Grass is nature?s perfect food for a horse, and nothing makes a coat glow like good grass. However, there can be too much of a good thing, especially when it comes to nutritionally supercharged spring grass.
Free-ranging horses have to travel considerable distances to find enough to eat, and that exercise is one of the important differences between the reaction of domesticated horses and wild horses to spring grass. In addition, commercial pasture-grass strains are selected to stand up to heavy traffic and grazing. Their carbohydrate levels are typically higher than wild-grass strains.
Think of spring grass as a diet change. it's very different from mature grasses or hay. When the dormant grass begins to regrow, it mobilizes storage forms of carbohydrate in its roots and base, converting them to sugars for growth.
Compared to other grass life stages, spring grass is high protein (typically over 20%), low fiber, high moisture and high sugars.
When the grass is abundant, and horses are eating as much as they can ? as fast as they can ? the grass may not remain in the small intestine long enough for these nutrients to be completely digested and absorbed. Instead, it spills over into the cecum and colon. The organisms in the cecum and colon take time to adjust to diet changes, and these rapidly fermentable grasses can lead to problems with bloating, diarrhea and colic. In extreme cases, inflammation of the intestinal wall may allow bacterial toxins to enter the blood and pose a risk for laminitis (see Gut pH sidebar).
The high-sugar levels in spring grass often cause problems for horses with insulin resistance. Even short periods of grazing on spring grasses can result in laminitis.
Treat spring grass like all diet changes: Gradually. Be alert for bloating, loose manure or foot tenderness. Feed hay, too.
Introduce pasture beginning with 15 minutes of grazing and increasing every three days, as tolerated. Alternatively, use a grazing muzzle for longer periods of turnout. The Best Friend Muzzle (www.bestfriendequine.com, 800-681-2495, $42.50) is our perennial choice. it's durable, lightweight, and you can adjust the amount of grass the horse can get (see March 2010).
Yeast-based digestive supplements (see sidebar) can help prevent the acidic conditions in the large intestine. Consider using one of these at least during the spring.
Horses showing symptoms of magnesium deficiency (see sidebar) should be supplemented.