Genetic relationships among calving ease, gestation length, and calf survival to weaning in the Asturiana de los Valles beef cattle breed.

The aim of this paper was to estimate the genetic relationships among calving ease (CE), calf survival (CS), and gestation length (GL) to assess the possibility of including this information in beef cattle breeding programs. A total of 35,395 field records were available for CE, 30,684 for GL, and 36,132 for CS from the Asturiana de los Valles beef cattle breed. The 3 traits were analyzed as traits of the calf fitting a multivariate linear mixed model. Estimates of heritability (+/-SE) for the direct genetic effects (CEd, GLd, and CSd) were 0.325 +/- 0.022, 0.331 +/- 0.026, and 0.226 +/- 0.018, respectively, whereas the estimates for maternal genetic effects (CEm, GLm, and CSm) were 0.066 +/- 0.018, 0.066 +/- 0.017, and 0.034 +/- 0.011. The estimates for the ratio of permanent environmental variance to phenotypic variance were CEc 0.090 +/- 0.011, GLc 0.066 +/- 0.011, and CSc 0.024 +/- 0.007. Genetic correlations between direct, maternal genetic, or permanent environmental effects involving CE and GL were, in general, positive and moderate, whereas those involving CE and CS were high. All were significant except for the pair CEm-GLm (0.277 +/- 0.172). Correlations between GL and CS were nonsignificant. Genetic correlations for CEd-CEm, GLd-GLm, and CSd-CSm were negative and high, ranging from -0.461 +/- 0.120 for GLd-GLm to -0.821 +/- 0.145 for CSd-CSm. The genetic correlations for CEd-CSm and for CSd-CEm were negative, significant, and high, whereas that for GLd-CEm was moderate (-0.323 +/- 0.124) and that for GLd-CSm was nonsignificant. The genetic correlations for GLm with the direct effects of the other traits were non-significant. Strong selection for CE will result in a significant correlated response in CS. Therefore, CE can be considered an early indicator of CS performance. The benefit of using GL as a correlated trait in a genetic evaluation with CE and CS seems limited.