Development of ovine digestive enzymes with special reference to ribonuclease

Twenty Merino lambs of four age groups (1 day, 2, 4 and 7 weeks) and 8 adult Merino wethers were killed. The development of pancreatic and gastrointestinal enzymes was followed by determining RNase, amylase, lipase, trypsin, chymotrypsin and total proteolytic (azocaseinase) activity. Pancreatic protein content, rumen and abomasal pH and abomasal clotting time were also determined. Pancreatic RNase was already present in the newborn lambs and significantly rose in the first 2 weeks of life and before reaching adult values. The increase was more marked and went to higher adult values than in the pig (Baintner and Farkas, 1989). The time-course resembled that of pancreatic amylase and chymotrypsin; pancreatic trypsin and azocaseinase also showed some similarities, but pancreatic lipase had a different time course. Small intestinal RNase also changed differently; it showed a maximum at 4 weeks and had trends opposite to total proteolytic activity, indicating partial digestion of the enzyme by intestinal proteases. Rumen and caecal RNase activities may be indicative of microbial growth and fermentation rate; they showed mostly opposite tendencies in the two localities. In contrast to the pig (Baintner and Farkas, 1989), pancreatic and small intestinal trypsin:chymotrypsin ratios did not show significant increase during development in sheep.