The effects of density and artificial substrate on intensive shrimp Litopenaeus vannamei nursery production

Recirculating aquaculture systems (RAS) can be installed indoors, allowing year-round production of tropical animals in nearly any climate. A nursery phase is commonly used in Litopenaeus vannamei production since it allows for enhanced biosecurity and better quantification of animals while reducing space requirements. However, it is unclear whether animal density and inclusion of artificial substrate may improve shrimp performance during the nursery phase. In this experiment, we compared shrimp production parameters in two stocking densities with or without the use of an artificial substrate by creating four treatments: low-density LD; 1500 PL/m⁻³, low-density with substrate LDS, high-density HD; 3000 PL/m⁻³), and high-density with substrate (HDS). The LDS and HDS treatments included 0.46-m² of high-density polyethylene 2.5-cm mesh as a substrate, which increased the tank surface area by 21 %. Each treatment was randomly assigned to four 160-l culture tanks, each with a biofilter. The shrimp had an initial weight of 4 mg and were grown for 50 days. The low-density treatments had significantly higher dissolved oxygen (DO) and pH than the high-density treatments (P ≤ 0.001). Specifically, LDS had the highest DO and pH followed by the LD, HD, and HDS treatments, respectively. High-density treatments had significantly higher NO₂-N levels than low-density treatments during week 2 of the experiment when an unusually high concentration of nitrite was observed. FCR was significantly lower in both low-density treatments than in high-density treatments. At harvest, the total biomass (kg m⁻³) was significantly higher in high-density treatments than in low-density treatments (P ≤ 0.001), and the HDS treatment had a significantly greater biomass output than HD. Producers should consider artificial substrate and higher densities during nursery production to maximize shrimp production; however, the effects on water quality should also be taken into account.     

兔病毒性出血症病毒高免血清的制备与应用效果

以兔病毒性出血症病毒组织灭活疫苗免疫家兔，经五次免疫之后，抗体效价可达12log2以上，采集兔血清，以此治疗攻毒兔，结果大部分兔都存活，临床应用效果表明：以此血清治疗自然感染兔病毒性出血症病毒的发病兔，治愈率达80％以上。     

提高中锰白口铸铁韧性的研究

为改善中锰白口铸铁的韧性以扩大其应用范围,本文探讨了C, Si, Mn等合金元素、变质处理和热处理工艺对中Mn白口铸铁组织和性能的影响.     

黑龙江省西部地区重瓣白玫瑰引种栽培及繁育技术

经在黑龙江省齐齐哈尔地区对重瓣白玫瑰引种栽培及繁育技术研究表明：该树种　１９９７～２０００年的平均抗寒指数为　２．７，冻害小于Ⅲ级，枝条冻伤长度小于　５０％，能正常开花，可以在此安家落户。同时对其形态特征、主要物候期、繁育技术和抚育管理作了介绍。     

向日葵[Helianthus annuus(L.)]白花粉突变体遗传研究初报

向日葵[IIelianlhus anuus (L.)]是我国的重要经济作物。其花粉通常呈深浅程度不同的黄颜色。据我们掌握和查新资料,目前世界上尚未见有关白花粉方面的报道。1989年7月下旬至8月上旬,我们在吉林农业大学向日葵育种试验田的恢复系C8711群体中,先后发现4株白花粉突变体。暂分别定名为C8711—1、C8711—2、C8711—3和C8711—4。在进行人工套袋之前,此4株突变体已经在一定程度上发生了开放授粉,其中C8711—4开放授粉程度较轻。成熟时单独收获这4株突变体的种子,以进行有关遗传学研究,本文拟对白花粉突变的遗传学机理进行初步的探讨。     

水牛牛巴贝斯虫体外培养的研究：Ⅱ.冷冻血清的应用和筛选

应用冷冻血清对１株采自自然感染的水牛牛巴贝斯虫进行了长达７２ｄ的体外连续培养，共继代２０次，培养７２ｈ红细胞染虫率最高达１４．１％，平均为８％～１０％。培养２０ｄ和３０ｄ的牛巴贝斯虫经液氮保存复苏后，接种于去脾水牛犊均引发了严重的牛巴贝斯虫病，从而说明已建立了水牛牛巴贝斯虫的体外连续培养，且经培养后的牛巴贝斯虫致病力没有改变。本试验利用６头份的冷冻健康水牛血清同时进行培养，结果发现，并非所有的健康水牛血清均适合于体外培养牛巴贝斯虫。这一发现对建立水牛牛巴贝斯虫的体外培养和研究水牛牛巴贝斯虫病均具有重要意义     

