L-Tryptophan

Description:

L-tryptophan is an essential amino acid. This means that it must be obtained through the diet in adequate quantities to meet the body’s needs, because it is not synthesized by the horse’s organism. L-tryptophan is obtained by the hydrolysis of protein by pancreatic enzymes during digestion.

Function:

A part from its incorporation into body proteins as a building block, tryptophan is known to play important biological roles, most of them being associated to metabolic pathways involved in tryptophan catabolism. Tryptophan is the precursor for the synthesis of serotonin, an important neuromediator associated to mood, stress response, sleep and appetite regulation. Tryptophan is also needed for niacin production (vitamin B3). Low tryptophan diets are known to depress feed intake. The relationship between tryptophan and serotonin is usually considered as the mechanism involved in the depressive effect of low tryptophan diet on appetite. L-tryptophan is also involved in other mechanisms such as modulation of insulin sensitivity and ghrelin secretion.

Source:

For horses, L-tryptophan is found in plant proteins. Soy meal is a good source.

Requirements:

Not established for horses. Horses usually acquire sufficient L-tryptophan from their diet.

Deficiency:

The effects of essential amino acid deficiency are generally nonspecific, and many of the signs do not differ from the effects of partial or total caloric restriction. In general, the horse will have growth impairment, poor quality hair and hoof growth, weight loss, and inappetence. Milk production is decreased in lactating mares. Tryptophan deficiency would contribute to horse’s excitability.

Excess:

Excess can’t occur with a well-balanced diet. In case of excessive protein intake the owner will not be face only with an L-tryptophan excess but with a whole protein excess, leading to decreased performance, ammonia excretion and water consumption increase. More particularly, excess of L-tryptophan supplementation can reduce endurance capacity with onset of fatigue and cause acute haemolytic anaemia if orally given in too large quantity, due to a toxic hindgut metabolite.

When problems may occur?

With a well-balanced diet, problems are likely to not happen.