Archive for March 27th, 2012

Drought and Its Impact on Your Pond

Tuesday, March 27th, 2012

Are Sugars, Starches and Grains “Evil” in Horse Diet

Tuesday, March 27th, 2012

Have you ever watched a pendulum swing? It swings way to the right, and then goes back to center. Then it swings way to the left, then returns to center again. In human nutrition, the sugar and starch pendulum appears to be returning to center. In equine nutrition, however, that sugar and starch pendulum seems to be hung up way off to the side.

Before we talk about the “evil” nature of sugars and starches (and therefore grains since they usually provide the majority of starches in a horse’s diet), we need to talk about carbohydrates. Sugars and starches are carbohydrates, but fibers are also carbohydrates. Fiber carbohydrates (structural carbohydrates) are important in a horse’s diet, and are primarily provided by the forages (grass or hay) that the horse eats. When people talk about feeding a “low carb” or “no carb” diet to horses, that implies that we need to reduce or eliminate the hay
or grass in the horse’s diet as well as the concentrate (or grain-based) feeds. That is usually not what we want to do, because fiber is essential to maintain the health of the horse’s digestive tract. The sugars and starches are nonstructural carbohydrates or NSC (sometimes referred to as soluble carbohydrates). In some situations it may be beneficial to reduce the NSC in a horse’s diet.

Are nonstructural carbohydrates “evil”? In the horse’s small intestine, most nonstructural carbs are broken down into glucose, a simple sugar. The glucose is then absorbed into the blood stream, and is carried to various tissues where it is used as fuel, or stored as glycogen (in the muscle or liver, where it later used as fuel) or as fat. Glucose is very important for the horse to function properly, as it is the only fuel that can be used by the brain, it is used to a large extent by the hooves, and it is the only substance that can be used for making glycogen. Studies have shown that horses that use up all their glycogen and are not provided glucose to replenish the glycogen stores show greatly reduced performance capabilities. So glucose is vital to the health and well-being of the horse. Again, glucose comes primarily from NSC.

So, again, are nonstructural carbohydrates “evil”? We know that too much NSC (particularly starch) in a horse’s meal can cause problems. We want the NSC to be digested in the small intestine, but if we feed a large meal that contains so much starch that it overflows from the small intestine into the large intestine, it may cause digestive disturbances such as colic or laminitis. Studies have shown that feeding no more than about 0.5% of a horse’s bodyweight of grain in one meal will reduce the risk of grain overload into the horse’s hindgut, therefore reducing the risk of colic or laminitis.

For laminitic horses (horses that have been previously been diagnosed with laminitis) feeding less NSC may be helpful in reducing the chance of a recurrence. Horses with chronic laminitis may be more susceptible and more sensitive to NSC in the diet.

There are some horses that suffer from disorders such as Cushing’s Syndrome. This disorder may cause a problem in the regulation and use of glucose in the body. The hormone insulin helps regulate glucose, by causing it to be removed from the blood into the tissues where it is used or stored. In horses that suffer from Cushing’s Syndrome, the insulin may not function properly to regulate the glucose, and we see high levels of glucose in the blood. We call these horses “insulin resistant”. In these situations, it may be beneficial to feed less NSC so that there will be less glucose provided by the diet.

Another situation in which low NSC diets are recommended is for horses diagnosed with “Equine Metabolic Syndrome”. These horses are usually obese, and blood tests show them to be apparently “insulin resistant”. However, in many cases if the horses are put on low calorie diets and lose weight, their glucose and insulin values return to normal.

Once again, are nonstructural carbohydrates “evil”? In my opinion, the answer is a firm “NO”. There are some situations in which some horses may benefit from lower levels of NSC in their diets. However, we need much more research to determine where the level of NSC needs to be, because the horse still needs glucose for brain, muscle and hoof function. We don’t know at this point where the lower limit of NSC in the diet is to ensure adequate glucose to supply the body’s needs. We also do not know where the upper limit is to reduce the potential for NSC in the diet to cause problems for insulin resistant horses. As an equine nutritionist, I try to ensure that the total diet includes
all the essential nutrients to meet the horse’s nutritional needs without exacerbating any medical conditions. For most typical horses, the amount of NSC in a standard diet of grass or hay and concentrate feed will cause no problems. In situations where the NSC may be an issue, there are factors to consider other than just how much grain is in the horse’s diet.

Horse owners almost always look at the grain portion of their horse’s diet to reduce the NSC. However, just because a feed contains grains, it does not mean that the feed is high in NSC. Conversely, just because a feed does not contain whole grains does not mean that it is low in NSC. Different ingredients in a feed contain different amounts of nonstructural carbohydrates, and it is the total mixture of ingredients that determines the NSC content of that feed. Purina Mills has several feeds available that are low in NSC. And more importantly, those feeds are formulated to contain all the nutrients necessary to meet the horse’s nutritional needs.

Further, we need to keep in mind that fresh grasses and some hays can contain fairly substantial amounts of NSC. When dealing with a horse that is suffering from a disorder that may be aggravated by high levels of NSC, it is vital to look at the forage portion of the ration as well as the concentrate to determine the best total diet for that horse.

