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

Basal losses

• Fasting of birds for 48 h^a

• 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 casein^b and ultrafiltration

• Feeding of highly digestible protein, e.g. wheat gluten, soy protein isolate, casein^b

• Linear regression, following feeding of diets containing graded levels of specific ingredient

Total losses

• Homoarginine

• Isotope-labelled markers