Autumn. Warm Days, cool nights. Time to put on a sweater. Time to admire the colorful leaves. And time to understand that autumn brings weather perfect for your pasture grass to store sugar.
We all know to limit our horse’s turnout on spring grass to prevent laminitis, the horribly painful inflammation of the tissues that connect the coffin bone to the hoof wall. After the winter, the increased sunlight, warmth and showers of spring awaken the dormant grass and its sugar content skyrockets.
In the fall, something similar happens. September rains can quickly revive grass burned and browned by the heat of July and August. Before you know it, your pastures are green and lush.
But it’s cooler, the horses have more energy. They are running, playing and burning more calories. It isn’t time to worry, is it? Yes. Hidden dangers lurk in fall grass.
During the day, grass uses sunlight to create sugar, a process we all learned in elementary school as photosynthesis. Overnight, the grass uses the sugar to grow. The sugar content of the grass drops through the night as the sugar feeds the growth. That’s why it’s generally safest to turn your horses out from early morning to mid-morning.
With fall grass, however, on those chilly nights below 60ºF, the grass might not grow very much and won’t use up all the sugar it created during the day. When you turn your horse out in the morning, the sugar content may still be quite high. This is especially true if there was an overnight frost or freeze. Then the grass may not have grown at all and will have used up virtually none of the sugar created the previous day. In addition, the frost or freeze will stress the grass and when grass is stressed, the sugar content goes up even more. On a side note, dew does not increase the sugar in the grass.
Autumn grass can thus contain a triple threat: sudden growth following a dry, hot summer; cool nights when the sugar is not consumed by growth; and increased stress from frosts and freezes.
Be careful with fall turnout and don’t think you’re home free until the grass becomes dormant in winter.
Photo by Bob MacInnes
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