Fiber, Protein, Water, and Electrolytes for Heavily Exercised Horses

Fiber (hay/pasture) is an energy source that is often overlooked in horse nutrition. Horses have a highly developed hindgut that houses billions of bacteria capable of fermenting large quantities of plant fiber. Volatile fatty acids (VFAs), the end product of fiber fermentation, are absorbed from the hindgut and transported to the liver. Once in the liver, VFAs can be converted to glucose and be stored as liver glycogen or be converted to fat, and be used to fortify the body’s fat stores. Fiber, therefore, can be used as an energy source for a horse being exercised for several hours since fermentation of fiber and absorption of VFAs continue long after a meal has been eaten.

A performance horse’s intestinal health is critical to success. Normally, the digestive system of the horse is active, moving feed ingredients through the length of the tract. Inactivity of the digestive system, due to dehydration or electrolyte imbalances, can cause severe colic and even death. Research conducted in Germany has underscored the importance of fiber in maintaining gut health for horses that exercise for several hours. Studies there have shown that a diet high in fiber resulted in an increased waterintake. Further, animals supplemented with a simple hay and salt diet had 73% more water in their digestive tracts after exercise and approximately 33% more available electrolytes than animals on a low fiber diet. The additional water and electrolytes in the digestive tract of the high-fiber animals is probably due to the high water-holding capacity of plant fiber. More importantly, the water and electrolyte pool created by a high-fiber diet can be used to combat dehydration and electrolyte imbalances that derail so many endurance horses.

Another important attribute of a digestive system full of fiber is maintenance of blood flow to the digestive system during exercise. The physical presence of fiber in the digestive system will help insure that blood is not totally diverted away from the digestive system with the onset of exercise. In one study, the percentage of cardiac output (blood flow) distributed to the digestive system was higher in fed ponies compared to fasted ponies during exercise. For performance horses, maintenance of blood flow to the digestive system will aid in the ability of gut tissue to remain active and could prevent colic.

In addition to hay and grass as fiber sources, there are so-called “super fibers” that have the same beneficial aspects of forage fibers for maintaining gut health and fluid and electrolyte balance, but contain more energy. The additional energy is the result of both a high fiber content and a low lignin (nondigestible fiber) component. Therefore, these ingredients have more fiber available for microbial digestion. These super fibers (beet pulp, soybean hulls, almond hulls, oat hulls) contain energy equivalent to oats and barley, but they are safer to feed because they do not produce the symptoms of grain overload.

If the protein intake of an exercising horse exceeds its requirement, then the extra protein can be used as a source of energy. The amino acids associated with the extra protein are broken down by the liver, and the nitrogen is excreted as ammonia. The carbon skeletons that are left can be oxidized to produce ATP or used to make glucose or fat. Excessive protein intake should be avoided in heavily exercised horses for a number of reasons. First, water requirements increase with increased protein intake. This can be devastating for horses performing some types of exercise such as endurance racing, where they typically struggle to maintain proper hydration. Second, accumulation of nitrogen end-products (ammonia and urea) in the blood can lead to nerve irritability and disturbances in intestinal function and carbohydrate metabolism. Further, increased ammonia excretion in the urine may lead to respiratory problems associated with ammonia buildup in the stall.

Energy metabolism within the body is not 100% efficient. A certain amount of energy is lost from each chemical reaction in the form of heat. In order for the horse to remain healthy and continue to exercise, excess heat must be dissipated from the body. If the horse is unable to rid itself of this heat, body temperature can rise to the point where it becomes life-threatening. For horses, the main route of heat dissipation is through a form of evaporative cooling known as sweating. In evaporative cooling, the sweat gland takes fluid from the circulatory system and secretes it out to the surface of the skin. Once the hot fluid (sweat) is on the skin, it spreads out and evaporates. This takes heat away from the body. Unfortunately, sweating also takes water and electrolytes away from the body.

As water is lost from the blood, the remaining blood becomes thicker. This increased blood viscosity decreases perfusion potential and negatively influences tissue oxygenation. With intense exercise, water loss can become so extreme that blood volume is decreased and further sweating is not possible. If the horse is not rehydrated, death from heat stroke will occur. Idle horses may drink 10 to 12 gallons of water each day, and for horses performing in hot, humid environments, this requirement may be doubled or tripled.

