Progress in ileal endogenous amino acid flow research in poultry

Abstract

The progress in our understanding of the endogenous protein concept over the past century is reviewed. Non-dietary proteins found in the digesta at the terminal ileum of poultry, known as endogenous protein loss, are comprised of digestive secretions, mucus and sloughed gut epithelial cells. The measurement of this loss is of fundamental importance because it is an indicator of gut metabolism and is essential to adjust apparent estimates of ileal amino acid digestibility. The ileal endogenous amino acid losses comprise of two components, namely basal and specific losses. The basal losses are fixed and associated with feed dry matter intake, whereas the specific losses are variable and induced by the presence of dietary components such as fibre and anti-nutrients. Currently there is no methodology available to directly measure the specific endogenous losses and these losses are calculated by determining the basal and total (basal plus specific) losses and, then subtracting the basal losses from total losses. The seminal features, specific applications and shortcomings of available methodologies are briefly outlined as well as the practical challenges faced in using the published endogenous amino acid loss values for true digestibility corrections. The relevance of taurine as a component of endogenous protein flow in poultry is identified for the first time.

Basal ileal endogenous amino acid flow in broiler chickens as influenced by age

“…The concentrations of EAA in the ileal digesta are within the range reported in the literature ( Ravindran, 2021 ). The higher proportions of Glu, Asp, Thr, and Ser determined in the endogenous protein were as expected.…”

“…The EAA values determined at the ileum therefore relate to the algebraic differences between that secreted and absorbed ( Moughan, 2003 ; Ravindran et al, 2004 ). The source of endogenous proteins and the entry point into the GIT further complicate this dynamic ( Ravindran, 2021 ). When digestive enzymes dominate the endogenous flow, the proteins pass through the duodenum and jejunum where there is greater opportunity for digestion and absorption.…”

“…It is generally assumed that the AA profile of endogenous protein is somewhat constant, although it is known that individual sources of endogenous protein have different AA composition ( Ravindran, 2021 ). The current findings suggest that the composition of the AA flow was altered by broiler age, ostensibly reflecting changes in the contribution of endogenous protein components with age.…”

“…Continuous flow of significant quantities of endogenous protein occurs during the process of digestion of ingested feed in poultry ( Ravindran, 2021 ). The sources of endogenous protein are various digestive secretions (bile, gastric, pancreatic, and intestinal secretions), mucoproteins and desquamated epithelial cells lining the gastrointestinal tract ( GIT ).…”

Comparative Study of Endogenous Ileal Amino Acid Flow and Digestive Physiology to Nitrogen-Free Diets with Differing Ratios of Dextrose to Corn Starch in Broiler Chickens

“…Generally, serum IGF-1 concentration is in uenced by nutritional status, particularly protein-energy malnutrition. It has been reported that serum IGF-1 concentration is reduced in models of severe energy restriction or protein restriction in young growing rats 15 . In this study, the serum IGF-1 concentration in four NFD groups decreased by varying degrees which could re ect some protein restriction.…”