Matthew L. Spangler
Date of this Version
Upperman, L.R. 2021. Estimation of breed effects and genetic parameters for age at slaughter and days to finish in a multibreed beef cattle population. PhD diss. University of Nebraska, Lincoln, NE.
Cattle efficiency during the finishing phase is a crucial factor in determining profit in the beef cattle industry. Economically relevant traits associated with efficient production include age at slaughter (AAS) and days to finish (DtF). Selection to reduce the number of days an animal takes to reach a finish endpoint would ultimately reduce production costs, increase net profits, and result in a more sustainable production system. However, most harvested animals are from commercial herds, necessitating the use of indicator traits from seedstock animals for selection. Potential indicator traits include ultrasound measurements that could be genetically correlated to DtF traits. The objectives of the current work were to i) estimate genetic parameters and breed effects for AAS and DtF and their relationships with routine carcass traits, and ii) estimate genetic correlations between AAS or DtF and ultrasound traits (ultrasound intramuscular fat percentage (UIMF), ultrasound rib fat (URF), and ultrasound ribeye area (UREA)). Performance records and pedigree information were obtained from U.S. Meat Animal Research Center (harvest data) and International Genetic Solutions (seedstock data). Univariate and bivariate animal models were fitted with ASREML (version 4.0) to estimate the genetic parameters. Days to finish and AAS are moderately to highly heritable and generally lowly correlated with routine carcass traits. The phenotypic variability in DtF was low. However, there was greater variability in AAS, which was due to differences in date of birth of the animals and thus the ages at weaning. Genetic correlations between AAS or DtF with UIMF were negligible. Genetic correlations were negative and low between DtF and UREA and were positive and moderate between AAS and UREA. Genetic correlations were negative and moderate to high between AAS or DtF and URF. Reducing AAS or DtF in commercial cattle is possible through selection in seedstock for ultrasonically measured fat.
Advisor: Matthew L. Spangler