Amino acids are protein building blocks that, depending on the combination in which the body assembles them, become enzymes, tissue, or hormones.

There are two kinds of amino acids:
1)    Non-essential amino acids, which can be manufactured in the body.
2)    Essential amino acids, which must be ingested in the diet.

Tryptophan is an essential amino acid that is converted to a chemical responsible for nerve transmission and brain health. It can be found in pasture grasses but often in marginal or deficient levels.

Unlike drugs that take effect immediately, nutrients such as tryptophan may not be directly active but are instead utilized by the body to manufacture the working hormones or chemical compounds.

Tryptophan is a precursor for the production of serotonin. Once tryptophan is absorbed and in the bloodstream, a portion of tryptophan crosses into the brain and is synthesized into serotonin. The serotonin within the brain is responsible for signal transmission between nerve cells and acts as a chemical messenger to keep thoughts and reactions flowing smoothly. Interestingly, medications to relieve anxiety and treat depression in people are often based on increasing serotonin levels in the brain.

In horses that have not recently consumed a large meal, it takes between 20 to 30 minutes for ingested nutrients to be absorbed from the intestinal tract. The maximum level of serotonin in the brain should occur approximately 2 to 3 hours following the ingestion of supplemental tryptophan. Once the serotonin level in the brain reaches the maximum level, it begins to taper off gradually. It is during a 12 hour period that a calming effect of tryptophan is likely to be the most effective.

Tryptophan supplementation in horses may be beneficial when given 2 to 3 hours prior to stressful events such trailer loading, hauling, grooming, farrier work, veterinary examinations, etc.

Long term tryptophan supplementation is also safe, and may be given daily. Once the nutrient tryptophan is given twice per day for approximately three days, the blood levels begin to become constant with minimal fluctuation. This daily feeding method would be useful for certain horses that are sensitive to stress on a daily basis, such as horses that show nervousness from separation anxiety, being stalled for extended periods, undergoing daily training, or impatient with stall rest due to injury or sickness.

Scott Gravlee, DVM, CNS
Equine Nutrition Consultant
Life Data Labs, Inc