Towards the sustainable intensification of agriculture—a systems approach to policy formulation

The sustainable intensification of agriculture involves providing sufficient food and other ecosystem services without going beyond the limits of the earth’s system. Here a project management approach is suggested to help guide agricultural policy to deliver these objectives. The first step is to agree measurable outcomes, integrating formal policy goals with the often much less formal and much more diverse goals of individual farmers. The second step is to assess current performance. Ideally, this will involve the use of farm-scale metrics that can feed into process models that address social and environmental domains as well as production issues that can be benchmarked and upscaled to landscape and country. Some policy goals can be delivered by supporting ad hoc interventions, while others require the redesign of the farming system. A pipeline of research, knowledge and capacity building is needed to ensure the continuous increase in farm performance. System models can help prioritise policy interventions. Formal optimization of land use is only appropriate if the policy goals are clear, and the constraints understood. In practice, the best approach may depend on the scale of action that is required, and on the amount of resource and infrastructure available to generate, implement and manage policy.     

UCP1基因变异与绵羊生长及胴体性状的关联分析

试验旨在探讨解耦联蛋白1（UCP1）基因核苷酸变异对绵羊生长性状的性别差异和胴体性状的影响，以期能够筛选出可以提升绵羊生长及胴体性状的核苷酸变异，为提高绵羊相关重要经济性状的分子遗传标记提供材料。以9个绵羊品种为研究对象，用PCR-SSCP方法检测不同性别绵羊中UCP1基因内含子5区和外显子6区变异。利用Minitab 16.0软件中一般线性模型分析内含子5区等位基因与不同性别绵羊生长性状、公羔胴体性状的关联性。结果显示，绵羊UCP1基因内含子5区和外显子6区共检测到8个核苷酸变异，其中位点c.910 G/A突变导致p.Ala304Thr氨基酸变异。生长性状关联分析结果表明，内含子5区等位基因对绵羊生长性状的影响存在性别特异性，母羔中携带等位基因A₁的群体较缺失群体具有较低的初生重（P<0.05），公羔中携带等位基因C₁的群体较缺失群体具有较高的断尾重（P<0.05），未发现其他等位基因与羔羊的生长性状存在性别特异性。胴体性状关联分析结果表明，携带等位基因A₁的群体具有较低后腿瘦肉量、腰部瘦肉量和较高的肩部瘦肉比例（P<0.05），携带等位基因C₁的群体具有较低的后腿瘦肉比例（P<0.05），其他胴体性状均没有发现与等位基因存在显著相关，基因型分析结果与等位基因分析结果一致。结果提示，UCP1基因对绵羊的生长性状影响具有性别特异性，且携带等位基因A₁的公羔群体具有较低的胴体生产性状，为提高公羔胴体生产性能提供了理论依据。     

伪狂犬病及其根除:美国经历的回顾——猪伪狂犬病根除指南:猪群PRV净化方案

正对猪群和猪场而言,伪狂犬病是可消灭的。当某一猪群被发现感染伪狂犬病,必须在考虑所有相关因素的基础上选择适当的计划并严格遵守。为利用特定设施,可对基础计划作出改动。但应严格遵守基本原则。本文对美国清群重建净化方案、旨在保留猪群种系并利用血清反应呈     

Growth and nutrient accumulation of Brazil nut trees (Bertholletia excelsa) in agroforestry at different fertilizer levels

The Brazil nut tree(Bertholletia excelsa) is a frequent component of agroforestry systems in the Amazon because of its adaptation to nutrient-poor upland soils and multiple uses.We investigated the aboveground biomass production(kg dry weight),nutrient uptake and requirements(N,P,Ca,Mg,K) of Brazil nut trees of different sizes grown under agroforestry conditions and fertilized at different levels.Eight of 70 experimental trees with different size were harvested and stem,branches and leaves were separated.Nutrient contents were determined for three trees of varying size.Average tree growth was fast,but variability was high,suggesting considerable potential for the improvement of this economically important species.The trees responded to increased levels of fertilizer and lime with significantly increased foliar nutrient contents and growth,probably because of the improved availability of Mg and Ca for which the species seems to have a relatively high demand.In contrast to Brazil nut trees grown in forest or dense plantations,the agroforestry trees invested a substantial part of their biomass and nutrients in large branches and developed spreading crowns.To improve stem form,reduce competition with associated crops for light and recycle nutrients,regular pruning of lower branches or planting arrangements that favor self-pruning are recommended.These measures would also increase the recycling of Ca and Mg,large quantities of which are contained in the branches.     

Effects of Rice Variety and Growth Location in Cambodia on Grain Composition and Starch Structure简

The effects of variety and growth location on grain composition and starch structures were investigated using three rice (Oryza sativa L.) cultivars (Phka Romduol, Sen Pidao and IR66) with different amylose contents. All the three cultivars were planted in three different agro-climatic zones (Phnom Penh, Coastal and Plateau) of Cambodia. The protein content of polished grains increased when rice was planted at a location with higher average temperature, but their lipid content decreased. The amylose content and degree of branching were not greatly affected by the minor temperature differences among the growing locations. Starch fine structures characterized by the chain-length distribution were significantly different among the cultivars, but not significantly among different locations. The results suggested that protein and lipid biosyntheses were more sensitive to the environmental temperature than that of starch in rice grains.     

伪狂犬病及其根除:美国经历的回顾——伪狂犬病的流行病学

本文由美国家畜保护研究所于1990年完成,两位作者David G博士和Jerry Torrison博士均来自明尼苏达大学兽医院。本文来源于《伪狂犬病及其根除报告:美国经历的回顾》报告中的附件,由美国农业部公开发布。     

澳大利亚改进一种倾斜筛能分离小麦中的害虫

作者通过改进非洲使用的袋筛发展为适合由一个人操作大量谷物的倾斜筛,达到从小麦中分离害虫成虫的目的。这种筛是用铝丝编制而成,4—5分钟内从30公斤小麦样品中筛出的害虫表明,对赤拟谷盗和谷蠹效果较好,而对米象效果较差。根据每次停筛后筛出总数的累加百分比是:一次停筛后筛出的最大数赤拟谷盗为98.8%,谷蠹为96.7%,米象为93.3%;二次     

粮堆水份的扩散

前言 Pixton和Griffiths(1971)曾经指出,贮藏小麦中水份的等温扩散是一个很缓慢的过程。然而,Griffiths(1964)的早期研究已表明,在通风和冷却通风的筒仓中,离墙身一定距离内存在着不同的热界面,在温度梯度作用下,产生了明显的扩散作用(Thorpe,1976)。这些部位经常是粮堆中最热的地方。因此,靠墙部位粮食的含水量的任何变化,都可能极大地影响贮粮害虫的活动、杀虫剂的效率和谷物的品质。鉴于这些原因,就应很好地弄清谷物水分的扩散机理。材料和方法 Pixton和Griffiths