Not long ago we got a question from a reader: “I am an equine conservationist in Maryland. I am working to promote rotational grazing for small horse property owners. I would really like to see some information about grass combinations for horses with insulin resistance and varieties that would allow for longer grazing times. We have exactly the opposite problem as most livestock producers. Many equine producers need a forage that does not promote weight gain as much as it provides turn out. Any help is appreciated.”
We asked Genevieve Slocum of King’s Agriseeds to provide an answer:
You are right that your quest is the opposite from that of most livestock producers – while dairy producers often look for feed with the highest energy and protein, you will want to seek out feed of a lower quality. This means more mature forages lower in sugar, and grass and legume species that are naturally lower in carbohydrates. Horses are not raised for production of milk or meat, so intake has to be carefully managed for pure maintenance. Horses still need good nutrition, but highly digestible fiber and energy are less critical components of the diet than they are for high-producing animals. However, nutrient requirements of horses will still vary depending on their discipline or current state of training/competing.
There are a variety of feeding strategies and grass species that you can focus on for managing horses with insulin resistance. Selecting the right forage crops are an important part, but just one piece of the management needed. Pasture grass is one of the highest sources of sugar in the diet, but carbohydrate content (which encompasses starch, ESC, WSC, and nonfiber carbohydrates) varies depending on the soil type, the climate, hours of sunlight, species, season, and time of day. Horses with insulin resistance should have carefully restricted access to pasture.
That said, species that are lower in sugars and allow for longer grazing times include timothy, brome orchardgrass, bermudagrass, and teff. Millet and crabgrass are acceptable as well, although millet can have higher sugars when nights are cooler. (Second cuttings of summer grasses like millet and crabgrass tend to be especially low in sugars because the hot, dry weather typical of midsummer.) Avoid ryegrasses, meadow fescue, and cereal hay, such as wheat and oats. Alfalfa is a good source of both protein and less-digestible fiber. When fed as the primary forage, it meets or can exceed horses’ calcium and protein requirements.
Cool season grasses accumulate more starches, sugars, and fructans (a carbohydrate that is digestible only in the large intestine), and are higher in total energy content. Although alfalfa hay is higher in total energy content than grass hays, most of the energy is from protein and fiber.
Grasses growing in cooler weather in general accumulate more sugars because they respire less. For this reason, warm season grasses are less apt to accumulate sugars and can help control weight and blood glucose concentrations.
Avoid grazing any pasture grasses when they’re growing rapidly or going through a dynamic phase – for example, after a summer rain, or entering dormancy in late fall.
Exercise should be carefully balanced against caloric intake. Animals should be limited to 2 percent of their body weight in feed on a dry matter basis. And intake should be carefully spaced out. If you’re feeding hay, for example, you would want to feed more frequent, smaller meals to keep blood sugar levels steady and prevent an insulin spike when hungry animals eat too much at once.
Make hay feeding a priority. Hay should be fed before animals are released onto pasture – one good scenario is to feed hay all night before turning animals out early in the morning, when sugar levels are lower. Keep in mind that given a choice, horses will consume lush pasture grasses before hay every time – no matter how good the quality.
Some horse owners find that soaking hay in cold water for 30 minutes lowers the sugar content.
Keep horses off of weedy pastures as well, since weeds can have a greater concentration of iron than forage grasses, potentially leading to elevated insulin. Depending on species, they can also be higher in sugar.
Cut back on fertilizing pastures more than you would for high-performing animals. This takes some balance to avoid encouraging overly lush pastures high in carbohydrates. Don’t neglect balanced fertility in the pasture, however – that’s the best way to encourage weediness. Clipping regularly to (ideally) a 6-8 inch height is also a good way to keep weeds back.
In spring, when grass is at its most lush and rapid growth, horses will want to consume more. This also can lead to excess carbohydrate consumption. Introduce them slowly and gradually to a pasture, and carefully restrict grazing time. Muzzles can also be used to limit intake.
While on pasture, horses should have plenty of access to good quality water, since dehydration can lead to high blood sugar levels. Muddy stock ponds and other substandard water sources will lead to lower intake. Water helps move the forage through digestion faster, which keeps insulin levels under control.
Some additional management considerations: Beware of grazing after a frost, since frost can greatly increase fructans in the plants within a few hours. Plus, fructans will be highest in the base of the plant – a good reason to avoid close grazing (which requires close management for horses). And, even hay can run the risk of higher sugar content if it is cut in bright sun.
In summary, graze more mature forages, keep animals active while watching their calorie intake, limit time grazing, and be sure to provide other feeds in supplement to the grasses – especially those that supply a greater lignin content. The species you graze the horses on are important, but the maturity stage of the grass is just as critical – aim to graze the animals on more mature forages than you would high-producing dairy or beef cattle.
Note: These are suggestions only and in no way guarantee the prevention of adverse effects of equine diabetes. Also, this is meant to be a holistic approach. Choosing to follow only one piece of this advice may or may not deliver the intended result, as there are many variables involved. Work with your nutritionist to analyze each of your feed sources so that your horse’s diet may be optimized for its individual needs (and of course, to avoid harm to an animal).