To evaluate an artificial insemination program in postpartum Bos indicus cows and by using deterministic models, to estimate the possible economic advantages of insemination by appointment over detected estrus, sixty-three multiparous animals were synchronized using a progestagen device inserted at day 31 and withdrawn after 9 days (average time for withdrawal was 40.9 ± 6.8 days). Cows were observed continuously from 0700 to 1800 during 72 h. The percentage of animals detected positive to estrus by riding behavior was 43.4%, transrectal palpation, 22% and heat detector patches, 4.6%. The percentage of cows ovulating as evidenced by progesterone samples taken at 9 and 11 days after the average estrus response was 73%. The economical assessment by using the values obtained in the present study afforded that the cost of semen, ovulation rate and fertility point to a definitive advantage of using AI at fixed time over a program based on estrus detection.