Decreasing doses of PGF2alpha (Cloprostenol; EstroPLAN) by intrauterine infusion caused luteolytic, induced estrus in Holstein Friesian crossbred dairy cows on days 8-10 of the estrus cycle. The trial cow were divided into 3 groups, the first group (n=26) (control) were induced by using PGF2alpha 500 mu g IM. The second (n=30) and the third group (n=30) cows were induced by using 125 mu g (1/4 IU) and 62.5 mu g (1/8 IU) infused into the middle of the uterine horn, ipsilateral to the corpus luteum by the AI technique. Estrus was determined by noting a decrease in the serum progesterone level to or less than 0.5 ng/ml within 3 days of the treatment. Estrus rates among the 3 groups were similar (P>0.05; 84.62%, 73.33% and 63.33% respectively). Serum progesterone levels on the day of treatment (Day 0) were similar (P>0.05) for the three groups (3.10+-1.52, 3.05+-1.13 and 3.4+-1.43 ng/ml respectively). Serum progesterone on day 1 and day 3 after the PGF2alpha was also similar (0.58+-0.75, 0.92+-1.01 and 1.20+-1.39 ng/ml respectively on day 1 and 0.53+-0.85, 0.54+-0.82 and 0.70+-1.03 ng/ml respectively on day 3). Estrus rates and progesterone levels were not affected by the different farm environments (P>0.05). Intrauterine infusion of reduced doses of PGF2alpha (1/4 and 1/8 doses) can induced luteolysis in dairy cows during the luteal phase within 3 days just as effectively as the IM route. These results can be used to assist estrus induction in postpartum dairy cows.
