Physical Sciences and Mathematics Commons^™

Using Cuticular Wax Alkanes And Computer Simulation To Estimate Diet Selection, Herbage Intake And Nutrient Cycling In Grazing Sheep, H Dove, R J. Simpson

IGC Proceedings (1997-2023)

In grazing ewes, plant cuticular wax alkanes were used as markers to estimate diet selection, herbage intake, N intake and N excretion in faeces. Pasture and animal data were then used as inputs to the decision-support system GrazFeed, which simulates grazing and digestion to predict herbage intake, N intake and N excretion. Estimated and predicted intakes agreed closely, especially for N intake, and it is concluded that, subject to further investigation of the possibility that GrazFeed slightly under-estimated faecal N excretion, the close agreement between estimated and predicted OM and N intakes suggests that this combined use of alkane methods …

Modelling Leucaena Biomass Under Rainfed Production Systems Of Semiarid Regions, M. J. D. Cândido, J. L. G. Santos, A. C. R. Cavalcante, S. R. Maranhão, M. A. Santos, J. M. Osorio Leyton

IGC Proceedings (1997-2023)

The climatic variability of semiarid regions is the main source of uncertainties associated with forage and animal production, indicating a need for tools that accurately estimate forage production in order to construct a forage budgeting plan for livestock. This study simulated the biomass of Leucaena (Leucaena leucocephala) using the PHYGROW model in four locations located in Brazilian Semiarid. The work was carried out based on field data collected from 2019 to 2021. After sowing in 2018, leucaena was harvested when it reached 200 cm and to a target residual height of 70 cm. The biomass (fresh matter) was …

Linking Community And Ecosystem Ecology By Developing A Grassland Ecosystem Model (Gemini) With Interactions Between Plant, Herbivore And Soil Microbial Populations, Jean-François Soussana, S. Witzmann, P. Loiseau, S. Fontaine, Pascal Carrère, Catherine Picon-Cochard, F. Louault

IGC Proceedings (1997-2023)

Simulation models may help to understand the functional role of plant and soil biodiversity for C and N cycles and for intake by herbivores in semi-natural grassland ecosystems. Detailed models of grassland ecosystems calculate C, N, water and energy fluxes without accounting for the species dynamics in the plant and soil communities. Schwinning & Parsons (1996) proposed a simple pasture growth model that includes mixed grass and clover components. This model was, however, restricted to 2 plant functional groups and it excluded the dynamics of the soil organic matter. The role of competitive interactions between at least 2 functionally distinct …

Development Of A Model Simulating The Impact Of Management Strategies On Production From Beef Cattle Farming Systems Based On Permanent Pasture, M. Jouven, R. Baumont

IGC Proceedings (1997-2023)

Grazing systems in Europe increasingly have to meet environmental objectives, which influence management strategies. A deterministic model describing farming system dynamics is being developed in order to elucidate interactions between nature-friendly management practices, as for example late (after flowering) hay harvest or moderate stocking rate, and agricultural output.

Enhancing Grasslands Education With Decision Support Tools, Helen G. Daily, J. M. Scott, J. M. Reid

IGC Proceedings (1997-2023)

We have successfully used Decision Support Tools (DST) relevant to the management of grazing enterprises to enhance problem solving skills of undergraduates in Australia. Tools such as GrassGro^tm (Moore et al., 1997) and GrazFeed^tm (Freer et al., 1997) are accessed from a central server by authorised users at many widely dispersed Universities across Australia using remote access to thin-client technology via an Internet portal. This has been supplemented with training for lecturers. Experience in developing appropriate teaching and learning materials and the reliable delivery of simulation software to many clients has enhanced learning outcomes at tertiary …

Systems Simulation Assists Land Capability Estimation In Australia’S Temperate Grasslands, Richard J. Simpson, L. Salmon, P. Graham, A. D. Moore, A. Stefanski, D. J. Marshall, J. R. Donnelly

IGC Proceedings (1997-2023)

Intensification of production in the water-limited grasslands of temperate Australia has increased the need to quantify their sustainable carrying capacity. Empirical rainfall-based rules for estimating stocking rate fail when used in districts with differing weather patterns, or when soil and pasture resources limit the utilisation of rainfall. Grazing systems simulation should help to overcome these problems because local conditions can be taken into account. This study investigated the impact of soil resources on potential stocking rate, profitability and production risk in a local climatic area of the southern tablelands of NSW, Australia.

