Genetic relationships among calving ease, birth weight and perinatal calf survival in Charolais cattle*

Perinatal calf mortality affects profitability of beef cattle production systems, hence, it would eventually be beneficial to include this trait in a breeding goal. The objectives of this study were to estimate the environmental effects and heritabilities of and genetic correlations among birth weight (BW), calving ease (CE) and calf survival (CS) in Charolais cattle, in the Czech Republic. The dataset contained 27,402 field records. Fixed effects in the 3-trait model were year of birth, age of dam, sex, and litter size of calf. Random effects in the model were direct and maternal genetic effects, maternal permanent environment, contemporary group (herd x year x season), and residual. Birth weight was modelled as a normally distributed trait, while for calf survival a linear logit model was applied. The CE score was either transformed to be normally distributed (T1) or treated as a binary trait (T2). For T1, heritabilities for the direct genetic effect were 0.23, 0.21 and 0.05 for BWd, CEd and CSd, respectively; while heritabilities for maternal genetic effects were 0.10, 0.02 and 0.05 for BWm, CEm, and CSm. Genetic correlations among BW, CE and CS were close to zero for both direct and maternal genetic effects with the exception of that between BWd and CEd (0.21 for T1 and 0.24 for T2). Results suggest that low additive direct and maternal genetic variances for calf survival and low to modest direct and maternal genetic correlations between BW, CE and CS would limit effectiveness of selection for calf survival in a breeding program, in spite of its economic importance in beef cattle production.