Steaming's Effect Horse Hay Studied

Soaking hay in water is a common practice used to reduce dust and non-structural carbohydrate (NSC) levels for horses with respiratory or metabolic conditions. But soaking can leach essential nutrients, such as phosphorus and magnesium, from hay and be labor-intensive.

In the last few years hay steaming has gained popularity as a soaking alternative, but how does it compare to soaking? University of Minnesota researchers, who recently studied soaking’s effect on hay, set out to answer that question.

“We had been receiving many questions from horse owners and professionals about the effectiveness of steaming on forage quality and no data (that we could find) existed,” explained Krishona Martinson, PhD, assistant professor in the Department of Animal Science.

The group set out to evaluate steaming’s effects on four factors:

  • Nutritive values, including dry mater (DM), crude protein, water soluble carbohydrates (WSC), ethanol soluble carbohydrates (ESC), calcium, and phosphorus among others;
  • Mold concentrations;
  • Airborne dust particles (TSP, or total suspended particulates); and
  • Horses’ voluntary (DM) intake.

Two hay producers harvested two lots of alfalfa-orchardgrass small-square bales at different moisture levels. The researchers randomly selected 40 bales from each lot and took core samples from 26 bales in each lot to analyze.

Then, the team classified the bales as having either low mold (LM) or medium mold (MM) concentrations. Researchers then selected 10 LM and 10 MM bales to steam for 90 minutes using The Professional Hay Steamer by Happy Horse Products, Ltd. Samples from the steamed bales were also analyzed.

Finally, the team fed six adult horses steamed and un-steamed LM and MM hay in a 10-day crossover design to measure the animals' hay intake. Horses received both steamed and un-steamed hay from one lot simultaneously for a 2-hour period each day.

The team concluded that steaming hay:

  • Reduced the DM concentration for LM and MM hay, by 14 and 11%, respectively;
  • Reduced WSC by 12% and ESC by 31% in MM hay, but had no effect on WSC or ESC in LM hay;
  • Did not affect other measured nutritive values in MM or LM hay;
  • Reduced mold concentrations in by 99% in LM hay and 91% in MM hay; and
  • Considerably reduced TSP in MM hay (by 55%) but did not affect TSP in LM hay.

Additionally, the researchers found that steaming did not increase horses' MM hay intake, but horses did consume more LM hay after steaming. Martinson explained this could be because steaming kills the mold, but doesn’t remove it: “If mold had an unpalatable flavor …. its mere presence, whether dead or alive, likely affected forage intake rates.”

Martinson said the main benefit of steaming appears to be the increase in consumption of good-quality hay. She added that “steamed hay might be useful for horses recovering from surgery, malnourished horses, older horses with poor teeth, or picky eaters.”

Martinson said soaking is likely “more affordable and a better solution when managing horses with respiratory issues or when the goal is leaching out NSC (for horse with laminitis, EMS, obesity) or potassium (for horses with HYPP).”

The study, “Effect of hay steaming on forage nutritive value and dry matter intake by horses,” was published in the December issue of Journal of Animal Science

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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