Finally, it is essential to keep in mind that each horse is an individual with individual needs. When we start looking at individuals with special needs such as those with Cushing’s Syndrome, or obese horses, or laminitic horses, there is no cookie cutter approach to meeting the horse’s nutritional needs as well as the medical needs.

At Purina Mills, we have a large variety of feeds available to meet the needs of horses in many different situations. We have a number of equine nutritionists and veterinarians involved in current research to determine the best blends of all ingredients and nutrients to provide the safest and most effective ways to feed horses. Our goal is to provide the best nutrition for your horse by supplying the nutrients necessary to support your horse’s health, performance, and longevity.

 

Katie Young, Ph.D., Consulting Equine Nutritionist

Formulating Horse Feeds

Tuesday, March 27th, 2012

When choosing a horse feed, looking at the guaranteed analysis can help you determine if the nutritional content of that feed is appropriate for the age and activity level of your horse.  You’d think that two products that both contain 14% protein, 6% fat, etc. would be pretty much the same feed.  However, products with similar guaranteed analyses may be manufactured using different formulation strategies and have very different formulas.  This can affect the nutritional value for your horse.  The most common formulation strategies are “Least-cost” formulas and “Fixed” or “Locked” formulas.  Both strategies have benefits and drawbacks.  There is a formulation strategy that Purina uses for premium horse feeds, “Constant Nutrition” formulation, which is more nutritionally accurate than either of the other strategies.

Least-cost formulation allows a manufacturer to adjust the ingredients in the formula based on cost.  As long as the formula still meets the guaranteed analysis, the manufacturer can change the ingredients used in the formula.  In some circumstances, the change in ingredients doesn’t change the effectiveness of the diet so it makes sense to meet the nutritional needs of the animal in the least expensive way.  There would be no benefit to making a more expensive ration to achieve the same results.  For instance, if you are feeding cattle and being paid for weight gain and a least-cost formula will not change the rate of gain or feed efficiency of the cattle, but will be less expensive to feed, that just makes good business sense.  However, in some cases, especially when feeding horses, a major change in ingredients can dramatically alter the effectiveness of the diet, even when the nutrient levels don’t change.  A good example of this would be substituting cottonseed meal for soybean meal in a diet for growing horses.  Soybean meal and cottonseed meal may both have similar total protein content and could be interchangeable in a formula to meet the protein guarantee.  However, cottonseed meal does not provide the same quality of protein to support growth as soybean meal, and young horses will not grow as well eating a feed with cottonseed meal as the protein source.  So, in this case, the least-cost formula may be less expensive per ton but the loss in animal performance will negate any cost savings.  In addition to potential for reduced performance, there is always the potential for reduced palatability or digestive upset in horses when large shifts in ingredients occur in their feed.

With fixed or locked formulas, the same ingredients and amounts of ingredients are used every time the feed is made, regardless of price or nutritional variation of those ingredients.   This sounds like the most consistent way to make horse feed; however, there is a significant drawback.  All ingredients, even high quality ingredients, have variation in nutritional content.  For instance, all oats will not have the same protein or mineral content.  If the formula is completely locked and not taking into account the nutritional content of the individual ingredients, the level of nutrition provided in the finished product will vary.  Horses do benefit from consistency in their diets, but they don’t have specific requirements for certain ingredients.  The purpose of ingredients is to provide nutrients the horse needs. So, while a fixed formula does provide the same amount of ingredient in every bag, it may not provide the same level of nutrition.  For example, a horse feed made of 49% oats, 20% beet pulp, 16% corn, 8% alfalfa and 7% soybean meal would average 14% protein, using the average book values for these ingredients.  However, with the typical range in protein content of these ingredients, the end product could range from 12.4% to 21.1% protein.  Other nutrient levels will vary as well.  So, while a fixed formula does insure a consistent ingredient profile, it won’t provide the most consistent level of nutrition for the horse.

“Constant Nutrition” formulation is a key component of the Purina FeedGuard™ Nutrition System.  This strategy provides consistent, reliable nutrition in every bag of premium Purina horse feed.  Under the Purina FeedGuard™ Nutrition System, stringent quality standards are set for ingredients which are purchased only from an approved list of suppliers that meet those strict criteria.  Then, when ingredients arrive at a manufacturing facility, the ingredients are inspected, sampled and analyzed for nutrient levels.  This is more accurate than using published book values or supplier averages for nutrient levels of ingredients.  If an ingredient is approved, then the tested nutritional content is entered into the formulation system, which then makes small adjustments in amounts of ingredients to maintain consistent nutrient concentrations in the finished product.  There are strict restrictions for how much adjustment is allowed to ensure consistency in formulation.  For example, the amount of soybean meal may be adjusted slightly to compensate for lower protein in another ingredient, but cottonseed meal could not be substituted for soybean meal.  This formulation strategy ensures that horses always receive the most consistent nutrition possible, and that horse owners always get exactly what they pay for.

Karen E. Davison, Ph.D.
Manager- Equine Technical Services
Land O’Lakes Purina Feed

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