What is the Arginine Requirement – Well It Depends

Arginine is classified as an essential amino acid for both swine and poultry. However, due to it historically being a less limiting amino acid and not generally a pressure point in formulation, it has not been extensively researched. Arginine is critical in numerous biological functions other than protein synthesis, which encompass gut integrity, immune modulation, vasodilation/blood flow and hence core temperature regulation. Arginine serves as a precursor for several biologically important molecules, including nitric oxide, polyamines, creatine, proline, glutamate and agmatine (Wu et al., 2009). These metabolites are essential for cellular proliferation, tissue growth and reproductive function. In poultry, arginine requirements are higher compared to mammals because birds excrete nitrogen primarily as uric acid, which requires glycine and arginine metabolism for efficient nitrogen utilization (Leeson and Summers, 2001).

The last swine NRC (2012) listed the SID arginine requirement expressed as a percent to SID lysine for grow–finish pigs at 44% and 55% for lactating sows. As the last Poultry NRC was published in 1994, most poultry nutritionists rely on Primary Breeder recommendations (Ross or Cobb) or the Brazilian Feed Tables for Poultry and Swine (2024) for guidance. Both the Ross (2022) and Cobb 500 (2022) guides recommend increasing digestible arginine to digestible lysine ratios from 106-108% in Starters up to 110 to 112% in withdrawal feeds. Whereas the Brazilian recommendations are lower for the Developer and withdrawal feeds.

Growth performance

The current Swine NRC (2012) reference for the arginine requirement (Southern and Baker, 1983), is outdated for current genetics and management practices. Recent work with nursery pigs suggests the arginine level for optimum growth performance is higher than currently formulated into today’s diets. Greiner et. al. (2023) reported an improvement in final body weight (9%, 1.9 kg) at 42 days with increasing SID arginine to 1.35 or 1.55% during the first three weeks of the nursery period. Perez-Palencia et. al. (2024) also reported linear increase in growth rate and FCR with increasing supplemental L-Arginine from 0.66 to 1.86% in the diet. Similarly, Hagen et. al. (2024) observed a linear increase in final nursery body weight with increased SID arginine to SID lysine ratio from 85 to 115% for the first three weeks of the nursery phase. Additional work by Jeffers et. al. (2026), demonstrated increasing the SID arginine to SID lysine ratio from 75 to 120% linearly increased body weight, average daily gain and feed efficiency in the 28 day old weaned pig. Humphrey et. al. (2024) conducted research to determine the optimal arginine requirement in nursery pigs using semi-synthetic diets with SID arginine to SID lysine ratios ranging from 45% (current NRC, 2012 recommendation) to 145%. They estimated the requirement for SID arginine to SID lysine ratio at 95 to 97% for the newly weaned pig. Recent data clearly shows that the SID arginine requirement for the young pig is at least 2X of NRC (2012) estimate.