contain three protein levels (36%, 41% and 46%), each with three lipid levels (8%, 12% and 16%), in order to produce a range of P/E ratios (from 19.8 to 28.6 mg protein kJ⁻¹). Each diet was randomly assigned to triplicate groups of 60 fish in sea floating cages (1.5×1.5×2.0 m). Fish were fed twice daily (06:30 and 16:30) to apparent satiation for 8 weeks. The water temperature fluctuated from 26.5 to 32.5 °C, the salinity from 32‰ to 36‰ and dissolved oxygen content was approximately 7 mg l⁻¹ during the experimental period. The results showed that the growth was significantly affected by dietary P/E ratio (P<0.05). Fish fed the diets with 46% protein (12% and 16% lipid, P/E ratio of 26.7 and 25.7 mg protein kJ⁻¹) had the highest specific growth rates (SGR) (4.26 and 4.24% day⁻¹). However, fish fed the diet with 41% protein and 12% lipid showed comparable growth (4.20% day⁻¹), and had higher protein efficiency ratio (PER), protein productive value (PPV) and energy retention than other groups (P<0.05). No significant differences in survival were found among dietary treatments. Carcass lipid content positively correlated with dietary lipid level irrespective of protein level and inversely correlated with carcass moisture content. Carcass protein and ash contents increased with increasing dietary lipid at each protein level. These results suggest that the diet containing 41% protein and 12% lipid with P/E of 25.9 mg protein kJ⁻¹ is optimal for Japanese seabass.     

仿刺参幼参对亮氨酸最适需求量的研究

为探究仿刺参幼参对亮氨酸的最适需求量,在基础饲料中分别添加0.00%、0.80%、1.60%、2.40%、3.20%和4.00%的包膜亮氨酸,配成亮氨酸含量分别为1.29%(D1,对照组)、1.63%(D2)、1.98%(D3)、2.22%(D4)、2.58%(D5)和2.97%(D6)的6组实验饲料,饲喂初始体质量为(16.40±0.14) g的仿刺参幼参60 d。结果显示,(1)随饲料亮氨酸含量从1.29%提高到1.98%,仿刺参幼参的增重率和特定生长率显著升高,在D3组增重率达到最大值100.84%,随亮氨酸含量进一步提高,增重率和特定生长率显著降低,但D3、D4和D5组增重率和特定生长率还是显著高于对照组;(2)随饲料亮氨酸含量从1.29%提高到1.98%,仿刺参体壁的粗脂肪含量显著升高,在D3组达到最大值5.50%,且显著高于其他组,随亮氨酸含量进一步提高,仿刺参体壁粗脂肪含量显著降低,各组间水分、粗蛋白质和粗灰分含量均无显著性差异;随饲料亮氨酸含量的升高,仿刺参体壁蛋氨酸含量显著提高;(3)随饲料亮氨酸含量从1.29%提高到1.98%,仿刺参肠道脂肪酶和蛋白酶活性显著提高,...     

仿刺参幼参对缬氨酸最适需求量的研究

为探讨仿刺参幼参对缬氨酸的最适需求量,在基础饲料中添加0、0.80%、1.60%、2.40%、3.20%和4.00%的包膜缬氨酸,配制缬氨酸含量分别为0.61%(D1,对照组)、1.14%(D2)、1.46%(D3)、1.73%(D4)、2.17%(D5)和2.64%(D6)的实验饲料,饲喂体质量为(9.20±0.12)g的仿刺参幼参8周。结果显示,①添加缬氨酸对仿刺参幼参的成活率(SR)无显著影响;增重率(WGR)和特定生长率(SGR)均呈先上升后下降趋势,D4组显著高于其他各组;②添加缬氨酸对肠壁比和肠长比均无显著影响;③体壁粗蛋白和粗脂肪含量均呈先上升后下降趋势,D4组粗蛋白含量显著高于其他各组,添加缬氨酸显著提高了体壁组氨酸、缬氨酸、必需氨基酸和总氨基酸含量,降低了亮氨酸、异亮氨酸和酪氨酸含量;④肠道中总超氧化物歧化酶(T-SOD)和总抗氧化能力(T-AOC)随缬氨酸添加量的增加呈上升趋势,D1组显著低于其他各组;丙二醛(MDA)呈先下降后上升趋势,D4组显著低于对照组;⑤肠道蛋白酶和脂肪酶活力均呈先上升后下降趋势,D3组蛋白酶显著高于其他各组,淀粉酶活力不受缬氨酸含量的影响。综上,饲料中添加适宜的缬氨酸显著提高了仿刺参的生长性能和非特异性免疫力,改变了体壁的常规成分和氨基酸含量。以增重率为评价指标,经折线回归分析得出,体质量为9.20 g的仿刺参其配合饲料中缬氨酸最适含量为1.79%(9.18%饲料蛋白质)。     

