Yolk and exogenous feed utilization in the posthatch chick.

This study examined in posthatch chicks the partition of yolk utilization between transport to the circulation and secretion to the intestine and determined absorption and plasma concentrations of some metabolites. The presence of feed in the gastrointestinal tract enhanced yolk secretion to the small intestines. Absorption of glucose, methionine, and oleic acid was determined in vivo close to hatch using 141Ce as a nonabsorbed reference substance. Glucose and methionine uptake was low posthatch and increased with age and feed intake. Oleic acid uptake was high at hatch and changed little with age. Increased intake of lipids depressed the percentage oleic acid absorption. Plasma concentrations of glucose, Na, phospholipids, and nonesterified fatty acids did not change with age. Triiodothyronine and triglyceride concentrations increased with age in the plasma of fed chicks but decreased during feed deprivation. Feed intake stimulated posthatch secretion of yolk to the small intestines and triggered uptake mechanisms for hydrophilic compounds.