Q: With the high price of hay, I’m researching alternative forages. Is it possible to feed horses haylage? I’ve heard that it’s only for cattle and will cause colic, but I’ve also read that if you open the plastic and feed it immediately it’s OK for horses. What’s the truth?Name withheld by request

A: Haylage can be safely fed to horses if some precautions are taken. Haylage is alfalfa and/or grass that is put up for storage with a relatively high water content (about 60 percent moisture) compared to dry hay (10 to 20 percent moisture). To preserve the forage and prevent spoilage, it is fermented in anaerobic environments, either in a silo (silage) or in large plastic-wrapped round or square bales (balage).

Silage is routinely offered to horses in Europe, but in this country it is mainly produced for cattle. While it can be fed to horses here, too, this must be done with extreme caution, because silage, especially balage, can often have spots of mold. Horses are more sensitive to quality issues than ruminants are. So you must know exactly what you are doing. Precautions that must be taken include:

  • Look out for mold. Molds can develop both in storage and after  the  silage is exposed to air—that is, when bales are opened and offered to the animals. Once opened, a bale usually has to be used in three to four days, even faster in warm weather.

Silage producers in Europe routinely apply additives to enhance fermentation and reduce spoilage and mold growth. Use of additives is less common in this country. Also, some producers in Europe sell silage in portions sized specifically for horses—that is rare in the United States. Here, most balage is put up as large round or large square bales, so owners with a small number of horses may not be able to use one fast enough to prevent spoilage after removing the plastic wrapping.

  • Protect your horse against botulism. The other major risk associated with silage is botulism—poisoning from the toxins created by the bacterium Clostridium botulinum, which is common in soil as well as decaying animal carcasses. The bacteria propagate in moist conditions and can get picked up with any soil that contaminates the forage when it is harvested.

In Canada, where feeding haylage is more common, several incidents of botulism occur each year among horses. Often the toxic silage doesn’t look or smell spoiled—two bales may look and smell the same, but one can be fine and the other one deadly.

Talk to your veterinarian about vaccinating your horses against botulism if you are planning to offer them haylage. And never feed them any that’s spoiled, moldy or otherwise poor in quality.

  • Calculate your horse’s dietary needs. Nutritionists generally recommend that haylage make up only part of a horse’s diet, not all of it. Good-quality silage can replace a third to half of the hay in the regimen—but you have to calculate the weights carefully to make sure your substitutions are proportional. That is, a 40-pound bale of hay typically contains about 35 pounds of dry matter and five pounds of water, whereas 40 pounds of silage at 60 percent moisture has only 16 pounds of dry matter and 24 pounds of water. So, to feed a horse the equivalent amount of forage, you’d need to offer more than twice (2.2 times) as much silage (by weight) than hay.

All that said, well-preserved, mold- and toxin-free haylage can be used to replace a portion of the hay in the equine diet. But because the feeding issues are more complex, horse owners who want to use it need to educate themselves on evaluating silage quality. If you make a mistake, the cost could be much higher than feeding hay, even at today’s prices.

Lester R. Vough, PhD
University of Maryland
College Park, Maryland