The Model webpage presents a comprehensive collection of nutrition models, analytical tools, and educational software developed for ruminant production systems. It includes major nutrition modeling platforms such as the Ruminant Nutrition System (RNS), Large and Small Ruminant Nutrition Systems (LRNS and SRNS), and the NRC-based beef and dairy requirement models.
Additional tools support growth and body composition analysis, individual animal value prediction, model evaluation, fiber digestion and gas production fitting, feeding behavior analysis, and ruminal pH dynamics. The site also features educational system-dynamics games designed to support teaching and decision-making in animal production.
Commonly used modeling terminology can be found here.
Nutrition Models
The Ruminant Nutrition System (RNS) is a comprehensive nutrition model that integrates cattle, sheep and goats into one platform. The RNS was developed to provide a framework that can be used for incorporating and implementing new scientific knowledge and submodels to more accurately predict nutrient requirements and biological values for ruminants currently used in food production. The RNS has a modern design and interface that uses an integrated object-oriented programming approach to allow for quicker and customized simulations. The RNS structure permits power users to expand their simulation routines through the R script programming.
The Large Ruminant Nutrition System (LRNS) is a computer program that estimates beef and dairy cattle requirements and nutrient supply under specific conditions of animal type, environment (climatic factors), management, and physicochemical composition of available feeds, using the computational engine of the Cornell Net Carbohydrate and Protein System (CNCPS) model as published by Fox et al. (2004).
The Small Ruminant Nutrition System (SRNS) model is the result of a joint collaboration among Texas A&M University, Cornell University, and Sassari University. The SRNS is a computer model to predict nutrient requirements of sheep and feed biological values on farms based on the structure of the Cornell Net Carbohydrate and Protein System (CNCPS) for Sheep.
The Beef Cattle Nutrient Requirements Model 2016 was developed to demonstrate the use of the empirical (ELS) and mechanistic (MLS) levels of solution in the calculations of the dietary supply and requirements of beef cattle for energy and nutrients (Chapter 19) of the 8th revised edition of the Nutrient Requirements of Beef Cattle.
The Beef Cattle Nutrient Requirements Model by the National Research Council (NRC, 1996, 2000) software was originally developed for Microsoft Disk Operating System (MS-DOS) or Personal Computer Disk Operating System (PC-DOS) of Intel x86 computers. Unfortunately, the software is incompatible with newer operating systems, such as Microsoft Windows XP, Windows Vista, Windows 7, and Windows 8, running on either 32-bit or 64-bit machines. Under the auspices of the National Animal Nutrition Program (NANP)⸻a National Research Support Project (NRSP-9) that started in 2010 and is supported by the Experiment Station Committee on Organization and Policy, the State Agricultural Experiment Stations, and Hatch Funds provided by the National Institute of Food and Agriculture, U.S. Department of Agriculture⸻the Nutrition Modeling Committee used DOSBox to allow users to continue using the Beef NRC (1996, 2000) software in modern computers and operational systems.
The Dairy Cattle Nutrient Requirements Model by the National Research Council (NRC, 2001)was developed using Microsoft Visual Basic 6. Under the auspices of the National Animal Nutrition Program (NANP)⸻a National Research Support Project (NRSP-9) that started in 2010 and is supported by the Experiment Station Committee on Organization and Policy, the State Agricultural Experiment Stations, and Hatch Funds provided by the National Institute of Food and Agriculture, U.S. Department of Agriculture⸻the Nutrition Modeling Committee performed several fixes in the original software to allow users to continue using the Dairy NRC (2001) software in modern computers and operational systems.
Growth and Development Models
The Cattle Value Discovery System (CVDS) was developed for use in individual cattle management for growing beef cattle. The CVDS provides (1) prediction of daily gain, incremental cost of gain and days to finish to optimize profits and marketing decisions while marketing within the window of acceptable carcass weights and composition, (2) predictions of carcass composition during growth to avoid discounts for under or over weight carcasses and excess backfat, and (3) allocation of feed fed to pens to individual animals for the purpose of sorting of individuals into pens by days to reach target body composition and maximum individual profitability.
The Modelo de Composição Corporal de Gado de Corte (MCCGC: Beef Cattle Body Composition Model) was developed to simulate body and gain compositions of growing beef cattle based on the growth model developed by Keele et al. (1992) and Williams et al. (1992). The model allows users to evaluate the impact of different plane of nutrition on the composition of the gain that are not associated with changes in empty body weight. This computer program was originally developed in Portuguese using Visual Basic 4 in 1997, and revamped using Visual Basic 6 in 2019 and revised in 2023.
Model Evaluation and Adequacy
The Model Evaluation System (MES) was developed to assist on the adequate evaluation of mathematical models using statistical analysis, including linear regression analysis, mean square error of the prediction, concordance correlation coefficient, distribution analysis, deviation analysis, graphics and histogram, robust statistics, and many more statistics.
