Q. We just got hay for our horses that was baled one week ago. I’ve heard from other horse owners that it could be too soon to feed it, or it might be too high in sugar at this point for my metabolic pony. Is this hay safe to feed? Can I soak it to help reduce the sugar content and make it safer for her?

A. The basics of the haymaking process include deciding the desired plant maturity level, cutting the plants, allowing them to dry in the field with processes called tedding (spreading) and raking to help with the drying process, and finally baling the dried forage. Farmers also monitor humidity and potential rainfall to try to ensure the best quality hay possible. Ideally, they bale hay when moisture content is less than 12%, which makes it safe to feed immediately.

Curing Horse Hay

Hay baled at a higher moisture content, or that was rained on at the time of baling, will need to go through a curing process, which will take two to four weeks. During this time the bales can get very hot and sometimes even catch fire, so the farmer or buyer should stack bales carefully and monitor them regularly during the curing process. You can use a long hay thermometer to measure the bale temperature. When the measurement stays close to ambient temperature, the curing process is complete. You can also feel an open bale with your hand—if it’s hot don’t feed it.  Hay baled wet can develop harmful mold and suffer losses in quality and nutrient content.

Hay Maturity and Cure Time for Metabolic Horses

Plant maturity and time of day forage was harvested influence nonstructural carbohydrate (NSC) levels in hay more than how recently it was baled. These NSCs include simple sugars, starches, and fructans. It’s best to feed equids sensitive to these levels, such as your metabolic pony, forages lower in NSCs. Talk with your hay dealer about the timing of the cut and evaluate for plant maturity. Photosynthesis in live plants produces carbohydrates, so content increases throughout the day, especially on sunny days. Therefore, hay cut in the morning tends to be lower in NSCs. Hays made up of more immature, leafy plants also tend to be higher in carbohydrates. How long the cut forages dry before baling can also affect the sugar levels. A longer curing time tends to decrease the NSC content.

For your pony, look for hay cut earlier in the day, allowed to dry in the field, and made up of mostly mature grass. You can also work with an equine nutritionist or county extension agent to test the hay (if the dealer does not already do this) to find the NSC content. If you have any concerns about sugar content beyond that, you can soak the hay for 30 to 60 minutes prior to feeding. Make sure to remove the hay from the water, and don’t give the pony access to the water. Soaking removes the sugars from the hay, but they remain in the water.

Take-Home Message

Horses can eat hay baled at 12% moisture or less immediately after baling. Higher-moisture hay needs time to cure, and owners should monitor for heat and mold during this process. For metabolic horses, harvest timing and plant maturity influence sugar content more than the hay’s age, while soaking can reduce NSC levels.