The difference between good hay and poor hay is often in the harvesting. Poor timing of harvest processes or bad harvesting conditions can render a good hay crop poor or unsafe for horses, as it might contain mold or dust. Hay must be baled at the proper stage of drying–if it is cured too long it can lose nutrients or be dusty, but it shouldn’t have so much moisture that it molds. Other factors that affect hay’s nutritional value include stage of maturity when cut, and whether it’s the first or a later cutting (after regrowth).

Stage of Maturity

Glenn Shewmaker, MS, PhD, a forage specialist and extension assistant professor at the University of Idaho, says hay producers should try to look at the field at least a week prior to when they think it might be ready to cut. “This is the best time to control the quality in terms of plant maturity,” he says. If it’s alfalfa, you can see whether it’s already blooming, which makes it more attractive to blister beetles–some species are deadly to horses if they are present during harvest and their bodies end up in the hay.

When buying hay, talk with the producer and agree on the stage of maturity at which it should be cut. Plants cut in early- to mid-maturity have higher levels of protein and other nutrients and would be a good choice for lactating mares or young growing horses. Mature hay would be more ideal for an adult, idle horse. Sometimes hay is cut later than planned because harvest is delayed by rain. Some hay producers let hay grow longer, since mature hay produces more tonnage per acre than immature hay.

“Hay prediction sticks measure stem length of the growing plant and have a scale (for bud and open flower stages) to give an index for estimating acid detergent fiber, neutral detergent fiber, and relative feed value, but most horsemen and hay producers just look at relative maturity,” says Shewmaker. “If it’s alfalfa, you look for buds or flowers. If it’s grass, you look for boot stage (when the seed head has not emerged, but it has begun to swell the top of the plant) or seed heads to indicate maturity. With mixed hay (grass and alfalfa), one species is generally ahead of the other in maturity, so timing of cutting must be a compromise.”

Differences in Cutting

The first cutting often grows slower in the cool spring weather. Later cuttings grow faster in the heat of summer. “First cutting, whether alfalfa, grass, or mixed, is often a nice all-purpose hay,” says Shewmaker.

First cutting hay usually has good yield, plenty of fiber, and adequate energy and protein. Although it might have a coarse stem (if it’s alfalfa), most animals like it, and it’s good feed because it grew slowly enough to accumulate nutrients.

“Hot-season cuttings are often very clean (fewer weeds, since they did not regrow), leafy, and fine-stemmed,” continues Shewmaker. “But generally the animals don’t like it as well because it grew too fast. There’s not a high concentration of sugars, for instance. But for a laminitic horse or any horse that’s sensitive to sugars and needs to be on a diet with less nonstructural carbohydrates, the hot-season cuttings are generally safer for that animal.

Other extension specialists have noted that many horses eat second-cut, fine-stemmed alfalfa hay in preference to first-cut hay, which is stemmy and less palatable.

“The end-season cutting is richer in nutrients again because of slower growth when nights are cool,” he continues. “Even if it’s blooming, it still may be very nutrient-dense. That cutting seems to still maintain its quality after bloom stage.”

Time of Day Makes a Difference

Hay cut in the late afternoon has higher nutrient content than hay cut in the morning. Plants accumulate sugars and starches during the day (through photosynthesis), then they use up nutrients at night as they grow, explains Shewmaker. For highest nutrient values, select hay cut in the late afternoon. “But a horse that is prone to insulin resistance problems or laminitis would do best with hay cut in early morning, when plants are lowest in sugars and starches,” he says.