This research was done on cyclic Holstein Dairy Cows in Moganlivestock, industry farm where 40 cows were selected randomly 45 days after parturition;The Presynch method was used for 40 cows and they were divided to two groups. In control group in zero day,3 ml PGF2a was injected and in 14th day, the PGF2a was injected again. In 28th day the Gonadorelin was injected and in 35th day the third injection of PGF2a was done. In 37th day the second injection of Gonadorelin was done, and 16 to 22 hours later, the cows were inseminated artificially. In treatment groupthe protocol was repeated and instead of second GNRH, adose ofhumanchorionicgonadotropin was injected about 5000 unites. Both groups from 30th day of protocol were examined by ultrasonography, and the follicular progress was studied and recorded. Also from 7th to 9th days of protocol, the cows were sampled. there was significant differences between control and treatment groups in the rate of estradiol in 36th, 37th, 38th and 39th days and between the great and small diameters of follicular and through the level of greatest diameter of follicular (p<0.05). The rate of recorded pregnant in day 30 after insemination, 16 cows of 20 cows were pregnant and 4 cows were not pregnant while, in control group, 11 cows of 20 cows were pregnant and 9 of them were not pregnant; so 55% of the control group were pregnant while in treatment group 88% of cows were pregnant.
