fats in the body. For- tunately, propionate can be converted to glucose in the liver to be used as an energy source for the brain, which can only use glucose. Since this process is not rapid, it does not result in large enough surges in blood glucose to stimulate signifi cant pancreatic release of insulin. As with any energy source in the body, if there is ex- cess it can be stored away in fat cells (adi- pose tissue) for use when the energy sup- ply does not meet demand. This is why a horse can maintain optimal body condi-
“Horses involved in various disciplines and of any breed may benefi t from a low-starch diet, depending on the individual. Horses that are easily excitable,
fractious to handle, obese, insulin resistant or diagnosed with muscle disorders or hindgut acidosis are all obvious candidates.”
tion or get obese on just forage. Because the digestive tract was beauti-
fully designed to handle fi ber, perhaps fi ber could be thought of as an ideal way to fuel horses. Feeding forage is considered a safe way to supply energy (calories) to the horse because it is a slow process and does not cause rapid changes in blood glucose or insulin. Forage is an obvious source of fi ber,
but things like beet pulp and soy hulls may not be as apparent. These are called “super fi bers” because they contain even more fermentable material per gram than hays and therefore are excellent energy sources. High-fi ber commercial products use super fi bers because they pack more calories and are manageable in the feed- making process. However, such fiber sources are not
as calorie-dense as starch, which is why starches were fed in the fi rst place. Fat is the other energy source that usu-
ally goes hand in hand with high-fiber feeds because it can increase the en- ergy density without adding to the bulk. Like fiber, fat does not have an effect on blood glucose and insulin release.
HOW HIGH IS HIGH-FIBER? Forage is naturally high in fi ber, but
how do you know if a commercial feed is truly a high-fi ber feed? The only nutrient specifi cation on the feed bag or tag that begins to give a hint is “crude fi ber” or “fi ber.” These ingredients are usually in- dicative of a high-fi ber feed: beet pulp, soy hulls, alfalfa, almond hulls and citrus pulp. Ingredients like oat hulls or rice hulls will also increase the fi ber value but are high in indigestible fi ber and are not a good source of fi ber or energy. So how high is high? Most high-fi ber
feeds have a crude fi ber value of 12% to 25% on the guaranteed analysis. Many of
these feeds will have added fat to help bring the energy up in line with that of a high-starch feed. The fat found in most high-fi ber feeds—usually in the form of oil—ranges between 6% and 12%.
WHAT IS STARCH? What is it about starch that has caused
it to get such a bad reputation? Starch is a long, complex chain of sugar molecules that is the energy store for the plant, found in particularly high content in seeds (grains). The opposite of fi ber (structural carbohydrates), starches are considered “nonstructural carbohydrates” because they are found inside the cell wall structure. When starch is consumed by a horse,
it gets broken down into small sugar mol- ecules in the small intestine by enzymes so it can be readily absorbed. At this point, starch and sugar in the diet are handled basically the same. Sugar in the diet can come from the cell contents in grass, molasses from feeds and treats (apples, carrots, sugar cubes, peppermints, etc). The small sugar molecules cross into the bloodstream and end up as glucose, which gets distributed to cells for use as energy throughout the body. The hormone that helps get glucose out of the blood and into the cells is insulin. This distribution system of getting glucose to the cells for energy, glycogen-building, or adipose (fat) storage is part of the energy-generation system for the working horse. The harder the horse is working, the more important the system is.
18 June | July 2010 •
WWW.TRAILBLAZERMAGAZINE.US
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