Componentes de (co)varianza de los días abiertos en bovinos Santa Gertrudis.

In order to estimate the genetic parameters of open days (OD), data from Santa Gertrudis cattle in the Turiguanó Island, Cuba, were analyzed. The first eight calvings of cows in 15 herds were considered. The sample included 16,209 calvings of 3,065 cows' daughters of 85 sires and 2,610 dams. Data was analyzed using the animal model, with the ASREML software. Four models were used: The univariate model (UM) for each independent calving; the repeatibility model (RM) which included all calvings; the bivariate model (BM) to estimate genetic correlations between OD in the different parities; and the random regression model (RRM). OD mean was 168.9 d with a trend to decrease from parities 1 to 4. OD heritability (h²) estimated by the UM and RRM increased from parity 1 (0.02 ± 0.02) to parity 7 (0.20 ± 0.08). Genetic correlations among OD for different parities were high, particularly for consecutive parities (≥ 0.90). Results show that OD heritability estimated using the RM does not differ from the values found in other dairy or beef cattle breeds. Despite of the fact that estimates obtained increased with both the UM and the RRM, OD h² model, together with the variation found, limit the usefulness of this trait as a selection criterion for Santa Gertrudis cattle in Cuba. [ABSTRACT FROM AUTHOR]