While you can't necessarily prevent or squelch every equine ailment by adjusting his diet, what he consumes can impact certain maladies. According to Meri Stratton-Phelps, DVM, MPVM, Dipl. ACVIM, ACVN, owner of All Creatures Veterinary Nutrition Consulting, in Fairfield, Calif., veterinarians and owners can use certain dietary ingredients to reduce a horse's risk of developing particular medical conditions such as colic, gastric ulcer syndrome, and developmental orthopedic disease and to help manage some pre-existing conditions such as obesity and equine metabolic syndrome. She presented on the topic at the 2011 Western Veterinary Conference, held Feb. 20-24 in Las Vegas, Nev.
Before delving into dietary details, Stratton-Phelps stressed that caretakers changing horses' diets should go about it very slowly, as a rapid change in feed could cause colic itself. She suggested stretching changes out over about 10 days (or more if the horse has a history of colic associated with feeding adjustments).
Impaction Colic
Impaction colic is a common condition in which feed material obstructs the large colon. According to Stratton-Phelps, a common cause of impaction colic is a decrease in water intake: "Many impaction colic cases can be prevented by ensuring an adequate water intake at all times."
Encouraging horses that only drink limited amounts of water to increase fluid intake is of paramount importance to preventing impaction colic, Stratton-Phelps said. She suggested a number of methods to encourage horses to drink:
Adding flavoring to water can entice certain horses to consume more liquids. One cup of flavoring (such as apple juice, cranberry juice, or Gatorade) should be enough to flavor 2-3 gallons of water. She cautioned that the sugar content of the flavoring should be monitored for some horses (i.e., those suffering from or prone to laminitis or horses with metabolic syndrome) and that a plain water source should always be available in the event the horse does not like the flavoring.
Salt or electrolytes can encourage some horses to drink. Stratton-Phelps advocates adding 1-3 teaspoons of salt once or twice daily to a horse's feed, cautioning that granular salt intake should not exceed 4 tablespoons daily, as this could have negative effects on the horse (it's not uncommon for horses to object to the taste of salt in their feed and refuse to eat, and in some cases, the horse will not be able to drink enough water to offset the higher salt intake, which could lead to problems if the salt cannot be excreted, Stratton-Phelps noted). As with any feeding adjustment, she advises gradual addition or removal of salt from the diet to avoid upsetting the horse's gastrointestinal tract.
Stratton-Phelps also suggested trying different types of buckets for the horse's water: Some horses are more likely to drink if they don't have to put their head all the way into a large tub to reach water at the bottom, she explained, while others prefer big, open water sources--these preferences reflect a horse's tendencies as a prey animal, valuing the ability to see what's coming and not feel trapped. At least two water sources should always be available, especially for horses that depend on an automatic waterer as their main water supply.
Especially during the winter, offer different temperatures of water as well, she said, as some horses prefer warmer water than others.
Soaking horses' feed in water can also increase fluid consumption as the horse eats his daily rations, she added.
Sand Colic
Another type of colic veterinarians and owners can manage with nutrition is sand colic. Normally, inadvertently consumed sand moves through the digestive tract with food and is passed in manure. If sand accumulates, however, it can weigh down the intestine and impair gastrointestinal motility, hindering proper digestive function. This can lead to more sand accumulation and, sometimes, blockage. Some cases are so severe that surgery is required for correction.
Stratton-Phelps suggests feeding horses either off the ground or on a mat or concrete slab to avoid an overabundance of sand or dirt in the feed. If horses are prone to consuming sand while eating, she recommends adding a psyllium supplement to the horse's diet; such supplements are designed to eliminate sand from the intestines.
"Recent studies have shown ... that it's very safe," she explained. "Why it works is still a mystery, but I'm a great proponent of feeding psyllium."
Equine Gastric Ulcer Syndrome
Ulcers affect horses of all ages, breeds, and walks of life, but you can reduce the likelihood of a horse developing equine gastric ulcer syndrome (EGUS) by carefully planning what--and how often--he eats.
Horses with EGUS generally have erosions and ulcers in the lower portion of the esophagus, the glandular and nonglandular portions of the stomach, and the proximal duodenum (the beginning of the small intestine). These form when there's an imbalance between the factors that buffer the ingesta (ingested feed) and protect the stomach (in the case of horses, saliva), and the factors that incite erosion (stomach acid). Clinical signs of EGUS typically are mild colic, poor body condition, and decreased performance.
