Ask the Nutritionist: Dr. Getty's Forum for Equine Nutrition
Welcome to my forum.
Here you will find more than 6 years of questions and my answers. It is searchable and offers a great deal of information.
Currently, I am discontinuing new questions. This may change in the future, but in the meantime, please know that It has been a true pleasure serving you.
Take a look at my Nutrition Library and Tips of the Month for a variety of answers on selected topics. Be sure to sign up for my monthly e-newsletter, Forage for Thought.
I also have a growing number of recordings on "Teleseminars on Nutrition Topics that Concern You" as well as the new, Spotlight on Equine Nutrition Series -- printed versions of favorite teleseminars.
And finally, look for my articles in a variety of local publications and online newsletters, as well as the Horse Journal, where I am the Contributing Nutrition Editor.
All the best,
Dr. Getty
Hello Sheila,
When MMX works, it indicates that the problem was a borderline deficiency in magnesium. So, in the case of your gelding, you determined the problem. When it doesn't work, as in the case of your mare, the behavioral problem is not magnesium-related. But, it is always best to start with a magnesium supplement (the B vitamins in MMX are also helpful) since much of the time behavior problems are due to not enough of this mineral.
Your mare's issue could be hormonally related. If you think that may be the issue, consider a preparation called Levelor.
All the best,
Dr. Getty 
Author of Feed Your Horse Like A Horse
Where are you from? Bayfield, CO