Pancreas size and trypsin and chymotrypsin activities in the pancreas and intestinal contents of pigs from birth to 5 weeks of age

Abstract

Pancreas size, and trypsin and chymotrypsin esterase activities were determined in the pancreas and small intestinal contents (digesta) from 84 pigs killed at 3 or at 5 weeks of age. Pancreases and digesta from 3-week-old pigs had low trypsin activity (averaging 0.33 unit/mg fresh tissue; 4.0 units/g of liquid digesta). At 5 weeks of age, trypsin activity per unit of tissue or digesta was about 3.5 times greater. Chymotrypsin activity was high at 3 weeks (0.84 unit/mg pancreatic tissue; 17.2 units/g digesta), and was only 1 to 2 times greater at 5 weeks. Digesta from three pigs killed at birth averaged 13.1 units chymotrypsin activity/g of digesta, but had no trypsin activity. The trypsin and chymotrypsin activities in the pancreases from these three pigs averaged 0.43 and 0.89 unit/mg of fresh tissue respectively. The "nonparallel" change in the rate of synthesis and secretion of pancreatic enzymes between 3 and 5 weeks of age reduced the proportion of chymotrypsin to trypsin activity (2.64 to 1.31 for pancreas; 3.39 to 1.41 for digesta). Possible mechanisms involved in this phenomenon are discussed. Increases in pancreas size and body weight were nearly proportional, but the rate of enzyme activity increased as much as 4.1 times (pancreatic trypsin) that of body weight increase. The size and enzyme activity of the pancreas were similar in male and female pigs. Three-week-old males had more trypsin activity in the digesta than did females of the same age. Body weight gains to 3 or 5 weeks of age were positively correlated with total trypsin (P < 0.05) and chymotrypsin (P < 0.01) activity in the digesta.