Do Photinias cause death in horses?

[hannarose]

Hello, this is my first time using the site. I live in Victoria Australia and my husband and I breed and race horses. We have a stud farm about an hour out of Melbourne. We have planted a long hedge of photinias next to one of our horse paddocks, however, someone recently told us they can kill horses. Is this true? If so we will have to transplant or fence off.
Thank you -
Hanna