The Truth About Grass Clippings

By NTFR Staff

Every summer, as lawn mowers start making their rounds, the same warning comes up among horse owners: “Don’t throw those grass clippings over the fence.” For many people, the explanation has always been that fresh grass clippings will cause an impaction. Like a lot of horse barn wisdom, the advice is sound, but the reason behind it isn’t quite what most people think.

Veterinarians and equine nutritionists generally agree that you should never intentionally feed horses lawn clippings. Their main worry isn’t impaction. Grass is highly digestible and holds a lot of moisture. Impaction colic is more commonly tied to dehydration, poor-quality forage, low water intake or other factors that slow the movement of feed through the intestines.

The bigger problem is how fast horses eat clippings. A grazing horse spends hours taking small bites of forage throughout the day. A pile of freshly cut grass lets a horse eat a large amount in minutes. That sudden intake can upset the balance of microbes in the horse’s hindgut, raising the risk of digestive upset, gas colic and, in some horses, laminitis.

Choke is another concern. Because clippings are already chopped short, horses often gulp them without chewing as thoroughly as they would in a pasture. If a large mouthful lodges in the esophagus, the horse can choke, and that needs prompt veterinary attention.

Grass clippings also start to change quickly once they are piled together. Heat builds as the clippings begin to ferment, and mold can develop fast, particularly in warm, humid weather. Never feed spoiled or moldy forage, and grass clippings are no exception.

One easy-to-miss hazard has nothing to do with the grass itself. Many residential lawns have been treated with herbicides, insecticides, fertilizers or other lawn care products that are not meant for grazing animals. Even if the grass looks healthy, chemical residues can remain on the clippings. A well-meaning neighbor tossing extra clippings over the fence may have no idea he is putting a dangerous substance into a horse’s diet.

Mowing a horse pasture is different from dumping a pile of lawn clippings into a pen. When you clip a pasture, the small pieces spread across the field, and horses keep grazing normally. They eat only small amounts of the clipped grass along with the standing forage. The concentrated pile creates the greatest risk, not the fact that someone cut the grass.

Rapid eating, digestive upset, spoilage and possible chemical contamination together make grass clippings a risk not worth taking. If your lawn needs mowing, keep the clippings out of the horse pasture. Compost them, bag them or dispose of them another way, but don’t treat them as a free snack.

Some horse advice gets passed from one generation to the next for good reason, and this old warning still deserves a place around every barn.