The prevalence and concentration of Escherichia coli O157 in faeces of cattle from different production systems at slaughter

Aims: To determine the prevalence and concentration of Escherichia coli O157 shed in faeces at slaughter, by beef cattle from different production systems. Methods and Results: Faecal samples were collected from grass-fed (pasture) and lot-fed (feedlot) cattle at slaughter and tested for the presence of E. coli O157 using automated immunomagnetic separation (AIMS). Escherichia coli O157 was enumerated in positive samples using the most probable number (MPN) technique and AIMS and total E. coli were enumerated using Petrifilm. A total of 310 faecal samples were tested (155 from each group). The geometric mean count of total E. coli was 5 x 10(5) and 2.5 x 10(5) CFU g(-1) for lot- and grass-fed cattle, respectively. Escherichia coli O157 was isolated from 13% of faeces with no significant difference between grass-fed (10%) and lot-fed cattle (15%). The numbers of E. coli O157 in cattle faeces varied from undetectable (

Farming Systems: Beyond Production Technologies for Dairy RD&E

The challenge of Research, Development and Extension (R,D&E) is to apply agricultural science to serve the real needs of production systems. The ideal is to have community partnerships involving a variety of stakeholders with equal representation, and a sharing in the design of R, D&E actions. R,D&E policy in Australia is stressing the participation of industry in new projects. The Dairy Research and Development Corporation (DRDC) in Australia, and the Brazilian Agricultural Research Corporation for Dairy (Embrapa Dairy), have developed initiatives to identify priorities for R,D&E design with participation of the industry. However, weaknesses in the methods have been identified. The present study describes the results of a strategy to involve a broader range of stakeholders in the identification of regional dairy industry needs. The findings show that overall communication, finance and marketing as the three major priorities of three study regions, meaning that primary needs for the industry are not in production technologies. This is an apparent contradiction with what some stakeholders considered valuable for dairy farms, which are pasture, genetics and nutrition technologies. The results reflect the large amount of research activity into production technology, and the relative success of R,D&E. However, it is necessary to consider issues beyond production technologies before developing R,D&E projects or presenting technologies.

An overview of APSIM, a model designed for farming systems simulation

The Agricultural Production Systems Simulator (APSIM) is a modular modelling framework that has been developed by the Agricultural Production Systems Research Unit in Australia. APSIM was developed to simulate biophysical process in farming systems, in particular where there is interest in the economic and ecological outcomes of management practice in the face of climatic risk. The paper outlines APSIM's structure and provides details of the concepts behind the different plant, soil and management modules. These modules include a diverse range of crops, pastures and trees, soil processes including water balance, N and P transformations, soil pH, erosion and a full range of management controls. Reports of APSIM testing in a diverse range of systems and environments are summarised. An example of model performance in a long-term cropping systems trial is provided. APSIM has been used in a broad range of applications, including support for on-farm decision making, farming systems design for production or resource management objectives, assessment of the value of seasonal climate forecasting, analysis of supply chain issues in agribusiness activities, development of waste management guidelines, risk assessment for government policy making and as a guide to research and education activity. An extensive citation list for these model testing and application studies is provided. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

Sugarcane water use from shallow water tables: implications for improving irrigation water use efficiency

The resource potential of shallow water tables for cropping systems has been investigated using the Australian sugar industry as a case study. Literature concerning shallow water table contributions to sugarcane crops has been summarised, and an assessment of required irrigation for water tables to depths of 2 m investigated using the SWIMv2.1 soil water balance model for three different soils. The study was undertaken because water availability is a major limitation for sugarcane and other crop production systems in Australia and knowledge on how best to incorporate upflow from water tables in irrigation scheduling is limited. Our results showed that for the three soils studied (representing a range of permeabilities as defined by near-saturated hydraulic conductivities), no irrigation would be required for static water tables within 1 m of the soil surface. Irrigation requirements when static water tables exceeded 1 m depth were dependent on the soil type and rooting characteristics (root depth and density). Our results also show that the near-saturated hydraulic conductivities are a better indicator of the ability of water tables below 1 m to supply sufficient upflow as opposed to soil textural classifications. We conclude that there is potential for reductions in irrigation and hence improvements in irrigation water use efficiency in areas where shallow water tables are a low salinity risk: either fresh, or the local hydrology results in net recharge. (C) 2003 Elsevier B.V. All rights reserved.

