The Myths and Reality of Beet Pulp Continued
Feeds with a low glycemic index, such as beet pulp, are those that cause little or no sharp rise to blood glucose levels and generally provide most of their energy in the form of volatile fatty acids, the energy by-product of fermentation in the equine cecum and large colon. With the exception of fat (which is high energy but does not directly affect blood glucose levels), the above table gives a general ranking of glycemic index-grains and grain by-products in general being the highest, forages the lowest and beet pulp midway between the two extremes.
Other than avoiding Rocket Rides, what difference does the glycemic index make? High-energy feeds like corn are still a more concentrated source of calories than beet pulp, right? Yes, they are-however, as mentioned above, high-glycemic feeds are also much more likely to cause nutritionally-related disorders such as colic, laminitis and polysaccharide storage myopathy. For these reasons, highly soluble carbohydrate sources must be fed in relatively small and carefully managed amounts to avoid the risk of intestinal upset. In contrast, the energy in beet pulp is primarily derived from both soluble and insoluble fiber-energy which is released relatively slowly after microbial fermentation in the cecum and large colon, as is the energy in other forage feeds such as hay. While hays can contain varying amounts of insoluble fiber, which affect its digestibility and energy content, a significant portion of the fiber in beet pulp is in soluble forms, such as pectin-the same substance that solidifies fruit juice into jelly. Pectin is still processed in the cecum, but is highly digestible and easily broken down to useable energy by the microbial flora. Since beet pulp does not contain large amounts of soluble carbohydrates which may cause intestinal upset, it can be safely fed in much larger amounts.
Therefore, although beet pulp contains somewhat less energy on a pound for pound basis than grains, it can provide more total calories to the horse when substituted for part of the forage portion of the ration, or used to extend and "dilute" a meal of grain. Although lower in fiber than most hays, beet pulp can be used to replace up to 50% of the forage portion of the ration-a feeding strategy which can significantly increase total calories without increasing the risk of colic or founder.
Contrary to popular belief, while beet pulp can and usually is soaked prior to feeding, it does not necessarily have to be. In fact, in some management situations, feeding beet pulp dry is the only alternative if beet pulp is to be fed at all. Horses consuming soaked beet pulp in hot weather may be unable to finish off a large portion before it begins to sour and becomes unpalatable. Likewise, horses in cold climates may not be able to finish their soaked beet pulp before it begins to freeze. Research conducted at several universities have fed dry beet pulp in amounts up to 45% of the total diet and saw no instances of choke or other adverse reactions. Likewise, many, many tons of dry beet-pulp based feeds are fed annually without incidence. Although beet pulp, particularly that in the pelleted form, can cause choke, the choke is often in response to the particle size and the horse's feeding behavior, not necessarily due to the actual feed itself. Horses which bolt their food without sufficient chewing, or do not have adequate access to water, are far more likely to choke, regardless of the type of feed, than horses which eat at a more leisurely rate. Efforts should be made to prevent gobbling in these "wolfers"by putting rocks into the feeder or mixing in other feeds such as chaff to slow intake and encourage chewing. In any case, it should be clearly understood that, for whatever reason, some horses are more prone to choking than others. Therefore, decisions to soak or not should be made on an individual basis, taking into consideration whether feeding dry beet pulp is a necessity, the feeding behavior of the horse, and competition from other horses which encourage wolfing. In some horses, feeding soaked beet pulp may be the only alternative.
Many horse owners are also concerned that, due to the amount of water that beet pulp soaks up, and the volume that it expands to, a large meal of dry beet pulp will somehow cause the stomach to swell up and rupture. A simple explanation of the equine stomach will allay this particular concern. The capacity of the equine stomach is 2-4 gallons, equivalent to approximately 4 to 9 pounds of dry beet pulp. Movement of food from the stomach to the small intestine can vary depending on a number of factors, but as the stomach begins to reach maximum capacity, stretch receptors in the walls of the stomach will trigger the release of motilin, a hormone which in turn stimulates the emptying of the stomach and passage of food into the small intestine, cecum and colon. As the capacity of the gastrointestinal system-approximately 38 to 48 gallons-is more than sufficient to adequately contain even a very large meal of beet pulp (or any other feed), the only horse in danger of a gastric rupture is one suffering from impaction or other severe lack of normal peristaltic movement.
Concerns about beet pulp "pulling water from the blood and into the stomach and causing dehydration" are also unfounded. Regardless of the type of feed, horses will generally drink approximately 3 to 4 liters of water for every kilogram of dry matter consumed (dry matter is what's left over in a feed after its own moisture content is disallowed). Assuming free access to clean, fresh water, horses will voluntarily consume enough water to adequately process any amount of beet pulp consumed. If soaked beet pulp is provided, drinking will be proportionately less as the moisture content of the soaked pulp supplies considerable water. In either case, it is unlikely that fluid shifts from blood plasma to the interior of the gastrointestinal tract will be significantly different from those occurring with any other type of feed with similar moisture content.
Aside from its energy density, beet pulp is also a relatively good source of calcium. Though not as high in calcium as alfalfa at 1.2%, beet pulp is sti ll a good source at .62%-higher than any other commonly fed horse feed except for dehydrated milk. While beet pulp probably does not contain sufficient available calcium to offset a high-phosphorus ration, due to beet pulp's oxalate content (which binds some of the calcium into an unavailable form), it is still a reasonable non-alfalfa source of calcium to help balance calcium-phosphorus ratios.
In addition, beet pulp does not contain excessive protein as does alfalfa. This adequate, but not excessive, level of calcium makes beet pulp a useful supplement for horses being fed a grass or cereal grain hay diet. Although most grass hays contain an acceptable ratio of calcium to phosphorus, orchardgrass, some grain hays and even individual crops of normally balanced hays can be slightly inverted below recommended levels. In addition, rations containing significant amounts of grain or bran (especially rice bran) can further create imbalances. By including several pounds of beet pulp as part of the daily ration, horse owners can supply an additional source of calcium to help ensure a balanced calcium-phosphorus ratio in the ration.
A final word on providing beet pulp to horses-it comes as no surprise that horses are creatures of habit and will often eye a new addition to their feed tub as Poison Until Proven Otherwise. Many owners have tried adding beet pulp to their horse's ration, only to have it stared at in horror, ignored or promptly dumped. Even if eventual plans are to feed the beet pulp dry, initially soaking a small amount of pulp until it becomes juicy and more palatable, and then mixing with grain or other already accepted feed, will usually help overcome reluctance on the horse's part to trying something new. Eventually, after a day or so, most horses will deign to try the new feed and will soon be climbing over fences to get their fair share (or preferably, more than their fair share). At that point, amounts may be gradually increased and soaking may be tapered off until dry pulp is accepted equally well. Once the pulp is being regularly consumed, it may also be utilized as a useful method for "hiding" many other additions such as vitamin supplements, fats or medications.