Stratton-Phelps suggested that horses with EGUS or horses at risk for the disease (including but not limited to equine athletes and horses under stress) consume a forage-based diet around the clock. The more time the horse spends eating, she said, the more saliva his body will produce to help protect the stomach from ulceration. The less time a horse spends eating throughout the day (for example, those who don't have constant access to hay or grass), the more time the stomach is empty and acids can erode the lining. Alfalfa hay in particular appears to buffer the pH of the stomach, Stratton-Phelps said.
Stratton-Phelps also suggested removing or limiting the amount of highly digestible carbohydrates the horse eats to reduce the amount of volatile fatty acids that are produced during the digestion process. Although these fatty acids aid in proper blood glucose distribution, they also can damage the stomach lining in the nonglandular part of the stomach and can increase the likelihood of ulcers developing. If more calories are needed in the horse's diet, she suggests supplementing with oil or other fat supplements.
If a horse currently has ulcers, Stratton-Phelps advised treating them medically and not relying on nutrition alone to fix the problem. She explained the nutritional aspect should be used as prevention, although proper nutrition also is an important part of EGUS treatment.
Obesity
"Obesity in the horse population is increasing in prevalence," Stratton-Phelps said, adding that the condition can be a precursor to several common medical problems, including laminitis and insulin resistance.
Stratton-Phelps considers a horse obese when its body condition score is 7 to 9 on the Henneke body condition scale, noting that she has seen horses that could be considered 9+. When a veterinarian diagnoses a horse with obesity, a nutrition- and exercise-based weight loss plan derived by the veterinarian should be put into place.
"Essentially the cause of obesity is more energy going into the horse's body (through calories in food) than is coming out (through exercise and basic daily requirements)," Stratton-Phelps said. Theoretically, the problem should be fixed by reducing the amount of calories the horse consumes and increasing the amount of exercise. Of course, things are always easier said than done.
Stratton-Phelps first suggested that horses undergo a full physical examination to identify medical problems that might complicate weight loss, such as lipid metabolism abnormalities, liver disease, and laminitis.
A healthy weight loss goal is 0.5-2% of a horse's body weight per week. Stratton-Phelps said she encourages her clients to take photographs of their horses to track visible weight-loss progress and also to keep weight records throughout the course of the program. She recommends updating these every other week.
She also recommended analyzing the horse's feed. In most cases a healthy weight-loss ration is about 70-80% of what a horse is eating at the start of the weight-loss program, she said, and any less than that percentage can be detrimental to the horse. It's particularly important to reduce or eliminate the amount of grain and concentrates in an obese horse's diet.
Additionally, Stratton-Phelps recommended analyzing the horse's hay. The total ration should be balanced, and in some cases, alfalfa can be used to provide supplemental protein if a grass hay-based ration has a poor protein concentration, or if the grass hay is poorly digestible, she noted.
Finally, consider a reduction--or elimination--of grazing time in pastures because fresh pasture is highly digestible and can promote unwanted weight gain. Limiting a horse's grazing time will aid in weight loss, as will keeping the horse in a drylot (preferably one large enough for him to get free-choice exercise in) and providing him with a suitable amount of hay for the weight-loss ration.
Exercise is also an important part of a weight loss program, Stratton-Phelps said, and owners should add it to the program gradually, providing the horse is sound. Horses that are overweight often will not self-exercise enough to significantly aid in weight loss.
Equine Metabolic Syndrome
Owners should feed overweight horses with equine metabolic syndrome (EMS) to promote weight loss (using the guidelines listed above), and all horses with EMS should have a reduced amount of nonstructural carbohydrates (NSCs) in their diet, Stratton-Phelps said.
To reduce the amount of NSCs, Stratton-Phelps advises limiting--or possibly eliminating--turnout time in grass pastures.
"Pasture grazing management is essential ... to reduce the consumption of fructans, the rapidly fermented carbohydrate that serves as a storage form of energy in cool-season grasses," she said, adding that fructans aren't as prevalent in grasses in the early morning, so owners should aim to turn their EMS-affected horses out in the early morning hours (before 9-10 a.m.), if possible. Additionally, as with obese horses, owners should provide EMS horses with a suitable amount of hay as a replacement for grass.
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