What is tryptophan?
Tryptophan is one of the 20 protein-forming amino acids and has an indole ring in its side chain, which makes it an aromatic amino acid. Animals cannot synthesise it, so it is essential in the diet. Its requirement is low in absolute terms compared with lysine, but its content in cereals, especially corn, is also low.
Beyond protein synthesis, tryptophan is the precursor of the neurotransmitter serotonin, the hormone melatonin and, through the kynurenine pathway, niacin (vitamin B3).
What does it do in animal feed?
- Feed intake: tryptophan supply is closely linked to appetite; a deficiency typically shows up first as reduced feed intake, especially in piglets.
- Growth: needed for protein synthesis, daily gain and feed conversion.
- Behaviour and stress: as the precursor of serotonin it is associated with calmer behaviour; it is studied in relation to stress and tail-biting in pigs and feather pecking in poultry.
- Niacin: part of the tryptophan supply can be converted to niacin, although species differ in how efficiently they do this.
- Immune response: tryptophan metabolism is involved in immune regulation, and demand may rise under health challenges.
Forms and sources
Feed-grade tryptophan is L-tryptophan produced by bacterial fermentation and purified to a crystalline powder, typically with a purity of at least 98%. Because the inclusion rate is very low, it is often added through a premix to ensure even distribution.
Among raw materials, soybean meal and animal proteins are better sources of tryptophan, while corn and corn by-products are notably poor. Diets with a high share of corn or corn DDGS are the most likely to need supplementation.
How is the tryptophan requirement set?
Tryptophan is formulated on a digestible basis, usually as a ratio to digestible lysine. Some nutritionists also consider its ratio to the large neutral amino acids (such as leucine, valine and the aromatic amino acids), because these compete with tryptophan for transport into the brain. Requirements depend on species, age, health status and the protein level of the diet.
When crude protein is reduced and lysine, methionine and threonine are supplemented, tryptophan becomes increasingly likely to limit performance and is added to close the gap.
Quality criteria
- Purity / L-tryptophan content (feed grade typically at least 98%).
- Moisture, ash, heavy metals and microbiological quality.
- Purity and impurity profile from a controlled fermentation and purification process.
- Fine, free-flowing particles for even distribution at low inclusion rates.
- Certificate of analysis (CoA) and lot traceability.
CTF Premix and tryptophan
Tryptophan can be included in CTF Premix's vitamin, mineral and custom premixes according to the customer's formulation; adding it through a premix helps distribute a low-dose amino acid evenly in the feed. Our premixes are produced at our Ankara facility under ISO 9001:2015 and GMP, with a certificate of analysis and lot traceability for every lot.
This page is for general information. Inclusion rates and product choice should be decided with a nutritionist, taking into account the species, the feed formulation and the applicable regulations.