Improved photobiological H-2 production in engineered green algal cells

Oxygenic photosynthetic organisms use solar energy to split water (H2O) into protons (H+), electrons (e(-)), and oxygen. A select group of photosynthetic microorganisms, including the green alga Chlamydomonas reinhardtii, has evolved the additional ability to redirect the derived H+ and e(-) to drive hydrogen (H-2) production via the chloroplast hydrogenases HydA1 and A2 (H(2)ase). This process occurs under anaerobic conditions and provides a biological basis for solar-driven H-2 production. However, its relatively poor yield is a major limitation for the economic viability of this process. To improve H-2 production in Chlamydomonas, we have developed a new approach to increase H+ and e(-) supply to the hydrogenases. In a first step, mutants blocked in the state 1 transition were selected. These mutants are inhibited in cyclic e(-) transfer around photosystem I, eliminating possible competition for e(-) with H(2)ase. Selected strains were further screened for increased H-2 production rates, leading to the isolation of Stm6. This strain has a modified respiratory metabolism, providing it with two additional important properties as follows: large starch reserves ( i.e. enhanced substrate availability), and a low dissolved O-2 concentration (40% of the wild type (WT)), resulting in reduced inhibition of H2ase activation. The H-2 production rates of Stm6 were 5 - 13 times that of the control WT strain over a range of conditions ( light intensity, culture time, +/- uncoupler). Typically, similar to 540 ml of H-2 liter(-1) culture ( up to 98% pure) were produced over a 10-14-day period at a maximal rate of 4 ml h(-1) ( efficiency = similar to 5 times the WT). Stm6 therefore represents an important step toward the development of future solar-powered H-2 production systems.

Modelling, nitrogen dynamics in sugarcane systems: Recent advances and applications

Substantial amounts of nitrogen (N) fertiliser are necessary for commercial sugarcane production because of the large biomass produced by sugarcane crops. Since this fertiliser is a substantial input cost and has implications if N is lost to the environment, there are pressing needs to optimise the supply of N to the crops' requirements. The complexity of the N cycle and the strong influence of climate, through its moderation of N transformation processes in the soil and its impact on N uptake by crops, make simulation-based approaches to this N management problem attractive. In this paper we describe the processes to be captured in modelling soil and plant N dynamics in sugarcane systems, and review the capability for modelling these processes. We then illustrate insights gained into improved management of N through simulation-based studies for the issues of crop residue management, irrigation management and greenhouse gas emissions. We conclude by identifying processes not currently represented in the models used for simulating N cycling in sugarcane production systems, and illustrate ways in which these can be partially overcome in the short term. (c) 2005 Elsevier B.V. All rights reserved.

Soil exploration by sorghum root systems in wide row cropping systems

Wide and ‘skip row’ row configurations have been used as a means to improve yield reliability in grain sorghum production. However, there has been little effort put to design of these systems in relation to optimal combinations of root system characteristics and row configuration, largely because little is known about root system characteristics. The studies reported here aimed to determine the potential extent of root system exploration in skip row systems. Field experiments were conducted under rain-out shelters and the extent of water extraction and root system growth measured. One experiment was conducted using widely-spaced twin rows grown in the soil. The other experiment involved the use of specially constructed large root observation chambers for single plants. It was found that the potential extent of root system exploration in sorghum was beyond 2m from the planted rows using conventional hybrids and that root exploration continued during grain filling. Preliminary data suggested that the extent of water extraction throughout this region depended on root length density and the balance between demand for, and supply of, water. The results to date suggest that simultaneous genetic and management manipulation of wide row production systems might lead to more effective and reliable production in specific environments. Further study of variation in root-shoot dynamics and root system characteristics is required to exploit possible opportunities.