To help clarify the actions of Prostoglandins on pregnancies, here is what I have found in these situations.
A cow does indeed have many different hormones through out the repro process, depending on when in the cycle you are working with. A pregnancy depends on primarily Progesterone to maintain the pregnancy, and for the first several months -- the level of hormone is derived primarily from the Corpus Luteum on the ovary -- some will call this a Yellow Body -- that is kind of old school.
The uterus will release it's own natural levels of Prostoglandin (What is in the Lut and Estrumate products) at certain times -- they all fit together like a puzzle.
If a high level of Prostoglandin is given to the pregnant cow during the time that she ONLY depends on her CL for maintaining the pregnancy, she WILL abort with a very high degree of accuracy -- HOWEVER, if the drug is given AFTER she is -- say 4 months along -- the placenta membranes are now giving off HUGE amounts of Progesterone -- and in a nut shel, no single shot of Lut will make her abort. It will take an additional steroid to get that done -- and as the above said, Dex will usually be that choice.
I do NOT advocate aborting any pregnancy past 75 days, too many things to talk about there. Short breds at or under 45 days are no problem usually, a couple of heats later and all is well.
Mainegirl -- your cows were most likely simply misdiagnosed earlier, and called open due to a smaller pregnancy. When you came back in the fall thinking they were open, and synced them as you said, the single dose of Lut would not get it done if they were past 4 months, basicly you got lucky!!
I certainly hope this little bit of cowboy talk will help you and others. I try to be pretty layman --
Best of luck to all -- Terry
