Studies on lipid digestion in the preruminant calf. The source of lipolytic activity in the abomasum

1. Lipolytic and proteolytic activities and pH values were determined in secretions collected from innervated abomasal pouches and in abomasal contents from preruminant calves given liquid diets. 2. No lipolytic activity was detected in pouch secretions collected during 1 h after feeding, though lipolytic activity was present in abomasal contents; pepsin (EC 3.4.23.1) and renin (EC 3.4.23.4) were present in both pouch secretions and abomasal contents. The pH values of pouch secretions ranged from 1-2 to 1-8 and those of abomasal contents from 4-2 to 5-9. 3. When diet was placed directly into the abomasal pouch soon after feeding, the pH values of pouch and abomasal contents decreased similarly (i.e. from 6-3 to approximately 5). Protease activity (U/ml) of pouch contents ranged from 0-1 to 0-8 and that of abomasal contents from 0-1 to 0-2. No lipolytic activity was detected in pouch contents, though abomasal contents contained 0-6 to 1-2 U/ml and when the diet contained milk-fat as the dietary fat source considerable lipolysis of triglycerides containing shorter-chain fatty acids was found. 4. It is concluded that there is no significant secretion of lipolytic enzymes by the fundal mucosa and that the lipolysis of triglycerides in the abomasum of the preruminant calf is due predominantly to a lipolytic enzyme in saliva.