Fitting Models
The Gamma Distribution-like Degradation and Passage Models (GnG1) was developed based on theoretical concepts and probability to generalize the rumen processes of fiber digestion, assuming a gamma distribution. It can be used to interpret fiber degradation and passage profiles. The GnG1 model was evaluated for quality of fit using in vitro fiber degradation profiles and in vivo fiber passage profiles. The integration of digestion and passage is based on the concept that fibrous digesta in the rumen is heterogeneous (Vieira et al., 2007a,b,c).
The in vitro gas production technique has been frequently used to assess biological values of feeds based on their pattern of accumulated gas during incubation with rumen fluid under anaerobic conditions. After data is collected, kinetic parameters that accurately describe the pattern of fermentation can be obtained. Several models have been described and used to fit in vitro gas production data to nonlinear functions (López et al., 1999). The GasFit System was developed to evaluate several nonlinear models in fitting gas production data.
A mechanistic model is presented to adjust the fractional rate of fermentation of available fiber based on the estimate of unavailable fiber and the computed theoretical unavailable fiber using lignin content. The object of this computer program is to generate a system by which values for rate of digestion and its retardation can be predicted and used in the field. At the present time there is no system for deriving digestion rates apart from those in the feed dictionary. Analytical values available in the field, include NDF, ADF, lignin, crude protein (CP) and sometimes in vitro digestibility at 24 or 30 h. Rates of digestion and DU will need to be predicted from these observations.
The Meal Criterion Calculation (MCC) software was designed to analyze cattle feeding behavior data collected by the GrowSafe System to compute feedbunk visit interval (BVI) and meal criterion (MC). MC is the longest non-feeding time that defines a meal. It is calculated as the intersection of two distributions: the non-feeding time within a meal and the non-feeding time between meals. MCC works with different distribution forms (normal, gamma, log-normal, Weibull) and unlimited number of animals and data records.
The Area and Time Under and Above the Curve (ATAUC) is a comprehensive analytical tool designed to evaluate ruminal pH measurements collected from indwelling sensors. The program imports data from Excel files and processes time-series pH data with support for multiple user-defined threshold limits, generating detailed visualizations and statistical summaries of ruminal pH evolution over time. ATAUC handles data from multiple sensors within the same animal by implementing advanced smoothing transitions between consecutive sensors, with adjustable time periods for preceding sensors to ensure continuous pH values. The analysis offers flexible interpolation and spline calculation methods, customizable plotting parameters, and options for polygon visualization of pH variations. ATAUC calculates trend lines, areas under (AUC) and above (AAC) thresholds. The program supports multiple classification variables for grouped analysis.
Games
The Hay Game is a stand-alone computer software based on the Beer Game. The Beer Game was developed to introduce students, managers, and executives to concepts of system dynamics. The purpose of the game is to illustrate the key principle that "structure produces behavior." Players of the Hay Game experience system complexity and provides insights of the long-term effects during the course of the game. The objective of the Hay Game is to minimize the total cost of hay utilization in a farm.
Nim is a classical, simple game of logic and strategy, but with finite possibilities. The rule is that you may remove as many matches within a row in one move. The looser is who removes the last match on the table. There are several variations of the Nim game, including different objects, rules (winner is the one that removes the last object), number of rows of objects, max number of objects that can be removed at a time, and amount of objects.
Utilities
The Personal Vault System (PVS) is a secure, locally managed desktop application designed to store, organize, and protect sensitive personal information such as account credentials, private notes, and encrypted content within an encrypted vault file. It uses strong, modern cryptography—centered on AES-256 encryption with password-derived keys—to ensure that all data remains confidential and tamper-resistant, accessible only with the user’s master password. PVS emphasizes full user control by keeping all data local, never storing passwords, and providing practical tools such as password generation, duplicate detection, flexible search and filtering, and customizable views, making it a robust yet approachable solution for personal data security.
The DocViewer is a Windows desktop component that allows users to open and view common document types directly within the application, without relying on external programs. It is designed to handle PDF, Word documents, rich text files, plain text files, and HTML in a consistent and user-friendly way. Whenever possible, documents are displayed as PDF to ensure reliable formatting, printing, and long-term compatibility. For files that are not already PDF, the DocViewer automatically converts them behind the scenes before displaying them. When documents are very large or web-based, it can switch to a built-in browser view to maintain performance and stability. Overall, the DocViewer provides a robust, self-contained solution for reading, printing, and exporting documents inside a Windows application.
This PDFViewer is a simple Windows application that allows users to open and view PDF documents in a dedicated viewer window. A PDF can be opened automatically when the program starts or selected manually through a standard file dialog. For very large PDF files, the program warns the user and offers the option to open the document in the system’s default PDF application instead. While a document is loading, the viewer displays status messages so users know progress is being made. The program also includes basic features such as saving, printing, and checking for software updates, making it a practical tool for everyday PDF viewing.
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