A brown quarter horse with black halter stands in profile.

January 29, 2016

By Matt McMillan, Ph. D, Equine Nutritionist, Hi-Pro Feeds

As any good scientist would say, the answer to this question is “It depends…”.  So what about starch?  It seems that starch is, and has been the hot topic of discussion when feeding your horse in recent years.  So what is starch, and how does it affect your horse? 

Starch can be defined as a non-structural carbohydrate which is composed of a long chain of glucose molecules (aka sugar molecules).  When found in the plant, it is stored within cell walls so that it can be later used by the plant for energy when needed for plant growth and/or reproduction.  Accumulation of starch can also be found in seeds such as corn, oats, and barley.  The plant places starch in high amounts in these seeds with the purpose of the seed having the necessary energy to grow and produce more plants during seed germination and maturation.

Historically, as horse owners and trainers, we have collected the corn, oats, and barley to feed to our horses to satisfy additional energy needs based on stage of life and level of activity that forage alone cannot provide.  Through this process and evolution of the horse industry we have found that all starch is not created equal and that all horses cannot effectively utilize starch in the same manner.  

In general, problems associated with horses consuming starch are sometimes due to genetic pre-disposal, sometimes due to management, and sometimes due to both.  Issues that may arise due to high levels of starch in the horse’s diet include Polysaccharide Storage Myopathy – PSSM (genetic), Extertional Rhabdomyolysis - tying-up (both), laminitis (both), insulin resistance (both), Cushing’s disease (genetic), ulceration (both), colic (both), lack of quality and quantity of forage (management), hyperactivity (both), as well as others.

So, once again, is starch bad for my horse?  Aside from problems associated with genetic pre-disposal and poor management practices, starch can actually be beneficial to the healthy horse when accompanied by the proper quantity and quality of forage, other essential nutrients, water, and good management practices.  When considering starch in the horse’s diet, the fact of the matter is, that pasture, hay, and grains all contain some levels of starch.  So how do we know what is the best amount of starch to feed our healthy horses?
 

Horses that are considered to be in maintenance, low activity, senior, or have genetic problems associated with starch intake can be fed what is considered a low starch diet.  A low starch feed is generally considered a feed that contains less than 20% starch.  These feeds are also generally found to be in a pelleted form.  Many of these diets are also considered to be high fat feeds, which typically contain between 6-10% fat.  Other feeds even lower in starch may be 10-12%, which is common for senior feeds due to the possibilities of the effects of Cushing’s Disease, etc.  Lastly, feeds that are less than 10% are typical for horses that may have issues due to genetic predisposal.

Horses that are considered to be in moderate to intense activity, are healthy, and do not have any pre-disposed genetic issues can actually benefit from feeds that are considered moderate to high in starch.  Research shows that in general, horses can consume a total diet (feed + hay) with 20% nonstructural carbohydrates without suffering any ill effects.  Typical grain feeds for performance horses will generally contain 30-35% non-structural carbohydrates (starch + sugars).  Other research indicates that the available starch and sugars in the diet, when accompanied by high fat levels also in the diet, will actually aid in glycogen sparing and help in decreasing the amount of time the horse spends in anaerobic metabolism post exercise which in turn allows for a faster recovery period.  Therefore, starch can certainly be beneficial to the performance horse under circumstances of high activity.

American Pharoah, in his recent quest and attainment of the Triple Crown, is one example of the positive effects of a high starch diet accompanied by good quality and quantity of forage and proper management.  Therefore, starch, while it must be managed according to each horse’s individual needs, actually does have a place and can provide a benefit in good nutrition for the horse.

Would you like to read more like this? Check out our Equine Resources page.