Genetic Parameters For Cow Weight And Height Using A Repeatability Model In American Angus Cattle

Estimates of genetic parameters were obtained from two samples of weights and heights of mature cows provided by the American Angus Association. The first sample consisted of 23,658 records for mature weight (MWT) and 13,012 for mature height (MHT) and the second sample consisted of 23,698 records for MWT and 13,310 for MHT. The four-generation pedigree file included 43,105 animals for the first sample and 44,141 animals for the second sample. Range in ages when cows were weighed was 2 to 11 years at the time of measurement. Variance components were estimated using the MTDFREML programs. Univariate and bivariate analyses were used to estimate genetic parameters for MWT, MHT, and the corresponding genetic correlation. The model included fixed effects of cow age and random cow permanent environmental, contemporary group (herd and year) and residual effects. Heritability estimates (SE) within contemporary group were 0.45 (0.012) for MWT and 0.64 (0.018) for MHT for sample 1 and 0.48 (0.011) for MWT and 0.62 (0.018) for MHT for sample 2. Estimates of repeatability were 0.64 and 0.77 for MWT and MHT, respectively for sample 1 and 0.66 and 0.70 for MWT and MHT, respectively for sample 2. The genetic and permanent environmental correlations between MWT and MHT were 0.80 and 0.75, respectively for sample 1 and 0.83 and 0.69 for sample 2. The estimates of genetic parameters will be used to estimate genetic changes in MWT and MHT from the complete data file.