poultry, diet, feed, nutrition, performance, amino acids


Poultry industry is rapidly moving towards utilizing the best ingredients to precisely feed the birds for better performance, welfare, health, and profitability. One of the practices that evolved over time with research is better optimization of amino acid utilization in the diets thus changing the crude protein landscape. Historically, if we compare the modern diets to diets from 1980, significant changes are visible in the use of unbound or crystalline amino acids leading to reduced levels of CP and reduced unutilized nitrogen in the diets. Multiple feed-grade amino acids are available in a cost-effective manner in poultry diets. Multiple research has been conducted over 80 years to better understand the optimal requirement of lower limiting amino acids in poultry, formulation with digestible amino acid values, and ideal amino acid formulation to achieve precision feeding of nutrients. Those findings enabled the nutritionist to incorporate crystalline amino acids, remove CP minimum, and crystalline amino acid maximum in the diets to lower the feed cost, reduce CP, reduce excess nitrogen in hindgut and improve the health of the birds and improve litter quality (Kidd 2000; Maia et al., 2021). A 1960 diet would only contain the Methionine as synthetic amino acid, whereas the 2023 diet would contain up to 5/6 limiting amino acids in USA-based broiler diets. The 4th, 5th and 6th limiting amino acids in USA-based poultry diets are usually Valine (Val), Isoleucine (Ile) and Arginine (Arg) depending on the ingredients used. With almost 90% of the industry using the 4th limiting amino acid, there is a need to understand the optimal requirement of 5th and 6th limiting amino acids for performance and other biological functionality. With Ile and Arg being the 5th and 6th limiting amino acid in most broiler, turkey, and layer diets, this article will discuss the importance of Ile and Arg in birds and the effect on performance and health.