Which measure accounts for basal endogenous losses when evaluating amino acid digestibility?

• A. Crude protein
• B. Net energy
• C. Standardized amino acid digestibility
• D. True digestible protein

Answer: (C)

The concept being tested is how digestibility values are adjusted to separate what the animal’s own body contributes to endogenous losses from what actually comes from the feed. Basal endogenous losses come from things like sloughed intestinal cells, mucus, and digestive enzymes, and they occur regardless of the diet. Standardized amino acid digestibility corrects the measured digestibility for these basal losses, so the resulting value reflects only the dietary amino acids that the animal can truly absorb at the ileum. This makes comparisons between feeds more accurate because the constant, diet-independent endogenous component is removed.

Apparent digestibility ignores endogenous losses altogether, which can inflate estimates. True digestible protein subtracts endogenous losses observed during feeding but isn’t specifically standardized for the basal, constant component.