Lipolysis of Milk Fat by Pregastric Esterase in Vivo

Three male Holstein calves, surgically fitted with rumen fistulas, were fed milk by nipple pail and by direct infusion into the abomasum. Samples withdrawn from the abomasum at .5, 1 and 2 hr postfeeding were analyzed for glyceride and fatt: acid composition. The molar percentages of tri-, di-and monoglycerides for calves fed by nipple pail were 57.5, 30.8 and 11.5; 53.3, 32.9 and 13.8; and 49.4, 35.0 and 15.6 at .5, one and two hours, respectively. For calves given milk directly into the abomasum, the molar percentages were 88.7, 8.9 and 2.4; 84.9, 11.2 and 3.9; and 75.0, 17.5 and 7.5, respectively. Fatty acid composition analysis of abomasal glycerides from orally fed calves revealed no butyric or caproic acids in monoglycerides. Smaller quantities of caprylic, capric, laurie and oleic acids were found in monoglycerides than in di-or triglycerides. Palmitic acid was present in greatest amounts in monoglycerides.