By Juliet M. Getty, Ph.D. - For owners of insulin resistant horses, pasture grazing may not be possible. Grass can be too high in sugar and starch. Since horses love to eat a lot of it, very quickly, this grass can significantly raise the level of insulin in the blood. While grass tends to be lower in sugar/starch during the summer, the situation changes as the night time temperatures drop below 40 degrees F, making it especially challenging (and dangerous!) to allow pasture grazing. Many a case of laminitis has occurred during the fall when the nights turn cool.