Estimation of genetic parameters for heifer pregnancy and carcass traits in Angus cattle

The genetic relationship between heifer pregnancy (HP) and carcass traits in purebred Angus cattle was evaluated in this study to expand industry knowledge of the impact of carcass trait selection on HP and the potential use of carcass traits as indicators of HP. Historical data consisting of 1,462 records for HP and 4,519 records for carcass traits from the Iowa State University McNay Memorial Research and Demonstration Farm were used in this study. A pedigree consisting of 10,455 individuals with parent generations ranging from 1 to 9 for sires and 1 to 11 for dams was used to build relationships among individuals. Genetic correlations between HP and carcass traits were analyzed using multivariate models consisting of HP, weaning weight (WWT), and a single carcass trait. Results from this study estimated a low heritability of 0.09 ± 0.06 for HP and estimates of 0.36 ± 0.04 for ribeye area (REA), 0.39 ± 0.04 for backfat thickness (FAT), 0.48 ± 0.04 for marbling score (MS) 0.38 ± 0.04 for hot carcass weight (HCW), 0.18 ± 0.03 for weaning weight direct (WWTd), and 0.07 ± 0.02 for weaning weight maternal (WWTm). Genetic correlations between HP and both carcass and weaning traits were negative with estimates of -0.32 ± 0.23 for REA, -0.22 ± 0.23 for FAT, -0.10 ± 0.22 for MS, -0.44 ± 0.21 for HCW, and -0.20 ± 0.25 for WWTd. All estimates of genetic correlation were accompanied by large standard errors. The results from this study suggest a potential antagonistic genetic relationship between heifer pregnancy and carcass trait performance in this herd of Angus cattle.