Age at first calving in Holstein dairy cows specialized in Costa Rica.
Keywords:dairy cows, inbreeding coefficient, heat stress in dairy cows, computerized records in cattle.
The objective of this work was to describe the age at first calving (AFC) of pure-bred Holstein cows in Costa Rica.A historical prospective longitudinal study with 46029 cows was conducted between 2000 and 2010. Data from cows with complete records for all study variables were included and reported in the 3.0 VAMPP Bovino program. The AFC were calculated by ecological zone, calving season, year of calving, inbreeding coefficient, lactation number of the dam and the type of calving that gave birth to the cow. The data were analyzed through descriptive statistics (percentages, mean, standar deviation [SD] and 95% confidence intervals [95% CI]. The average AFC was 30.7 months (SD: 6.8; 95%CI: 30.6 – 30.8). During the period, the AFC ranged between 30 and 31 months; however, in 2006 and 2007, it tended to decrease. The AFC showed significant differences between strata according to the calving season and the lactation number of the dam; the ecological area, year of calving, type of birth and the inbreeding coefficient of the cow. As in global trends, the AFC showed a tendency to decrease in Costa Rica; and the variables animal, time and environment showed an effect on the AFC. Except for the inbreeding coefficient (medium and long-term), these factors are not modifiable under the grazing conditions that prevail in most of the studied farms.
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