Submitted to: Journal of Animal Science Supplement
Publication Type: Proceedings
Publication Acceptance Date: 5/15/1996
Publication Date: N/A
Interpretive Summary: These results show the potential of threshold model methods for predicting individual genetic merit for female reproduction. Breed-wide evaluations may be implemented, but will require collection of sufficient data. Inventory-based reporting schemes may facilitate collection of the needed information. This information includes complete breeding records of all females exposed, not just those that became pregnant and calved. Records of different management treatments, service sires, breeding pastures, and other factors affecting pregnancy are needed to compare females within appropriate contemporary groups. These evaluations will provide breeders with the opportunity to select sires based on expected differences in pregnancy of their daughters.
Technical Abstract: While reproductive performance is a primary factor influencing profitability of cow-calf production, genetic evaluation and sire selection for female fertility have received little attention. Except for measures of puberty, fertility traits are regarded as too lowly heritable to allow improvement through selection. Most national cattle evaluations have not addressed reproduction, leaving producers unable to include EPD for reproductive traits in selection criteria. Stayability evaluations, implemented by the Red Angus Association of America (Snelling et al., 1994), predict EPD for the probability that a cow who enters production will reproduce and stay in production for a number of years. The stayability EPD, however, provide no indication of which heifers will enter production. Because pregnancy is the major criteria determining which potential replacement heifers will be kept in the cow herd, EPD for heifer pregnancy are a logical compliment to stayability EPD. Considering the investment required to develop potential replacements, selection based on heifer pregnancy EPD should reduce the amount of that investment wasted on heifers that do not conceive and remain pregnant. Initial results are encouraging for development and implementation of heifer pregnancy EPD using threshold model methods.