Evaluating The Economic And Environmental Sustainability Of Integrated Farming Systems, C. A. Rotz, M. A. Sanderson, M. Wachendorf, F. Taube

IGC Proceedings (1997-2023)

Economic and environmental sustainability has become a major concern for forage-based animal production in Europe, North America and other parts of the world. Development of more sustainable farming systems requires an assimilation of experimental and modelling research. Field research is critical for supporting the development and evaluation of models, and modelling is needed to integrate farm components for predicting the long-term effects and interactions resulting from farm management changes. Experimentally supported simulation provides a tool for evaluating and comparing farming strategies and predicting their effect on the watershed, region and beyond.

Development Of A Model Simulating The Impact Of Management Strategies On Production From Beef Cattle Farming Systems Based On Permanent Pasture, M. Jouven, R. Baumont

IGC Proceedings (1997-2023)

Grazing systems in Europe increasingly have to meet environmental objectives, which influence management strategies. A deterministic model describing farming system dynamics is being developed in order to elucidate interactions between nature-friendly management practices, as for example late (after flowering) hay harvest or moderate stocking rate, and agricultural output.

A New Agro-Meteorological Simulation Model For Predicting Daily Grass Growth Rates Across Ireland, R. P. O. Schulte

IGC Proceedings (1997-2023)

Grass growth rates and herbage yields depend on weather conditions, soil characteristics and grassland management and differ from year to year and from site to site. In the past, grass growth has been predicted using both mechanistic and statistical models. The accuracy of mechanistic models is commonly insufficient for practical application, while statistical models generally apply to one test site only (e.g. Han et al., 2003). In this paper a semi-empirical grass growth model is presented which is numerically accurate, but which can be applied to contrasting sites across Ireland at the same time.

Enhancing Grasslands Education With Decision Support Tools, H. G. Daily, J. M. Scott, J. M. Reid

IGC Proceedings (1997-2023)

We have successfully used Decision Support Tools (DST) relevant to the management of grazing enterprises to enhance problem solving skills of undergraduates in Australia. Tools such as GrassGro™ (Moore et al., 1997) and GrazFeed™ (Freer et al., 1997) are accessed from a central server by authorised users at many widely dispersed Universities across Australia using remote access to thin-client technology via an Internet portal. This has been supplemented with training for lecturers. Experience in developing appropriate teaching and learning materials and the reliable delivery of simulation software to many clients has enhanced learning outcomes at tertiary level. We …

Using The Grassgro Decision Support Tool To Evaluate The Response In Grazing Systems To Pasture Legume Or A Grass Cultivar With Improved Nutritive Value, H. Dove, J. R. Donnelly

IGC Proceedings (1997-2023)

Decision support tools (DST) based on models of grazing systems allow the evaluation of changes in enterprise management on productivity and profitability. The Grassgro DST (Moore et al., 1997) uses historical weather data on a daily time step to simulate pasture growth and the resultant productivity of either grazing sheep or cattle. Different pasture species are represented within a parameter set that describes the response of pasture species to their environment. Manipulation of these parameters provides a means of evaluating, a priori, the likely responses of livestock production to ‘improved cultivars’. We report the results of simulations conducted …

Pasture Land Management System Decision Support Software, G. E. Groover, S. R. Smith, N. D. Stone, J. J. Venuto, J. M. Galbraith

IGC Proceedings (1997-2023)

Controlled or rotational grazing provides benefits to producers and society through profitable and sound management of grazing land and livestock. Pasture land management system (PLMS) is a decision support system developed to help university, government, and professionals provide technical pasture management assistance to beef and dairy producers. The PLMS focuses on the balance between seasonal forage supply and nutrient demand in a dairy or beef cattle operation. It allows users to explore and compare alternatives (dividing fields into multiple paddocks, changing stocking rates, and forage species) through a visual display and embedded simulation. Users enter a description of the farm …

Grass Growth Modelling: To Increase Understanding And Aid Decision Making On-Farm, P. D. Barrett, A. S. Laidlaw

IGC Proceedings (1997-2023)

Key points

1. Crop and grass growth models have been developed over the last 50 years, or so, but general appreciation of their benefits and potential has been recognised only relatively recently. The most popular application of grass growth models has traditionally been for knowledge understanding.

2. There is growing awareness of the potential of models in decision support systems (DSS) applications to aid pasture management and grassland budgeting on dairy farms.

