Mouth size and predicted food size preferences of larvae of three cyprinid fish species

Mouth size was examined in larvae and juveniles of three cyprinid fish species: grass carp (Ctenopharyngodon idella Val.), silver carp (Hypophthalmichthys molitrix Rich.) and bighead carp (Aristichthys nobilis Rich.). A linear relationship was found between mouth size and the total length of fish, from the initial exogenous feeding stage up to 20–30 mm. Based on the mouth size, the size of the prey which could be consumed was calculated assuming 45° of mouth opening for optimum prey width and 90° for maximum prey width. Food particle size considered to be suitable for commencement of feeding amounted to 50–90 μm for silver carp larvae, 90–150 μm for grass carp larvae and 150–270 μm for bighead carp larvae. These criteria can be applied to moving rotifiers and nauplii as well as to the motionless particles of compound, dry diets.     

Influence of initial weight during the change from live to compound feed on the survival and growth of four cyprinids

In a series of trials, larvae of common carp (Cyprinus carpio L.), silver carp (Hypophthalmichthys molitrix Rich.), grass carp (Ctenopharyngodon idella Val.) and bighead carp (Aristichthys nobilis Rich.) were transferred directly from a diet of zooplankton to a dry, compound feed. The dry diet was based on a previously described diet of yeast and freeze-dried animal tissues. Common carp larvae showed the best growth on live zooplankton (46.3 mg individual weight after 14 days) compared to fish fed solely on dry feed (13.8 mg). Transfer of common carp larvae to dry diet when they reached 4.27 mg significantly improved growth, but no dependence was observed on two diets tested. Grass carp larvae grew equally well on live food and on the best compound diet (8.7 mg after 15 days), but fish transferred to dry diet at 4.3 mg showed significantly improved growth. The growth rate, however, depended on the diet (12.9–23.5 mg). Silver carp grew better when fed solely on dry diet (23.5 mg), compared to live zooplankton (15.8 mg after 15 days), but this was due to an insufficient supply of suitable live food. Transfer of fish at 6.8 mg to dry diet improved the growth only slightly, and dependence on the kind of dry diet was observed. Bighead carp larvae showed better growth on live zooplankton (42.2 mg after 15 days) than on the best compound diet (18.6 mg). Fish transferred at 5.6 mg to dry diets showed good growth, but high mortality was observed. It was concluded that common carp larvae are the most “difficult” to raise solely on dry diet, whereas silver carp larvae are the “easiest”. The present study has shown that the transfer of four cyprinids to dry diet improved their growth rate and that the transfer is possible at the individual wet weight of 5–6 mg.     

Molecular characterization of cholecystokinin in grass carp (Ctenopharyngodon idellus): cloning, localization, developmental profile, and effect of fasting and refeeding on expression in the brain and intestine

Cholecystokinin (CCK) is a multi-functional brain–gut peptide in fish and mammals. To investigate the role of CCK in appetite regulation in fish, a 770-bp full-length cDNA sequence of CCK gene was obtained by RT-PCR and rapid amplification of cDNA ends methods in grass carp Ctenopharyngodon idellus. Homology analysis showed that the CCK cDNA sequence of grass carp had the highest similarity (90 %) to that of goldfish Carassius auratus and a higher similarity (>70 %) to those of other teleosts than to mammals. The PCR amplification using genomic DNA identified that the CCK gene of grass carp was comprised of three exons and two introns. Real-time quantitative PCR was used to detect CCK mRNA expression in adult tissues. High levels of gene expression were found in the hypothalamus and pituitary; moderate levels in the intestine, muscle and white adipose tissue; and low levels in other tissues. During early development (i.e., fertilized eggs to 35-day post-hatching larvae) the levels of CCK mRNA expression were higher during embryonic developmental stages than during post-hatch larval stages. Fasting decreased CCK mRNA expression levels in the brain and intestine, whereas refeeding resulted in an increase of expression. The results suggest that CCK mRNA expression has obvious tissue specificity and may have a role in feed intake regulation in grass carp.     

