Like a celebrity on a downward spiral, starch has been getting a lot of press in the last few years…and most of it negative. Unlike celebrities, starch doesn’t gain anything from the media exposure. Although it may be unpopular, I’d like to take a moment to say a few words in defense of starch; a (recently) under appreciated, yet useful nutrient in horse diets.
But first, let’s start with what it is. Starch is a complex chain of sugar molecules, which is the main source of energy for plants. It is stored within the cell walls of the plant and therefore, considered a nonstructural carbohydrate (NSC). Starch in horse feeds are most commonly sourced through grains such as oats, barley, corn, rice or wheat and the co-products of these grains such as corn distillers grains, rice bran or wheat midds.
When ingested, starch molecules are broken down into smaller sugar molecules (glucose) that are readily absorbed. With the help of insulin, the glucose in the bloodstream is ‘picked up’ by muscles and other tissues to either be used to support activity or stored (as glycogen) for future energy needs. Hard working and active horses need glucose and glycogen to support their activity levels and recovery from activity. It’s also worth pointing out that NSC’s are a very efficient pathway to providing energy to the horse and to aid in muscle recovery (glycogen repletion), particularly in horses performing athletic activities.
Most horse owners know that too much starch at one time can overwhelm the horse’s digestive system. That excess, undigested starch could leak into the hind gut where it can rapidly ferment, leading to an overproduction of gas and lactic acid, which in turn, could cause gas colic and/or acidosis which could then lead to laminitis or other issues.
You’re probably wondering, if it’s needed by horses for energy, but also potentially dangerous then how does the horse get what he needs without wreaking havoc? The answer lies in the QUANTITY of starch consumed in each meal.
The majority* horses can tolerate a moderate level of starch each day. This is not to say, all at one time. There is a big difference! Consider the digestive system of a horse to be like a waterway – it can tolerate a certain quantity of water running through it (or in this example starch) but if there is too much at one time, the water overflows and goes where it is not supposed to go. Same with starch in the digestive system – the body can handle a moderate quantity of starch released at a controlled rate, but too much at one time (or from too big of a meal) and the whole system gets out of whack.
I offer up one last nugget to consider: oats – the long-time staple of ‘safe’ feedstuffs for horses, actually contains approximately 40% starch. Now there’s something to think about…
So, in defense of starch, I’d just like plead the following. When consumed in moderate amounts/meals, frequently over time, starch is a useful and practical source of energy for most horses.
In my next post, we’ll talk about how to evaluate starch levels in feeds. Stay tuned for more….
*Horses diagnosed with a form of Equine Metabolic Disease (EMS) require a diet that is closely managed to control and limit the amount of NSC (including fructan from forage) in their diet.