Is It Safe To Feed My Horses Fresh Hay Off the Field?

Find out if you can feed newly harvested hay or if you should wait and let it “sweat” or “cure.”
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Is It Safe To Feed My Horses Fresh Hay Off the Field?
Hay baled at 12% moisture content or less should be safe to feed horses immediately after harvest. | Photo: iStock

Q. This year I’m buying hay directly off the field from a local grower. My haybarn will almost be empty when it is delivered, and I’m wondering if I can start feeding the new hay right away? I’ve heard I need to wait for it to cure so it’s safe to feed. Is that true and, if so, how do I know when it’s ready?

A. If your hay producer has cured the hay properly prior to baling, it can be fed directly off the field. The emphasis here though is on “cured properly.” This means the hay has been given the correct amount of time to dry. Hay baled while it’s still too damp will continue to cure after it is baled and, depending on its moisture level, the plant type, and bale tightness, this could take days to weeks. For this reason, many old-time horse owners will tell you hay needs to “sweat” for two to four weeks when it comes off the field before it can be fed safely.

When hay cures in the bale, it produces heat. This heat results from fermentation, and you certainly don’t want to feed fermenting hay to your horse. This shouldn’t happen if hay is baled with 12% or less moisture; hay baled under these conditions should be safe to feed immediately. Hay baled with higher moisture content might require some time before horses can eat it safely. Hay shouldn’t be baled if the moisture content is over 18%.

If you’re unsure whether your hay is ready to feed, open it and see whether you can feel heat. If you feel heat, it’s not safe to feed. Additionally, hay that generates heat in the bale might not be safe to feed even after it’s finished curing, because too much moisture can result in mold and dust. Such hay can self-combust, causing barn fires, so be extremely careful if the insides of your bales are warm to the touch.

Make sure the person you buy hay from is an experienced grower. Much goes into growing and baling the ideal hay for horses, and this can be hard to achieve when you take weather into account. Rain can delay cutting, resulting in plants that are more mature than ideal with lower nutritional value. Note that this might be a benefit if you are feeding easy keepers. Hay can get rained on after it is cut, increasing the time needed to reach optimal moisture content. How the plants are handled after cutting while drying also impacts final quality. Often the hay is raked while drying to turn it over to help it dry better. But if done at the wrong moisture content or too aggressively, leaf material can be lost or damaged.

Producing good hay is both an art and a science. An experienced grower will have the knowledge and tools needed to put up a quality product that you can feel good about feeding your horse right away.


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Written by:

Clair Thunes, PhD, is an equine nutritionist who owns Clarity Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club.

2 Responses

  1. To Lisa Dyre: Fermenting mowed grass can create serious tummy/intestinal issues. Intestinal ‘clog’ – impaction, stomach bloat, other colic-y problems. I’ve read there have been cases of stomach rupture from extreme gas pressure. I’ve read this; I don’t know it. I hope Clair Thunes will respond to your question, then we’ll KNOW. My Oreo & Cookie are both half paint & half pig…. I would never let them into a mowed, unbaled pasture!

  2. This came up for me the other day just regarding mowed “grass”(weed?) clippings and my horse at liberty free grazing. Do the same concept apply? Fermenting mowed grass can cause issues as well?
    thanks in advance for your reply.

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