A new high in fish production in India with record yields by composite fish culture in freshwater ponds

Composite fish culture of the Indian major carp, Catla catla, Labeo rohita and Cirrhinus mrigala together with the Chinese silver carp Hypophthalmichthys molitrix and grass carp Ctenopharyngodon idella and the Indonesian strain of common carp (Cyprinus carpio communis) was carried out in experimental ponds in 1971–1972 and 1973–1974. The management techniques adopted aimed at high yields of marketable fish (around 1 kg) in 1 year.In the first year, production varied from 3 889 to 5 600 kg/ha/year and this rose to an average of 8 200 kg/ha/year with a maximum of 9 389 kg/ha/year in the second year. The important changes made to the management schedule in 1973 were increased stocking density, greater use of feed and fertilizers, and provision of more weeds for grass carp.The experimental studies demonstrate the practicability of raising large crops of healthy marketable fish in India.     

Effects of dietary 60 g kg−1 dried distiller's grains in least‐cost practical diets on production and gut allochthonous bacterial composition of cage‐cultured fish: comparison among fish species with different natural food habits

Dried distiller's grain (DDG) is considered as an alternative ingredient of dietary feed due to its high contents of protein, fibre and fat. In this study, 60 g kg^‐1 of DDG was used to feed grass carp (Ctenopharyngodon idella), bluntnose black bream (Megalobrama amblycephala), gibel carp (Carassius gibelio) and black carp (Mylopharyngodon piceus) for 8 weeks, and its effect on fish production and gut allochthonous microbiota was investigated for the development of a suitable fish feed high in nutrients and low in cost for polyculture freshwater fish. DDG supplementation resulted in the less weight gain and higher feed conversion ratio of black carp (P < 0.05), but had no significant effects on other fish or parameters. PCR–denaturing gradient gel electrophoresis (DGGE) analysis indicated that all four fish species had some common and unique bacteria in their digestive tracts, and the gut microbiota of bluntnose black and gibel carp fed the control diet and DDG diets were very similar (Cs > 91%); of them, the total counts of intestinal bacteria studied by qPCR increased in grass carp (P < 0.05) and depressed in black carp (P < 0.05) when fed dietary DDG. Thus, we assumed that dietary DDG modulated production and gut microbiota of fish in a host‐specific way.     

Strategies and Tactics for Larval Culture of Commercially Important Carp

This paper reviews state-of-the-art techniques for culture of larval common carp, Cyprinus carpio, silver carp, Hypophthalmichthys molitrix, bighead carp, H. nobilis, and grass carp, Crenopharyngodon idella. Water temperature, food, and predation are important factors influencing larval survival and growth. Lower and upper lethal temperatures range from 3 to 44°C. Optimum growth temperatures range from 38 to 40°C. Lethal and optimum temperatures vary with acclimation temperature, fish age, and development stage of fish. Water temperatures are close to optimum for larval culture in tropical regions but are often too low in temperate climates. Intensive culture in temperature-controlled systems is important in temperate climates. The first food eaten by larvae in ponds consists mainly of protozoa, rotifers, and copepod nauplii. As fhe larvae grow, they quickly shift to larger food items, including cladocera and insect larvae. Management practices to enhance natural food development in earthen ponds include bottom drying, soil preparation, liming, fertilization, and agricultural crop cultivation. The development of food organisms in freshly filled ponds follows a pattern of succession. For best results, a pond should be stocked at the stage of succession when the size relationship between fish larvae (predators) and zooplankton (prey) is proper. A common practice is to stock larvae 3-7 days after filling. If ponds are filled too long before larvae are stocked, food relationships between fish and invertebrates can be reversed. Predator control includes biological, chemical, physical, and mechanical methods. Although great progress has been made in the development of dry starter diets, prepared feeds are not yet available for successful large-scale production. This problem is usually overcome by starting larvae with live food or with a mixture of live food and dry feed and by shifting larvae to dry diets as they grow. Live food either is collected from zooplankton ponds or is produced in intensive culture conditions. Systems for larval culture can range from ponds to intensive culture with water recirculation systems. Choice of the best system depends on the local climate, technical, and socio-economic conditions.     

