By: Aditya Ananda Putra – Technical Marketing, CJ Bio

Heat stress is not merely a temperature-related problem; it is also a metabolic challenge. When poultry are exposed to high ambient temperatures, feed intake declines, the need to maintain homeostasis increases, and nutrient and energy distribution undergoes changes. The consequences can be seen in reduced growth, poorer feed efficiency, carcass quality, intestinal health, and immune responses. Under these conditions, a nutritional approach cannot focus solely on meeting amino acid requirements for protein deposition. Functional amino acids are needed to support multiple physiological processes simultaneously.

One such functional amino acid is arginine (Arg). Unlike the concept of amino acids as protein building blocks, arginine occupies a strategic position as a metabolic hub, as it can enter various metabolic pathways and produce bioactive metabolites such as nitric oxide (NO), ornithine, polyamines, guanidinoacetic acid (GAA), creatine, and citrulline. These metabolites have complementary functions that help poultry cope with heat stress.

Arginine → Nitric Oxide: Supporting Thermoregulation

One of the major pathways involving arginine is the production of nitric oxide (NO) through the enzyme nitric oxide synthase (NOS). NO acts as a signaling molecule that causes relaxation of vascular smooth muscle, or vasodilation. Under heat stress conditions, vasodilation and increased peripheral blood flow are part of the body’s mechanism for enhancing heat dissipation.

Therefore, arginine availability is important because it provides the nitrogen required for NO synthesis. Evidence from broilers and layers indicates that arginine supplementation can influence NO metabolism and physiological responses to heat stress. Recent research has also shown that increasing the SID Arg ratio to 125% can enhance nitric oxide synthase activity while improving performance and intestinal morphology in broilers exposed to cyclic heat stress (Anderson et al., 2024; Lee et al., 2026).

In addition, research by Anderson et al. (2024) showed that increasing the arginine-to-lysine ratio (Arg/Lys ratio) to 116% significantly reduced body temperature in broiler chickens exposed to heat stress.

Arginine → Ornithine & Polyamines: Supporting Gut Integrity

Heat stress often has a direct impact on the gastrointestinal tract. Changes in blood flow, oxidative stress, and impaired intestinal barrier function can increase the risk of intestinal permeability and reduce nutrient utilization efficiency.

Arginine can be converted into ornithine, which subsequently serves as a precursor for the synthesis of polyamines, including putrescine, spermidine, and spermine. Polyamines play important roles in cell proliferation, tissue repair, and the maintenance of tissue integrity. Because intestinal epithelial cells undergo rapid regeneration, the availability of substrates for the polyamine pathway becomes increasingly relevant when poultry are under stress.

By supporting the arginine–ornithine–polyamine pathway, nutrition can help maintain intestinal integrity and support the regeneration of intestinal tissues during heat stress.

Arginine + Glycine → GAA → Creatine: Maintaining Cellular Energy

Heat stress is also an energy challenge. When feed intake declines, poultry must maintain vital functions and homeostasis with more limited energy sources.

Arginine, together with glycine, is used to produce guanidinoacetic acid (GAA) through the enzyme arginine amidinotransferase (AGAT). GAA is then methylated into creatine, which can be converted into phosphocreatine. The creatine–phosphocreatine system serves as a rapid energy buffer, particularly in tissues with high energy demands, such as muscle.

This is one reason why the arginine–GAA–creatine pathway is of interest as part of nutritional strategies for managing heat stress.

However, it is important to understand that GAA cannot replace the requirement for arginine. There is no reverse reaction that allows GAA to be converted back into arginine. Therefore, when arginine is required for NO production, polyamine synthesis, protein synthesis, or immune function, only arginine itself can fulfill those roles.

A recent meta-analysis also showed that the arginine-sparing effect of GAA is limited when the diet has an extreme arginine deficiency (Gao et al., 2026).

From Amino Acid to Functional Nutrition

When temperatures rise, poultry require simultaneous support for thermoregulation, intestinal integrity, energy metabolism, antioxidant defenses, and immune responses. Arginine has unique characteristics because its metabolism is connected to multiple pathways that contribute to these functions.

Therefore, optimizing arginine is not simply about meeting protein requirements, but about providing metabolic flexibility when poultry face stress.

In modern feed formulation, arginine can be viewed not merely as an amino acid requirement, but as a functional nutrient for enhancing poultry resilience to heat stress.