Steaming Versus Soaking Hay for a Horse With Allergies

Steaming might be the more effective option for reducing allergens in hay.
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Draining soaked hay in haynet
Soaking hay is an effective management strategy for horses with allergies, but it does not eliminate microbial allergens. | Alexandra Beckstett/The Horse

Q: My horse has respiratory allergies, and I’m trying to reduce the amount of dust to which he’s exposed. I’ve seen recommendations for steaming and soaking hay. Does one offer more advantages than the other for horses with respiratory issues?

A:  Both soaking and steaming hay are effective management strategies to reduce your horse’s exposure to dust present in dry hay. However, there are other potential microbial allergens present in hay, including bacteria and mold spores, that can be problematic for horses with respiratory allergies.

Study results have shown the most effective way to reduce microbial allergens in hay is through steaming, due to the high heat application. In one study comparing the effect of soaking and steaming hay, only steaming effectively reduced the concentrations of both bacteria and mold contamination (Moore-Colyer et al., 2014). In fact, submerging hay in water (soaking) can increase the bacterial counts in hay, and the longer the soaked hay sits before being consumed, the greater the increase. However, despite the significant decrease in mold counts, the clinical benefits of feeding steamed hay versus soaked hay to horses with asthma have been inconsistent (Orard et al., 2018). Therefore, employing additional management strategies to reduce allergen exposure and using appropriate medical treatments recommended by a veterinarian are also critical when managing horses with respiratory allergies.

Overall, steaming hay for horses with respiratory allergies is more advantageous than soaking, due to the decrease in both dust and microbial contamination. Commercially available steamers are safe and easy to use following manufacturers’ directions. You will need a hose and an electrical outlet to connect the steamer. Capacities range from a few flakes of hay to an entire bale, and the steaming cycle takes approximately 60 to 90 minutes as it heats the hay to at least 212°F (it might take longer in cold weather). You can find instructions for building homemade hay steamers online, but the associated safety concerns cause these versions to be risky.

If you don’t have access to a hay steamer, soaking hay is a good alternative because it will effectively reduce dust exposure compared to feeding unsoaked hay. One effective hay soaking method is to submerge a full hay-net in a large muck tub filled with water for 30 to 60 minutes, drain for 5 to 10 minutes, and discard the water prior to feeding the soaked hay, which should be fed immediately to prevent excessive bacterial proliferation.


Moore-Colyer et al. The effect of five different wetting treatments on the nutrient content and microbial concentration in hay for horses. PLoS One. 2014;9:e114079.

Orard et al. The influence of hay steaming on clinical signs and airway immune response in severe asthmatic horses. BMC Vet Res. 2018; 14:345.

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Written by:

Kelly Vineyard, MS, PhD, is a senior nutritionist in equine technical solutions with Purina Animal Nutrition. She consults with veterinarians, professional riders, and horse owners across the United States and is directly involved with new product innovation, research, and technical support at Purina. Vineyard earned her BS in animal and dairy sciences from Auburn University and her MS and PhD in animal sciences from the University of Florida. Her doctorate research focused on the effects of omega-3 fatty acid supplementation on immune function in horses. Vineyard is a frequent lecturer on equine nutrition topics, with expertise in omega-3 fatty acids, immune function, and performance horse nutrition. She is an avid dressage rider and is proud to have earned her USDF bronze and silver medals on an off-track Thoroughbred.

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