饲料中添加生物素对草鱼幼鱼生长、体成分和血清生化指标的影响

在纯化饲料中分别添加生物素0、0.05、0.10、0.20、0.40、0.80、1.60 mg/kg投喂初始质量为(5.92±0.25)g的草鱼(Ctenopharyngodon idellus)幼鱼8周,研究了不同生物素添加量对草鱼幼鱼生长性能、饲料系数、机体营养成分、血清生化指标的影响。试验结果显示:与对照组相比,添加生物素提高了草鱼幼鱼的增重率、特定生长率,降低了饲料系数。添加量为0.40 mg/kg时草鱼幼鱼的特定生长率和增重率最大,饲料系数最低,并与对照组存在显著差异(P<0.05);添加不同水平生物素对草鱼幼鱼全鱼水分、粗蛋白、粗脂肪含量无显著影响,但添加量为0.40 mg/kg时粗蛋白含量最大。0.10 mg/kg组和0.20 mg/kg组的全鱼灰分含量显著高于对照组(P<0.05);添加生物素对血清总蛋白(TP)、血糖(GLU)和总胆固醇(TC)无显著影响,但显著提高了血清甘油三酯(TG)含量,各添加组TG含量均显著高于对照组(P<0.05),1.60 mg/kg添加组的高密度脂蛋白胆固醇(HDL-C)和低密度脂蛋白胆固醇(LDL-C)含量显著高于对照组(P<0.05)。综合本试验结果,草鱼幼鱼饲料中生物素适宜添加量为0.40 mg/kg。     

复方中草药制剂对草鱼肝胆综合症的防治研究

试验以患肝胆综合症的草鱼（C tenopharyngodon idellus）种苗为研究对象,选用复方中草药制剂为试验药物,设置3个质量分数分别为0.50%、0.75%和1.00%的复方中草药药饵组,1个不含该复方制剂的常规饲料组,1个青饲料组,饲喂4周;结合组织病理学方法,探讨了草鱼肝胆综合症的病理及复方中草药制剂对该病的治疗效果。结果表明,草鱼病变肝组织出现大片自溶性坏死和弥散性病变,肝细胞核偏移,发生空泡变性和水样变性;0.50%、0.75%和1.00%3个药饵试验组与青饲料和不含药物这2个非药饵对照组中,患病草鱼的成活率分别为60.0%、80.0%、96.7%、36.7%和16.7%。试验组草鱼比对照组草鱼肝胆综合症症状有明显好转,表现为鱼的体色、体表粘液和肝脏形态、色泽、质地恢复正常;背鳍、尾鳍边缘发白以及鳃部淤血、充血现象消失,鳃部粘液明显减少。1.00%试验组草鱼肝脏肝小叶分界清楚,肝细胞之间的界限清晰可见,肝细胞的核膜与核仁容易辨认,肝细胞核位移细胞中部,肝细胞逐渐恢复正常。     