Electrolytes are substances that dissociate in solution into electrically charged particles called ions. In horses, electrolytes play an important role in maintaining osmotic pressure, fluid balance and nerve and muscle activity. During exercise, sodium, potassium, chloride, calcium, and magnesium are lost in the feces, urine and sweat. Loss of these electrolytes causes fatigue and muscle weakness, and decreases the thirst response to dehydration. Therefore, it is vital to replenish electrolyte losses in performance horses that sweat heavily. Excellent commercial electrolyte supplements are available in both powder and paste forms.

SOURCE: KER

Do Horses Need Magnesium Supplements?

Magnesium has an important role in muscle and nerve function. Horses that are deficient inmagnesium may be unusually spooky and excitable, and they may have muscle tremors or cramping. However, this deficiency is rare because grass and hay normally contain sufficient magnesium to meet the horse’s requirements. Giving a horse too much supplemental magnesium may have no effect at all on nervous behavior or muscle cramping, and may cause serious digestive and metabolic problems.

There are several factors that can decrease the magnesium content of pasture plants. If the soil in a region is deficient in magnesium, growing plants will have a lower content. Lush spring grass has a high moisture content that tends to dilute other nutrients, so each mouthful of this grass will have less magnesium than what would be found in a similar mouthful of summer grass. Diets that are unusually high in potassium can reduce the horse’s ability to absorb magnesium. Finally, intensely exercised horses lose some magnesium in their sweat.

Even if one or more of these conditions exists, horses are not likely to need much, if any, supplementary magnesium. A veterinarian can draw blood for analysis to see if the horse is low in magnesium, and an equine nutritionist can suggest the best way to supplement if this is needed. Because horses are always replenishing magnesium as they graze or eat hay, owners who decide to supplement this nutrient should err on the low rather than the high side to avoid diarrhea and other problems in their horses.

SOURCE: KER

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Vital Signs: Know What’s Normal for Your Horse

When you read a book or magazine article that talks about a horse’s vital signs, the normal rates are almost always given as a range rather than a single number. That’s because an individual equine’s pulse, respiration, temperature, and other signs will be influenced by the horse’s age, stress level, location, health status, fitness, and the time of day, to name a few factors. A young horse taken to its first show or trail ride might have a much faster pulse than an older horse that’s relaxing in its familiar stall at home, and a horse with an infection would probably have a higher temperature and faster breathing rate than one in good health.

When a veterinarian is called to examine your horse for any reason, he will probably check these vital signs and use the results to help determine what may be wrong. You should know the ranges that are normal for your particular horse in order to compare them with whatever the veterinarian has found. To learn about your horse’s vital signs, it will be necessary to take several readings at various times and note any changes you observe.

Checking heart rate is easiest with a stethoscope placed on the girth line just behind the horse’s left elbow. You may have to move the stethoscope around a bit to find the “lub-dub” sound that the heart makes. You can also slide your fingers under the horse’s jaw and feel for the pulse; keep checking by pushing your fingertips outward against the jawbone. The horse’s pulse will rise when you enter the stall, especially if you are carrying tack or are accompanied by a stranger. It will also be higher when the horse is excited or stressed for any reason such as being at an unfamiliar location, in the presence of strange horses, or faced with an unusual stimulus of any kind. The pulse will generally rise with fever, pain, fear, stress, or exertion. It may be lower in horses in top athletic condition and also in horses that are in shock or hypothermia. The normal range is from about 30 to 45 beats per minute for mature horses; foals will have a more rapid pulse.

Counting respiration can be done by watching the ribcage expand and contract, by seeing the horse’s nostrils flare, or by cupping a hand loosely over a nostril and feeling the exhaled breath. The normal range is about 8 to 16 times per minute, generally faster in horses that are nervous or in pain and slower in those in shock, hypothermia, or drug-induced depression. Fit horses also breathe somewhat more slowly; those with colic, discomfort, or heat exhaustion breathe faster, as do horses that have been exercised recently.

Finding the horse’s temperature is probably the simplest chore because a digital thermometer is used for this reading. While someone else is holding the horse, pull the tail out of the way with one hand and slip the lubricated tip of the thermometer about two inches into the horse’s rectum with the other hand. Don’t let go; the thermometer can disappear if the horse tightens its sphincter muscles! When the thermometer beeps or indicates the reading is complete (this make take a minute or two), withdraw the thermometer and check the temperature. The normal range is about 99.5 to 101.5 degrees F, but can be higher in horses with infection, pain, or exposure to strenuous exercise. Horses that have been exposed to high environmental temperatures may also show a rise in body temperature. Lower readings will be seen in horses that are in shock or have hypothermia.

