As the owner of a Head Shaker that 1st came on after Spring shots (Flu/Rhino), I would be much more concerned about using pharmaceutical medications to control the HS in a broodmare rather than the Head Shaking being hereditary. I do not believe it is hereditary.
If you search my previous posts you can read that I am currently using a very safe homeopathic remedy, Colocynthis, to control our horse's HS.
Thank you. Horsezee, for your suggestion. I will look up the thread and talk to my homeopathic vet about using Colocynthis.
Currently she is treated with APF Pro (for the first time this year we will be giving it prophylactically), and staying in the barn days during the height of summer. She isn't symptomatic year round, but onset has not yet been correlated with any particular blooming season or anything else that we can identify. The only other medications she received were antibiotics for the Lyme, and that was two years ago.
I'd be thrilled if the Colocynthis worked, but I'd still be thinking about breeding her.
They don't call me frugal for nothing.
Proud and achy member of the Eventing Grannies clique.