Starch Levels in Feed

In my previous blog post on this topic, we explored the role starch plays in the horse’s diet.  After (hopefully) warming you up to the idea of how useful this nutrient can be, I’d like to now dig in to how you can compare and contrast the varying levels of starch (and sugar*)  in feeds and hopefully this information will  help you compare and contrast to choose the best option for your horse.

Contrary to what you may have been told or read, most horses can tolerate a moderate level of starch each day.  If you have a horse that has been diagnosed with a form of equine metabolic disease, you will need to limit your horse to a ‘low’ controlled starch and sugar diet….which includes forage (hay and pasture).  Fructans, the sugars in forages, are too often overlooked when assessing the total diet of an EMS horse.  

Even if your horse has not been diagnosed with EMS, it is still important to understand the starch level in his diet and take it into consideration for your overall program. Think you know how to compare starch levels from one feed to another?  You might be surprised to find out that a bit of math is required. Simply comparing the percentage of starch on feed tags doesn’t quite tell the whole story.  To get to a true comparison, it is important to factor in the recommended feeding rate, which is, after all, what the horse experiences.

Let’s compare two feeds that are marketed as ‘low starch’; one has a starch maximum guarantee of 7% while the other has a maximum of 11%.  Pretty easy to tell which one is the lowest, right? 

Look beyond the percentage to find what's really in the feed

Not quite.  For our example,  let’s say we have a 1,000 pound horse at maintenance level activity.  Feed A, with 7% starch is recommended to be fed at a rate of 6 pounds per day, meanwhile, Feed B has a starch maximum of 11% and is recommended to be fed at a rate of 2.5 pounds per day.

Here is the formula to use:  Starch % * pounds fed/day *454 (converts to grams) = grams of starch fed/day

 

Applied to our example scenario, here’s how the math works out:

Feed A:  7% starch x 6 pounds fed x 454 = 190.68 grams of starch per day.

Feed B: 11% x 2.5 pounds of feed x 454 = 124.85 grams of starch per day.

Wow – a big surprise!  Not only is the 11% starch feed actually lower in grams of starch per day than the 7% product, the difference is actually rather significant given how different the percentages were.   It is important to keep in mind that it all comes down to what your horse actually ingests, so understanding the recommended feeding rate in pounds and then weighing your feed to hit that mark is what will make the difference.

It’s also important to understand that horses who do not experience a form of EMS have a higher tolerance for starches and sugar in their diet…and in fact, the performance horse will actually need those nutrients to support their activity levels.  It all comes to down to understanding what’s in your feed and how much you’re giving them.

*Though this blog article addresses ‘starch’ the same principles apply to determining the amount of other nutrients in a feed. 

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. 

Hay Soaking: All Washed Up or Good Management?

This article is courtesy of Krishona Martinson, PhD, University of Minnesota.

Soaking hay in water is a common strategy used to manage the nutrition of some diseased horses.  Current hay soaking recommendations include soaking hay for 30 minutes in warm or 60 minutes in cold water for removal of carbohydrates (Watts, 2003).  Soaking hay is commonly done to manage horse diagnosed with laminitis, Polysaccaride Storage Myopathy (PSSM), hyperkalemic periodic paralysis (HYPP), and chronic obstructive pulmonary disease (COPD). 

  • Researchers have suggested that diets contain less than 12 and 10% nonstructural carbohydrates (NSC) for horses affected with laminitis (Frank, 2009) and PSSM (Borgia et al., 2009), respectively. 
  • Reynolds et al. (1997) determined that a diet less than 1% K is necessary for horses diagnosed with HYPP.
  • Moore-Colyer (1996) determined that soaking hay for 30 minutes reduced respiratory problems for horses diagnosed with COPD or heaves. 

However, how efficient is hay soaking, and are additional essential nutrients lost during the soaking process?  Researchers at the University of Minnesota set out to determine the impact of water temperature and soaking duration on removal of NSC, crude protein (CP), minerals, and dry matter (DM) from alfalfa and orchardgrass hays. 

Four hay types were soaked, including bud and flowering alfalfa, and vegetative and flowering orchardgrass.  Individual flakes were submerged for 15, 30 and 60 minutes in 25 liters of cold (72°F) and warm (102°F) water, and for 12 hours in cold water.  A control (non-soaked) sample was also evaluated.  Water temperatures were determined by using the cold or warm only faucets, similar to practices implemented by horse owners and managers.  Subsamples of entire flakes were submitted for nutrient analysis at a commercial laboratory.