种青养鱼模式下的草鱼肌肉营养成分和品质特性

为探究种青养鱼养殖模式对草鱼肌肉营养成分和品质特性的影响,随机选取以种青喂草为主养殖模式下养殖的草鱼(生态草鱼)和投喂人工配合饲料进行养殖的草鱼(饲料草鱼)各16尾,测定其肌肉系水力和质构特性指标,以及肌肉常规营养成分、矿物元素、氨基酸和脂肪酸含量。结果显示,生态草鱼和饲料草鱼肝体比和空壳率无显著性差异;生态草鱼肌肉系水力指标中滴水损失显著低于饲料草鱼,冷冻渗出率不显著地低于饲料草鱼,失水率不显著地高于饲料草鱼,p H值无显著性差异;肌肉的硬度、弹性、凝聚性、胶黏性和回复性均无显著性差异;生态草鱼粗脂肪含量显著低于饲料草鱼,水分、灰分、粗蛋白含量均无显著性差异;生态草鱼P和Fe含量均显著高于饲料草鱼,Mg、Mn和Cr含量均极显著高于饲料草鱼;生态草鱼和饲料草鱼肌肉氨基酸组成基本一致,均含有17种氨基酸,其中人体必需氨基酸总量分别为6.85%和6.27%。生态草鱼必需氨基酸指数(EAAI)为76.07,而饲料草鱼为77.29,饲料草鱼略高于生态草鱼。生态草鱼和饲料草鱼肌肉均含19种脂肪酸,其中棕榈酸、花生四烯酸(ARA)、亚油酸(LA)、油酸、二十二碳六烯酸(DHA)和硬脂酸含量较高,为主要脂肪酸,而花生五烯酸(EPA)+DHA含量分别为8.95%和10.70%,且差异显著。研究表明,生态草鱼和饲料草鱼在肌肉质构特性方面无显著性差异,与饲料草鱼相比,生态草鱼具有肌肉系水力强、低脂肪和矿物元素含量高的特点。     

Dietary taurine can improve the hypoxia-tolerance but not the growth performance in juvenile grass carp Ctenopharyngodon idellus

This study was conducted to evaluate the effects of dietary taurine, as a feed additive, on the hypoxia-tolerance and growth performance of the juvenile grass carp Ctenopharyngodon idellus, one of the most important and intensively cultured freshwater fish, with the largest production in China. Graded levels of taurine (0, 0.5, 1, 1.5, 2 and 2.5 g kg^–1 dry diet) were fed to grass carp juveniles (mean weight: 5.26 ± 0.03 g) for 8 weeks. The survival time during acute hypoxia increased as dietary levels of taurine increased, with the highest dose of taurine resulting in the best acute hypoxia-tolerance. The erythrocyte osmotic fragility in grass carp was significantly improved when dietary taurine level was at least 1.5 g kg^?1 diet and can be improved much more when dietary taurine level was up to 2.5 g kg^?1 diet. A significant correlation between hemolysis rate of the erythrocyte osmotic fragility test and the survival time of acute hypoxia (r = ?0.873, P = 0.023 < 0.05) strongly suggested that the biomembrane stabilization function of taurine may contribute to its role of enhancing acute hypoxia-tolerance in grass carp. Dietary taurine cannot improve growth performance of grass carp, but it can increase the value of mesenteric fat index, indicating that dietary taurine influences the lipid metabolism. This study provides valuable information to improve hypoxia-tolerance of grass carp.     

草鱼SREBP-1基因的克隆及糖对其在肝脏中表达的影响

固醇调节元件结合蛋白(SREBPs)是调控糖脂代谢相关基因表达的关键核转录因子。为获知草鱼SREBP-1基因的序列及其在肝脏中的表达规律,本实验采用同源克隆和RACE方法获得了草鱼SREBP-1基因的部分cDNA序列,并通过生物信息学方法对该基因及所编码蛋白的结构特征进行了分析;采用实时荧光定量PCR技术,对SREBP-1基因在8种不同组织的表达规律及低糖(糖含量24%)和高糖(糖含量42%)投喂条件下肝脏中的表达水平进行了研究。结果显示,所克隆到的草鱼SREBP-1基因cDNA长4 760 bp,其中包括开放读码框3 426bp,编码1 141个氨基酸;草鱼SREBP-1具有一个典型的碱性螺旋-环-螺旋亮氨酸拉链结构(bHLH-zip);氨基酸序列比对结果显示,草鱼SREBP-1与其他鱼类的同源性在76%~88%之间,与斑马鱼的进化关系最近;草鱼SREBP-1基因在脑中的表达量最高,肝脏和肠次之,在肾脏、脾脏、肌肉、脂肪和性腺中均有少量表达;与对照组相比,SREBP-1基因在高糖诱导下表达量显著提高(P0.05),低糖诱导下没有显著性差异。研究表明,在高糖负荷条件下,草鱼肝脏中SREBP-1可能会促进糖的利用和转化,从而参与糖代谢调节过程,为丰富鱼类糖代谢调控机理提供研究资料,并有望为提高鱼类对饲料糖的利用效率提供理论依据。     

Digestibility of low-cost ingredients in pelleted feed by grass carp (Ctenopharyngodon idella C. et V.)

