As the seasons transition from winter to spring, it’s time to start thinking about horses’ nutritional needs, as well as changes in the forage available to horses grazing on pasture. The spring also brings an increased risk for several health conditions, including laminitis and insulin resistance, in all horses on pasture. Here are some tips for turning your horses out on spring pasture safely.
First, it’s important to understand the significance of the nonstructural carbohydrate (NSC, a measurement of sugar and starch levels in forages and grains) component of grass. Researchers know that an overabundance of NSCs in a horse’s diet has the potential to cause problems, including colic or laminitis.
(Editor’s note: For more a detailed description of NSCs, see Carbohydrates: Sugars and Starches.)
Therefore, when reintroducing green grass to a horse after the winter, it’s important to consider NSC concentrations in pasture grass.
Current research shows that NSC concentration in pasture is lowest in the evening and peaks at mid-day, so it’s best to turn horses out at night and remove them from pasture by mid-morning.
Studies supported by the USDA have shown that NSC levels are highest in early spring grasses, while studies in England have shown that putting a grazing muzzle on a horse or pony can decrease pasture intake by up to 80%. Thus, it’s advisable to use a grazing muzzle if horses are on 24-hour-a-day turnout when transitioning from winter to early spring pasture.
Researcher also shows that as the plants mature, NSC levels decrease as fiber levels increase
This depends on many situations, such as pasture management, pasture plant species, weather, and geographic location. Generally speaking, however, it takes plants approximately two to three weeks to go from the leafy stage to the prebud stage.
Once the plants begin to mature (i.e., transitioning from the prebud staged to the fully bloomed stage), you can remove the horse’s muzzle or increase his turnout time gradually.
For all horses prone to laminitis or insulin resistance, restrict turnout to a drylot only and provide adequate amounts of hay as a forage source.
Choose late cut hay that is likely to be lower in NSC
When dealing with at-risk horses, it’s advisable to have forage analyzed prior to feeding to determine its nutrient content.
Aim to keep your horse in a moderate body condition, between 5 and 6 (moderate) out of 9 on the Henneke Body Condition Scale. In addition, monitor a horse’s fat deposition, as it could be a sign of an impending medical condition. Insulin resistant horses, for example, tend to deposit large amounts of fat on the crest of the neck, shoulders, loin, tailhead, and above the eyes.
If a horse begins to show an excess of fat, consult a veterinarian or nutritionist to review the animal’s diet. In many cases of spring weight gain, the horse’s calorie intake from pasture will need to be restricted with either a grazing muzzle or by stalling the horse during the day, as described above.