Leo E. Lucas

Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Animal Science


The relationship between rate and efficiency of gain, and the environmental factors affecting them, are of major importance in a selection program. Selection within recent years has tended to be mainly for improvement of breed type. As a result of this selection, improvement in type has taken place in the beef breeds, but a comparable improvement in performance does not seem to have occurred. It then seems likely that is breeders in the future intend to improve the performance of the beef breeds, they cannot do it by selection for type alone. A breeding program based on selection for performance, as well as type, will have to be used. In order that progress can be made by selection I any breeding program, variations must exist between animals. As will be shown later and by other studies variations do exist between animals for rate and efficiency of gain, the performance factors studied in this problem. The fact that these variations do exist is important, as selection for them is possible because they are genetically inherited. Through trials conducted by colleges and experiment stations it has been found that rate of gain is relatively easy to measure, but that measuring efficiency of gain requires additional time and labor in individual feeding and weighing of feed consumed. Most beef producers, on an economical basis, could not endure the expense of additional labor involved, if many calves were tested. A method of predicting the genetic make-up for efficiency of gain, without individual feeding by the cattle producer, will have to be determined before there will be any large scale of use of efficiency of gain in a selection program commercially. The solution to this problem is a criterion that maintains a close relationship to efficiency of gain and is easily computed and measured. When obtained from a weight-constant feeding period, rate of gain seems to meet these requirements because it is related to efficiency and is easily measured and computed. A correlation must exist between rate and efficiency of gain because gain is common to both factors. If a close relationship exists between rate and efficiency of gain, selection for rate of gain would automatically bring some improvement in efficiency of gain. Then cattle producers can perform rate of gain trials only. However, if the relationship between rate and efficiency of gain is low, selection for rate of gain would not be expected to improve efficiency of gain. Studies show that a high correlation does exist over a weight-constant period; however, it would not be practical for the cattle producer to feed each calf through a definite weight period. If by adjusting for environmental factors, calves fed over a constant-time period can be corrected to a weight-constant period, then selection for rate of gain would improve efficiency of gain. This would save the producer considerable labor and time. The purpose of this investigation then is to determine environmental factors which affect rate and efficiency of gain, to correct for these factors, then get a reliable estimate of the correlation between rate and efficiency of gain.

Library of Congress Subject Headings

beef cattle -- Feeding and feeds


Includes bibliographical references (pages 49-50)



Number of Pages



South Dakota State University


No Copyright - Non-Commercial Use Only