Question
I have been boarding my horse at a barn where he is kept in a small paddock. I am preparing to move him to another farm where he will be turned out on a well-established pasture with high-quality forage. How can I introduce my horse to the pasture without causing colic or founder?
Answer
Lush pasture can contain 30% or more digestible energy. When excessive amounts of highly digestible and fermentable sources of energy reach the hindgut, they can disrupt the normal balance of microbes that break down the fibrous portion of the diet. This disruption can lead to gaseous colic or, in the most serious instances, laminitis.
A few simple steps should be taken before a horse is allowed to graze unrestricted on a new pasture. First, assess the condition of the horse. A horse that has fat built up along the crest of the neck, over the withers and back, and around the tailhead is likely overweight. Such a horse may be predisposed to laminitis when given all-out access to abundant pasture. Ideally, a horse should be maintained in a leaner, more moderate condition. One way to determine condition is to feel along the barrel of the horse for its ribs. If the ribs cannot be seen but can be felt, a horse is considered to be in moderate condition. If, however, it is impossible to feel ribs, the horse is probably overweight. Obesity can cause numerous health problems, so maintaining moderate body condition is advisable.
How much pasture your horse requires is not only determined by his body condition but also by his metabolic rate. Is he an easy keeper or hard keeper? That is, does he seem to gain weight easily, or does he have a difficult time maintaining weight? His metabolic rate affects his energy requirements. Horses with low energy requirements (easy keepers) may require less time on pasture than horses with higher energy demands (hard keepers). Body condition will play an important role in how the horse is managed on pasture.
Second, the pasture should be evaluated. Horses prefer to eat young plants, and fresh growth provides more energy than older stands of forage. Pastures that are overgrazed or contain tall, seeded-out grasses provide little energy to the horse. Variations in pasture quality may occur from season to season and even within a season depending on rainfall and other climatic conditions.
Once you have determined the condition of the horse and pasture, you can develop a turnout schedule. In addition to the pasture, you should have a stall or drylot available to keep the horse in during periods of pasture restriction. Throughout the acclimation period other energy- rich feedstuffs such as grain or alfalfa hay should be offered sparingly, if at all. If your horse is in moderate body condition, begin turning out your horse for short periods of time (one or two hours) following a large hay meal. A horse may, for example, be allowed two or three periods of restricted turnout daily. Gradually increase the amount of time you allow the horse on pasture by hour or two-hour increments. In addition to a regimented turnout schedule, a grazing muzzle can be used to limit the amount of grass ingested. An overweight horse may have to wear a muzzle at all times when he is on pasture. The adaptation period may last 10 to 14 days, and the horse should be observed closely during this time for signs of colic and laminitis.
Horse’s unaccustomed to fresh grass may experience moderately loose stool due to the gastrointestinal tract’s unfamiliarity with the high moisture content of fresh forage. This is not cause for concern. Once the digestive tract becomes fully adapted to the new diet, this side effect will diminish.
After acclimation to the new pasture is complete, continue to observe the horse for weight gain or loss. If you have a question regarding the nutritional management of your horse, ask a veterinarian or equine nutritionist. The advice of knowledgeable professionals can help you avoid potential problems with your horse.