If you have trouble checking your horse’s vital signs, ask your veterinarian to help you learn the proper procedures. You can also find out how to check gum color, dehydration, gut sounds, and the horse’s digital pulse (taken at the fetlock). Knowing the normal readings for your equine will help you and your veterinarian determine what may be wrong with the horse.

Source:KER Newsletter

Swollen or Filled Legs: What’s Wrong With Your Horse?

Horses can rapidly develop swelling or “filling” in one or more legs. Is it serious? What causes it?

A common reason for filling is inactivity in a horse that is accustomed to moving around. An example might be a horse that is usually turned out in the pasture but has been kept in a stall overnight, maybe at a show or in preparation for an early ride the next day. The owner notices that the horse’s rear legs are puffy and swollen as he’s led out of the stall. The legs are not uncommonly warm, and the horse may move somewhat stiffly but is not truly lame. Caused by inactivity and reduced lymph flow, this “stocking up” is usually not serious and will dissipate as the horse is exercised. It’s more common in older horses and can affect all four legs, though stocking up is often seen only in the hind legs.

If your horse has leg swelling accompanied by lameness, warmth in the leg or hoof, or an elevated body temperature, it’s time to call the veterinarian. This is more than simple stocking up.

Swelling in a single leg is likely to signal a serious condition. Horses can “blow up” a leg in response to a scratch, cut, or puncture wound that may be so insignificant that it’s hard to find. The leg may be warm in addition to being swollen. This swelling isn’t likely to go down until the wound is cared for and any infection is treated.

A horse that has significant swelling in all four legs may have some type of systemic illness. This could be a sign of heart trouble, liver or kidney disease, or a bacterial or viral infection. It’s defintely a situation that calls for a veterinary examination. 

Source: KER Newsletter

Importance of Vitamin E for Horses

Vitamin E has numerous functions in the body, many of which are still not completely understood. Vitamin E is essential for the integrity and optimum function of reproductive, muscular, circulatory, nervous, and immune systems.

Its action as a natural antioxidant is seen as the underlying factor of most vitamin E functions. Vitamin E is considered to be the most effective natural lipid-soluble chain-breaking antioxidant. The action of vitamin E is very important in cell membranes, protecting them from peroxidative damage. This is especially important in the mitochondrial membrane, where enzymes involved in respiratory chain energy production are located. Selenium, like vitamin E, also acts to prevent lipid peroxidation, but with differing mechanisms. The two complement each other, one appearing to be able to compensate for the absence of the other to a certain extent. Signs of vitamin E deficiency, such as nutritional muscular dystrophy, are often the same as those seen with selenium deficiency. Other diseases associated with low serum vitamin E include degenerative myelopathy and degenerative myeloencephalopathy.

There are at least eight forms of vitamin E found widely distributed in nature: four tocopherols and four tocotrienols. The majority of vitamin E activity in animal tissues is generally assumed to be alpha-tocopherol and when it is present it is used preferentially. Tocopherols are extremely resistant to heat but readily oxidized. Natural vitamin E is subject to destruction by oxidation, a process that is accelerated by heat, moisture, rancid fat, and certain trace minerals. Horses have the capability to store much less vitamin E than vitamin A. However, stores are thought to be able to compensate for about four months or more of inadequate vitamin E intake.

Vitamin E is abundant in green growing pastures, particularly in alfalfa (lucerne). The content diminishes with maturation, especially after the plants go to seed. Harvesting the forage diminishes the quantity of vitamin E present, and storage of the hay further decreases the amount of vitamin A by as much as 50% in the first month. Vitamin E is abundant in the germ of grains and oils pressed from the germ. Vegetable oils such as corn and soybean oil are relatively high in vitamin E. In practice, the vitamin E content of other feedstuffs is variable and not readily predictable because of handling and storage time. Therefore, it is common practice to supplement animal feeds with vitamin E. Since esterification stabilizes vitamin E, commercial supplements usually contain tocopheryl acetates.

Vitamin E appears to be the most researched vitamin at this time in production animals. Several studies have reported evidence of oxidative stress occurring with exercise in both humans and rodents. Since the main function of vitamin E is to protect the cell against peroxidative damage, lipid peroxidation as a result of exercise may be influenced by the concentration of vitamin E present in the diet. Signs of vitamin E toxicity in the horse have not been produced.