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Table 3 Methods used for the determination of basal and total endogenous amino acid losses in poultry

From: Progress in ileal endogenous amino acid flow research in poultry

Item Methods
Basal losses • Fasting of birds for 48 ha
• Feeding of a protein-free diet
• Feeding of diets with very low levels of protein
• Protein-free diet supplemented with synthetic amino acids
• Protein-free diets with intravenous amino acid infusion
• Natural proteins devoid of specific amino acids
• Enzyme hydrolysed caseinb and ultrafiltration
• Feeding of highly digestible protein, e.g. wheat gluten, soy protein isolate, caseinb
• Linear regression, following feeding of diets containing graded levels of specific ingredient
Total losses • Homoarginine
• Isotope-labelled markers
  1. aSpecific to precision-fed rooster assays [29, 30] and measured in the excreta. Measurement units are function of time (mg/bird/d) rather than intake (mg/kg dry matter intake) and cannot be used as correction factor in other digestibility assays
  2. bThese proteins are assumed to be (almost) 100% digestible and that excreted amino acids therefore represent endogenous losses