The digestion coefficients of nutrients in 37% protein MARDI feed as well as in napier and carpet grass meals were evaluated in grass carp. Cr₂O₃ was used as an internal marker for the evaluation of digestibility. In the MARDI feed, the fish meal and soya bean meal were digested most by the fish: the digestion coefficients for protein were 90.81% and 96.21%, respectively; for fat the values were 100% and 98.79%, respectively; and for gross energy the values were 83.37% and 82.71%, respectively. These results indicate that it may be feasible to replace fish meal partially with soya bean meal in the MARDI feed for grass carp. The digestion coefficients for dry matter and carbohydrate of maize were 64.76% and 87.85%, respectively, although protein, fat and gross energy in maize were poorly utilized by the fish. Copra cake and rice bran were poorly digested by the fish. These two ingredients should be deleted in feed formulations for this fish.The digestion coefficients of nutrients in napier and carpet grass meals were much higher than those of maize, copra cake and rice bran in the fish, which suggests that grass meals may possibly be used as ingredients in feed formulation for grass carp.     

生态基对草鱼生长性能、肠道及水体微生物的影响

将无纺布生态基应用于草鱼养殖生产中,研究生态基对草鱼生长、免疫和养殖水质的影响,并利用PCR-DGGE技术分析了草鱼肠道和养殖水体微生物群落结构的动态变化。结果显示,实验组草鱼的末重、增重率均显著高于对照组(P0.05),饲料系数显著低于对照组(P0.05);草鱼血清碱性磷酸酶(AKP)、酸性磷酸酶(ACP)、超氧化物歧化酶(SOD)、溶菌酶(LSZ)活性水平均显著高于对照组(P0.05),诱导型一氧化氮合酶(iNos)和总一氧化氮合酶(tNos)均显著低于对照组(P0.05);除了在第30天时实验组TSS水平显著低于对照组(P0.05),整个过程挂设无纺布生态基对养殖水质参数影响不明显(P0.05)。PCR-DGGE检测结果显示:Cetobacterium somerae是对照组养殖水体和对照组草鱼肠道特异细菌;维氏气单胞菌是养殖水体和对照组草鱼肠道特异细菌,对照组养殖水体的分布明显比实验组丰富,在生态基中不存在;生态基的细菌群落构成和挂设生态基的实验组养殖水体相似性较高,最高时达到63%;绿弯菌占生态基细菌总量的10%左右,而在养殖水体中仅为5%。研究表明,生态基的应用有效促进了草鱼的生长,降低了饲料系数,提高了草鱼的非特异性免疫功能,降低养殖水体TSS浓度。生态基的应用改变了水体细菌群落组成,减少了养殖水体和草鱼肠道中一些条件致病菌的存在。     

Effects of traditional Chinese medicines (TCM) on the immune response of grass carp (Ctenopharyngodon idellus)

The use of traditional Chinese medicine (TCM) in aquaculture has been widely investigated. It is believed that herbal supplements could enhance the immunity and promote fish growth. The powdered TCM or its decoction can be easily applied in the form of feed supplements by direct incorporation into fish feeds and side effects are seldom found. In this study, Radix scutellaria (Rs) and Rhizoma coptidis (Rc) showed strong bacterial inhibition on Aeromonas hydrophila out of the sixteen selected herbal extracts. Four TCMs, R. scutellaria, R. coptidis, Herba andrographis (Ha), and Radix sophorae flavescentis (Rsf) were selected to form a compound formulation in the ratio of 1:1:2:3. A feeding experiment on grass carp was conducted with addition of the above TCM formulation (0.5, 1 and 2 % w/w) in the fish feed, and bactericidal activity, total protein and immunoglobulin in blood plasma, and nitroblue tetrazolium activity in the whole blood were measured. 2 % supplementation significantly improved (p < 0.05) the bactericidal activity and total immunoglobulin in the plasma after feeding for 21 days. Compared to control, 2 % TCM feeding groups showed a significantly lower mortality after A. hydrophila challenge at the end of experiment and the same result was archived in field trial. In the cost evaluation, the use of the TCM formulation in grass carp culture was insignificant and could be compensated by improved yield. TCM formulation contained different active ingredients including some immuno-stimulant and antimicrobial agents and therefore could be applicable to multiple diseases. Application of this TCM formulation would be a cost-effective and prophylactic approach for disease control in aquaculture, replacing the use of antibiotics for treating enteritis and even other general diseases.     

