I finally have a more settled mare!
My mare was always one that was basically quiet until she was not! And when she was not, she was on edge and quick to drop her shoulder and spin in alarm over nothing. I tried other types of magnesium supplements with no effect. Based on a recommendation of a friend with a similar type of mare, I tried Nupafeed. I did not immediately see a difference, but just as I was about to stop using it, bam! She suddenly felt softer in her muscle tension and just generally more settled and calm in life. At one point I thought, okay, magnesium is magnesium and used a less expensive supplement. Within about 3 weeks my mare was back to her old tightness and spooky behavior. I returned to Nupafeed and again, after three weeks, she returned to calmness. I'm convinced this supplement is vital to her mental and physical health!