Effect of Treatment with Additional Doses of Prostaglandin F2 Alpha during the Middle Stage of the Oestrus Cycle on Luteolysis Process and Reproduction Performance in Holstein Dairy Cows

For the manipulation of the oestrus cycle, the prostaglandin F2 alpha (PGF2α) is a commonly used strategy in dairy cows. The objective of the study was to evaluate the luteolysis response and reproductive performance after treatment with one or two injections of PGF2α. A total of 84 Holstein dairy cows, being in the middle stage of the oestrus cycle (between days 7 and 12) were enrolled in a completely randomized design and divided into three groups: group 1 (n=30), received a single dose of PGF2α injection, whereas, group 2 (n=24) and group 3 (n=30), were treated with two doses of PGF2α injections at 12 and 24 hours intervals, respectively. The corpus luteum diameter was measured using the ultrasound at the beginning, 24, 48 and 72 hours after PGF2α injection. Blood samples were collected to assess progesterone (P4) on day 0 and 72 hours after treatment. Oestrus expression, PGF2α-oestrus interval and first service conception rate were evaluated. The results showed that the luteolysis process, the mean of PGF2α-oestrus interval and progesterone concentration at the beginning (day 0) and 72 hours after treatment were similar for all the groups. Oestrus expression (PGF2α+PGF2α-24 h=76.7% vs. PGF2α+PGF2α-12 h=66.7% and control=56.7%, P 0.05) and the first service conception rate (PGF2α+PGF2α-24 h=41.2% vs. PGF2α+PGF2α-12 h=40.0% and control=33.3%, P 0.05) were relatively higher in cows receiving two doses of PGF2α injections at 24-hour-interval (P 0.05). In conclusion, treatment with an additional dose of PGF2α during the middle stages of the oestrus cycle has no significant effect on luteolysis or reproductive performance.