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University of Minnesota Extension

Determining the value of rained-on hay

Quick facts

Rained-on hay can be a suitable forage, especially for horses prone to laminitis. Forage quality tends to be retained if:

  • The rain occurs soon after cutting when the forage has had little time to dry

  • The rainfall was a single, short event

  • The rainfall intensity was higher versus a longer, lower intensity event

  • The forage wasn’t re-wetted many times

The best way to check the quality of rained on hay is to have it tested.

Rainfall on cut hay laying in the field causes yield and quality losses. This lowers the value of the crop as an animal feed and a marketable commodity.

Rainfall reduces dry matter yield

Dry matter loss is most crucial to the hay producer. Dry matter loss results in decreased income since there’s less hay for baling, feeding and selling.


How does rainfall reduce dry matter yield?


How does rainfall intensity and forage moisture affect losses? 

Given the same amount of total rainfall, a low intensity rain will result in more leaching of soluble compounds than a high intensity rain.

As forage moisture declines, it’s more prone to dry matter loss from rain. In Wisconsin rainfall studies, the maximum loss in dry matter (54 percent) occurred when 2.5 inches of rain fell on nearly dry hay.

How does rainfall affect forage quality?


Authors: Krishona Martinson, Extension equine specialist and Dan Undersander, professor of agronomy, University of Wisconsin

Reviewed in 2021

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