I highly recommend Mare Magic. It's in exspencive and all natural stuff. I use it in my mare durning shows so that is she is in heat. It's the best product I've used and that all my friends have used. If you can't g it from a store they have it on horse.com ect.
Some brands offer supplements for mares, formulated with herbs recognized to regularize the functioning of the ovaries. It is also intended to alleviate the abnormal behavioral manifestations of some mare and facilitate their daily management and work.
There is Ovary Stab, Ovaphyt, Jubitop, … The best thing to do is ask your veterinarian.
I hope this helps,