Response to Therapeutic Abortion in Lactating Dairy Cows Carrying Dead Twins during the Late Embryo/Early Fetal Period.

This study examined the dose-response effect of prostaglandin F (PGF) when used to induce abortion in cows with two dead twins at pregnancy diagnosis 28-34 days post-AI (late embryonic period: LE) or at pregnancy confirmation 49-55 days post-AI (early fetal period: EF). The study population consisted of 415 cows receiving a single PGF dose (PG1 group: 254 LE and 161 EF cows) and 200 receiving a 1.5 × PGF dose (PG1.5 group: 121 LE and 79 EF cows). The induced abortion rate was significantly lower (chi-square test; < 0.0001) in the EF (34.6%) than LE cows (88%), and was also reduced ( = 0.001) in the EF PG1 group (28%) compared with the EF PG1.5 group (48.1%). High milk production (≥45 kg) was the only factor influencing the induced abortion rate in LE cows (odds ratio 0.2; < 0.0001), whereas the odds ratio for induced abortion of PG1.5 cows was 2.3 ( = 0.005) in EF cows. In conclusion, an increased PGF dose had no effect on abortion induction during the late embryonic period and its rate was inversely associated with milk production. This higher PGF dose did, however, offer benefits during the early fetal period.