Etiology
- Horses that are overfed and underworked, particularly when stalled, may exhibit excitable behavior.
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A large part of the problem can be attributed to the diet and feeding behavior of the stabled horse.
- Instead of grazing for 16 to 18 hours per day, the stabled horse may spend as little as 1 to 2 hours per day engaged in feeding activity.
- Long intervals between meals where the horse is confined and idle have been associated with the occurrence of behavioral problems and may also contribute to the formation of gastric and colonic ulcers.
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Many horses in training are traditionally fed large quantities of grain relative to forage components of their ration, in an effort to meet increased caloric requirements, as grains are typically more energy dense than forages.
- Feeding large amounts of grain in a single meal can lead to starch and sugar overload in the hindgut and can result in serious gastrointestinal disturbances (excessive gas production, acidosis) and metabolic disorders such as colic, laminitis and insulin resistance.
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Grain meal feeding is linked to an increase in serotonin, a brain neurotransmitter that modulates mood, activity and alertness.
- High serotonin levels observed after eating meals high in starch have been implicated in expressions of behavior described as sugar “highs” or “hot” seen in some horses following a grain meal high in starch.
Symptoms
- Horses exhibit stereotypic behaviors such as stall walking and weaving, as well as vices such as cribbing and wood chewing, as a means to relieve stress.
Dietary Recommendations
- To support athletic performance and glycogen repletion after an intense exercise bout, providing highly palatable, energy dense concentrates with controlled starch and sugar in addition to good quality forage is a viable solution.
- As with any change in a horse’s diet, additions or increases in dietary concentrates should be done gradually, and large daily rations should be broken up into multiple evenly spaced meals, and the size of any given meal should never exceed 0.5% of the horse’s body weight.
- Ingredients like vegetable oils and soluble fibers, most notably beet pulp, and soybean hulls do not contain high levels of starch and sugar and can be blended into the ration to help increase its digestible energy/caloric intake without increasing the risk of starch and sugar overload.
- Fats and fibers do not result in large increases in blood glucose. Therefore, rations where the total dietary (hay or forage + grain or supplement products) DE comes predominantly from fat and digestible fiber help decrease the occurrence and degree of excitable behaviors associated with the diet, and grain concentrates in particular.