https://www.sciencedirect.com/science/article/pii/S0032579121000705?via=ihub
Poultry Science Volume 100, Issue 5 May 2021
"Amino acid requirements for laying hens: a comprehensive review"
Shemil P.Macellin,
MehdiToghyani,
Peter V.Chrystal,
Peter H.Selle,
Sonia YunLiu
From the Abstract
"The main aim of this review is to consolidate the relevant published data examining amino acid requirements of layer hens and to reach a new set of recommendation based on these data. There are inconsistences in lysine, sulphur-containing amino acids, threonine, tryptophan, branched-chain amino acids, and arginine recommendations in data that have surfaced since 1994. This review finds that breed, age, basal diet composition, and assessment method have contributed toward inconsistencies in amino acid recommendations....
Increasing inclusions of nonbound amino acids into layer diets modifies protein digestive dynamics, and it may influence amino acid requirements in layer hens. This review considers present amino acid recommendations for layer hens and proposes refinements..."
From the intro
"Amino acids and energy density are 2 critical components in the least-cost feed formulations for layers; however, amino acid requirements, will vary depending on breed, age, feeding strategies, housing conditions, and the accuracy with which requirements have been assessed. Moreover, genetic improvements and enhanced performance of laying hens have modified the optimum inputs of amino acid and energy, which are interdependent. The increasing availability of nonbound (synthetic or crystalline) amino acids demands a better appreciation of amino acid levels in layer diets simply because their digestive dynamics differ from protein-bound amino acids (
Liu and Selle, 2017)....This review consolidates the relevant data in a comprehensive manner. The purpose of this review is to identify the shortfalls and to recommend directions that research should be taken in the future..."