Use of injectable progesterone to replace the intravaginal progesterone device on the ovulation synchronization protocol reduces the pregnancy rate in Bos indicus cows.

The aim of this study was to evaluate the effectiveness of using different doses of injectable progesterone (P4i) in a new ovulation synchronization protocol in place of progesterone (P4)-releasing intravaginal devices in Bos indicus cows. For this, three experiments were carried out. To determine the P4-release curve (Experiment 1), 55 Bos indicus cows were distributed into 5 experimental groups for the administration of different doses of P4i at D0 (P4i60, n = 11; P4i105, n = 11; P4i150, n = 11; P4i195, n = 11 and P4i240, n = 11) and submitted to the ovulation synchronization protocol (D0: P4i + EB; D8: PGF2α + EC + eCG).