3. Although some models have been developed for DSS, their widespread uptake in industry has been slow; challenges still exist which need to be addressed in order to improve their precision …

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Adoption And Influence: Industry Evaluation Of The GrassgroTm Decision Support Tool, E. M. Salmon, A. D. Moore

IGC Proceedings (1997-2023)

The GrassGro Decision Support tool (DS tool) (Donnelly and Moore, 1999) was released for commercial use in Australia with a training package in late 1997. An assessment of its adoption was made by a survey of 53 registered users in March 1999. An evaluation of the software and training package was made at training workshops by 92 users between 1997 and December 1999. The response rates to the survey and the evaluation were 62% and 82% respectively. Seventy six percent of survey respondents had analysed at least one problem with GrassGro and 27% had applied GrassGro to five or more …

The Role Of Forages In Sustainable Cropping Systems Of Southern Australia, William D. Bellotti

IGC Proceedings (1997-2023)

The historical context, recent trends, and possible future role of forages in cropping systems are reviewed. Three recent themes will be developed: 1) The successful exploitation of genetic diversity resulting in commercial development of new legume species as pasture cultivars with specific traits better suited to the needs of current farming systems. 2) Improved understanding of key soil processes under grazed pastures, particularly soil water and soil nitrogen, and how these processes impact on indicators of sustainability like deep drainage and nitrate leaching. 3) An emerging capacity for predicting the effect of pasture-crop sequences on soil processes, crop growth and …

Simulation Of Alternative Plans For Community Based Goat Breeding Program In Arid, Semi-Arid And Mixed Production Systems In Ethiopia, T. Jembere, Barbara Rischkowsky, T. Dessie, K. Kebede, A. Okeyo Mwai, T. Mirkena, A. Haile

IGC Proceedings (1997-2023)

On station small ruminant researches in Ethiopia were ineffective due to various factors. As alternative, community based breeding program (CBBP) has emerged. In the current CBBPs, sire side selection only (SN1) is practiced. The objective of the present work was to compare SN1 by simulating alternative breeding scenarios for Abergelle (AB), Centeral Highland (CH) and Woyto-Guji (WG) goat breeds in Ethiopia. Three scenarios including selection on dam side (SN2) in addition to SN1, application of genomic selection (SN3) onto SN1 and use of sires from SN1 for mating in additional flocks (SN4) were simulated and compared with SN1 based on …

Simulation Of Alfalfa Production With Epic, L. Chun, X. Xin, H. Tang

IGC Proceedings (1997-2023)

No abstract provided.

Integrating Dual‐Purpose Wheat Crops Into Different Sheep Production Systems In Southern Australia: Impacts On Livestock, Economic Returns And Risk, Andrew D. Moore, H. Dove, W. M. Kelman

IGC Proceedings (1997-2023)

No abstract provided.

Ever Graze‐Prime Lamb Production On Perennial Based Grasslands In Southwest Australia, Paul Sanford, J. Ryan, P. Jakobsson, E. Dobbe, E. Mccready

IGC Proceedings (1997-2023)

No abstract provided.

Pasture Growth Forecasts For Temperate Regions In Southeastern Australia, Brendan R. Cullen, Richard J. Eckard, I. R. Johnson

IGC Proceedings (1997-2023)

No abstract provided.

Dot: Gene-Set Analysis By Combining Decorrelated Association Statistics, Olga A. Vsevolozhskaya, Min Shi, Fengjiao Hu, Dmitri V. Zaykin

Biostatistics Faculty Publications

Historically, the majority of statistical association methods have been designed assuming availability of SNP-level information. However, modern genetic and sequencing data present new challenges to access and sharing of genotype-phenotype datasets, including cost of management, difficulties in consolidation of records across research groups, etc. These issues make methods based on SNP-level summary statistics particularly appealing. The most common form of combining statistics is a sum of SNP-level squared scores, possibly weighted, as in burden tests for rare variants. The overall significance of the resulting statistic is evaluated using its distribution under the null hypothesis. Here, we demonstrate that this basic …

Economic Review Of Pasture Development Options For North Australian Beef Enterprises, Neil D. Macleod, Dianne Mayberry, Lindsay Bell, Ian Watson

IGC Proceedings (1997-2023)

Beef cattle grazing (~14 million head) native pastures is the dominant economic use of northern grazing lands (2.3 million km2). Few enterprises make positive economic returns in most years or achieve the necessary productivity gains (~2% per annum) to offset an ongoing cost-price squeeze (McCosker et al., 2010). A significant contributor to poor performance is low reproductive performance, management of first calving heifers, calf growth and weaning rates and liveweight gain - linked to nutrition and the low quality of pastures. Pasture development technologies (Gramshaw and Walker, 1988) are available but uptake has been poor. Three pasture development options …

Improved Modelling Of Lucerne (Medicago Sativa L.) Production For Grazing Livestock, Andrew Smith

IGC Proceedings (1997-2023)

Lucerne (or alfalfa; Medicago sativa L.)-based pastures play an important role in livestock and mixed farms (croplivestock) in Australia. If lucerne is to be more widely adopted, it will be important that landholders are able to plan to maximize its benefits to their livestock enterprises (usually as a part of a diverse feed base), as well as assess the benefits and minimizing the costs of lucerne phases to subsequent crops. However, the ability to accurately model lucerne plant physiology across the full spectrum of environments, genotypes and cultivars remains elusive. This study aimed to review and revise the description of …

