Tour the Equine Digestive Tract

Ever wonder how your horse’s digestive system works? What goes on in there? Why are they so sensitive? And why should I divide the feed ration into 2 or 3 feedings per day? Let’s take a closer look to better understand.

The Equine Digestive Tract:

Digestive Horse Cecum_logo

Mouth & Teeth: Teeth are the beginning of the entire process. Designed to grind foodstuffs into smaller pieces, the act of chewing also stimulates three glands in the mouth to produce saliva. These glands can produce up to 10 gallons per day of saliva. The saliva contains bicarbonate (a natural acid buffer) and amylase (assists with carbohydrate digestion). Teeth are an important component to digestion and should be checked annually to insure proper function. A horse that is unable to effectively chew long stem forage, such as a senior horse, is at higher risk of impaction colic. If you have a horse like this, be sure to consult with your veterinarian for a comprehensive care and feeding program.

Esophagus: The purpose of the esophagus is to funnel food from the mouth to the stomach. Approximately sixty inches in length, this is a one-way passage. Unlike humans, horses cannot vomit. This is why horses who ‘bolt’ their feed (eat too fast and don’t chew adequately) can get into trouble and feeding practices need to be adjusted to reduce the risk of bolting feed.

Stomach: Small in size compared to the rest of the horse’s body, food will only spend about 15 minutes in the stomach before it moves on. The stomach is designed to function best when it is ¾ full; therefore, care takers are encouraged to provide horses with a steady supply of forage throughout the day. Because of the small size, a horse should not be fed more than 0.5% of body weight in one meal. Meals of grain are best divided into 2 or 3 portions per day.

Small Intestine: After leaving the stomach, food will spend anywhere from 30 to 60 minutes here; a good thing with the many nutrients that are absorbed. Nutrients such as proteins (amino acids), vitamins A, D, E and K, calcium, phosphorus, and other minerals along with starches and sugars. Cereal grains such as oats, barley, and corn that are high in carbohydrates (starch and sugar) are easily digested here. The horse doesn’t have a gall bladder, so bile from the liver flows directly into the small intestine to aid in the digestion of fat.

Large Intestine: is comprised of the cecum, large colon, small colon and rectum.

  • The cecum is located on the right side of the horse and is where fiber is digested and converted to energy and heat. The shape of the cecum is unique because the entrance and exit are located at the top of the organ. Able to hold up to 10 gallons of food and water, the cecum contains populations of bacteria and microbes which further break down food (fiber) for digestion and absorption. These microbes are accustomed to digesting a horse’s ‘normal’ diet, so any adjustments in feed or forage should be done slowly, allowing the microbes to adjust.
    • If a horse consumes too much starch in one meal, it is unlikely to be digested fully in the small intestine. It would pass through the small intestine into the cecum where the microbial organisms rapidly ferment the starch, producing excessive gas and lactic acid that could ultimately cause digestive upset or colic.
  • The large colon continues the digestive process by absorbing additional fiber components and water. This is where B vitamins are absorbed.
  • The small colon is where excess moisture is reclaimed to the body. This is also where the formation of fecal balls occurs.
  • The rectum is where the fecal balls are expelled.

With this short tour and explanation, we hope you have a better understanding of how your horse digests and absorbs nutrients, and that this also sheds light on why good feeding management and regular dentistry care are important aspect for the digestive health and overall well-being of your horse.

In Defense of Starch

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. 

Glycemic response of oats and controlled starch diets, in horses

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. 

Pre and Probiotics in Horse Feed

While scanning information about various horse feeds, you may have come across the phrase ‘contains prebiotics and probiotics’….Hmmm, sounds impressive, but what are they, what do they do for your horse, and why are they important?  Pre- and probiotics are considered “functional ingredients” that are added to horse feed to provide benefits to your horse. Here is some information about them and what they can mean for the digestive tract and overall wellbeing of your horse.

Healthy, inside and out
Rosie shows a dappled coat, indicating good health shining from the inside out.

It starts with the gut. The environment of the intestine (a.k.a. gut) contains naturally occurring beneficial microorganisms commonly called  ‘bugs’. Gut bugs are found in all species, including humans, and are essential to the digestion process. For the horse, gut bugs work to break down components of forage and feed as they pass through the digestive tract.  The bugs deconstruct complex molecules within feedstuffs, which releases nutrients and allows the synthesis of energy substrates and important vitamins. Those nutrients are then absorbed through the intestines into the bloodstream, where they become available to cells in the body to support basic maintenance, growth and activity.

