It is tempting to allow horses unlimited access to spring pastures as soon as the grass turns green, particularly after a long winter. But management practices which make this transition a slow and steady one are beneficial to both the horse and the pasture.
In natural rangeland conditions, the new spring grasses are covered with a dry forage mat from the past growing season, so horses grazing on these lands consume a mix of old-stand forages and new-growth grasses. Since horses are very sensitive to diet changes, especially to a much richer feedstuff, this seasonal transition over three to four weeks is very beneficial to the horse.
Slowly introducing horses to spring pasture allows the microbial population responsible for digestion to adjust to the changes in the diet. When the diet change occurs gradually, the microbes have the opportunity to shift and benefit the horses once again.
Gradually introduce your horse to grazing, extending the number of hours grazed daily over two to three weeks until access is unlimited. Avoid sudden turnout to lush, green pastures. To ensure your horse’s health, it may be necessary to limit access to rich spring grasses.
Be especially careful if your horse is an easy keeper who tends to deposit fat along the crest of his neck, abdomen, and tail head. Horses with these physical signs are particularly susceptible to laminitis, or inflammation within the hoof, also known as founder. Unsupervised grazing of spring pastures is associated with approximately half of all the cases of founder/laminitis.
Grass plants grow most vigorously in the spring and are very high in simple sugars. Intake of these sugar-laden grasses can trigger a cascade of events culminating in laminitis/founder.
Grazing management will continue to be important for those horses or ponies that are predisposed to obesity when allowed unlimited access to grass. Obesity in horses, like people, is linked to numerous metabolic disruptions. In horses these diabetes-like illnesses are labelled Cushing’s syndrome, insulin resistance, or equine metabolic syndrome. These horses are predisposed to founder/laminitis.
Proper grazing management can often avoid the onset of these diseases in individuals that are susceptible. When managing them on pasture they are best turned out for limited grazing in the early morning when pasture sugars tend to be at the lowest level.
Environmental conditions such as drought, excessive heat, cold nights and overnight frosts stress the grasses, causing them to accumulate sugars in the plant, as these sugars are not converted into growthy fibre overnight. Thus the plants remain relatively high in sugars. Limited grazing at these times may be essential to ensure the health and longevity of your horse or pony.
Gradual spring turnout is beneficial for the pasture as well. Pasture grasses need sufficient growth and photosynthetic machinery to ensure a vigorous root stock. The ability of the pasture to provide for the horse declines when the grass plants are grazed before reaching to six to eight inches of height in the spring.
On average, two to three acres of well-managed pasture can provide the forage needs for one horse from spring to fall. It may be necessary to designate a sacrifice area to optimize pasture productivity.
The one thing you do not want to introduce to your spring pastures when you introduce your horses is a parasitic burden. Strategically deworming horses prior to pasture turnout dramatically reduces egg shedding and larval contamination of pastures. Deworm horses and place them in drylot or sacrifice area for three to five days before moving them to the pasture area. It is an opportune time to effectively interrupt the parasite’s life cycle, and in turn benefit the horse.
Carol Shwetz is a veterinarian specializing in equine practice at Westlock, Alberta.