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
Hi Cynthia,
I'll chime in here. 
Selenium is listed in parts per million (ppm), but this is a concentration. The real safety zone to know about is 2 to 5 mg of Selenium per day. Lisa is feeding 3 lbs of Ultium per day, which provides approximately .7 grams of selenium. And, one ounce of Pre Ox provides 1 mg of selenium. So, she has room for more from the hay and still be safe as long as other supplements are not added that contain this mineral.
You're right about it being toxic. Selenium is very tricky and some parts of the country have too much and some have not enough, which is why I offer products that offer both options.
Bloodwork is always a good idea -- it gives you a snapshot of what's going on inside your horse. We'll certainly talk about what tests, if any, are appropriate for your horse when we visit. I'll look forward to it!
All the best,
Dr. Getty 
Where are you from? Bayfield, CO