Type of Document Master's Thesis Author Mahrt, Garry Sonn URN etd-11172012-040158 Title Comparison of expected and actual progeny growth differences in crossbred calves Degree Master of Science Department Animal Science Advisory Committee
Advisor Name Title Notter, David R. Committee Chair Eller, A. L. Jr. Committee Member Pearson, Ronald E. Committee Member Vinson, William E. Committee Member Keywords
- Beef cattle
Date of Defense 1987-06-05 Availability restricted Abstract
The growth performance of Angus-Polled Hereford F1 calves was compared to the expected progeny differences (EPD) estimated by the American Polled Hereford Association to evaluate the usefulness of EPD estimates for improving commercial beef production.
Polled Hereford sires were selected from the high accuracy sires listed in the American Polled Hereford Association's sire summary. Four types of sires were used: 1) Sires with high yearling weight and high maternal EPD's; 2) Sires with high yearling weight and low maternal EPD‘s; 3) Sires with low yearling weight and high maternal EPD's; and 4) Sires with low yearling weight and low maternal EPD's.
The resulting progeny were weighed at birth, approximately 135 d, weaning and approximately 1 yr. Hip heights were also measured at weaning. Linear regressions of progeny performance on EPD indicated that birth and yearling weights were accurately predicted by their respective EPD estimates. Weight and height at weaning were not accurately predicted by weaning weight EPD. Partial regressions of progeny performance on yearling weight and maternal EPD's were also calculated. Regression of progeny performance on yearling weight EPD resulted in .16 ±.09 kg/kg for 135-d weight, .28 ± .09 kg/kg for weaning weight, .073 ± .020 cm/kg for weaning hip height and .93 ±.19 kg/kg for yearling weight. Comparable regression values for maternal EPD were .44 ± .18 kg/kg, .31 ± .17 kg/kg, .100 ± .040 cm/kg and .22 ± .36 kg/kg for 135-d, weaning weight, weaning hip height and yearling weight, respectively. These results indicate that maternal EPD values predicted some differences in preweaning growth that were not predicted by yearling weight EPD.
The progeny performance data was also used to calculate independent EPD estimates for birthweight, weaning weight, and yearling weight. Correlations between these EPD estimates and those made by the American Polled Hereford Association were .49 for birthweight, .26 for weaning weight and .66 for yearling weight. The low correlation between weaning weight EPD estimates was significantly below expectation and indicates that the American Polled Hereford Association estimates were inadequate for predicting preweaning growth differences in these crossbred calves.
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