Cystic ovarian disease (COD) has been recognized as a one of most important problem in dairy farm, it is a managerial and financial problem.120 Holstein cows with average age between 3 to 5 years were used in this study to determine whether giving GnRH at 14th day and 21st day after parturition (using two different types of GnRH) has a role in decreasing incidence of cystic ovaries during days open, and is there is any effects of this program on fertility parameters, (the interval from calving to conception, number of service per conception, first service conception rate,). Also, we refered to the season of milking to see how it affects in the incidence of COD. The findings of this study suggest that using two dose of GnRH (Receptal or Cystorlin), at 14 and 21 days after parturition did not give a significant difference comparing with the costs of the programs in preventing COD except a moderate result by using Cystrolin especially with cow more than one season which decreased the incidence by 11%. COD may reach to 42% in herd especially the high yielding Holstein cow. No significant effect on fertility parameters positively or negatively by using GnRH in postpartum period.
Key words: GnRH,cystic ovaries, cows