This latest deep dive explores the complexities of endogenous secretions—the proteins, enzymes, and cells that the body itself contributes to the digestive tract—and how they complicate our understanding of nutrient absorption. We examine the crucial shift from "apparent" digestibility to "standardized" and "true" measurements, while also uncovering how heat processing can "trap" amino acids like lysine, rendering them useless despite what a lab report might say.

Topic Outline

• The Concept of Endogenous Loss

◦ Defining secretions that originate from the body rather than the diet, including digestive enzymes, mucins, bile acids, and sloughed epithelial cells.

◦ The continuous nature of these secretions and their impact on measuring what an animal a ...