Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Science

First Advisor

M. Peter Hoffman

Second Advisor

Allen H. Trenkle


Developments in personal computer equipment are providing us with the capability to compile and utilize the vast amounts of numerical data collected over the years and facilitate it's application to everyday life. An example of this can be observed in the latest version of the Iowa State Extension's Feedlot Monitoring Program, whereby many of the documented principals regarding the conversion of feedstuffs to weight in growing cattle have been compiled into PC software and made available to commercial beef feedlots. Along with the primary focus of projecting weight gain, this program also has the capabilities to utilize the developments in live animal evaluation in terms of ultrasonic imaging. This provides a means by which development of the carcass can be assessed on a continual basis along with weight. The primary outputs for analysis involve the live weight, the carcass weight, yield grade, and the quality grade. The commercial aspect of the system then requires monetary aspects to be related to these calculated values of the animal. Determination of animal weight has been defined by standards set be the National Research Council. Development of the ribeye area and backfat depth used for the yield grade calculation along with the intramuscular fat, used to estimate the quality grade, was numerically described to a fair degree of success on observed lots (R2=.97, .81, and .79, respectively) using both animal evaluation and feedlot performance. Equations developed from historical feedlot data used to estimate carcass weight and percent kidney-pelvic-heart fat for yield grade estimation, likewise showed fair accuracy (RMSE = 14.27,.29) when applied to independent data. The implications of this system, in terms of commercial feedlots, may result in new paths by which animal value can be estimated prior to slaughter and is a means of sorting cattle into management groups.



Digital Repository @ Iowa State University,

Copyright Owner

Garland Roman Dahlke



Proquest ID


File Format


File Size

66 pages