Effect of age on small intestinal enzyme activities in grazing sheep

Eight groups of Alpine Fine-wool lambs were used to study the development of pH and five enzyme activities in duodenum, proximal jejunum, middle jejunum, distal jejunum, and ileum mucosa or digesta from birth to d56.From duodenum to ileum the acdity of intestinal mucosa and digesta decreased. pH changed in a very little range in all small intestine with age.The trypsin,chymotrypsin, lipase, lactase, and α-amylase activities were observed at birth but decreased at d3.Thereafter they showed a non-uniform change pattern in different parts. From d 3 to 21 the trypsin activity tended to increase and reached peak at d21,thereafter it began to decrease In duodenum, proximal jejunum and middle jejunum. In distal jejunum and ileum it reached peak at d 7. From d 14 to 28 the chymotrypsin activity increased charply and reached peak at d 28 in duodenum.The gradual nonsignificant increases were abserved from d 3 to 56 in proximal jejunum.From d 3 to 21 the chymotrypsin activity increased and reached peak at d 21 in middle jejunum digesta,thereafter it tended to decrease.In distal jejunum the chymotrypsin activity increased from d 3 to 14 ,d 28 to 56 and decreased from d 14 to 28.And reached peak at d 14 and 56 respectively.In ileum it tended to increase with age and at d21 it had a sharply increase. The chymotrypsin activity in duodenum and proximal jejunum digesta was lower than that in other parts,and it was the highest in middle jejunum. The lipase activity of small intestinal mucosa changed little with age.In duodenum mucosa lipase activity was the highest and pre-jejunum was lowest.In all small intestinal mucosa α-amylase activity was near at birth. Duodenum and proximal jejunum was a little low.At 3d α-amylase activity in the two parts mucosa was close to birth, and increased at 7d or 14d respectively.After 21d α-amylase activity in duodenum mucosa was the highest,followed middle jejunum mucosa, and in ileum mucosa it seemed to be the lowest.The lactase activity was high at birth and decreased at 21d.It was the highest in proximal- and midddle-jejunum mucaosa,but lowest in ileum mucosa.The activity changed little in duodenum mucosa,but decreased with age in other parts.