Modelling Complex Sheep Systems Using AusFarm

Simulation modelling can be a valuable method for extrapolating experimental findings to different weather or management conditions. However, most of the decision support tools which are available for sheep grazing systems, for example GrassGro® (Donnelly et al. 1997), are limited to modelling of relatively simple sheep management. This makes validation of simulations against experimental results difficult where management changes from year to year, and where more complex sheep management is used. This study evaluated the use of the AusFarm® decision support tool (Moore et al. 2007) to model a split-joined sheep system, using different ram breeds against experimental results

Describing the Sward Structure of Wheat and Annual Ryegrass Swards Grazed by Lambs in Southern NSW

Dual-purpose wheats are now an established part of the feed base on many mixed-farms in southern NSW. However agronomic practices can vary and it is unknown whether row spacing will impact the availability of forage for grazing by sheep. Intake has been shown to be affected by a range of factors including tiller length, pasture height, sward density and pasture mass (Allden and Whittaker 1970; Black and Kenney 1984). This study sought to describe the differences in sward structure of grazed wheat swards at two different row spacings in terms of mean height, row height and bulk density and compare this to an annual ryegrass pasture presented as a continuous pasture

Does Targeted Short-Term Grazing of Lucerne Increase Twinning Rates in Unsynchronised Merino Ewes?

Reproduction is one of the key profit drivers in the sheep industry and increased reproductive output is needed to address the decline in sheep numbers in Australia to maintain supply to export markets (Curtis 2009). Increased nutrition around mating, or ‘flushing’, is a well-known means of increasing twinning rates. Studies using synchronisation methods have shown that short-term (acute) supplementation can increase prolificacy if targeted at days 9-14 of the oestrous cycle (Stewart and Oldham 1986). However, synchronisation involves increased chemical and labour costs, so may not suit extensive production systems. This study aimed to test whether an increase in twinning rate was possible using a short-term grazing of lucerne pasture in unsynchronised ewes

The Role Modelling and Farming Systems Research Can Play in Redesigning Grazing Systems for Improved Productivity and Environmental Sustainability

Achieving production and natural resource outcomes from farming systems is critical with growing demand for livestock products, increasing pressure on land and water resources and the desire of farmers to improve profit and standard of living. In many countries this brings to the fore a number of policy dilemmas and conflicts in terms of pastoral household livelihood, regional economic growth and development, as well as natural resource management. By using two case studies; (1) Temperate Grasslands in Southern Australia (EverGraze project); and (2) Western Grasslands in North West China (ACIAR project), this paper considers how farming systems can be redesigned for production and environmental outcomes using modelling and farming systems research. Farming systems, as well as the regions and economies in which they operate, are complex and under constant change. The use of models combined with good science, relevant data and regional validation is essential to examine alternative systems that are better suited to changed operating conditions. Bio-economic modelling helps to understand trade-offs between production and enterprise performance and environmental sustainability over time and, most importantly, where multiple benefits from farming systems are possible. We contend that it is possible to redesign farming systems with both enterprise and environmental sustainability in mind. However the approach used to design and test alternative farming systems is important in an era of declining research resources and increasing complexity

EverGraze: A Partnership between Researchers, Farmers and Advisors to Deliver Effective Grassland Management

The profitable and sustainable management of livestock production from grassland systems is challenging and it can be difficult to develop a research structure that addresses farmer’s needs and has acceptable rigour and on-ground impact. This paper describes the attributes of research, development and extension (RD&E) programs that are required for a successful partnership between researchers, farmers and advisors. Insights are provided from the EverGraze program that designed, tested and implemented farming systems based on perennial pastures across southern Australia. With this project farmers and advisors were involved in setting research direction, designing experiments, providing strategic guidance over the management of the systems experiments and then the synthesis of regionally applicable key messages. This involvement ensured the relevance of the research and aided in the extension and uptake of the information. The result has been an effective partnership between researchers, farmers and advisors that had a high level of impact across the high rainfall zone (HRZ) of southern Australia, with 1950 farmers or ~8% of those in the HRZ documented as having changed practice over an area of 816,000 ha over a five year period (2009 to 2014)

Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron Features Identified in the Sloan Digital Sky Survey

Two newly identified magnetic cataclysmic variables discovered in the Sloan Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5, have spectra showing highly prominent, narrow, strongly polarized cyclotron humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs, respectively. In the former, the spacing of the humps indicates the 3rd and 4th harmonics in a magnetic field of ~60 MG. The narrowness of the cyclotron features and the lack of strong emission lines imply very low temperature plasmas and very low accretion rates, so that the accreting area is heated by particle collisions rather than accretion shocks. The detection of rare systems like these exemplifies the ability of the SDSS to find the lowest accretion rate close binaries.Comment: Accepted for publication in the Astrophysical Journal, vol. 583, February 1, 2003; slight revisions and additions in response to referee's comments; 17 pages, 6 figures, AASTeX v4.

Impact of Orientational Glass Formation and Local Strain on Photo-Induced Halide Segregation in Hybrid Metal-Halide Perovskites.

Band gap tuning of hybrid metal-halide perovskites by halide substitution holds promise for tailored light absorption in tandem solar cells and emission in light-emitting diodes. However, the impact of halide substitution on the crystal structure and the fundamental mechanism of photo-induced halide segregation remain open questions. Here, using a combination of temperature-dependent X-ray diffraction and calorimetry measurements, we report the emergence of a disorder- and frustration-driven orientational glass for a wide range of compositions in CH3NH3Pb(Cl x Br1-x )3. Using temperature-dependent photoluminescence measurements, we find a correlation between halide segregation under illumination and local strains from the orientational glass. We observe no glassy behavior in CsPb(Cl x Br1-x )3, highlighting the importance of the A-site cation for the structure and optoelectronic properties. Using first-principles calculations, we identify the local preferential alignment of the organic cations as the glass formation mechanism. Our findings rationalize the superior photostability of mixed-cation metal-halide perovskites and provide guidelines for further stabilization strategies

Use of Preclinical Models to Improve Treatment of Retinoblastoma

Dyer and colleagues examine the most promising preclinical models that recapitulate the molecular, genetic, and cellular features of retinoblastoma