Economic characteristics of extensive shrimp farms in the Mekong delta

Abstract

Extensive forms of shrimp aquaculture have become an important source of income for farm households in the brackish water region of the Mekong Delta, Vietnam. The economic and production characteristics of farms are discussed in this paper, based on a 1997 farm survey, with particular emphasis on shrimp farming practices. Two types of shrimp fanning practice were observed, one based on natural recruitment of seedstock with few supplementary inputs, and the other based on relatively high cash investments in Penaeus monodon seedstock and other inputs. Households practising monodon culture made significantly more income, but faced high risk associated with shrimp mortality. An investigation of the factors affecting monodon yields indicated that investment in higher quality inputs had a positive effect on yield and income. However, further research is needed on the extent to which management can reduce risk of shrimp mortality by investing in such premium quality inputs.     

不同基因型和营养对山羊生长性能、胴体品质及肉质的影响

【目的】探讨不同基因型和营养物质在改善老挝山羊的生长性能、胴体特征和肉质中的效果。【方法】采用2×2双因素试验,以本地山羊品种Lat为对照,对Lat与越南Bach Thao公山羊的杂交F1（BT×L）进行比较。从每个基因型中选择30头7月龄的成长公山羊并分成两组,其中一组采用传统饲喂方法即自由放牧,另一组采用改良饲喂方法,即放牧并任意采食木薯渣和矿物砖。试验期间测量山羊平均日增重（ADG）,在后期每组选择3只山羊宰杀并测定胴体特性（胴体组成和初分切肉）、肉质（剪切力、肉色、pH、滴水损失率和蒸煮损失率）。【结果】杂交山羊F1的平均日增重（60．02g／头）明显高于本地山羊（38．45g／头）,增幅为56．09％;饲喂补充木薯渣和矿物砖的山羊平均日增重（55．45g／头）则显著高于未添加对照组（43．02g,头）,增幅为28．89％。杂交繁育和饲喂补充物对山羊胴体品质如屠宰率、前肢百分率、后肢百分率及胸肌率没有显著影响,但杂交F1山羊的脖子极显著大于本地山羊,而其腰腹部切口极显著小于本地山羊。在两种不同饲喂管理条件下,Lat和杂交F1山羊的肉质特性没有显著差异。【结论】老挝本地山羊Lat与Bach Thao公山羊杂交及在饲料中补充木薯渣和矿物砖,可提高山羊肉产量且对其肉质无任何负作用。     

Temperature and Precipitation Suitability Evaluation for the Winter Wheat and Summer Maize Cropping System in the Huang-Huai-Hai Plain of China

The Huang-Huai-Hai Plain is the most important winter wheat and maize production region in China. In response to the increasing population pressure, the Chinese authorities strongly invested in improving the irrigation systems and increasing ground and surface water exploitation within the plain to increase the crop productivity. This resulted in a reduction of water resource availability and in turn indirectly affected the suitability of various agricultural ecosystems in the plain. The main purpose of this study was to review the suitability of temperature and precipitation for the winter wheat and summer maize cropping system in the Huang-Huai-Hai Plain, in order to provide a preliminary irrigation scheme. This analysis provides a first attempt to enhance the water resource management as well as to increase the water use efficiency. For this aim, a GIS-based multicriteria analysis procedure has been developed consisting of (1) definition of objectives (evaluated entities) and database building; (2) definition of evaluation criteria; (3) standardization of the criteria; (4) combination of the criteria; (5) classification of the objectives; and (6) integration of the objectives. The land suitability classification maps were transformed into maps of required irrigation amounts for each growing stage of the winter wheat and summer maize cropping system. The study also exemplified the limitations and proposed future research activities that will improve the detail and accuracy of the evaluation results.     

The possible role of bovine herpesvirus type‐4 infection in cow infertility

Experimental and field studies have proven that the bovine herpesvirus type‐4 (BHV‐4) infection leads to various reproductive system problems. In this study, the role of BHV‐4 infection in repeat breeding was investigated serologically. Eighty‐four samples were obtained from repeat‐breeding diagnosed cows in two organized dairy herds; an equal number of healthy cows were sampled from the same farms. The rest of the samples (105) were obtained from reproductively normal cows that were breeding in 18 small enterprises as a control group. The seropositivity proportion in repeat‐breeding diagnosed cows was found to be significantly higher (69% (58/84)) than other cows (44% (37/84)) on the same farms. The lowest antibody positivity value for BHV‐4 was detected as 24.7% (26/105) in the samples from family‐type small farms. The odds ratio (OR) value was calculated as 2.834 in repeat‐breeding diagnosed and healthy cows on the same farms, while 6.778 was determined in cows with and without reproductive problems on organized farms compared to small farms. As a result, the BHV‐4 infection can be considered one of the reasons for repeat breeding besides other reproductive disorders.     

