Genetic parameters and trends for traits of the Hereford and Braford breeds in Brazil

The objective of this study was to estimate genetic parameters and genetic trends of Hereford and Braford breeds for growth traits and visual scores. Data consisting of records for 205-day weight (W205), 550-day weight (W550), 345-day post weaning gain (PWG345), scrotal circumference at 550 days (SC), and muscling (MUS) and frame (FRA) scores also recorded at 550 days of age came from the PampaPlus genetic evaluation system. A series of animal models were fit to the data using Bayesian inference with uninformative priors. Genetic variance for W205 was partitioned into direct (W205(d)) and maternal (W205(m)) components. Posterior means of heritability estimates and 95% support intervals (2.5% <= h(2) <= 97.5%) for W205(d), W205m, W550, PWG345, SC, MUS, and FRA were 0,12 <= 0.13 <= 0,14; 0.08 <= 0,09 <= 0.11; 0.13 <= 0.16 <= 0.19; 0.04 <= 0.10 <= 0.18; 0.05 <= 0.15 <= 0.32; 0.10 <= 0.19 <= 0.29 and 0.06 <= 0.11 <= 0.20, respectively. Genetic correlations with W205(d) were positive for W550 (0.72 <= 0.82 <= 0.90), MUS (0.25 <= 0.53 <= 0.74) and FRA 0.29 <= 0.59 <= 0.80 and negative for W205(m) (- 0.63 <= - 0.57 <= - 0.50). The genetic correlation of PWG345 and W550 was also positive and large (0.59 <= 0.76 <= 0.88). Genetic correlations of MUS and FRA with each other (0.30 <= 0.53 <= 0.73) and with PWG (0.08 <= 0.33 <= 0.55 and 0.20 <= 0.44 <= 0.64) and W550 (0.10 <= 0.39 <= 0.63 and 0.07 <= 0.38 <= 0.64) were all positive. Use of performance information in selection decisions is supported by positive genetic trends for direct effects on W205(d), PWG345, W550, MUS and FRA. However, the genetic trends were less than the expected gains that would result from use of a recommended selection index, suggesting that the index is not the only criterion currently used in the selection by Pampaplus breeders. It may be concluded that breeders favored larger, more rapidly growing, and more muscular animals in their selection decisions.