Genetic relationships among yearling weight, frame score and fertility traits in Charolais heifers

Abstract

The objective was to estimate heritability, genetic correlations and expected genetic superiority (EGS) by direct selection, and expected correlated genetic superiority of selected sires for yearling weight (YW), frame score (FS), age at first calving (AFC) and heifer fertility (HF) of Mexican Charolais females. Records were provided by the Charolais-Charbray Herd Book de México. Estimates of (co)variance components were estimated applying a four-trait animal model that included direct genetic effect, contemporary group, and the linear and quadratic effect of dam age, except for AFC. Heritability estimates were 0.18, 0.13, 0.15, and 0.13 for YW, FS, AFC and HF, respectively. Genetic correlations (r2) estimates were 0.60, -0.14, 0.14, -0.24, 0.26 and -0.92 for YW-FS, YW-AFC, YW-HF, FS-AFC, FS-HF and AFCHF, respectively. The EGS with 5 and 500 half-sib progeny per sire was 4.72 and 10.58, 0.10 and 0.26, 23.98 and 57.92, and 0.15 and 0.38 for YW, FS, AFC and HF, respectively. The moderate r2 for YW-FS suggests that direct selection to increase YW would increase FS. The strong r2 for AFCHF indicates that direct selection to decrease AFC would improve HF. The low r2 for YW-AFC and YW-HF indicate direct selection for YW would not alter AFC and HF.