The present study aimed at evaluating the effect of single over-dose of PGF2α on postpartum anestrus
due to retained corpus luteum in dairy cows. A total of 40 dairy cows, 3-8 years old and 1-6 parities
used in these study, were assigned into two comparable groups; control group of 20 cows were injected
by 500μg from PGF2α and over-dose group of 20 cows were injected by 750 μg from PGF2α i.m. The
obtained results indicated the presence of a significant increase in the heat response (85 vs. 65%),
decrease in the time elapsed from treatment to heat (2.47 vs. 4.53 days) and the serum progesterone
level, 24 hrs. and 48 hrs. after treatment, in the over-dose group than that in the control; there was a nonsignificance
difference in the number of service per conception and the conception rate between both
groups.