Evaluation of dietary protein requirement for the growth performance of minor carp,Cirrhinus reba (Hamilton, 1822) fingerlings

An experiment was designed to evaluate the requirement of dietary protein for Reba carp, Cirrhinus reba fingerlings using semi‐purified diet. Five isocaloric diets were prepared containing 20%, 25%, 30%, 35% and 40% level of protein using casein, gelatin as a major protein source. The experiment was conducted for 105 days in triplicates to evaluate the growth, survival, feed utilization, carcass composition of C. reba. Mean weight gain was highest (p < .05) in T3. Specific growth rate was highest in T3 and lowest in T1. Similarly, significantly (p < .05) highest net fish yield were recorded in T3. No significant difference was recorded in survivability. Feed conversion ratio, protein efficiency ratio, feed conversion efficiency and protein conversion efficiency were significantly (p < .05) higher for T3 compared with other treatments. Highest carcass protein and lipid values were recorded in T3. So, conclusion can be drawn that 30% crude protein is optimum for overall performance. Furthermore, broken‐line analysis for specific growth rate, final biomass and net fish yield indicated that dietary protein level of 28.148 to 28.253% is optimum for the best growth performance of fingerling C. reba.     

Growth, feed efficiency, digestibility and nutrient distribution in Atlantic cod (Gadus morhua) fed two different fish meal qualities at three dietary levels of vegetable protein sources

Atlantic cod were fed six diets where the ratio of protein from fish meal to vegetable protein were varied from 91%, 67% to 46%, respectively. The experimental groups were performed in triplicate in a 20 week growth trial, increasing fish weight from about 167 g to 690 g. The vegetable protein sources constituted full-fat soybean meal and corn gluten meal at a fixed ratio of 1:2, and replaced either a high quality fish meal (DC_Mink 92.3%) or a lower quality fish meal (DC_Mink 85.6%) in the diet. All diets were extruded and balanced to be equal in gross energy, crude protein, lipid, carbohydrate, lysine and phosphorus. No difference in growth (SGR 1%) was observed comparing the two fish meal qualities. However, feed intake was significantly higher (9%) and feed efficiency lower (10%) for lower quality fish meal compared to high quality fish meal. Protein and amino acid digestibility was significantly reduced in the lower quality fish meal, while unaffected by vegetable protein inclusion for both fish meal qualities. Protein utilization as measured by protein efficiency ratio and net protein value was not affected by fish meal inclusion, except in the diet using lower quality fish meal and high vegetable protein inclusion. Lipid and energy digestibility was significantly reduced by vegetable protein inclusion for both fish meals. The lower fish meal quality increased lipid deposition in the liver and affected slaughter quality of cod by increasing HSI and dressing out percentage at low and intermediate substitution levels. Muscle composition showed small dietary changes except for arginine, while liver fatty acid composition clearly reflected fatty acid profile of full-fat soya in the diets. Corn gluten meal and full-fat soybean meal (2:1) can replace approximately 50% of dietary protein without affecting feed intake, growth, protein digestibility or slaughter quality of cod when exchanging high quality fish meal. For the lower quality fish meal diets some lower inclusion of vegetable protein sources seem to be acceptable.     

