Gastric function and its contribution to the postprandial metabolic response of the Burmese python Python molurus.

The large intact prey ingested by Burmese pythons require considerable processing by the stomach before passage into the small intestine. To investigate the function and cost of gastric digestion and its contribution to postprandial metabolic response for the Burmese python, I examined the rate of gastric digestion, the postprandial profile of gastric pH and the effects of decreasing gastric workload on the metabolic cost of digestion, referred to as specific dynamic action (SDA). Ingested meal mass (equivalent to 25% of snake body mass) was reduced by 18% within 1 day postfeeding, by which time intragastric pH had decreased from 7.5 to 2. Gastric pH was maintained at 1.5 for the next 5-7 days, after which it returned to 7.5. The SDA generated by digesting an intact rat meal was reduced by 9.1%, 26.0%, 56.5% and 66.8%, respectively, when pythons were fed steak, ground rat, liquid diet or ground rat directly infused into the small intestine. The production of HCl and enzymes and other gastric functions represent an estimated 55% of the python's SDA generated from the digestion of an intact rodent meal. Additional contributors to SDA include protein synthesis (estimated 26%), gastrointestinal upregulation (estimated 5%) and the activities of the pancreas, gallbladder, liver, kidneys and intestines during digestion (estimated 14%). Operating on a 'pay before pumping' principle, pythons must expend endogenous energy in order to initiate acid production and other digestive processes before ingested nutrients can be absorbed and channeled into metabolic pathways.