ABSTRACT
This chapter shows that the ileal rather than fecal analysis method should be the method of choice for determining amino acid digestibility. The fecal analysis method measures the amount of each of the amino acids consumed and excreted in feces. The amino acid digestibilities determined according to the ileal analysis method are calculated based on the intake and amount of each amino acid passing through the distal ileum. The chapter examines the different methods that are used to collect ileal digesta from surgically modified pigs. It discusses the considerations in methodology, for example, the use of the direct or difference method on the determination of amino acid digestibility. The digestibilities of amino acids in feedstuffs can be determined directly or indirectly according to the difference method. The metabolic fecal protein excretion constitutes a relative higher proportion of the total protein excretion at the lower protein levels.
