Pasture grazing is often considered one of the most natural sources of nutrition for a horse. While this is largely true, both lush pastures and grain-based concentrates can also contain staggering levels of unhealthy sugars. Here’s what you can do.
When compared to the feral horse eating a natural diet on rangeland, the maintenance horse on lush pasture is much like a kid in a candy store. While a feral horse spends a substantial amount of time walking and selecting food sources, such as native grasses and shrubs, a horse on pasture is often surrounded with high-calorie grass that’s full of hidden sugars he can consume to his heart’s content. Similarly, providing a horse with a large bucket of grain-based concentrate gives him a meal replete with calories and carbohydrates.
Horses choose to eat what tastes good to them, and they won’t stop eating once they’ve fulfilled their nutritional requirements. This situation can quickly lead to an overload of sugar which, under the right circumstances, can cascade into laminitis. Even in the absence of laminitis, the overconsumption of lush pasture grasses or grain-based concentrates can quickly lead to obesity and insulin resistance.
With these consequences in mind, it might seem as if carbohydrates should be avoided in the equine diet. However, not all carbohydrates are created equal. There are simple sugars, such as glucose, and more complex carbohydrates, such as starch and fiber. Let’s take a closer look.
Simple sugars vs. fiber
- Simple sugars and starch produce lactic acid when fermented in the hindgut (cecum and colon). Substantial lactic acid production alters fluid and electrolyte absorption and makes the hindgut more acidic, which can result in the death of certain types of microbes. When this process occurs on a large scale, the massive death of microbes can combine with other compromising factors, leading to endotoxemia which can result in laminitis.
- Fiber is a complex carbohydrate, and one of the most important components of an equine diet. Not only is it essential for gut health, but it is also a major source of energy. When fiber is fermented in the horse’s hindgut, it produces volatile fatty acids, which can provide the vast majority of calories he requires when he’s on a forage-only diet. Additionally, the microbes that perform the fermentation produce other beneficial by-products, such as vitamin K and B vitamins.
Comparing these effects may lead to the conclusion that fiber is a “good carb” and simple sugars and starches are “bad carbs”. However, simple sugars and starch only become “bad” when they are in the wrong place at the wrong time – much like the kid in the candy store.
Simple carbohydrates aren’t so simple
During the normal digestion process, starch is broken down into simple sugars by enzymes in the small intestine. These simple sugars are quickly absorbed and enter the bloodstream to be used as an energy source for the body. As long as this process occurs, large amounts of starch and sugar won’t make it to the hindgut where they can cause trouble.
However, there are limitations to the amount of starch and sugar a horse can digest in the small intestine. When a large meal of sugars and starches is consumed at once, it often results in a spillover of some of these sugars and starches into the hindgut. Additionally, certain types of sugars and starches nearly always end up in the hindgut because they are not able to be digested in the small intestine (these include fructans and resistant starches).
Fructans are chains of fructose molecules that serve as a common form of energy storage for cool-season pasture grasses. Resistant starches cannot be broken down in the small intestine because of their specific chemical structure, or because they are contained within a feed that has to be broken down in the hindgut (typically grains).
Planning your horse’s diet
To avoid these issues, it is necessary to minimize the amount of starch and sugar load a horse receives, particularly through fructans and resistant starches. To minimize the starch and sugar load, split grain-based concentrate feedings into multiple small meals. If possible, find a substitute for grain-based concentrate altogether. Either of these options will limit your horse’s exposure to grains – the primary source of resistant starch in a horse’s diet.
Avoid grazing your horse on pasture during periods of rapid growth (e.g. after a sudden increase in rainfall or on fresh spring grass) or when the plants are undergoing stress (e.g. in cases of drought and overgrazing). This will help minimize his exposure to fructans. Consider restricting your horse’s access to pasture, if necessary.
For a horse that is especially sensitive to the effects of sugars and starches, such as an overweight animal with a cresty neck, you may want to consider restricting turnout to the late evening and early morning, or removing him from pasture entirely and substituting with hay. For horses that are less prone, pasture grasses are still an excellent nutritional option. However, the limitations of starch and sugar digestion depend on what the horse has been adapted to, so make any changes gradually. Overall, carbohydrates are an essential part of a horse’s diet, but it is important to keep starch and sugar in the foregut where they belong.
Forage balancer/supplement – Most classes of horse are able to obtain their calorie needs from hay or pasture alone. For those horses, a forage balancer or vitamin-mineral supplement is often all that is needed to ensure they’re getting the nutrients they need without adding extra calories. You can feed the balancer or supplement alone, or as a meal topper on beet pulp (soaked until it puffs up) for horses that could stand to gain a few extra pounds.
Beet pulp – This is an example of a feed that provides calories primarily from fiber and fat, rather than starch and sugar. It is a highly digestible source of fiber, meaning it is a good source of calories, but is also low in sugar. Additionally, you can easily mix other things into it (like that vitamin-mineral supplement we mentioned) and/or top-dress it with vegetable oil to provide even more calories.
Salt – A salt block, or loose salt, is another dietary addition every horse should have. It’ll help ensure he is getting the right amount of sodium, and will aid in keeping him hydrated. Just be sure to provide constant access to fresh clean water!