digesta

Digesta refers to the contents of the digestive tract at a given time, from the mouth to the anus. It includes ingested food, swallowed liquids, digestive secretions, and, as it progresses, microbial biomass. Digesta is distinct from feces, the solid waste that is excreted. The composition of digesta changes along the gastrointestinal tract: in the stomach it is chyme, a semi-liquid mixture; in the small intestine it contains partly digested nutrients; in the large intestine it is enriched with undigested fiber and microbes.

In nutrition and physiology, digesta is studied to evaluate digestion and absorption. Experiments compare intake with digesta content at different sites or after passage to estimate apparent and true digestibility of protein, fat, carbohydrate, and minerals. Measurements include digesta flow and passage rate, ileal digesta versus fecal output, and retention time. Handling and timing of digesta samples are important for accurate analysis.

In veterinary science and animal nutrition, digesta-transit characteristics influence feed efficiency and health. In humans, the term is encountered mainly in GI physiology literature, but the underlying idea—the material inside the digestive tract that has not yet left the body—applies broadly to comparative anatomy and digestive research.