The evaluated animals has been bred fed only with grass, without any complementary alimentation during the dry season from 1988 to 1996. A total of 1206 observations of the gestation lenght (LG) was taken from the archives of the regional technical office of ABCZ (Escritório Técnico Regional da ABCZ) in Fortaleza - CE and from zoo-technical registers of the farm. For the statistical analyses of the data was used the SAS (Statistical Analysis System, 1990), through procedure GLM (general linear model). Had been includ in the model the random effect of the sire of the cows, the fixed effects of the genetic group of the calf, month and year of calving, Sex of calf and the interactions between groups of the sex beyond he age of the cow at used as covariat. The LG was influenced by month of the calving, year of the calving and by the calf sex. The estimated average by minimum square and its respective standard error (EP) and coefficient of variation (CV) had been, 284.73 ± 3.65 days and 1.28%. The gestation length generally did not suffer significant influences from the environment, except on the determination of the calf sex , such as occurred in this work. The estimated average for the gestation length obtained can be considered normal for the species and the studied breed.
bovines; Nelore; gestation lenght; reproduction
