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 Kristy,
It is best to introduce a new forage gradually. So, start your horses on pasture for 30 minutes the first day, an hour the next, and so on, until they are on it full time (if that's your goal).
Pasture safety, however, depends on the horse and the sugar/starch level in the grass. This time of year, grasses tend to be lower in sugar and starch. However, if your nights get cold -- below 40 degrees F, followed by sunny days, they can be too high in sugars and starches to be safe for horses that are prone toward insulin resistance and/or laminitis.
Unfortunately, you have two types of horses -- drafts and minis (they must be cute together! 
) that are genetically predisposed to insulin resistance. So, your best course of action would be to have your pasture analyzed. Choose a warm day, late in the afternoon, when the sugar/starch levels are at their highest. You can mail in a sample to Equi-Analytical Labs: www.equi-analytical.com or contact your local county extension service.
The safest time of day would be before the sun rises, through the early morning. Once the grass is exposed to sunlight, it produces more sugar/starch. So, you can conider letting them graze in the early morning. But, watch those night time temps. Also, grass that is drought stressed is also higher in sugar/starch.
If any of your horses has had an experience with laminitis, it may not be advisable to let them pasture graze. But, there again it depends on the horse, his condition, his history, and the state of your pasture.
Once you get your pasture analyzed, you may find a phone consultation helpful. That way, I can assess your horses' situations in depth.
All the best,
Dr. Getty 
Where are you from? Bayfield, CO