Nutrition is an important part of the management and treatment of sick horses. Stresses (eg, surgery, severe orthopedic problems, or infection) can significantly increase caloric needs due to an increase in catabolism. In addition, anorexia or dysphagia can lead to inadequate intake. The consequences of not providing proper nutrition include impairment of the immune system, delayed wound and fracture healing, hypoproteinemia, muscle wasting, and weakness. Generally, supportive nutritional therapy should be considered if an adult horse has been hypophagic for ≥3 days. Neonatal foals require energy and protein supplemental intake within 24 hours of deprivation.
The order of nutrient priorities for clinically ill equines is water, energy, electrolytes, and protein for most. All water-soluble vitamins are poorly stored in the body and should be supplemented during periods of prolonged (more than a day or two) stress.
There are several methods to provide nutritional support to a sick horse. The simplest is to encourage the horse to eat on its own, if possible. Unusual feed preferences may be seen. Offering a variety of appropriate feeds and letting the horse choose can best determine what is most palatable to the animal. Many horses will eat fresh, green grass even if they refuse other feeds. Alfalfa hay is more palatable than grass hays but may be contraindicated in some cases. Sweet-feed mixtures of grains and molasses usually are the most appetizing of concentrates but should be used sparingly in most cases. Bran mashes are usually palatable, but the calcium and phosphorus intake should be balanced. The addition of molasses, applesauce, carrots, and flavors such as peppermint may increase acceptance of feed in anorectic horses.
If pain or fever are causing inappetence, analgesics can improve food intake. Anti-inflammatories such as dipyrone, flunixin meglumine, meclofenamic acid, and phenylbutazone can be used with caution, depending on the disease process. Prolonged use of phenylbutazone should be avoided because of the adverse effects of gastric and small-intestinal ulceration.
Nasogastric tube feeding is another way to provide nutrition to horses that will not (or cannot) eat voluntarily. A nasogastric stomach tube may be passed several times a day or may be left in place, secured with tape or sutures as an indwelling feeding tube. This is an especially effective method to provide nutrients to sick neonates. It is also an inexpensive method to replace fluid and electrolyte losses. Soaking a complete pelleted feed in water also can make a slurry for tube feeding, but it needs to be sufficiently dilute to prevent clogging the tube.
The third method to provide energy nutrition to sick horses is through use of total or partial parenteral nutrition (TPN or PPN). Fluid administration (IV) can maintain hydration in horses unable to maintain hydration, for whatever reason, voluntarily. The most common clinical fluid replacement solutions are sodium chloride, lactated Ringer’s, and 5% dextrose. The nutritional value of these fluids is insignificant. Fat and amino acid solutions are available but are expensive and require dedicated IV administration lines. TPN is costly and requires intensive care and monitoring, which limits its usefulness in adult horses.
Recurrent airway obstruction, also known as chronic obstructive pulmonary disease (COPD), may be caused by sensitivity to dust and molds found in hay. Affected horses may improve when hay is soaked in water before feeding or, less desirably, removed from their ration and the horse placed on a complete ration that is pelleted or contains an alternate roughage source such as beet pulp. However, some horses with COPD are allergic to pollens and weeds, so a thorough clinical work-up as to cause should be done before drastically altering the ration/management.
Diarrhea in horses is primarily a colonic disease. Traditionally, affected horses are fed less grain and more hay. This increase in dietary fiber can bind water and may result in better formed feces. If weight loss is a concurrent problem, it may be better to maintain grain intake. Grain is digested mainly in the small intestine, and hay in the large intestine. Unless the small intestine is also affected, feeding grain or grain-based concentrates may help maintain body mass. (Also see Colic in Horses and see Intestinal Diseases in Horses and Foals.)
In horses with hepatic disease , major concerns are to provide adequate energy, thus easing the liver’s role in energy production and decreasing the amount of metabolic waste to which the liver is exposed. Parenteral or enteral glucose administration may be important as an energy source in anorectic horses. In horses that are eating, cereal grains should provide adequate carbohydrates. Corn is the grain of choice because of its low-protein, high-carbohydrate content. High-protein feeds, such as alfalfa hay, should be avoided.
Horses excrete significant amounts of calcium in their urine. In cases of renal disease, low-protein, low (but not deficient) calcium diets should be fed. Corn and grass hay are the primary feeds of choice. Due to high calcium content, legumes should be avoided.