EVALUATION OF BEEF SIRES FOR MATERNAL GENETIC EFFECTS ON WEANING WEIGHT AND MEASUREMENT OF GENETIC TRENDS

Abstract

Procedures for evaluating beef sires for maternal genetic effects for weaning weight were developed and used in the calculation of genetic trends. Using the maternal grandsire (MGS) and error variance components, predicted differences (PDs) of MGSs for parity one daughter performance were calculated using Record of Performance data from the Angus, Charolais and Hereford breeds. Best linear unbiased prediction (BLUP) methods were used with a mixed model which included herd-year and MGS effects. The average number of daughter records per MGS was 5.44, 5.26 and 5.12 for Angus, Hereford and Charolais, respectively. As a result of these small numbers of daughter records, the PDs of most MGSs had very large standard errors of prediction. Weighted averages of MGS PDs for each breed in each of the 5 years from 1975 to 1979 were calculated to determine if there was any genetic trend in MGS PDs. There were small trends evident but not sufficient to indicate that any selection pressure was being exerted on maternal ability. Key words: Beef sire evaluation, maternal effects, genetic trends