Diffusion of chemicals into archaeological waterlogged hardwoods obtained from the Thang Long Imperial Citadel site,Vietnam

This study shows a method to easily develop suitable impregnation procedure of chemicals for preserving the archaeological waterlogged wood (WW) using diffusion constant. The steady-state diffusion coefficients of polyethylene glycol 4000 (PEG4000), trehalose, and keratin through eight archaeological waterlogged wood species were obtained from the total amounts of the chemicals diffused through the wood samples. The diffusion coefficients were strongly affected by the anatomical structures of the wood species and degree of wood deterioration. Within the same species of wood, the highest diffusion rates were measured in the longitudinal direction, followed by those in the radial and tangential directions. The longitudinal diffusion coefficients were 1.5- to 8.1-times higher than the radial diffusion coefficients, which were in turn approximately 1.1- to 5.7-times higher than the tangential diffusion coefficients. The diffusion rates were found to be inversely proportional to the molecular weight of the diffusing chemical. The diffusivity of trehalose through the waterlogged woods was found to be higher than those of keratin and PEG4000. This study provides a potential method to easily estimate chemical diffusion coefficients for dip-diffusion treatments.     

Foliar application of vanillic and p-hydroxybenzoic acids enhanced drought tolerance and formation of phytoalexin momilactones in rice

In this study, two rice cultivars including a drought tolerant (Q8) and a drought susceptible (Q2) were foliar applied with exogenous vanillic acid (VA) and p-hydroxybenzoic acid (PHBA) to examine their effectiveness on drought-tolerant levels and induction of pigments, antioxidants, phenolics, flavonoids, and phytoalexin momilactones A (MA) and B (MB). Generally, the tolerant level of Q2 was more accelerated than those of Q8. Total contents of phenolics, flavonoids, pigments, and antioxidant activity were positively promoted, although the difference between Q8 and Q2 was negligible. In the quantitative induction of phenolic acids, VA, PHBA, and VA+PHBA showed dose-dependent variable effects, of which Q2 was more influenced than Q8. In all treatments, PHBA appeared to have a more significant role toward drought tolerance than VA. Although MB was found only in non-treated Q8, treatments of VA+PHBA caused formation of both MA and MB, however the induced quantities of MA and MB varied among applied doses and rice cultivars. This research is the first to show that, besides increasing antioxidant activity and total pigments, phenolics, and flavonoids, application of VA and PHBA induced phytoalexins MA and MB to enhance rice drought tolerance, of which MB may play a greater role than MA.     

北京市汉石桥湿地浮游植物调查与水质评价

2007年对北京汉石桥湿地水系进行浮游植物和水质理化指标的评价调查。浮游植物群落由蓝藻、绿藻、硅藻、隐藻、裸藻和甲藻构成,平均密度为2.4×10^8个/L,其中绿藻占55.7%。湿地水体4项指标透明度、全氮、全磷、化学需氧量的卡尔森营养指数分别为87.80、88.70、98.15和98.69,水质明显富营养化,夏秋季水面有微囊藻藻胞层（微囊藻藻水华）。V形水道水域夏秋季水面也出现裸藻水华。     

皖贝母茎尖脱毒组织培养技术研究

应用ELISA方法对茎尖培养和热处理结合茎尖培养脱毒生产无病毒皖贝母种苗效果进行研究,结果表明,茎尖培养〈0.5 mm的茎尖无法成活;1～2 mm茎尖虽然成活率高但没有脱毒效果;0.8～1 mm茎尖的脱毒率为20%;0.5～0.8 mm的茎尖脱毒率为40%;0.3～0.5 mm茎尖脱毒率为60%。0.8～1.0 mm茎尖经50±1℃热处理20 min脱毒效果最好,脱毒率达100%;愈伤组织和不定芽的诱导需要不同的激素配比,诱导愈伤组织的合适培养基为：MS＋6-BA 0.5 mg/L＋NAA 4 mg/L,诱导不定芽并能一次成苗的合适培养基为：MS＋2,4-D 1.0 mg/L＋6-BA 1.0 mg/L＋NAA 0.2 mg/L,平均每个外植体产生2～3个不定芽。