Swayback in a horse can be caused by weak abdominal muscles and oer subluxations within the spine.
The simple backward walking in hand up an incline can help develop these muscles. Also lifting one front leg and slightly pushing back on the sternum will also exercise the core.
Chiropractic adjustments along with activity will help correct this weakness.
Please call me at 781-337-1180 or email at Indekchiropractic@gmail.com