Modelling Complex Sheep Systems Using Ausfarm, Susan M. Robertson, Michael A. Friend

IGC Proceedings (1997-2023)

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 …

Challenges And Techniques For Simulating Line Emission, Karen P. Olsen, Andrea Pallottini, Aida Wofford, Marios Chatzikos, Mitchell Revalski, Francisco Guzmán, Gergö Popping, Enrique Vázquez-Semadeni, Georgios E. Magdis, Mark L. A. Richardson, Michaela Hirschmann, William J. Gray

Physics and Astronomy Faculty Publications

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a …

Parallelization Of A Three-Dimensional Full Multigrid Algorithm To Simulate Tumor Growth, Dylan Goodin, Chin F. Ng, Hermann B. Frieboes

Commonwealth Computational Summit

We present the performance gains of an openMP implementation of a fully adaptive nonlinear full multigrid (FMG) algorithm to simulate three-dimensional multispecies desmoplastic tumor growth on computer systems of varying processing capabilities. The FMG algorithm is applied to solve a recently published thermodynamic mixture model that uses a diffuse interface approach with fourth-order reaction-advection-diffusion PDEs (Cahn-Hilliard-type equations) that are coupled, nonlinear, and numerically stiff. The model includes multiple cell species and extracellular matrix (ECM), with adhesive and elastic energy contributions in chemical potential terms, as well as including blood and lymphatic vessels represented as continuous vasculatures. Advection-reaction-diffusion PDEs are employed …

Simulating Within-Vector Generation Of The Malaria Parasite Diversity, Lauren M. Childs, Olivia F. Prosper

Mathematics Faculty Publications

Plasmodium falciparum, the most virulent human malaria parasite, undergoes asexual reproduction within the human host, but reproduces sexually within its vector host, the Anopheles mosquito. Consequently, the mosquito stage of the parasite life cycle provides an opportunity to create genetically novel parasites in multiply-infected mosquitoes, potentially increasing parasite population diversity. Despite the important implications for disease transmission and malaria control, a quantitative mapping of how parasite diversity entering a mosquito relates to diversity of the parasite exiting, has not been undertaken. To examine the role that vector biology plays in modulating parasite diversity, we develop a two-part model framework …

Using The Vehicle Routing Problem To Reduce Field Completion Times With Multiple Machines, Hasan Seyyedhasani, Joseph S. Dvorak

Biosystems and Agricultural Engineering Faculty Publications

The Vehicle Routing Problem (VRP) is a powerful tool used to express many logistics problems, yet unlike other vehicle routing challenges, agricultural field work consists of machine paths that completely cover a field. In this work, the allocation and ordering of field paths among a number of available machines has been transformed into a VRP that enables optimization of completion time for the entire field. A basic heuristic algorithm (a modified form of the common Clarke-Wright algorithm) and a meta-heuristic algorithm, Tabu Search, were employed for optimization. Both techniques were evaluated through computer simulations in two fields: a hypothetical basic …

Assessing The Probability That A Finding Is Genuine For Large-Scale Genetic Association Studies, Chia-Ling Kuo, Olga A. Vsevolozhskaya, Dmitri V. Zaykin

Olga A. Vsevolozhskaya

Genetic association studies routinely involve massive numbers of statistical tests accompanied by P-values. Whole genome sequencing technologies increased the potential number of tested variants to tens of millions. The more tests are performed, the smaller P-value is required to be deemed significant. However, a small P-value is not equivalent to small chances of a spurious finding and significance thresholds may fail to serve as efficient filters against false results. While the Bayesian approach can provide a direct assessment of the probability that a finding is spurious, its adoption in association studies has been slow, due in part to the ubiquity …

Functional Analysis Of Variance For Association Studies, Olga A. Vsevolozhskaya, Dmitri V. Zaykin, Mark C. Greenwood, Changshuai Wei, Qing Lu

Olga A. Vsevolozhskaya

While progress has been made in identifying common genetic variants associated with human diseases, for most of common complex diseases, the identified genetic variants only account for a small proportion of heritability. Challenges remain in finding additional unknown genetic variants predisposing to complex diseases. With the advance in next-generation sequencing technologies, sequencing studies have become commonplace in genetic research. The ongoing exome-sequencing and whole-genome-sequencing studies generate a massive amount of sequencing variants and allow researchers to comprehensively investigate their role in human diseases. The discovery of new disease-associated variants can be enhanced by utilizing powerful and computationally efficient statistical methods. …