High heat and low moisture are drying up many Kentucky horse pastures made of cool-season Kentucky bluegrass and orchardgrass. That means horse owners should be monitoring those pastures and considering supplementing with hay, according to Laurie Lawrence, an animal nutritionist at the University of Kentucky.

Although a brief pasture walk is helpful in evaluating the quantity of edible grass available, Lawrence says the best test is to offer hay and see whether horses consume it. “If they devour the hay in a short time, then pasture quality is probably poor and hay is needed.”

Providing hay is important not only for the horse’s nutritional state, she notes, but also for preventing pasture conditions from deteriorating further. It also reduces overgrazing.

Even though cool-season grasses may not be growing in the pasture during this hot, dry period, Lawrence cautions, less desirable plants may continue to thrive. Some of these plants, like early johnsongrass shoots, may be harmful or even toxic to horses during stressful growing conditions.

When horses can satisfy their hunger with hay or with desirable pasture plants during good growing conditions, they will be less likely to consume toxic or injurious plants, she says.

The amount and type of hay fed depends on the type and condition of the horses as well as the condition of the pasture. Mature idle horses in good body condition need a mid-maturity grass or grass-legume hay to substitute for pasture during summer. Lactating mares, foals and weanlings require legume hays or early maturity grass-legume mixes. Horses with a low body condition, or are too thin, should also be fed hay with a higher nutritive value.

A mature idle horse will eat about 20 lbs of pasture or hay forage per 1,000 lbs of body weight per day. Lactating mares will eat about 5-10 lbs more, and an allowance should also be made for their nursing foals. Because pasture may provide some of the needed forage, the amount of hay fed each day may vary. A common recommendation is to adjust the hay offered to an amount that horses will clean up between feedings.

Horses with high nutrient requirements also will usually require concentrate supplementation, such as sweet feed or pellets, in addition to hay and pasture. Concentrate, however, should not be substituted for all hay or pasture as this could result in gastrointestinal problems.

For more information, contact Lawrence at 859-257-7509 or llawrenc@uky.edu.