ENVIRONMENTAL FACTORS THAT AFFECT THE AGE OF FIRST CALVING AND CALVING INTERVAL IN COWS UNDER THE DOUBLE-PURPOSE SYSTEM

Objective. To determinate the factors that influence the age at first calving (AFC) and first calving interval (FCI) in female cows under the double purpose system on the farm "Rodeo", municipality of Magangué, Bolivar, Colombia. Materials and Methods. Using 379 dates from production records between 1993 and 2002, we applied the GLM program of the Statistical Analysis System (SAS, 2001) to determine the mean and the standard deviation for each source of variance. The analysis considered the effects year, season, age at first calving (this was not considered for AFC), gender and weight at 24 months. Results. The mean for AFC and FCI were of 38.9 ± 3.9 months and 469.2 ± 9 days, respectively, and the effect of season of calving had a significant affect on FCI. Gender, weight at 24 months and season were not significant on AFC. Year, age at first calving, gender and weight at 24 months had no significant affect on FCI. Conclusions. The AFC and FCI were affected by the year of calving and season of calving, respectively.