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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Donald M. Marshall


Several methods have been used in an attempt to estimate biological efficiency. Calf weaning weight by itself has been used. Other measures of efficiency have used the ratio of calf weaning weight to cow body weight or metabolic cow body weight to include an estimate of maintenance requirements of the cow. These ratios are prone to be biased in favor of the small cow and are used primarily when feed consumption data is unavailable. Using the ratio of calf weight weaned per cow exposed to breeding incorporates a function of cow fertility and calf survival rate along with milking ability of the dam and the calf's genotype for pre-weaning growth. A common measure of biological efficiency has been to use the ratio of calf weaning weight to energy consumed by the calf and dam. This ratio, and others like it, attempts to measure efficiency as an amount of input per unit of output. Final product weight relative to energy consumed has been a common measure of efficiency to slaughter. Several of these measurements have included cull cow weight as another unit of output. With common measures of efficiency to weaning utilizing the ratio of calf weaning weight to either cow weight or combined cow and calf intake, efficiency cannot be determined until at least one calf has been produced. Selection for efficiency in replacement heifers could be aided greatly if efficiency could be predicted prior to the production of the first calf. Data collected from Davis et al. indicated that this would be difficult due to the low correlations with early age growth parameters. However, there was a tendency for those females exhibiting more efficient weight gains from 240 days of age to first calving to become more efficient producers of calf weaning weight as dams. This study is part of a comprehensive experiment designed to identify various factors affecting efficiency of feed utilization for beef production, with the possibility of manipulating these through management. This particular study contained two objectives. First, to evaluate the effects of various biological variables on efficiency of feed utilization by the cow-calf pair to weaning with emphasis on cow size, milk production and cow body condition. To attempt to evaluate the possibility of early selection for efficiency this study will also attempt to identify predictors, prior to the heifer producing her first calf, of subsequent intake levels and efficiency of feed utilization for first-calf production of the cow-calf unit to weaning.

Library of Congress Subject Headings

Beef cattle -- Feed utilization efficiency

Beef cattle -- Cow-calf system

Beef cattle -- Breeding



Number of Pages



South Dakota State University