Edward M. Smith

A body composition model for predicting beef animal growth

Abstract Two beef animal growth computer simulations were compared as to the effects of altering feed energy density. Steers of varying initial degrees of fatness were evaluated. The BEEF-NC114 model used NRC regression equations to predict growth while the BEEF-S156 model used physiological age and body components. Otherwise, the models were essentially identical. On average, the predictions of both models were reasonably close to each other. However, the BEEF-S156 model was more sensitive to extreme conditions of high or low nutrition.

Mathematical-Logic to Simulate the Growth of Two Perennial Grasses

ABSTRACT MATHEMATICAL-logic was developed to reflect the relationships between growth (accumulation of dry matter) and air temperature, day length, leaf area, photoperiod, and rainfall. These relationships were incorporated in a nonspecific crop growth model (GROWIT). The validity of the model was demonstrated by simulating experiments with fescue and coastal bermuda grass. The simulated yields of dry matter did not differ significantly from the experimental yields. Yields of fescue were significantly lower in 1976 than in 1977, and the model indicated that insufficient water during critical periods was responsible, even though the rainfall for 1976 was only 5% below normal. Yields of coastal bermuda grass were lower in 1965 than in 1966, and the model showed that air temperature and rainfall were constraints on growth during 1965 as compared to 1966.

Incorporation of environment and feed quality into a net energy model for beef cattle

Abstract The California net energy system has gained wide acceptance as a method for predicting rates of gain in growing and finishing beef animals. Researchers at the University of Kentucky, in co-operation with agricultural scientists in two regional research projects, NC-114 and S-156, have developed an interactive model that enhances the usefulness of the net energy system by including skeletal size, feed quality, temperature and relative humidity to determine feed intake and utilisation. Basically, the intake based on feed availability, nutrient composition, potential skeletal size and heat loss potential. After the feed is consumed, it is utilised according to the productive status of the animal, i.e. growth, lactation, foetal development, etc., using a modified form of the net energy system to predict weight change. The model allows a researcher to easily modify environment, feed, breed characteristics and productive status so as to evaluate their influence on the performance of the animal.

Dynamic Simulation of Animal Growth and Reproduction

ABSTRACT A rather unique systems analysis approach has been made to simulate the utilization of dry matter by ruminant animals, and the natural breeding and reproduction process within a herd. Physiological factors occurring over time and the time related effects of these factors are simulated.

A Simulation Model for Assessing Alternate Strategies for Beef Production with Land, Energy and Economic Constraints

ABSTRACT A computer model has been developed to analyze alter-nate management strategies and energy and economic constraints. Daily production of beef animals and growing crops is simulated in response to prevailing conditions and system interactions using the GASP IV simulation language. Complete inventories of plant dry matter, animal status, production resources and economic net worth are maintained over the simulation period.

A simulation model for managing perennial grass pastures. Part I--structure of the model

Abstract A simulation model has been structured to facilitate stochastic evaluations of grazing management systems on perennial grass pastures. The output data, stored in a direct-access data set, can be used as input to statistical programs which will perform desired statistical analyses of the data. The model was originated to provide a practical method for estimating the effects of grazing frequency, duration, and grazing rate on the performance of grazing systems for perennial grass pastures. The model provides 32 different attributes for characterizing the performance of a grazing system.

RELATIVITY OF GROWTH IN LABORATORY AND FARM ANIMALS: I. REPRESENTATION OF PHYSIOLOGICAL AGE AND THE GROWTH RATE TIME CONSTANT

This article presents a modification of the growth function of Bridges et al. (1986) that incorporates a known biological time unit (gestation period) to represent physiological time for a given animal species. Gestation time was incorporated into the weight-age equation and modified by the growth rate time constant, c, which relates the inflection point of the growth curve to a relatively fixed time unit. Relating the inflection point of the growth curve to an animal’s gestation period provides a mathematical basis for changing growth curves to account for the “external” influences of management, diet, environment and health that may impact an animal’s growth in approaching mature size. Examples are shown using the developed mathematical expression to predict changes in the growth of two different cattle under the effects of early weaning and different nutritional and environmental conditions.

Ground Driven Powered Tillage

ABSTRACT Aground driven powered tillage device is described which utilizes a passive rolling coulter propelled through the soil by a prime mover. The reaction torque imparted by the soil to the coulter is delivered via a tor-que transfer unit to a powered tillage blade. The tillage blade rotates counter to the direction of the passive roll-ing coulter and prepares a tilled furrow of some predeter-mined depth for seed placement and coverage. Analysis is presented in which the torque developed by a passive rolling coulter engaging the soil is predicted. A relationship is presented for determining the velocity ratio between the coulter and tillage blade. Finally, the shape and number of teeth a tillage blade has is express-ed in terms of tillage depth and speed of the tillage blade.

Visceral Organ Growth of Swine as a Function of Physiological Age

ABSTRACT Amathematical equation is presented to describe visceral organ growth of both large and small type swine as a function of physiological age of the animal. The equation parameters are represented physiologically in terms of the described organ and the presented equation overcomes some objections researchers have raised to the traditional allometric method.

Analysis and Testing of Powered Tillage Blades

ABSTRACT FUNDAMENTAL design considerations for powered rotary tillage blades are presented and discussed. The relationship between blade angular velocity and the geometric dimensions of cutting edges is specified for tillage blades rotating counter to the direction of travel and assuming a typical forward speed for tillage. Analyses showed that a powered blade rotated op-posite to the direction of travel can be operated at relatively lower angular velocities than can one rotated in the direction of travel to achieve equivalent blade velocity and acceleration relative to the soil. Furthermore, a blade rotated opposite to the direction of travel requires relatively lower power to achieve equivalent blade velocities relative to the soil. Experiments revealed that, in order to minimize power requirements, the ratio of the tangential velocity of cutting edges on a blade divided by the ground speed should be as low as possible as long as a proper tillage action is obtained.