Date of Award
Master of Science
Harold J. Smith, John D. Smalling
The profits realized from beef cattle herds depend upon the per cent calf crop weaned, the weight and grade of the calves weaned, the current market price, and the cost of production. The information obtained on the performance of the calves at weaning should be particularly useful in increasing profits through selection for increased weight and grade. These records can be used in culling cows from the herd, in selecting heifers for replacements, and in selecting prospective herd sires. Also, these records can be used in evaluating the herd sires, the dams of the calves, and the manage-ment program of the herd. Sire sampling programs have been devised to maximize improvement in traits concerned with more efficient beef production. Primary emphasis in sire analysis should be given to those traits or qualities which will make the largest economic contribution through the per-formance of the daughters of selected sires. The improvement of these traits involved in beef production is the most important key to economic success. In addition to economic considerations, the heritability of the traits is also important. The opportunity to select among sires should not be wasted on traits which give little promise of being responsive to selection. Comparison of sires based on the initial production of their daughters could be very important in predicting future performance of the sires. At this time a major portion of the bull's productive life may be ahead of him, and he could be placed into heavy service without waiting for proof from additional daughters. With reference to dairy cattle, the theory has been proposed that selection of sires on first lactation performance records of daughters fosters the development of animals with short productive lives. However, no direct support for this contention has been demonstrated. The evidence indicates that higher producers during the first lactation remain in the herd for a longer period and con-tinue to produce at a higher level than animals with lower first records, (Parker et al., 1960). The objectives of this study weres (1) To determine if sire differences can be measured through their daughter productivity; (2) To separate the direct effect of sires through genetic contribution to traits expressed in their daughters' progeny from the indirect effect as measured by their daughters' maternal performance; (3) To estimate the heritability of performance traits of calves from first calving heifers; and (4) To determine the phenotypic and genetic association between preweaning traits.
Williams, William Lafayette, "Variation in beef sires as measured by differences in their daughter productivity. " Master's Thesis, University of Tennessee, 1963.