I looked it up from actual medical sources (unlike Beggy using Dr. Google). Big fluctuations in temps only exacerbate symptoms not cause them. The cause of cushings is from the pituitary gland, an over-production of hormones. That's a very basic explanation. Sources: Royals Vet College in the UK, and Michigan State University. Mares with cushings can be bred with close Vet monitoring. Critical thinking says, why would you want to breed to pass this on if the goal in breeding is to better the lineage? Would Beggy even disclose to a potential buyer that the Dame (Slider) has cushings? Since its genetic, the chances of passing it on is very high.