Graze: A model of selective grazing by beef animals

Loewer, O. J.; Taul, K.L.; Turner, Loren; Muntifering, Russell B.

doi:10.1016/0308-521x(87)90040-0

Cited by 28 publications

(10 citation statements)

References 13 publications

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“…These include the Alberta Beef Production Simulation System (Pang et al, 1999), a cow-calf model for Montana rangeland (Tess and Kolstad, 2000), a cow-calf operation in Nebraska (Werth et al, 1991), and an integrated production system in eastern Canada (Koots and Gibson, 1998). More comprehensive models include "SPUR" for simulating beef production in rangeland ecosystems (Carlson and Thurow, 1996) and "GRAZE" for simulating intensive production in humid climates (Loewer et al, 1987). The scope of the farm system is limited in each of these models, however, and nutrient management and its resulting effect on the environment are not addressed.…”

Section: Introductionmentioning

confidence: 99%

A beef herd model for simulating feed intake, animal performance, and manure excretion in farm systems1

Rotz

Buckmaster

Comerford

2005

Journal of Animal Science

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A beef herd submodel was created for integration with other farm components to form a whole-farm model capable of simulating a wide range of beef production systems. This herd submodel determined the best available feed or feed mix to meet the fiber, energy, and protein requirements for each of up to six animal groups on the farm. The groups comprised any combination of cows, nursing calves, young heifers, yearling heifers, stockers, and finishing cattle. Protein, energy, and mineral requirements were determined for each group using the Cornell Net Carbohydrate and Protein System, Level 1. Diets were formulated to meet these requirements with available feeds, and the resulting feed intake, growth, and manure DM and nutrient (N, P, and K) excretions were predicted. Required feed characteristics included CP, ruminally degradable protein, acid detergent insoluble protein, NDF, P, and K concentrations. Feed intake was predicted by considering energy intake, potentially limited by fill, and exceeding a minimum roughage requirement. Fill and roughage limits were functions of feed NDF concentrations adjusted to consider particle size distribution and the relative rate of ruminal digestibility or the physical effectiveness of the fiber. The herd submodel was verified to predict feed intakes, nutrient requirements, diets, and manure excretions similar to those recommended or measured for beef animals. Incorporation of the beef herd submodel with other farm components, including crop growth (alfalfa, grass, corn, small grain, and soybean), harvest, storage, feeding, grazing, and manure handling, provided the Integrated Farm System Model. This comprehensive farm-simulation model is a useful research and teaching tool for evaluating and comparing the long-term performance, economics, and environmental impact of beef, dairy, and crop production systems.

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Section: Introductionmentioning

confidence: 99%

A beef herd model for simulating feed intake, animal performance, and manure excretion in farm systems1

Rotz

Buckmaster

Comerford

2005

Journal of Animal Science

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“…La producción de calor metabólico es directamente controlada por el sistema nervioso central (Hammel 1968), por el sistema endocrino a través de la modificación del apetito y procesos digestivos, e indirectamente por alteraciones de la actividad de enzimas respiratorias y síntesis de proteína (Yousef 1985). A la fecha existen diversos estudios que intentan predecir el balance térmico del ganado en condiciones de producción comercial (Bakken 1976, McArthur 1987, Loewer 1998 . Sin embargo, la mayoría de los modelos basa sus resultados en una serie de supuestos en torno a variables fisiológicas involucradas en el balance térmico, existiendo en la práctica una gran variabilidad en la respuesta entre animales.…”

Section: Balance Termico Y Temperatura Corporalunclassified

Factores climáticos que afectan el desempeño productivo del ganado bovino de carne y leche

2008

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SUMMARYThe effect of climate on dairy and beef cattle is variable and complex because it affects the environment in which the animals are raised and reproduced. Its influence on animal welfare and production have been recognized and studied since 1950's. Climate affects livestock directly and indirectly, since it modifies the quality and/or quantity of food available, the requirements of water and energy, and the amount of energy consumed and the use of it. The animals cope with these adverse conditions of climate by altering physiological and behavioral mechanisms in order to maintain their body temperature within a normal range. As a result it is possible to observe changes in the food intake, behavior and productivity. These changes are magnified under extreme conditions of heat or cold, implying drastic reductions in the indices of production, such as average daily gain and daily milk production. Most of the research conducted in this area has been done mainly in controlled environmental chambers, with emphasis on the animal response and its productivity. Currently, the major scientific focus is on the development of thermal stress indices as practical tools for cattle handling under unfavorable environmental conditions. The objectives of this review are to describe and discuss the most important climatic factors affecting cattle performance as well as the major mitigation alternatives. It also presents a brief overview of the research carried out in Chile and possible lines of research in this field.Palabras clave: estrés, ganado de leche y carne, bienestar animal, factores climáticos. INTRODUCCIONAlgunos de los principales resultados de la actividad antropogénica han sido el incremento de los niveles atmosféricos de CO 2 , las alteraciones de las propiedades biológicas y químicas del suelo, así como el continuo uso y cambio de uso de la tierra (Vitousek 1994). En su conjunto estos hechos han provocado cambios climáticos a través del planeta aumentando las temperaturas mínimas y máximas para el período 1951 -1990 (Karl y col 1993. Esta asimetría entre mínimas y máximas ha sido detectada a través de todas las estaciones del año en el planeta, particularmente en las regiones del hemisferio norte. Asimismo, diversos modelos climáticos pronostican cambios en el clima del mundo, con un aumento en la concentración de CO 2 atmosférico, incrementos de temperaturas y cambios en la distribución de las precipitaciones (Klohn y Faurès 2006). Las estimaciones de incremento en la temperatura superficial media global son de un rango de 1,5 a 4,5 °C (Khalifa 2003). Todo esto tendría profundos efectos en la producción agropecuaria y de alimentos tanto para los animales como para el ser humano. Schimmelpfennig y col (1996) reportaron la existencia de numerosos informes que indican potenciales daños a los animales en función de los cambios de clima proyectados. El efecto del clima en la producción animal ha sido estudiado desde hace aproximadamente medio siglo, lográndose importantes avances en el entendimiento de los aspec...

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“…In addition to dry matter intake, diet selection has been modeled by several authors. Loewer et al . (1987) proposed selective grazing logic to interface their plant model and animal model, and Senft (1989) proposed a hierarchical foraging model which incorporated the effects of palatability and relative and absolute availability of feed plants on ruminant foraging behavior.…”

Section: Introductionmentioning

confidence: 99%

Systems approaches to beef cattle production systems using modeling and simulation

Hirooka

2010

Animal Science Journal

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Systems approach techniques have been applied to modeling production systems for beef cattle from the relatively micro-level of tissues and organs to the macro-level of farms and geographical regions. This paper reviews the various types of beef cattle production models already in operation in order to analyze beef cattle production systems and their components. It may be theoretically possible to construct system models which describe such complex production systems and can be generally used in various genetic, nutritional, management and economic situations as well as in training, extension and educational programs. Moreover, the systems approach can assist in the organization of information and identification of knowledge gaps and thereby open an avenue to multi-disciplinary research projects.

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Graze: A model of selective grazing by beef animals

Cited by 28 publications

References 13 publications

A beef herd model for simulating feed intake, animal performance, and manure excretion in farm systems1

A beef herd model for simulating feed intake, animal performance, and manure excretion in farm systems1

Factores climáticos que afectan el desempeño productivo del ganado bovino de carne y leche

Systems approaches to beef cattle production systems using modeling and simulation

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