Livestock don't like to eat dry, brittle hay -- it's unpalatable and carries little nutrition -- and extremely dry hay can cut the inside of an animal's mouth. However, in a pinch, even hay with as little as 5% moisture or less can make adequate feed for the maintenance requirements of a cow if prepared properly.

Livestock prefer to eat soft, green hay, says Juan Guerrero, University of California-Davis. The preferred moisture range for livestock is 18-22%. Hay with more than 20% moisture can mold, and mold is probable at 22% moisture.

At about 12% moisture, hay starts to be brittle. Brittle hay can be softened, however, with the addition of water. Though moistening of dry hay will improve its palatability to livestock, it won't improve its nutritional quality.

"In our desert area, hay is generally tarped not to keep it dry but to protect it from the intense heat, which can sap the protein from 22% down to 14-18%, and 4-5% moisture," Guerrero says. "In more moderate climates, good grass hay that's been left in the field too long and unprotected, and that isn't weathered too bad, can be rewetted and it will suffice for maintenance on cows if it's not moldy or black," Guerrero says.

Water can be added in two ways:

  • Add the water directly to the bale, then let the moisture spread (equalibrate) throughout the bale for about 4-6 hours. This softened bale can then be broken and fed as "flakes" or, more preferably, ground.
  • Water can be added to ground hay, mixed, equilibrated and then fed.
Once water has been added to hay, all the rewetted hay must be fed during the same day -- do not store rewetted hay, he cautions.

Below is a table with suggested levels of water addition for differing moisture levels of dry hay. Do not rewet dry hay to more than 24% moisture, and less than 10% is too dry. Unfortunately, many commercial hay moisture meters don't read less than 8% moisture.

"As an example, let's say I have hay baled in April 2007 that was stored roadside all summer. I want to feed it to some goats. Since the hay was left uncovered at roadside all summer, I'll assume it has 5% moisture. According to the table, if I want to feed it at 22% moisture, I must add 52 gals. of water to each ton of hay," Guerrero says. Weigh each bale separately and add the corresponding amount of water.

"Either measure or eyeball the water volume -- we all know about what a 55-gal. drum holds. Then pump it or throw it on the big round or square bales, and let it equilibrate. It won't be perfect. The top will get more wet than the bottom but one-half to two-thirds of the bale will be okay as compared to none of it," he says.

-- Juan Guerrero, UC-Davis