Genetic variability and relationships among six grass carp Ctenopharyngodon idella populations in China estimated using EST-SNP Markers

The grass carp, which is one of the most important farmed fish species in China, is widely distributed in different river basins. In this study, 21 single nucleotide polymorphism markers, developed in the grass carp expressed sequence tag database, were used with the snapshot genotyping method to analyze the genetic structure of six grass carp populations (SS, JL, HH, YJ, NX, and FS) from the Yangtze River and the Pearl River. The effective numbers of alleles (Ne) of the six grass carp populations was 1.7680–1.8038, the observed heterozygosity (Ho) was 0.5938–0.6305, the expected heterozygosity (He) was 0.4420–0.4443, and the polymorphic information content (PIC) was 0.3241–0.3403. The PIC, Ne, and He of the JL population were the highest among all populations, whereas those of the YJ population were the lowest. The NJ tree analysis based on genetic distance of the grass carp populations revealed that the six populations clustered into two branches: the SS, JL, and HH populations clustered first into one branch, which then clustered with YJ population; the FS and NX populations constituted a separate branch. The established genetic structures and phylogenetic relationships of some of the grass carp populations of the Yangtze River and Pearl River may lay the foundation for selecting core breeding populations.     

Optimization of fish to mussel stocking ratio: Development of a state-of-art pearl production mode through fish–mussel integration

Integrated aquaculture has been widely used for pearl production in the freshwater pearl mussel Hyriopsis cumingii farming in China, but the production technology has not reached the state of the art. This study explored the optimal stocking ratio of fish to mussel (fish–mussel) through a 90-day experiment conducted in land-based enclosures. The integrated system included pearl mussel, grass carp, gibel carp, silver carp and bighead carp, with four fish–mussel stocking ratios by number: 1:1 (R1), 2:1 (R2), 3:1 (R3) and 4:1 (R4). The pearl yield was higher in the R2 enclosures than in the R1 and R4 enclosures, whereas the fish yield was higher in the R3 and R4 enclosures than in the R1 and R2 enclosures. The phosphorus (P) utilization efficiency was higher in the R2, R3 and R4 enclosures than in the R1 enclosures. The wastes of nitrogen (N) and P enhanced with the increase of fish–mussel ratio. Regression analyses indicated that the fish–mussel ratio was 2.3:1 for the maximal pearl yield, and 3.6:1 for the maximal fish yield, and 1.6–2.3:1 for the minimal N waste, and 1.9–2.9:1 for the minimal P waste. This study indicated that the suitable fish–mussel stocking ratio was 2:1 in the integrated culture of H. cumingii, grass carp, gibel carp, silver carp and bighead carp.     

Effects of modified pond management on limnological parameters in small‐scale aquaculture ponds in mountainous Northern Vietnam

In mountainous Northern Vietnam, traditional pond aquaculture is part of the integrated farming activity contributing to food safety and to income generation for small‐scale farmers of ethnic minorities. Traditional pond management consists of a polyculture of macro‐herbivorous grass carp with 3–5 other fish species that are cultured in small ponds with constant water flow through. The main limitations to production are species‐specific mass mortalities of grass carp, a poor feed base especially for all species but grass carp, and poor water quality. In this study, we compared the traditional pond management to a semi‐intensive pond management that was based on the traditional management system but included changes designed by researchers to increase fish production. The modifications consisted of water inflow control, supplemental fertilization and feeding, and a polyculture dominated by common carp. The changes in management significantly reduced the turbidity and increased oxygen supply, as well as the natural food base within the pond. These changes in pond management provide farmers with the possibility to improve their pond aquaculture scheme and overcome previous limitations.     

