Role of Pregastric Esterase in the Abomasal Hydrolysis of Milk Fat in the Young Calf

Abstract

The hydrolysis of milk fat in the abomasum of the young calf was studied. Whole milk either was nipple-fed (oral feeding) or was placed directly into the abomasum (abomasal feeding). The purpose of the latter system was to minimize the entrance of pregastrie esterase. At 1, 2, and 3 hr. after feeding, the contents of the abomasum were sampled and analyzed for total free fatty acids (FFA). The FFA from the oral-fed samples were also separated into three fractions: butyric, valerie, and higher fatty acids. The mean concentrations of total FFA (~M/5 g. contents) were as follows for the oral and abomasal systems of feeding, respectively: 1 hr., 86, 19; 2 hr., 101, 20; and 3 hr., 120, 30. For the oral-fed samples, the mean concentrations of butyric, valeric, and higher fatty acids were as follows, respectively: 1 hr., 34, 7, 53; 2 hr., 19, 4, 77; and 3 hr., 11, 3, 119. Previous investigations of pregastric esterase in the young calf have included origin (8), substrate specificity (1-3, 9), and factors that affect its secretion The extent to which pregastric esterase is involved in gastrointestinal Iipolysis, however, has not been ascertained. Thus, an investigation was initiated to study the participation of this enzyme in the abomasal hydrolysis of milk fat.