  • Prior to soaking, both alfalfa hays were below the 10 and 12% NSC threshold for horses diagnosed with PSSM and laminitis, respectively, and would not have required soaking. The orchardgrass hays were above these thresholds, however, after soaking for 15 to 30 minutes were at or below 10 to 12% NSC. 
    • Although soaking hay for longer durations did further reduce NSC content, it is not recommended.  All horses, even diseased ones, require carbohydrates in their diet. 
    • The severely limited NSC content in hay soaked for greater than 1 hour, combined with increased fiber amounts (fiber components are not water soluble, thus they are concentrated in soaked hay), brings into question the palatability and availability of nutrients in hay soaked for longer periods of time.
  • Crude protein leaching was variable in soaked hays, something other researchers have also observed (Moore-Colyer, 1996).  More importantly, previous research looked at the nutrient availability and quality of rained-on hay fed to steers and suggested the nitrogen remaining in rained-on hay is more stable, water-insoluble (Rotz and Muck, 1994), and possibly less digestible by ruminants (Licitra et al, 1996).  Additional research is needed to evaluate this concept when feeding soaked hay to horses.        
  • Calcium (Ca) is not as prone to leaching during soaking compared to other minerals, and appears to be dependent on hay maturity.  As soaking duration increased, leaching of Ca increased in alfalfa bud and vegetative orchardgrass hays (immature hays).  However, soaking had no effect on Ca leaching in the more mature hays. 
    • Conversely, magnesium (Mg) Mg and phosphorus (P) levels were reduced in all hay types as a result of soaking, with longer soaking durations leading to greater reductions.  Because Ca is not as water soluble as P, high Ca:P ratios were observed in hays soaked for  longer durations, specifically after 12 hours. 
    • Ideally, Ca:P ratios should range from 1:1 to 3:1 (up to 6:1) in horse diets (NRC, 2007).  The high Ca:P ratios observed after longer soaking durations were exaggerated in alfalfa hays which had higher Ca:P ratios prior to soaking. 
    • After 12 hours of soaking, a deficiency in P was observed and ranged from a shortage of 1 to 8 grams for a 500 kg horse in light work (NRC, 2007), and Krook and Maylin [32] suggested that osteochondrosis may be associated with excess dietary Ca. 
  • Soaking both alfalfa and orchardgrass hay for 12 hours was necessary to sufficiently reduce K concentration to recommend levels prior to feeding horses diagnosed with HYPP (Reynolds et al, 1997).  Although K levels can be reduced by soaking, neither alfalfa nor orchardgrass hay is an appropriate option for horses diagnosed with HYPP due to the naturally high levels of K. 

Owners should rely on forage analysis as the primary method of determining the appropriate hay for horses, especially when feeding horses diagnosed with laminitis, PSSM, HYPP or COPD.   Hay soaking for short durations (15 to 30 minutes in duration) is an acceptable management method, but should only be used if ideal hay is not available.  Hay should not soak hay for greater than 1 hour.  Soaking hay for long durations resulted in severely reduced NSC content, high Ca:P ratios, shortage of P in the diet and significant losses in DM.

Types of Carbohydrates in Horse Feed Diets

The topic of carbohydrates for horses has gotten a lot of people asking questions and has created a certain amount of confusion, particularly when comparing carbohydrates in equine diets to human dietary recommendations.  Starches, carbohydrates, sugars, non-structural carbohydrates (NSC) and non-fibrous carbohydrates (NFC), among others, are terms thrown around for equine diets, and all those terms can get very intimidating, when it comes to what these nutrients mean to your horse  and how much your horse needs or doesn’t need. 

Here is a list of each of the common terms, and what they include:

  • Structural Carbohydrates – This category includes primarily the carbohydrates that are part of the cell wall in plants. 
    • This will include the Neutral Detergent Fibers (NDF), primarily lignin, cellulose and hemicelluloses. 
    • These carbohydrates are all fiber sources that give cell walls strength and shape.
    • Some types of fiber analysis, such as the Total Digestible Fiber (TDF) measurement used in human nutrition, will include the structural carbohydrates plus pectins, gums, beta glucans and some polysaccharides. 
    • These are the carbohydrates that are not broken down by enzymes and need to be fermented in the hind gut of the horse.
  • Non-Structural Carbohydrates (NSC) - This includes the sugars and starches, and is a very important group of nutrients for horses because these are the carbohydrates that can be broken down by enzymes and absorbed from the small intestine into the blood stream as glucose and stored as glycogen in the muscles and in the liver. 
    • Ideally, NSCs get absorbed entirely in the small intestine before they reach the cecum and large intestine, where they can be problematic for horses.  When people ask about a “low-carb” diet, they are frequently really asking about a low NSC diet.
    • Water Soluble Carbohydrates (WSC) - This includes ethanol soluble carbohydrates (ESC) which are primarily sugars, both monosaccharides and disaccharides.  WSC will include various oligosaccharides and polysaccharides.  Fructans in forages are included in the WSC.  When looking at a feed or hay analysis report, ESC should be a small proportion than WSC of the NSC.
  • Non-Fiber Carbohydrates (NFC) – This is a different nutrient which is calculated in certain analytical techniques.  NFC is equal to (100-Water-Ash-Fat-Protein-NDF).  NFC is calculated by difference and is not measured by a specific analysis.  NFC will contain all of the organic acids, starch, sugars, oligosaccharides, polysaccharides, beta glucans, pectins and gums.  For this reason, NFC will be a larger number than NSC in a feed or hay analysis report.

Carbohydrates in Horse Diets

There is a lot of discussion these days about carbohydrates, the good and the bad.  In reality, they are all related.  Carbohydrates contain carbon, hydrogen and oxygen in varied chemical relationships. 

  • Sugars are the simplest of the carbohydrates and can be simple sugars such as glucose or more complex sugars. 
  • Starches are strings of sugars linked together in such a way that most starches can be broken down into glucose by the action of enzymes, primarily amylase. 
  • Fibers (lignin, cellulose, hemicelluloses etc.) are also chains of sugars that cannot be broken down easily by enzymes and must be fermented by the animal to release the energy. 

Starches and sugars are produced by plants as a means to store energy, so they contain energy that is more readily available than the energy in fiber.

Because horses produce less amylase, the enzyme used to break down starch, than some other animals, say perhaps pigs, they are more limited in their ability to digest large quantities of starch. However, they digest smaller quantities very efficiently and very effectively! 

Starches and sugars are a fairly concentrated source of Calories to be used as a source of energy when extra energy is required to maintain body condition and do more work.  In the wild, horses would consume seed heads (grain) when available in the fall to help them gain weight (added Calories) to be ready for winter, so starches and sugars are a part of the diet in horses in the wild.  Today’s working horse requires Calories, and a combination of fiber, starch, sugar and fat can be the best way to support the horse to maintain the balance of optimal health and optimal performance.