Intensive rearing of grass carp larvae Ctenopharyngodon idella (Valenciennes 1844) under controlled conditions

This paper describes an indoor feeding experiment with grass carp larvae. It was intended to identify rates of survival and growth of newly hatched larvae in a hatchery using dry feed only until they reached a size which allowed stocking in growing ponds without additional nursing. The larvae fed on Alkan yeast reached a mean total length of 10.3 mm with negligible mortality rates within a feeding period of 1 week. Problems concerning optimal feeding with dry feed and optimal stocking densities in rearing tanks are briefly discussed.     

Freeze‐dried forms of mosquito larvae for feeding of Siamese fighting fish (Betta splendens Regan, 1910)

Live diets are preferably used for rearing Siamese fighting fish (Betta splendens Regan, 1910) since they provide superior growth over the dry feed. In the current study, three different preparations of mosquito larvae were prepared (frozen at ?20°C, F–20; freeze‐dried and kept at 4°C, FD4; freeze‐dried and kept at ambient temperature, FDAT) and were individually fed to 1‐month‐old red male fighting fish (1.18 ± 0.01 g initial body weight) over 6 weeks duration. At the end of experiment, there were no significant differences in growth performance and feed utilization across three dietary treatments (p ? 0.05). Specific activity of lipase was significantly lower in fish fed FD4 and FDAT than with the F–20 diet, while no differences in other enzymes were observed. The fish fed with FDAT diet significantly increased in viscerosomatic index relative to F–20 and FD4 treatments. Significant improvements in skin redness and flesh quality (RNA and RNA/protein ratio) were observed in the fish fed with FDAT diet relative to the other treatments. This preferred FDAT treatment also maintained the carcass composition. Analysis of digestive enzymes in FDAT mosquito larvae demonstrated the presence of protein‐, carbohydrate‐, and lipid‐digesting enzymes after 1 month of storage. The findings from our experiments indicate that the freeze‐dried form (FDAT) of mosquito larvae is suitable for rearing Siamese fighting fish. However, effective preparation protocol and appropriate storage times should be further studied.     

饲料中添加谷胱甘肽对草鱼生长、生理指标和抗病力的影响

选用初始体质量约8.50 g的草鱼(Ctenopharyngodon idella),在56 d的饲养期中分别投喂添加5种不同剂量谷胱甘肽(GSH)(添加量分别为0 mg/kg、100 mg/kg、200 mg/kg、300 mg/kg和400 mg/kg)的试验饲料,观察GSH对草鱼生长、生理指标和抗病力的影响。结果表明,饲料中添加GSH能够提高草鱼特定生长率、存活率和饲料效率。其中,300 mg/kg GSH组草鱼的特定生长率和400 mg/kg GSH组草鱼的存活率显著高于对照组;添加GSH各组草鱼的饲料效率均显著高于对照组,当添加量为200 mg/kg时草鱼饲料效率达到最高。与对照组相比,饲料中添加GSH的各组草鱼肝胰指数明显升高,其中200 mg/kg组达到显著水平。饲料中添加GSH能够提高血清IGF-1水平,其中300 mg/kg和400 mg/kg组显著高于对照组。与对照组相比,各实验组草鱼血液白细胞数目有不同程度升高,其中300 mg/kg和400 mg/kg组均达到显著水平。饲料中添加GSH可以提高草鱼对嗜水气单胞菌的抵抗能力,其中200 mg/kg GSH组草鱼攻毒后存活率达到最高。以特定生长率为判定指标,GSH在草鱼饲料中的适宜添加量为350 mg/kg。