No, they do not always abort. The shot is designed to PREVENT mass abortion in bred mares in herds on farms. Last I knew, there was always a chance of abortion after giving the shots, but the good breeders kept an eye on mares, rechecked for losses. Then bred mares back again after a loss. At the time of the discussion, you gave a series of 3 shots, could lose foal on any of the shots.
We only had one bred mare. Trying to be the “good” owners, she was vaccinated for Rhino. She lost her foal after the third shot. Mare was older, never got her bred again. NO ONE had said anything about mares regularly aborting after a Rhino vaccination or we would not have vaccinated her.
The Sporthorse Group discussing, was international, extremely knowledgeable people, assured me that for them, the Rhino shots were helpful in the multiple bred horse setting. They could rebreed, not lose the entire year with the mare.
So I now warn friends about the chance of foal loss after Rhino vaccination with any of the series. If they do vaccinate, get mare checked shortly after each shot to make sure she did not abort.
You may want to ask for more current Rhino information on the Sporthorse Breeders forum here. Things change over the years, I may be way out of date on Rhino side effects. With our bad experience, we never vaccinated for Rhino on our bred mares again. Never lost another foal either!
Again, with our bad experience, I probably not vaccinate for Rhino on this rescued mare. Just treat her visible problems, maybe antibiotics if she has a flu, to prevent pneumonia problems. Your Vet could better inform you of how to deal with your mare’s condition.