仿刺参幼参对维生素A最适需求量

为了探讨仿刺参幼参对配合饲料中维生素A(V_A)的适宜需求量，实验在基础饲料中分别添加维生素A乙酸酯，配制V_A含量分别为3 250 (D1)、5 187 (D2)、7 054 (D3)、8 970(D4)、12 975 (D5)和16 400 (D6) IU/kg的6组等氮等能的实验饲料，饲喂初始体重为(15.48±0.01) g仿刺参幼参8周。结果显示，(1) V_A对仿刺参存活率(SR)无显著影响，显著提高了增重率(WG)和特定生长率(SGR);(2) V_A显著提高了体壁粗脂肪和V_A含量，降低了羟脯氨酸含量；(3)肠道脂肪酶(LPS)活性呈上升趋势，D1组显著低于其他组，淀粉酶(AMY)活性呈先下降后上升的趋势；(4)肠道谷草转氨酶(AST)、总抗氧化能力(T-SOD)及过氧化氢酶(CAT)活性均呈先升后降趋势，AST及CAT活性均在D4组出现最高值，D2～D5组T-SOD活性显著高于D1组，碱性磷酸酶(AKP)活性呈上升趋势，D1组显著低于其他组，丙二醛(MDA)含量逐渐降低...     

Total and available tryptophan requirement of Nile tilapia,Oreochromis niloticus,fingerlings

The dietary total and available requirement of tryptophan of Nile tilapia fingerlings was determined using linear regression analysis. Six hundred fish (3.4 ± 0.0 g) were fed diets containing 296.4 g/kg of crude protein and 14.1 MJ/kg of digestible energy. Five extruded diets containing 2.5, 3.0, 3.4, 3.8 and 4.2 g/kg of total tryptophan were evaluated. Fish were fed four times a day during 45 days. Final body weight, weight gain, feed intake, feed conversion ratio and net protein utilization of fish fed Trp 3.4 and Trp 3.8 diets were improved compared to fish fed Trp 2.5 and Trp 4.2 diets. No significant differences in survival rate, whole‐body moisture and ash were observed. Whole‐body amino acid profile of fish fed different diets did not differ statistically (p > .05). Fish fed Trp 3.0 and Trp 3.4 diets showed higher tryptophan retention compared to fish fed Trp 2.5 and Trp 4.2 diets. Excepting blood glucose, no effects of dietary tryptophan on haematological parameters were observed. The dietary total tryptophan requirement of Nile tilapia fingerlings based on weight gain was estimated to be 3.4 g/kg (11.0 g/kg of dietary crude protein) or 3.0 g/kg of available tryptophan (11.0 g/kg of dietary digestible protein).     

Effects of dietary protein and energy levels on spawning performance of Nile tilapia (Oreochromis niloticus) broodstock in a recycling system

The effects of dietary protein and energy level on spawning performance of Nile tilapia broodstock and hatchability of their eggs were studied. Nine diets containing three protein (30, 35 and 40%) and three energy (14.6, 16.7 and 18.8 MJ GE/kg) levels were prepared. The diets were fed to duplicate groups of broodfish (average weight of 60.5 ± 4.6 g for males and 39.4 ± 3.1 g for females) at 2–3% of their body weight, twice a day, for 150 days. At low protein level (30%), time to first spawning was significantly longer than at 35 and 40% protein levels, and increased with increasing dietary energy (decreasing protein-to-energy (P/E) ratio). At 35 and 40% protein levels, time to first spawning was not affected by dietary energy. Inter-spawning intervals (ISI) showed irregular patterns in relation to dietary protein and energy, however, at 40% protein the females tended to spawn at shorter intervals, regardless of dietary energy. Spawning performances, including total number of spawnings per tank, number of spawnings per female, absolute fecundity and average number of eggs per spawn, were all significantly lower (P < 0.05) at 30% CP than at higher protein levels. At all protein levels, increasing dietary energy from 14.6 to 18.8 MJ GE/kg (and decreasing P:E ratio) resulted in a significant decrease in fish fecundity. Egg size was not significantly affected by dietary protein and energy. At all energy levels, egg hatchability increased with increasing dietary protein levels (P < 0.05). Eggs produced from broodstock fed 30 and 35% CP, exhibited significantly lower hatchability (P < 0.05) and needed less time for hatching and yolk-sac absorption, and resulted in lower larval length than those fed a 40% protein diet. However, increasing energy level at each dietary protein level did not significantly affect these parameters. These results revealed that the best spawning performance of Nile tilapia broodstock reared in a recycling system was achieved at 40% dietary protein and 16.7 MJ GE/kg, with a P/E ratio of 23.6 g/MJ.