We've tried raspberry leaf, which seems to have very little effect.
We've been thinking about spaying, but we don't have the facilities to keep her in constantly(she also stocks up very badly), nor do we really have the finances.
My mom keeps mentioning the old technique of putting a marble or steel ball bearing in the uterus to fool the mare into thinking she's pregnant. The thing has to be placed by a vet, and would need to be removed once a year and replaced.
We do not have the finances for Regumate.
Has anyone successfully used the marble method? Or anything else that has worked that we could try? She's too good a mare to just toss her aside, and we have no reason to keep her bred(except that she's registered).