Detection, identification and significance of phytoplasmas in grasses in northern Australia

Sugarcane yields have been severely reduced by white leaf and grassy shoot phytoplasma diseases in many parts of Asia. Australian sugarcane crops are not known to be affected by these diseases, but plant pathogenic phytoplasmas found in other introduced and native grasses in northern Australia could pose a serious threat to the Australian sugarcane industry. To further evaluate this threat, leaves from plants of 20 grass species, with and without symptoms, were collected during field surveys in northern Australia and tested to determine whether phytoplasmas were present and whether symptoms were reliable indicators of phytoplasma presence. Molecular tools were used to detect and characterize phytoplasmas. Four different phytoplasmas were found in seven grass species known to grow near healthy sugarcane crops. All the phytoplasmas were closely related to sugarcane white leaf phytoplasma (SCWL), one of the phytoplasmas that causes disease in sugarcane in Asia. Four of the host plant species and two of the phytoplasmas were new records. The relationship between symptoms and phytoplasma presence was poor. Because some plants with symptoms tested negative for phytoplasmas, a series of surveys was carried out in which flowers, leaves, roots and stems of two known host plant species, Whiteochloa cymbiformis and Sorghum stipoideum, were tested separately on nine occasions during two wet seasons. This was done to investigate the distribution of phytoplasmas within plants over time. Results showed that spatial and temporal variation of phytoplasmas occurred in these two host plant species. Hence, evaluation of disease distribution within a region requires repeated testing of all plant parts from plants without symptoms, as well as those with symptoms. To date, there is no report of a vector capable of transmitting to Australian sugarcane the phytoplasmas found in grasses in this study. If one is present, or occurs in the future, then native and introduced grasses could constitute a large reservoir of phytoplasma for vectors to draw on. This work provides an early warning for the sugarcane industry that the potential for infection exists.     

生姜对鸡生长性能及血液生化指标的影响

用1日龄健康地方鸡300只按完全随机设计分成3个处理组,每组100只,分别饲喂添加新鲜生姜粉1％(处理2)、喹乙醇80mg/kg(处理3)、不添加生姜和喹乙醇,(处理1,对照组)的日 粮,观察至60日龄。添加生姜组的日增重、饲料增重比和成活率明显优于对照组(P<0.05)。血清 胆固醇含量较对照组和喹乙醇组均低,血清总蛋白含量较对照组和喹乙醇组略高。     

Serum bile acids: reference values in healthy dogs and comparison of two kit methods

Serum bile acid (SBA) reference intervals were established by use of a radioimmunoassay method for fasting dogs to be 0.2 to 4.3 micro mol/L (n = 60) and for 2 hour postprandial samples to be 0.6 to 24.2 micro mol/L (n = 37). The SBA reference intervals estimated using an enzymatic method were 0 to 8.6 micro mol/L for fasting (n = 26) and 0 to 29.8 micro mol/L for 2 hour postprandial samples (n = 36). The correlation between the two methods including samples from healthy dogs and clinical cases is good (n = 128, r = 0.82, p < 0.0001). The radioimmunoassay method is linear to 50 micro mol/L and the enzymatic method is linear to 100 micro mol/L, thus both methods require serum dilutions to be made in many cases of primary liver disease. The enzymatic method is less expensive and more convenient for use in a clinical laboratory but requires a greater sample volume (400 micro I) than the RIA method (50 micro I). Both methods have adequate precision and accuracy to be useful as diagnostic tests of liver function in dogs.     

A review of feline serum protein electrophoresis

A review of the current literature available on feline serum proteins is presented. Early studies concentrated on comparative aspects of species variations in the electrophoretic pattern. The feline electrophoretogram was divided into five basic regions: albumin, alpha-1, alpha-2, beta and gamma. Different subdivisions of these areas were recognized depending on the support medium used. Current papers have compared the relative migration distances of each globulin peak to the migration of albumin. This "Rf" value enables reliable peak identification. To date, no data exists identifying the individual proteins responsible for the peaks in the alpha and beta regions. The only feline globulin to be studied is haptolobin; however its precise location on the electrophoretic strip was not identified.