Amount and amino acid composition of basal endogenous protein losses at the terminal ileum of broilers

Abstract

In this report literature data on endogenous ileal protein and amino acid losses in broilers are reviewed. The aim was to propose an estimated value for the flow of basal endogenous protein at the terminal ileum and to determine the amino acid composition of the basal endogenous protein. The proposed basal endogenous ileal amino acid flows can subsequently be used to calculate standardized ileal digestible amino acid values for feedstuffs for poultry from experimentally determined apparent ileal digestible amino acids. Basal endogenous ileal amino acids losses are expressed in mg per kg dry matter intake. The quantitative flow of basal endogenous amino acids at the terminal ileum is dependent on the methodology used for quantification, the age of the animals and the presence of phytate and phytase in the diet. From our literature survey we concluded that the nitrogen free feeding method (NFD) and the regression method (REG) are most suitable to determine basal endogenous amino acids at the terminal ileum in broilers. Based on 29 observations from 25 studies with NFD, 6 observations of 4 REG studies, 5 observations of 3 HDP studies and 2 observations from 2 EHC studies, we calculated the basal ileal endogenous amino acid flow in broilers aged 15 to 45 days. The total flow of basal endogenous ileal amino acids amounts 5.90 g AA per kg dry matter intake. The values for basal endogenous ileal flow of the individual amino acids are used by CVB to estimate standardized ileal amino acid digestibility values from apparent amino acid digestibility values of feedstuffs for broilers (see CVB Documentation Report no. 61). Ileal endogenous protein is rich in GLU, ASP, GLY, THR, SER and PRO and rather closely reflects the composition of mucoproteins.