Progesterone therapy in mares with abnormal oestrous cycles.

In two studies in Holland and France a total of 41 mares found either to be in anoestrus or showing continuous oestrous behaviour during the early part of the covering season were treated with a progesterone releasing intravaginal device. Of the 32 mares in the first study, 24 ovulated after treatment and 11 became pregnant to a covering at the induced oestrus. In the second study all but one of the nine mares showed oestrus, seven ovulated and six became pregnant at the post treatment oestrus. By the end of the covering season 15 of the 21 mares treated for anoestrus and seven of the 11 mares treated for persistent oestrus were found to be in foal.