A study was conducted to evaluate calving interval (CI) in the Nellore breed, using a total of 578 data of calving interval from animals raised in pasture, from 1988 to 1996. The GLM procedure of the SAS Program was used to analyze the data. The model included the sire of the cow random effect, the fixed effects of genetic group of last calf, of the year and the month of the last calving and the interactions between last genetic group and month of the last calving, genetic group and year of the last calving, and the age of the cow at calving as covariate. The sire of the cow and last year of calving influenced the IDP. The estimated minimum square mean and its respective error standard (EP) and coefficient of variation (CV) were 431.83 ± 142.76 days and 33.06%, respectively. The environment in addition of the sire of the cow effect, influenced the calving interval. The reproductive performance of the studied herd, for the tropical climate conditions, could be considered as satisfactory, and is in accordance with the parameters obtained by other authors in different regions.
bovines; calving interval; Nellore; reproduction