Feed that is broken down and digested more completely allows for more nutrients to be readily available for absorption.  This is essentially what probiotics do. Adding probiotics to a horse feed means adding more beneficial bugs to the existing population in the horse’s gut. Probiotics such as yeast culture, work with the naturally occurring bug population to enhance the digestive process, further breaking down complex protein and fiber fractions in the gut and making them more available for absorption into the blood stream. As a probiotic, yeast culture has also been shown to balance and stabilize the digestive microbial ecosystem in the cecum of the horse, as well as help prevent the colonization of bad bacteria in the gut.  A stable microbial ecosystem is beneficial to the horse beyond improvements in digestive and absorption efficiency, it also reduces the risk of digestive upset, such as gas colic, that a horse might experience with changes in feed or hay, or while under stress from transportation, shows, changes in weather or other.

Prebiotics can be thought of as an energy jolt for the gut bugs.  Prebiotics are a rich nutrient source for the gut bugs (e.g. lactobacilli, bifidobacterial) which in turn stimulates their growth and activity, making them more effective at their job. Research has shown that prebiotics help stabilize the population of gut bugs even through sudden changes in the diet, which helps to reduce incidents of digestive upset.  For performance horses who require energy dense diets that include higher levels of starches and sugars, prebiotics can help reduce the incidence of digestive disorders and support optimal performance.  Prebiotics such as inulin and oligofructose are selectively fermented by the gut bugs, stimulating their growth and activity, which benefits the horse by enhancing the absorption and retention of certain minerals, which in turn can support the immune system, skeletal tissue, and more.

The population of bugs in the gut are sensitive to changes in their environment brought on by stress, illness or the ingestion of undesirable materials .The addition of pre- and probiotics to a diet has been shown to be beneficial in reducing the incidence of digestive upset, namely diarrhea. For senior horses, the use of pre- and probiotics in feeds has been shown to improve the digestibility and absorption of nutrients, which can translate into an enhanced quality of life.  In summary, pre- and probiotics work with the naturally occurring gut bugs to support optimal gut health, aid in the digestion process, as well as provide a buffer against negative bacteria.

Horse Feeds & Supplements: What to feed?

Horse owners often wonder if they are providing enough nutrition to their horses.  In today’s world of hundreds of supplement selections available at the local tack shop or on-line, owners can start to feel as if they must be doing something wrong if they aren’t supplementing the normal hay and grain rations provided.  Here’s a few key tips to make sure you are doing everything right for your favorite equine friend – keeping in mind, of course, that quality hay/pasture fed at approximately 1.5% of body weight is the key base to all horse rations.

Feeding a commercially prepared grain:

  1. There are a myriad of choices available on the market today, to fit all types of horses.  Work with your local feed retailer, or contact your feed company of choice, for assistance in selecting what suits your horse best.
  2. Then, make sure you are feeding within the directions on the feed tag or bag.
    1. If you are feeding above the recommended range in order to keep condition on your horse, consider moving up to a higher fat feed that packs more calories per pound.
    2. On the flip side, and much more common, is feeding below the recommended feeding allowance because the horse is an “easy keeper”.  In that case, the concentrate is not providing enough of the nutrients for the horse, and you should look for a lower calorie or lower feeding rate product to ensure your horse is receiving the nutrition it needs.

Feeding supplements:

  1. If you are feeding a quality commercially prepared feed, and you are feeding within the recommended amount for your size horse, then vitamin and mineral supplements are not needed, and often recommended against.
    1. There are a host of nutritional inter-dependencies, such as copper and zinc or calcium and phosphorus working together, that commercial feed companies account for when designing products, and adding a vitamin and/or mineral supplement can interfere with those ratios and potentially cause problems.
  2. Gut health, as well as hoof & hair coat, supplements abound.  Before you buy one, check your feed tag to see what it might already be providing.  Many premium horse feeds today already contain yeast and/or probiotics for gut health, and several contain biotin & methionine – the two key components of a lot of hoof supplements.  Depending on your feeding program, you just might save time & money by not needing to supplement those.
  3. Joint and other supplements – while good joint health starts with proper nutrition from a young age (think “an ounce of prevention is worth a pound of cure”) many horses require additional support. However, there are limitations on what feed companies can put in to feeds, so these are often necessary as “extras” in the diet.