do horses on pasture during the day need hay at night
Q.In the past few weeks our pasture grass has really come in. My horses are now out on pasture all day and come in at night—I turn them out around 7 a.m. and they come in between 5:30 and 6 p.m. Since they’ve been grazing all day, I haven’t been giving them hay overnight. They’re in good condition and clearly not lacking for calories, plus I figure they sleep at night. Is this okay, or should I be giving them hay at night?

—Janet Bryant, Templeton, Massachusetts

A.In many areas with climates that support good grazing, grass is typically abundant by this time of year. As a result, many horses can meet their calorie demands and maintain condition if they have access to good pasture and aren’t working too hard.

Feeding to condition is a major component of any equine nutrition program. If your horses are maintaining a body condition score of 5 (or slightly above or below), your feeding program is meeting their calorie requirements. And good news: It does sound as though your horses’ caloric needs are being met at this time from consuming only pasture all day.

Horse Digestion 101

However, another important consideration for any nutrition program is maintaining a healthy gastrointestinal tract. In their natural environment, horses are what we call trickle feeders, meaning they eat small amounts almost constantly over a 24-hour period. This method of eating is the basis on which their digestive tract has evolved. The horse’s stomach empties fairly rapidly with liquid leaving the stomach within about 30 minutes and complete gastric emptying of a forage meal occurring within 24 hours.

Gastric Ulcer Risk

It sounds as though your horses are in at night without access to food for about 13 hours. Certainly, by the early hours of the morning most of the pasture consumed during their previous turnout will have left their stomachs. This increases their risk of developing gastric ulcers, because gastric acid is released constantly, whether or not they’re eating. A stomach with little to no food in it is less able to buffer stomach acid than a full one, and it lacks the well-developed forage barrier that otherwise floats on the stomach acid, helping to reduce the amount of acid that splashes upwards into the unprotected squamous tissue (the esophageal region, or squamous mucosa, covers approximately one-third of the equine stomach).

Rapid Consumption

Another point to consider: Horses that are turned out after a period of no pasture access might consume more grass in the initial hours post-turnout than they normally would. This could result in a couple of scenarios. First, they might be stimulated to consume more pasture than they actually need, because they’re hungry when they first go out; over time, this could lead to extra weight gain. Second it might mean that, having gorged in the morning, they consume grass at a slower rate as the day goes on. If this were the case, they might, in fact, have less forage in their stomach when you bring them in than you might think, such that they are in fact standing without food for longer than 13 hours.

Fast Fixes

As long as it doesn’t lead to weight issues, I like to keep forage in front of horses for as many hours of the day as possible. This is often a challenge, but this is where slow feeders are so valuable—they allow small amounts of forage to last far longer than when the same amount of hay is fed loose. Feeding a small slow-feeder-net of hay at night when you bring them in would reduce the number of hours standing without food.

I am not sure of the reason you bring the horses in at night, but another possible option would be to leave them out 24 hours a day and put grazing muzzles on them at night. This would allow them to continue to consume a small amount of pasture over night and has the benefits of increased movement, which is good for both maintaining weight and promoting a healthy digestive tract.